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1

Symmetric Density Functionals  

E-Print Network [OSTI]

Variations in distinct restricted spaces of wave functions generate distinct density functionals. In particular, angular momentum projected Slater determinants define a new density functional, compatible simultaneously with angular momentum quantum number and mean field descriptions.

B. G. Giraud

2005-07-13T23:59:59.000Z

2

Laboratory Density Functionals  

E-Print Network [OSTI]

We compare several definitions of the density of a self-bound system, such as a nucleus, in relation with its center-of-mass zero-point motion. A trivial deconvolution relates the internal density to the density defined in the laboratory frame. This result is useful for the practical definition of density functionals.

B. G. Giraud

2007-07-26T23:59:59.000Z

3

Density Functional Theory for Superconductors  

E-Print Network [OSTI]

Density Functional Theory for Superconductors LATHIOTAKIS, A. MARQUES, 1,2,3 LU DERS, L. FAST, 2004 words: theory superconductors; density functional theory; critical temperature; exchange matter physics theoretical chemistry is density functional theory (DFT). foundations were established mid

Gross, E.K.U.

4

Relativistic Nuclear Energy Density Functionals  

Science Journals Connector (OSTI)

......research-article Articles Relativistic Nuclear Energy Density Functionals Dario Vretenar...196, 2012 137 Relativistic Nuclear Energy Density Functionals Dario Vretenar...and P. Ring 2. Relativistic nuclear energy density functionals Even though......

Dario Vretenar; Tamara Niksic; Peter Ring

2012-10-01T23:59:59.000Z

5

Density Functional Theory for Superconductors  

E-Print Network [OSTI]

Density Functional Theory for Superconductors N. N. LATHIOTAKIS,1,2 M. A. L. MARQUES,1,2,3 M. LU; density functional theory; critical temperature; exchange and correlation; phonon and theoretical chemistry is density functional theory (DFT). Its foundations were established in the mid-1960s

Gross, E.K.U.

6

Density Functional Theory (DFT) Simulated Annealing (SA)  

E-Print Network [OSTI]

. . . . . . . . 9 2009 #12;! " # $ % & - " # $ %' ! " # # $ % & # ( # " ) Density Functional Theory) % Lattice-Boltzmann (LBM) #12;! " # $ % & - " # $ %' ! " # # $ % & # ( # " ) Density Functional Theory (DFT;! " # $ % & - " # $ %' ! " # # $ % & # ( # " ) Density Functional Theory (DFT) Simulated Annealing (SA) Monte Carlo &$ ' ' (GCMC

7

Jacek Dobaczewski Density functional theory and energy  

E-Print Network [OSTI]

Jacek Dobaczewski Density functional theory and energy density functionals in nuclear physics Jacek Functional #12;Jacek Dobaczewski Mean-Field Theory Density Functional Theory · mean-field one? Density Functional Theory: A variational method that uses observables as variational parameters. #12;Jacek

Dobaczewski, Jacek

8

Open problems in nuclear density functional theory  

E-Print Network [OSTI]

This note describes five subjects of some interest for the density functional theory in nuclear physics. These are, respectively, i) the need for concave functionals, ii) the nature of the Kohn-Sham potential for the radial density theory, iii) a proper implementation of a density functional for an "intrinsic" rotational density, iv) the possible existence of a potential driving the square root of the density, and v) the existence of many models where a density functional can be explicitly constructed.

B. G. Giraud

2009-11-30T23:59:59.000Z

9

Density functional theory of electrowetting  

E-Print Network [OSTI]

The phenomenon of electrowetting, i.e., the dependence of the macroscopic contact angle of a fluid on the electrostatic potential of the substrate, is analyzed in terms of the density functional theory of wetting. It is shown that electrowetting is not an electrocapillarity effect, i.e., it cannot be consistently understood in terms of the variation of the substrate-fluid interfacial tension with the electrostatic substrate potential, but it is related to the depth of the effective interface potential. The key feature, which has been overlooked so far and which occurs naturally in the density functional approach is the structural change of a fluid if it is brought into contact with another fluid. These structural changes occur in the present context as the formation of finite films of one fluid phase in between the substrate and the bulk of the other fluid phase. The non-vanishing Donnan potentials (Galvani potential differences) across such film-bulk fluid interfaces, which generically occur due to an unequal partitioning of ions as a result of differences of solubility contrasts, lead to correction terms in the electrowetting equation, which become relevant for sufficiently small substrate potentials. Whereas the present density functional approach confirms the commonly used electrocapillarity-based electrowetting equation as a good approximation for the cases of metallic electrodes or electrodes coated with a hydrophobic dielectric in contact with an electrolyte solution and an ion-free oil, a significantly reduced tendency for electrowetting is predicted for electrodes coated with a dielectric which is hydrophilic or which is in contact with two immiscible electrolyte solutions.

Markus Bier; Ingrid Ibagon

2014-02-10T23:59:59.000Z

10

Combining Density Functional Theory and Density Matrix Functional Theory Daniel R. Rohr1  

E-Print Network [OSTI]

Combining Density Functional Theory and Density Matrix Functional Theory Daniel R. Rohr1 , Julien and CNRS, 4 place Jussieu, 75252 Paris, France We combine density-functional theory with density cleavage is an ubiquitous process for chemistry. Density-matrix functional theory (DMFT) (see, e.g., Refs

Paris-Sud XI, Université de

11

Time Dependent Density Functional Theory An introduction  

E-Print Network [OSTI]

Time Dependent Density Functional Theory An introduction Francesco Sottile LSI, Ecole Polytechnique) Time Dependent Density Functional Theory Palaiseau, 26 May 2014 1 / 62 #12;Outline 1 Introduction: why and Resources Francesco Sottile (ETSF) Time Dependent Density Functional Theory Palaiseau, 26 May 2014 2 / 62

Botti, Silvana

12

DENSITY FUNCTIONAL THEORY OF FIELD THEORETICAL SYSTEMS  

E-Print Network [OSTI]

DENSITY FUNCTIONAL THEORY OF FIELD THEORETICAL SYSTEMS E. Engel Inst. fur Theor. Physik background of relativistic density functional theory is emphasized and its consequences for relativistic Kohn-Sham equations are shown. The local density approximation for the exchange energy functional is reviewed

Engel, Eberhard

13

Density functional theory George F. Bertsch  

E-Print Network [OSTI]

Density functional theory George F. Bertsch #3; Institute for Nuclear Theory and Department of Physics University of Tsukuba Tsukuba 305-8577 Japan Abstract Density functional theory is a remarkably Time-dependent density functional theory: the equations 34 A Optical properties

Bertsch George F.

14

DENSITY FUNCTIONAL THEORY, THE MODERN TREATMENT OF  

E-Print Network [OSTI]

DENSITY FUNCTIONAL THEORY, THE MODERN TREATMENT OF ELECTRON CORRELATIONS E.K.U. Gross and Stefan The basic idea of density functional theory is to describe a many-electron system exclusively and completely-consistent scheme, known as the Kohn-Sham scheme [2], is the heart of modern density functional theory

Gross, E.K.U.

15

KH Computational Physics-2009 Density Functional Theory (DFT) Density Functional Theory  

E-Print Network [OSTI]

KH Computational Physics- 2009 Density Functional Theory (DFT) Density Functional Theory of interacting particles. Kristjan Haule, 2009 ­2­ #12;KH Computational Physics- 2009 Density Functional Theory functional of n. Kristjan Haule, 2009 ­3­ #12;KH Computational Physics- 2009 Density Functional Theory (DFT

Haule, Kristjan

16

HIGHLIGHT OF THE MONTH Orbital Functionals in Density Functional Theory  

E-Print Network [OSTI]

HIGHLIGHT OF THE MONTH Orbital Functionals in Density Functional Theory: The Optimized E#11;ectiveurzburg, Am Hubland, D-97074 Wurzburg, Germany The success of density functional theory hinges the development of modern density functional theory. In present-day language, the exact OEP should be called

Gross, E.K.U.

17

Gedanken densities and exact constraints in density functional theory  

SciTech Connect (OSTI)

Approximations to the exact density functional for the exchange-correlation energy of a many-electron ground state can be constructed by satisfying constraints that are universal, i.e., valid for all electron densities. Gedanken densities are designed for the purpose of this construction, but need not be realistic. The uniform electron gas is an old gedanken density. Here, we propose a spherical two-electron gedanken density in which the dimensionless density gradient can be an arbitrary positive constant wherever the density is non-zero. The Lieb-Oxford lower bound on the exchange energy can be satisfied within a generalized gradient approximation (GGA) by bounding its enhancement factor or simplest GGA exchange-energy density. This enhancement-factor bound is well known to be sufficient, but our gedanken density shows that it is also necessary. The conventional exact exchange-energy density satisfies no such local bound, but energy densities are not unique, and the simplest GGA exchange-energy density is not an approximation to it. We further derive a strongly and optimally tightened bound on the exchange enhancement factor of a two-electron density, which is satisfied by the local density approximation but is violated by all published GGA's or meta-GGAs. Finally, some consequences of the non-uniform density-scaling behavior for the asymptotics of the exchange enhancement factor of a GGA or meta-GGA are given.

Perdew, John P. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States) [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States); Ruzsinszky, Adrienn; Sun, Jianwei [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States)] [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Burke, Kieron [Department of Chemistry and Department of Physics, University of California, Irvine, California 92697 (United States)] [Department of Chemistry and Department of Physics, University of California, Irvine, California 92697 (United States)

2014-05-14T23:59:59.000Z

18

Scalar Nature of the Nuclear Density Functional  

E-Print Network [OSTI]

Because of the rotational invariance of the nuclear Hamiltonian, there exists a density functional for nuclei that depends only on two scalar densities. Practical calculations boil down to radial, one-dimensional ones.

B. G. Giraud

2008-01-22T23:59:59.000Z

19

Quantum critical benchmark for density functional theory  

E-Print Network [OSTI]

Two electrons at the threshold of ionization represent a severe test case for electronic structure theory. A pseudospectral method yields a very accurate density of the two-electron ion with nuclear charge close to the critical value. Highly accurate energy components and potentials of Kohn-Sham density functional theory are given, as well as a useful parametrization of the critical density. The challenges for density functional approximations and the strength of correlation are also discussed.

Paul E. Grabowski; Kieron Burke

2014-08-09T23:59:59.000Z

20

Some challenges for Nuclear Density Functional Theory  

E-Print Network [OSTI]

We discuss some of the challenges that the DFT community faces in its quest for the truly universal energy density functional applicable over the entire nuclear chart.

T. Duguet; K. Bennaceur; T. Lesinski; J. Meyer

2006-06-20T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Density functional theory for carbon dioxide crystal  

SciTech Connect (OSTI)

We present a density functional approach to describe the solid?liquid phase transition, interfacial and crystal structure, and properties of polyatomic CO{sub 2}. Unlike previous phase field crystal model or density functional theory, which are derived from the second order direct correlation function, the present density functional approach is based on the fundamental measure theory for hard-sphere repulsion in solid. More importantly, the contributions of enthalpic interactions due to the dispersive attractions and of entropic interactions arising from the molecular architecture are integrated in the density functional model. Using the theoretical model, the predicted liquid and solid densities of CO{sub 2} at equilibrium triple point are in good agreement with the experimental values. Based on the structure of crystal-liquid interfaces in different planes, the corresponding interfacial tensions are predicted. Their respective accuracies need to be tested.

Chang, Yiwen; Mi, Jianguo, E-mail: mijg@mail.buct.edu.cn; Zhong, Chongli [State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China)

2014-05-28T23:59:59.000Z

22

Testing the kinetic energy functional: Kinetic energy density as a density functional  

E-Print Network [OSTI]

is to the exchange-correlation energy as a functional of the density. A large part of the total energy, the kinetic contexts. For finite systems these forms integrate to the same global ki- netic energy, but they differTesting the kinetic energy functional: Kinetic energy density as a density functional Eunji Sim

Burke, Kieron

23

Instabilities in the Nuclear Energy Density Functional  

E-Print Network [OSTI]

In the field of Energy Density Functionals (EDF) used in nuclear structure and dynamics, one of the unsolved issues is the stability of the functional. Numerical issues aside, some EDFs are unstable with respect to particular perturbations of the nuclear ground-state density. The aim of this contribution is to raise questions about the origin and nature of these instabilities, the techniques used to diagnose and prevent them, and the domain of density functions in which one should expect a nuclear EDF to be stable.

M. Kortelainen; T. Lesinski

2010-02-05T23:59:59.000Z

24

Density and pair-density scaling for deriving the Euler equation in density-functional and pair-density-functional theory  

SciTech Connect (OSTI)

A link between density and pair density functional theories is presented. Density and pair density scaling are used to derive the Euler equation in both theories. Density scaling provides a constructive way of obtaining approximations for the Pauli potential. The Pauli potential (energy) of the density functional theory is expressed as the difference of the scaled and original exchange-correlation potentials (energies).

Nagy, A. [Department of Theoretical Physics, University of Debrecen, H-4010 Debrecen (Hungary)

2011-09-15T23:59:59.000Z

25

Time Dependent Density Functional Theory Application to Extended Systems  

E-Print Network [OSTI]

Time Dependent Density Functional Theory Application to Extended Systems Francesco Sottile Facility (ETSF) Donostia, 25 July 2007 Time Dependent Density Functional Theory Francesco Sottile #12 Density Functional Theory Francesco Sottile #12;Linear Periodic systems ALDA The Quest for the Holy

Botti, Silvana

26

Density Functional Theory Approach to Nuclear Fission  

E-Print Network [OSTI]

The Skyrme nuclear energy density functional theory (DFT) is used to model neutron-induced fission in actinides. This paper focuses on the numerical implementation of the theory. In particular, it reports recent advances in DFT code development on leadership class computers, and presents a detailed analysis of the numerical accuracy of DFT solvers for near-scission calculations.

N. Schunck

2013-01-20T23:59:59.000Z

27

Modern applications of covariant density functional theory  

E-Print Network [OSTI]

Modern applications of Covariant Density Functional Theory (CDFT) are discussed. First we show a systematic investigation of fission barriers in actinide nuclei within constraint relativistic mean field theory allowing for triaxial deformations. In the second part we discuss a microscopic theory of quantum phase transitions (QPT) based on the relativistic generator coordinate method.

P. Ring; H. Abusara; A. V. Afanasjev; G. A. Lalazissis; T. Niksic; D. Vretenar

2011-09-19T23:59:59.000Z

28

Master's Thesis Density Functional Theory for  

E-Print Network [OSTI]

of the information found during my work. v #12;vi #12;Contents Abstract #12;Abstract This thesis presents a number of results for basic quantum mechanical models intended to be used in the development of density functional theory for systems with edges. Following previous work

Armiento, Rickard

29

DENSITY FUNCTIONAL THEORY OF NORMAL AND SUPERCONDUCTING ELECTRON LIQUIDS: EXPLICIT  

E-Print Network [OSTI]

DENSITY FUNCTIONAL THEORY OF NORMAL AND SUPERCONDUCTING ELECTRON LIQUIDS: EXPLICIT FUNCTIONALS VIA?th University Nathan, Queensland 4111, Australia Abstract The basic idea of density functional theory is to map potential which is a functional of the density. The central task of density functional theory is to #12;nd

Gross, E.K.U.

30

ORBITAL-FREE KINETIC-ENERGY DENSITY FUNCTIONAL THEORY  

E-Print Network [OSTI]

Chapter 5 ORBITAL-FREE KINETIC-ENERGY DENSITY FUNCTIONAL THEORY Yan Alexander Wang and Emily A Theory (DFT), there was the Thomas-Fermi (TF) model, which uses the electron density ¢¡ r£ (a function-dependent DFT Density-Functional Theory DI density-independent DM1 first-order reduced density matrix EDF energy

Wang, Yan Alexander

31

The problem of the universal density functional and the density matrix functional theory  

SciTech Connect (OSTI)

The analysis in this paper shows that the Hohenberg-Kohn theorem is the constellation of two statements: (i) the mathematically rigorous Hohenberg-Kohn lemma, which demonstrates that the same ground-state density cannot correspond to two different potentials of an external field, and (ii) the hypothesis of the existence of the universal density functional. Based on the obtained explicit expression for the nonrel-ativistic particle energy in a local external field, we prove that the energy of the system of more than two non-interacting electrons cannot be a functional of the inhomogeneous density. This result is generalized to the system of interacting electrons. It means that the Hohenberg-Kohn lemma cannot provide justification of the universal density functional for fermions. At the same time, statements of the density functional theory remain valid when considering any number of noninteracting ground-state bosons due to the Bose condensation effect. In the framework of the density matrix functional theory, the hypothesis of the existence of the universal density matrix functional corresponds to the cases of noninteracting particles and to interaction in the Hartree-Fock approximation.

Bobrov, V. B., E-mail: vic5907@mail.ru; Trigger, S. A., E-mail: satron@mail.ru [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2013-04-15T23:59:59.000Z

32

Density Functional Theory applied to the solid state...  

E-Print Network [OSTI]

Density Functional Theory applied to the solid state... An introduction to VASP Jeremie Zaffran 2nd Marom (PhD) #12;Contents I- DFT and its functionals A. On the density functional theory... B #12;I- DFT and its functionals #12;I-DFT and its functionals A- On the density functional theory Why

Adler, Joan

33

Symmetry energy in nuclear density functional theory  

E-Print Network [OSTI]

The nuclear symmetry energy represents a response to the neutron-proton asymmetry. In this survey we discuss various aspects of symmetry energy in the framework of nuclear density functional theory, considering both non-relativistic and relativistic self-consistent mean-field realizations side-by-side. Key observables pertaining to bulk nucleonic matter and finite nuclei are reviewed. Constraints on the symmetry energy and correlations between observables and symmetry-energy parameters, using statistical covariance analysis, are investigated. Perspectives for future work are outlined in the context of ongoing experimental efforts.

W. Nazarewicz; P. -G. Reinhard; W. Satula; D. Vretenar

2013-07-22T23:59:59.000Z

34

Density-functional theory of nonuniform classical liquids: An extended modified weighted-density approximation  

E-Print Network [OSTI]

Density-functional theory of nonuniform classical liquids: An extended modified weighted-density the approximationstreat long-rangeand short-rangepotentials. I. INTRODUCTION The density-functional theory of nonuniform of density- functional theory to the problem of freezing of classical liquids,4 and in particular

Likos, Christos N.

35

Covariant density functional theory for antimagnetic rotation  

E-Print Network [OSTI]

Following the previous letter on the first microscopic description of the antimagnetic rotation (AMR) in 105Cd, a systematic investigation and detailed analysis for the AMR band in the frame-work of tilted axis cranking (TAC) model based on covariant density functional theory are carried out. After performing the microscopic and self-consistentTAC calculations with an given density functional, the configuration for the observed AMR band in 105Cd is obtained from the single-particle Routhians. With the configuration thus obtained, the tilt angle for a given rotational frequency is determined self-consistently by minimizing the total Routhian with respect to the tilt angle. In such a way, the energy spectrum, total angular momenta, kinetic and dynamic moments of inertia, and the B(E2) values for the AMR band in 105Cd are calculated. Good agreement with the data is found. By investigating microscopically the contributions from neutrons and protons to the total angular momentum, the "two-shears-like" mechanism in the AMR band is clearly illus-trated. Finally, the currents leading to time-odd mean fields in the Dirac equation are presented and discussed in detail. It is found that they are essentially determined by the valence particles and/or holes. Their spatial distribution and size depend onthe specific single-particle orbitals and the rotational frequency.

P. W. Zhao; J. Peng; H. Z. Liang; P. Ring; J. Meng

2012-05-04T23:59:59.000Z

36

Benchmark density functional theory calculations for nanoscale conductance  

E-Print Network [OSTI]

Benchmark density functional theory calculations for nanoscale conductance M. Strange,a I. S. The transmission functions are calculated using two different density functional theory methods, namely state density functional theory DFT . The resulting NEGF- DFT formalism provides a numerically efficient

Thygesen, Kristian

37

THE MANY-ELECTRON ENERGY IN DENSITY FUNCTIONAL THEORY  

E-Print Network [OSTI]

THE MANY-ELECTRON ENERGY IN DENSITY FUNCTIONAL THEORY From Exchange-Correlation Functional Design to the configuration of its electrons. Computer programs based on density functional theory (DFT) can calculate applicable within the field of computational density functional theory. Sammanfattning Att förutsäga

Armiento, Rickard

38

Path integral Monte Carlo and density functional molecular dynamics simulations of hot, dense helium  

Science Journals Connector (OSTI)

Two first-principles simulation techniques, path integral Monte Carlo (PIMC) and density functional molecular dynamics (DFT-MD), are applied to study hot, dense helium in the density-temperature range of 0.3875.35?g?cm?3 and 500?K1.28108?K. One coherent equation of state is derived by combining DFT-MD data at lower temperatures with PIMC results at higher temperatures. Good agreement between both techniques is found in an intermediate-temperature range. For the highest temperatures, the PIMC results converge to the Debye-Hckel limiting law. In order to derive the entropy, a thermodynamically consistent free-energy fit is used that reproduces the internal energies and pressure derived from the first-principles simulations. The equation of state is presented in the form of a table as well as a fit and is compared with different free-energy models. Pair-correlation functions and the electronic density of states are discussed. Shock Hugoniot curves are compared with recent laser shock-wave experiments.

B. Militzer

2009-04-08T23:59:59.000Z

39

Electronic excitations in complex systems: beyond density functional theory  

E-Print Network [OSTI]

Electronic excitations in complex systems: beyond density functional theory for real materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 3 Time-dependent density functional theory 19 3.1 The Runge-Gross theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 4 Model kernels from many-body perturbation theory 29 4.1 Time-dependent density functional theory

Botti, Silvana

40

A Guided Tour of TimeDependent Density Functional Theory  

E-Print Network [OSTI]

A Guided Tour of Time­Dependent Density Functional Theory Kieron Burke 1 and E.K.U. Gross 2 1 outlook. 1 Introduction and User's Guide Density functional theory is the study of the one in density functional theory, driven largely by its applications in quantum chemistry[3]. This is due

Gross, E.K.U.

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

EFFECTIVE MAXWELL EQUATIONS FROM TIME-DEPENDENT DENSITY FUNCTIONAL THEORY  

E-Print Network [OSTI]

EFFECTIVE MAXWELL EQUATIONS FROM TIME-DEPENDENT DENSITY FUNCTIONAL THEORY WEINAN E, JIANFENG LU and magnetic fields are derived starting from time-dependent density functional theory. Effective permittivity with the density functional theory [2­4] instead of the many-body Schr¨odinger or Dirac equations. This is because

Bigelow, Stephen

42

1 Density Functional Theory for Emergents Robert O. Jones  

E-Print Network [OSTI]

1 Density Functional Theory for Emergents Robert O. Jones Peter-Gr¨unberg-Institut PGI-1 and German the widespread use of density functional (DF) theory in materials science and chemistry and the physical insight as basic variable 3 3 An "approximate practical method" 5 4 Density functional formalism 7 4.1 Single

43

RELATIVISTIC DENSITY FUNCTIONAL THEORY: FOUNDATIONS AND BASIC FORMALISM  

E-Print Network [OSTI]

1 Chapter 10 RELATIVISTIC DENSITY FUNCTIONAL THEORY: FOUNDATIONS AND BASIC FORMALISM E. Engela a An overview of relativistic density functional theory (RDFT) is presented with special emphasis on its field-Cluster schemes in recent years density functional theory (DFT) still represents the method of choice

Engel, Eberhard

44

Building a Universal Nuclear Energy Density Functional  

SciTech Connect (OSTI)

During the period of Dec. 1 2006 Jun. 30, 2012, the UNEDF collaboration carried out a comprehensive study of all nuclei, based on the most accurate knowledge of the strong nuclear interaction, the most reliable theoretical approaches, the most advanced algorithms, and extensive computational resources, with a view towards scaling to the petaflop platforms and beyond. The long-term vision initiated with UNEDF is to arrive at a comprehensive, quantitative, and unified description of nuclei and their reactions, grounded in the fundamental interactions between the constituent nucleons. We seek to replace current phenomenological models of nuclear structure and reactions with a well-founded microscopic theory that delivers maximum predictive power with well-quantified uncertainties. Specifically, the mission of this project has been three-fold: ? First, to find an optimal energy density functional (EDF) using all our knowledge of the nucleonic Hamiltonian and basic nuclear properties; ? Second, to apply the EDF theory and its extensions to validate the functional using all the available relevant nuclear structure and reaction data; ? Third, to apply the validated theory to properties of interest that cannot be measured, in particular the properties needed for reaction theory.

Carlson, Joe A. [Michigan State University; Furnstahl, Dick; Horoi, Mihai; Lust, Rusty; Nazaewicc, Witek; Ng, Esmond; Thompson, Ian; Vary, James

2012-12-30T23:59:59.000Z

45

Charge constrained density functional molecular dynamics for simulation of condensed phase electron transfer reactions  

SciTech Connect (OSTI)

We present a plane-wave basis set implementation of charge constrained density functional molecular dynamics (CDFT-MD) for simulation of electron transfer reactions in condensed phase systems. Following the earlier work of Wu and Van Voorhis [Phys. Rev. A 72, 024502 (2005)], the density functional is minimized under the constraint that the charge difference between donor and acceptor is equal to a given value. The classical ion dynamics is propagated on the Born-Oppenheimer surface of the charge constrained state. We investigate the dependence of the constrained energy and of the energy gap on the definition of the charge and present expressions for the constraint forces. The method is applied to the Ru{sup 2+}-Ru{sup 3+} electron self-exchange reaction in aqueous solution. Sampling the vertical energy gap along CDFT-MD trajectories and correcting for finite size effects, a reorganization free energy of 1.6 eV is obtained. This is 0.1-0.2 eV lower than a previous estimate based on a continuum model for solvation. The smaller value for the reorganization free energy can be explained by the fact that the Ru-O distances of the divalent and trivalent Ru hexahydrates are predicted to be more similar in the electron transfer complex than for the separated aqua ions.

Oberhofer, Harald; Blumberger, Jochen [Department of Chemistry, University of Cambridge, Cambridge CB2 1EW (United Kingdom)

2009-08-14T23:59:59.000Z

46

Constrained Density-Functional Theory--Configuration Interaction  

E-Print Network [OSTI]

In this thesis, I implemented a method for performing electronic structure calculations, "Constrained Density Functional Theory-- Configuration Interaction" (CDFT-CI), which builds upon the computational strengths of Density ...

Kaduk, Benjamin James

2012-01-01T23:59:59.000Z

47

Functional designed to include surface effects in self-consistent density functional theory R. Armiento1,  

E-Print Network [OSTI]

Functional designed to include surface effects in self-consistent density functional theory R 2005 We design a density-functional-theory DFT exchange-correlation functional that enables an accurate density functional theory1 DFT is a method for electronic structure calculations of unparalleled

Armiento, Rickard

48

Scaled Density Functional Theory Correlation Functionals Mohammed M. Ghouri,a  

E-Print Network [OSTI]

Scaled Density Functional Theory Correlation Functionals Mohammed M. Ghouri,a Saurabh Singh,a and B by Density Functional Theory (DFT)2 correlation functionals without significant deterioration that a simple one parameter scaling of the dynamical correlation energy estimated by the Density Functional

Ramachandran, Bala (Ramu)

49

Ions in solution: Density corrected density functional theory (DC-DFT)  

SciTech Connect (OSTI)

Standard density functional approximations often give questionable results for odd-electron radical complexes, with the error typically attributed to self-interaction. In density corrected density functional theory (DC-DFT), certain classes of density functional theory calculations are significantly improved by using densities more accurate than the self-consistent densities. We discuss how to identify such cases, and how DC-DFT applies more generally. To illustrate, we calculate potential energy surfaces of HOCl{sup ?} and HOH{sub 2}O complexes using various common approximate functionals, with and without this density correction. Commonly used approximations yield wrongly shaped surfaces and/or incorrect minima when calculated self consistently, while yielding almost identical shapes and minima when density corrected. This improvement is retained even in the presence of implicit solvent.

Kim, Min-Cheol; Sim, Eunji, E-mail: esim@yonsei.ac.kr [Department of Chemistry and Institute of Nano-Bio Molecular Assemblies, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul 120-749 (Korea, Republic of)] [Department of Chemistry and Institute of Nano-Bio Molecular Assemblies, Yonsei University, 50 Yonsei-ro Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Burke, Kieron [Department of Chemistry, University of California, Irvine, California 92697 (United States)] [Department of Chemistry, University of California, Irvine, California 92697 (United States)

2014-05-14T23:59:59.000Z

50

Particle-Number Projection and the Density Functional Theory  

E-Print Network [OSTI]

In the framework of the Density Functional Theory for superconductors, we study the restoration of the particle number symmetry by means of the projection technique. Conceptual problems are outlined and numerical difficulties are discussed. Both are related to the fact that neither the many-body Hamiltonian nor the wave function of the system appear explicitly in the Density Functional Theory. Similar obstacles are encountered in self-consistent theories utilizing density-dependent effective interactions.

J. Dobaczewski; M. V. Stoitsov; W. Nazarewicz; P. -G. Reinhard

2007-08-03T23:59:59.000Z

51

Density Functional Theory Study of Oxygen Reduction Activity...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Study of Oxygen Reduction Activity on Ultrathin Platinum Nanotubes. Density Functional Theory Study of Oxygen Reduction Activity on Ultrathin Platinum Nanotubes. Abstract: The...

52

Covariance analysis for Energy Density Functionals and instabilities  

E-Print Network [OSTI]

We present the covariance analysis of two successful nuclear energy density functionals, (i) a non-relativistic Skyrme functional built from a zero-range effective interaction, and (ii) a relativistic nuclear energy density functional based on density dependent meson-nucleon couplings. Such a study is crucial for assessing the information content of an observable when predicted by a given model. The covariance analysis is a useful tool for understanding the limitations of a model, the correlations between observables and the statistical errors. We also provide a brief review, partly connected with the covariance analysis, of some instabilities displayed by several energy density functionals of current use in nuclear physics.

Roca-Maza, X; Col, G

2014-01-01T23:59:59.000Z

53

Density Functional Study of the Structure, Stability and Oxygen...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Study of the Structure, Stability and Oxygen Reduction Activity of Ultrathin Platinum Nanowires. Density Functional Study of the Structure, Stability and Oxygen Reduction Activity...

54

Subsystem functionals in density-functional theory: Investigating the exchange energy per particle R. Armiento*  

E-Print Network [OSTI]

Subsystem functionals in density-functional theory: Investigating the exchange energy per particle; published 31 October 2002 A viable way of extending the successful use of density-functional theory for slowly varying densities and discuss the implications of our findings on the future of functional

Armiento, Rickard

55

ORBITAL FUNCTIONALS IN STATIC AND TIME-DEPENDENT DENSITY FUNCTIONAL THEORY  

E-Print Network [OSTI]

ORBITAL FUNCTIONALS IN STATIC AND TIME-DEPENDENT DENSITY FUNCTIONAL THEORY E.K.U. Gross, T-97074 Wurzburg Germany INTRODUCTION Density functional theory (DFT) is among the most powerful quantum statements: 1 #12; 1. The ground-state density n uniquely determines the ground-state wave function [n

Gross, E.K.U.

56

Time-dependent density-functional theory for open systems  

E-Print Network [OSTI]

By introducing the self-energy density functionals for the dissipative interactions between the reduced system and its environment, we develop a time-dependent density-functional theory formalism based on an equation of motion for the Kohn-Sham reduced single-electron density matrix of the reduced system. Two approximate schemes are proposed for the self-energy density functionals, the complete second order approximation and the wide-band limit approximation. A numerical method based on the wide-band limit approximation is subsequently developed and implemented to simulate the steady and transient current through various realistic molecular devices. Simulation results are presented and discussed.

Xiao Zheng; Fan Wang; Chi Yung Yam; Yan Mo; GuanHua Chen

2007-02-27T23:59:59.000Z

57

The Performance of Density Functionals for Sulfate-Water Clusters  

SciTech Connect (OSTI)

The performance of 24 density functionals, Hartree-Fock, and MP2 is assessed with respect to the energetics of 49 sulfate-water clusters with between three and six water molecules. Included among the density functionals are GGA, meta-GGA, hybrid GGA, hybrid meta-GGA, and double hybrid density functionals, as well as the LDA. Three types of dispersion corrections (VV10, XDM, and -D) are tested in conjunction with these functionals. The functionals are compared using the relative and binding energies of the sulfatewater clusters as the main criteria. It is discovered that a majority of current density functionals are unable to simultaneously capture the physics necessary to describe both the relative and binding energies of the anionic solvation clusters. The only density functionals that perform acceptably with respect to both measures are XYG3 and XYGJOS, primarily due to their balanced treatment of exchange and correlation. On the other hand, density functionals with exact exchange that lack nonlocal correlation tend to perform well only for the relative energies. However, there is evidence that hybrid density functionals that provide a more comprehensive treatment of local correlation through their dependence on the kinetic energy density and their ability to treat the inhomogeneities in the present system can partially resolve this issue. While dispersion correction functionals cannot replace the accuracy provided by MP2 correlation, it is shown that the proper combination of a hybrid GGA functional with a dispersion correction functional can lead to drastic improvements in the binding energies of the parent functional, while preserving its performance with respect to the relative energies.

Mardirossian, Narbe; Lambrecht, Daniel S.; McCaslin, Laura; Xantheas, Sotiris S.; Head-Gordon, Martin P.

2013-03-12T23:59:59.000Z

58

Introduction to Density Functional Theory and Exchange-Correlation Energy Functionals  

E-Print Network [OSTI]

Introduction to Density Functional Theory and Exchange-Correlation Energy Functionals R. O. Jones.jones@fz-juelich.de Density functional calculations of cohesive and structural properties of molecules and solids can the theory and discuss the local density approximations basic to most applications, and we discuss ways

59

The benchmark of gutzwiller density functional theory in hydrogen systems  

SciTech Connect (OSTI)

We propose an approximate form of the exchange-correlation energy functional for the Gutzwiller density functional theory. It satisfies certain physical constraints in both weak and strong electron correlation limits. We benchmark the Gutzwiller density functional approximation in the hydrogen systems, where the static correlation error is shown to be negligible. The good transferability is demonstrated by applications to the hydrogen molecule and some crystal structures.

Yao, Y.; Wang, Cai-Zhuang; Ho, Kai-Ming

2012-02-23T23:59:59.000Z

60

Density functional theory and optimal transportation with Coulomb cost  

E-Print Network [OSTI]

We present here novel insight into exchange-correlation functionals in density functional theory, based on the viewpoint of optimal transport. We show that in the case of two electrons and in the semiclassical limit, the exact exchange-correlation functional reduces to a very interesting functional of novel form, which depends on an optimal transport map $T$ associated with a given density $\\rho$. Since the above limit is strongly correlated, the limit functional yields insight into electron correlations. We prove the existence and uniqueness of such an optimal map for any number of electrons and each $\\rho$, and determine the map explicitly in the case when $\\rho$ is radially symmetric.

Codina Cotar; Gero Friesecke; Claudia Klppelberg

2011-04-04T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Nuclear Energy Density Functionals Constrained by Low-Energy QCD  

E-Print Network [OSTI]

A microscopic framework of nuclear energy density functionals is reviewed, which establishes a direct relation between low-energy QCD and nuclear structure, synthesizing effective field theory methods and principles of density functional theory. Guided by two closely related features of QCD in the low-energy limit: a) in-medium changes of vacuum condensates, and b) spontaneous breaking of chiral symmetry; a relativistic energy density functional is developed and applied in studies of ground-state properties of spherical and deformed nuclei.

Dario Vretenar

2008-02-06T23:59:59.000Z

62

Energy Density Functional for Nuclei and Neutron Stars  

SciTech Connect (OSTI)

Background: Recent observational data on neutron star masses and radii provide stringent constraints on the equation of state of neutron rich matter [ Annu. Rev. Nucl. Part. Sci. 62 485 (2012)]. Purpose: We aim to develop a nuclear energy density functional that can be simultaneously applied to finite nuclei and neutron stars. Methods: We use the self-consistent nuclear density functional theory (DFT) with Skyrme energy density functionals and covariance analysis to assess correlations between observables for finite nuclei and neutron stars. In a first step two energy functionals a high density energy functional giving reasonable neutron properties, and a low density functional fitted to nuclear properties are matched. In a second step, we optimize a new functional using exactly the same protocol as in earlier studies pertaining to nuclei but now including neutron star data. This allows direct comparisons of performance of the new functional relative to the standard one. Results: The new functional TOV-min yields results for nuclear bulk properties (energy, rms radius, diffraction radius, and surface thickness) that are of the same quality as those obtained with the established Skyrme functionals, including SV-min. When comparing SV-min and TOV-min, isoscalar nuclear matter indicators vary slightly while isovector properties are changed considerably. We discuss neutron skins, dipole polarizability, separation energies of the heaviest elements, and proton and neutron drip lines. We confirm a correlation between the neutron skin of 208Pb and the neutron star radius. Conclusions: We demonstrate that standard energy density functionals optimized to nuclear data do not carry information on the expected maximum neutron star mass, and that predictions can only be made within an extremely broad uncertainty band. For atomic nuclei, the new functional TOV-min performs at least as well as the standard nuclear functionals, but it also reproduces expected neutron star data within assumed error bands. This functional is expected to yield more reliable predictions in the region of very neutron rich heavy nuclei.

Erler, J. [UTK/ORNL/German Cancer Research Center-Heidelberg; Horowitz, C. J. [UTK/ORNL/Indiana University; Nazarewicz, Witold [UTK/ORNL/University of Warsaw; Rafalski, M. [UTK/ORNL; Reinhard, P.-G. [Universitat Erlangen, Germany

2013-01-01T23:59:59.000Z

63

Correlation Testing in Nuclear Density Functional Theory  

E-Print Network [OSTI]

Correlation testing provides a quick method of discriminating amongst potential terms to include in a nuclear mass formula or functional and is a necessary tool for further nuclear mass models; however a firm mathematical foundation of the method has not been previously set forth. Here, the necessary justification for correlation testing is developed and more detail of the motivation behind its use is give. Examples are provided to clarify the method analytically and for computational benchmarking. We provide a quantitative demonstration of the method's performance and short-comings, highlighting also potential issues a user may encounter. In concluding we suggest some possible future developments to improve the limitations of the method.

M. G. Bertolli

2012-08-07T23:59:59.000Z

64

Parameter-free calculation of response functions in time dependent density functional theory  

E-Print Network [OSTI]

Parameter-free calculation of response functions in time dependent density functional theory - Quasiparticle approach - Density functional approach Mapping theory to describe spectra of solids in TDDFT Towards an efficient (fast) theory Conclusions #12;Dielectric function of the material Vtot = -1 Vext Non

Botti, Silvana

65

Density functional theory for self-bound systems  

E-Print Network [OSTI]

The density functional theory is extended to account for self-bound systems. To this end the Hohenberg-Kohn theorem is formulated for the intrinsic density and a Kohn-Sham like procedure for an $N$--body system is derived using the adiabatic approximation to account for the center of mass motion.

Nir Barnea

2007-11-06T23:59:59.000Z

66

Assessing the performance of recent density functionals for bulk solids  

E-Print Network [OSTI]

We assess the performance of recent density functionals for the exchange-correlation energy of a nonmolecular solid, by applying accurate calculations with the GAUSSIAN, BAND, and VASP codes to a test set of 24 solid metals ...

Csonka, Gabor I.

67

A density functional study of actinyl containing complexes.  

E-Print Network [OSTI]

??Density functional (DFT) methods are first used to study 22 of the most stable solution-phase UN4O12 isomers containing uranyl nitrate, UO2(NO3)2. Based on relative free (more)

Berard, Joel J.

2008-01-01T23:59:59.000Z

68

Preface: Special Topic on Advances in Density Functional Theory  

SciTech Connect (OSTI)

This Special Topic Issue on the Advances in Density Functional Theory, published as a celebration of the fifty years of density functional theory, contains a retrospective article, a perspective article, and a collection of original research articles that showcase recent theoretical advances in the field. It provides a timely discussion reflecting a cross section of our understanding, and the theoretical and computational developments, which have significant implications in broad areas of sciences and engineering.

Yang, Weitao [Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708 (United States)] [Department of Chemistry and Department of Physics, Duke University, Durham, North Carolina 27708 (United States)

2014-05-14T23:59:59.000Z

69

Dynamical density functional theory for colloidal particles with arbitrary shape  

E-Print Network [OSTI]

Starting from the many-particle Smoluchowski equation, we derive dynamical density functional theory for Brownian particles with an arbitrary shape. Both passive and active (self-propelled) particles are considered. The resulting theory constitutes a microscopic framework to explore the collective dynamical behavior of biaxial particles in nonequilibrium. For spherical and uniaxial particles, earlier derived dynamical density functional theories are recovered as special cases. Our study is motivated by recent experimental progress in preparing colloidal particles with many different biaxial shapes.

Raphael Wittkowski; Hartmut Lwen

2011-06-12T23:59:59.000Z

70

Molecular Binding Energies from Partition Density Functional Theory  

SciTech Connect (OSTI)

Approximate molecular calculations via standard Kohn-Sham density functional theory are exactly reproduced by performing self-consistent calculations on isolated fragments via partition density functional theory [P. Elliott, K. Burke, M. H. Cohen, and A. Wasserman, Phys. Rev. A 82, 024501 (2010)]. We illustrate this with the binding curves of small diatomic molecules. We find that partition energies are in all cases qualitatively similar and numerically close to actual binding energies. We discuss qualitative features of the associated partition potentials.

Nafziger, J.; Wu, Q.; Wasserman, A.

2011-12-21T23:59:59.000Z

71

Density Functional Theory with Dissipation: Transport through Single Molecules  

SciTech Connect (OSTI)

A huge amount of fundamental research was performed on this grant. Most of it focussed on fundamental issues of electronic structure calculations of transport through single molecules, using density functional theory. Achievements were: (1) First density functional theory with dissipation; (2) Pseudopotential plane wave calculations with master equation; (3) Weak bias limit; (4) Long-chain conductance; and (5) Self-interaction effects in tunneling.

Kieron Burke

2012-04-30T23:59:59.000Z

72

Linear response of homogeneous nuclear matter with energy density functionals  

E-Print Network [OSTI]

Response functions of infinite nuclear matter with arbitrary isospin asymmetry are studied in the framework of the random phase approximation. The residual interaction is derived from a general nuclear Skyrme energy density functional. Besides the usual central, spin-orbit and tensor terms it could also include other components as new density-dependent terms or three-body terms. Algebraic expressions for the response functions are obtained from the Bethe-Salpeter equation for the particle-hole propagator. Applications to symmetric nuclear matter, pure neutron matter and asymmetric nuclear matter are presented and discussed. Spin-isospin strength functions are analyzed for varying conditions of density, momentum transfer, isospin asymmetry, and temperature for some representative Skyrme functionals. Particular attention is paid to the discussion of instabilities, either real or unphysical, which could manifest in finite nuclei.

Pastore, A; Navarro, J

2014-01-01T23:59:59.000Z

73

Linear response of homogeneous nuclear matter with energy density functionals  

E-Print Network [OSTI]

Response functions of infinite nuclear matter with arbitrary isospin asymmetry are studied in the framework of the random phase approximation. The residual interaction is derived from a general nuclear Skyrme energy density functional. Besides the usual central, spin-orbit and tensor terms it could also include other components as new density-dependent terms or three-body terms. Algebraic expressions for the response functions are obtained from the Bethe-Salpeter equation for the particle-hole propagator. Applications to symmetric nuclear matter, pure neutron matter and asymmetric nuclear matter are presented and discussed. Spin-isospin strength functions are analyzed for varying conditions of density, momentum transfer, isospin asymmetry, and temperature for some representative Skyrme functionals. Particular attention is paid to the discussion of instabilities, either real or unphysical, which could manifest in finite nuclei.

A. Pastore; D. Davesne; J. Navarro

2014-12-07T23:59:59.000Z

74

Relationship of Quantum Entanglement to Density Functional Theory  

E-Print Network [OSTI]

The maximum von Neumann entropy principle subject to given constraints of mean values of some physical observables determines the density matrix. Similarly the stationary action principle in the case of time-dependent (dissipative) situations under similar constraints yields the density matrix. The free energy and measures of entanglement are expressed in terms of such a density matrix and thus define respective functionals of the mean values. In the light of several model calculations, it is found that the density matrix contains information about both quantum entanglement and phase transitions even though there may not be any direct relationship implied by one on the other.

A. K. Rajagopal; R. W. Rendell

2005-12-13T23:59:59.000Z

75

Optimal-transport formulation of electronic density-functional theory  

E-Print Network [OSTI]

The most challenging scenario for Kohn-Sham density functional theory, that is when the electrons move relatively slowly trying to avoid each other as much as possible because of their repulsion (strong-interaction limit), is reformulated here as an optimal transport (or mass transportation theory) problem, a well established field of mathematics and economics. In practice, we show that solving the problem of finding the minimum possible internal repulsion energy for $N$ electrons in a given density $\\rho(\\rv)$ is equivalent to find the optimal way of transporting $N-1$ times the density $\\rho$ into itself, with cost function given by the Coulomb repulsion. We use this link to put the strong-interaction limit of density functional theory on firm grounds and to discuss the potential practical aspects of this reformulation.

Giuseppe Buttazzo; Luigi De Pascale; Paola Gori-Giorgi

2012-05-21T23:59:59.000Z

76

Free-energy density functional for hard spheres  

Science Journals Connector (OSTI)

A free-energy density functional for a system of hard spheres is derived on a semiempirical basis. It is constructed to reproduce the thermodynamics and direct correlation function of a homogeneous fluid and then is tested in two highly inhomogeneous situations: the hard-wallhard-sphere interface and the hard-sphere solid. The results are very good in both cases, showing that this density-functional model may be used with advantage in the study of the hard-sphere model by itself, or used as a reference system in a perturbative analysis.

P. Tarazona

1985-04-01T23:59:59.000Z

77

Generalized time-dependent density-functional-theory response functions for spontaneous density fluctuations and nonlinear response: Resolving the causality paradox in real time  

E-Print Network [OSTI]

Generalized time-dependent density-functional-theory response functions for spontaneous density shifted the focus of elec- tronic structure theory from the many-body wave function to the charge density response and spontaneous fluctuations of many-electron systems. The pth-order density response functions

Mukamel, Shaul

78

Improved association in a classical density functional theory for water  

SciTech Connect (OSTI)

We present a modification to our recently published statistical associating fluid theory-based classical density functional theory for water. We have recently developed and tested a functional for the averaged radial distribution function at contact of the hard-sphere fluid that is dramatically more accurate at interfaces than earlier approximations. We now incorporate this improved functional into the association term of our free energy functional for water, improving its description of hydrogen bonding. We examine the effect of this improvement by studying two hard solutes (a hard hydrophobic rod and a hard sphere) and a Lennard-Jones approximation of a krypton atom solute. The improved functional leads to a moderate change in the density profile and a large decrease in the number of hydrogen bonds broken in the vicinity of the hard solutes. We find an improvement of the partial radial distribution for a krypton atom in water when compared with experiment.

Krebs, Eric J.; Schulte, Jeff B.; Roundy, David [Department of Physics, Oregon State University, Corvallis, Oregon 97331 (United States)] [Department of Physics, Oregon State University, Corvallis, Oregon 97331 (United States)

2014-03-28T23:59:59.000Z

79

Nuclear Density Functional Theory and the Equation of State  

E-Print Network [OSTI]

A nuclear density functional can be used to find the binding energy and shell structure of nuclei and the energy gap in superconducting nuclear matter. In this paper, we study the possible application of a nuclear density functional theory to nuclear astrophysics. From energy density functional theory, we can deduce the interaction between nucleons to find a rough estimate of the charge radius of the specific nuclei. Compared to the Finite-Range Thomas Fermi model, we include three-body forces, which might be important at densities several times that of nuclear matter density. We also add the momentum dependent interaction to take into account the effective mass of the nucleons. We study matter in the neutron star crust using the Wigner-Seitz cell method. By constructing the mass-radius relation of neutron stars and investigating lepton-rich nuclear matter in proto-neutron stars, we find that the density functional can be used to construct an equation of state of hot dense matter.

Yeunhwan Lim

2011-04-06T23:59:59.000Z

80

Taming Density Functional Theory by Coarse-Graining  

E-Print Network [OSTI]

The standard (``fine-grained'') interpretation of quantum density functional theory, in which densities are specified with infinitely-fine spatial resolution, is mathematically unruly. Here, a coarse-grained version of DFT, featuring limited spatial resolution, and its relation to the fine-grained theory in the $L^1\\cap L^3$ formulation of Lieb, is studied, with the object of showing it to be not only mathematically well-behaved, but consonant with the spirit of DFT, practically (computationally) adequate and sufficiently close to the standard interpretation as to accurately reflect its non-pathological properties. The coarse-grained interpretation is shown to be a good model of formal DFT in the sense that: all densities are (ensemble)-V-representable; the intrinsic energy functional $F$ is a continuous function of the density and the representing external potential is the (directional) functional derivative of the intrinsic energy. Also, the representing potential $v[\\rho]$ is quasi-continuous, in that $v[\\rho]\\rho$ is continuous as a function of $\\rho$. The limit of coarse-graining scale going to zero is studied to see if convergence to the non-pathological aspects of the fine-grained theory is adequate to justify regarding coarse-graining as a good approximation. Suitable limiting behaviors or intrinsic energy, densities and representing potentials are found. Intrinsic energy converges monotonically, coarse-grained densities converge uniformly strongly to their low-intrinsic-energy fine-grainings, and $L^{3/2}+L^\\infty$ representability of a density is equivalent to the existence of a convergent sequence of coarse-grained potential/ground-state density pairs.

Paul E. Lammert

2010-08-10T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Addressing spectroscopic quality of covariant density functional theory  

E-Print Network [OSTI]

The spectroscopic quality of covariant density functional theory has been accessed by analyzing the accuracy and theoretical uncertainties in the description of spectroscopic observables. Such analysis is first presented for the energies of the single-particle states in spherical and deformed nuclei. It is also shown that the inclusion of particle-vibration coupling improves the description of the energies of predominantly single-particle states in medium and heavy-mass spherical nuclei. However, the remaining differences between theory and experiment clearly indicate missing physics and missing terms in covariant energy density functionals. The uncertainties in the predictions of the position of two-neutron drip line sensitively depend on the uncertainties in the prediction of the energies of the single-particle states. On the other hand, many spectroscopic observables in well deformed nuclei at ground state and finite spin only weakly depend on the choice of covariant energy density functional.

A. V. Afanasjev

2014-09-17T23:59:59.000Z

82

Addressing spectroscopic quality of covariant density functional theory  

E-Print Network [OSTI]

The spectroscopic quality of covariant density functional theory has been accessed by analyzing the accuracy and theoretical uncertainties in the description of spectroscopic observables. Such analysis is first presented for the energies of the single-particle states in spherical and deformed nuclei. It is also shown that the inclusion of particle-vibration coupling improves the description of the energies of predominantly single-particle states in medium and heavy-mass spherical nuclei. However, the remaining differences between theory and experiment clearly indicate missing physics and missing terms in covariant energy density functionals. The uncertainties in the predictions of the position of two-neutron drip line sensitively depend on the uncertainties in the prediction of the energies of the single-particle states. On the other hand, many spectroscopic observables in well deformed nuclei at ground state and finite spin only weakly depend on the choice of covariant energy density functional.

Afanasjev, A V

2014-01-01T23:59:59.000Z

83

Diffusion of the Cu monomer and dimer on Ag(111): Molecular dynamics simulations and density functional theory calculations  

Science Journals Connector (OSTI)

We present results of molecular dynamics (MD) simulations and density functional theory (DFT) calculations of the diffusion of Cu adatom and dimer on Ag(111). We have used potentials generated by the embedded-atom method for the MD simulations and pseudopotentials derived from the projected-augmented-wave method for the DFT calculations. The MD simulations (at three different temperatures: 300, 500, and 700 K) show that the diffusivity has an Arrhenius behavior. The effective energy barriers obtained from the Arrhenius plots are in excellent agreement with those extracted from scanning tunneling microscopy experiments. While the diffusion barrier for Cu monomers on Ag(111) is higher than that reported (both in experiment and theory) for Cu(111), the reverse holds for dimers [which, for Cu(111), has so far only been theoretically assessed]. In comparing our MD result with those for Cu islets on Cu(111), we conclude that the higher barriers for Cu monomers on Ag(111) results from the comparatively large Ag-Ag bond length, whereas for Cu dimers on Ag(111) the diffusivity is taken over and boosted by the competition in optimization of the Cu-Cu dimer bond and the five nearest-neighbor Cu-Ag bonds. Our DFT calculations confirm the relatively large barriers for the Cu monomer on Ag(111)69 and 75 meVcompared to those on Cu(111) and hint a rationale for them. In the case of the Cu dimer, the relatively long Ag-Ag bond length makes available a diffusion route whose highest relevant energy barrier is only 72 meV and which is not favorable on Cu(111). This process, together with another involving an energy barrier of 83 meV, establishes the possibility of low-barrier intercell diffusion by purely zigzag mechanisms.

Sardar Sikandar Hayat; Marisol Alcntara Ortigoza; Muhammad A. Choudhry; Talat S. Rahman

2010-08-03T23:59:59.000Z

84

Relativistic Nuclear Energy Density Functionals: adjusting parameters to binding energies  

E-Print Network [OSTI]

We study a particular class of relativistic nuclear energy density functionals in which only nucleon degrees of freedom are explicitly used in the construction of effective interaction terms. Short-distance (high-momentum) correlations, as well as intermediate and long-range dynamics, are encoded in the medium (nucleon density) dependence of the strength functionals of an effective interaction Lagrangian. Guided by the density dependence of microscopic nucleon self-energies in nuclear matter, a phenomenological ansatz for the density-dependent coupling functionals is accurately determined in self-consistent mean-field calculations of binding energies of a large set of axially deformed nuclei. The relationship between the nuclear matter volume, surface and symmetry energies, and the corresponding predictions for nuclear masses is analyzed in detail. The resulting best-fit parametrization of the nuclear energy density functional is further tested in calculations of properties of spherical and deformed medium-heavy and heavy nuclei, including binding energies, charge radii, deformation parameters, neutron skin thickness, and excitation energies of giant multipole resonances.

T. Niksic; D. Vretenar; P. Ring

2008-09-08T23:59:59.000Z

85

Nonlinear eigenvalue problems in Density Functional Theory calculations  

SciTech Connect (OSTI)

Developed in the 1960's by W. Kohn and coauthors, Density Functional Theory (DFT) is a very popular quantum model for First-Principles simulations in chemistry and material sciences. It allows calculations of systems made of hundreds of atoms. Indeed DFT reduces the 3N-dimensional Schroedinger electronic structure problem to the search for a ground state electronic density in 3D. In practice it leads to the search for N electronic wave functions solutions of an energy minimization problem in 3D, or equivalently the solution of an eigenvalue problem with a non-linear operator.

Fattebert, J

2009-08-28T23:59:59.000Z

86

A Classical Density-Functional Theory for Describing Water Interfaces  

E-Print Network [OSTI]

We develop a classical density functional for water which combines the White Bear fundamental-measure theory (FMT) functional for the hard sphere fluid with attractive interactions based on the Statistical Associating Fluid Theory (SAFT-VR). This functional reproduces the properties of water at both long and short length scales over a wide range of temperatures, and is computationally efficient, comparable to the cost of FMT itself. We demonstrate our functional by applying it to systems composed of two hard rods, four hard rods arranged in a square and hard spheres in water.

Jessica Hughes; Eric Krebs; David Roundy

2012-08-31T23:59:59.000Z

87

Dynamics of localized particles from density functional theory  

E-Print Network [OSTI]

A fundamental assumption of the dynamical density functional theory (DDFT) of colloidal systems is that a grand-canonical free energy functional may be employed to generate the thermodynamic driving forces. Using one-dimensional hard-rods as a model system we analyze the validity of this key assumption and show that unphysical self-interactions of the tagged particle density fields, arising from coupling to a particle reservoir, are responsible for the excessively fast relaxation predicted by the theory. Moreover, our findings suggest that even employing a canonical functional would not lead to an improvement for many-particle systems, if only the total density is considered. We present several possible schemes to suppress these effects by incorporating tagged densities. When applied to confined systems we demonstrate, using a simple example, that DDFT neccessarily leads to delocalized tagged particle density distributions, which do not respect the fundamental geometrical contraints apparent in Brownian dynamics simulation data. The implication of these results for possible applications of DDFT to treat the glass transition are discussed.

Johannes Reinhardt; Joseph Michael Brader

2011-11-23T23:59:59.000Z

88

Relativistic density functional theory for finite nuclei and neutron stars  

E-Print Network [OSTI]

The main goal of the present contribution is a pedagogical introduction to the fascinating world of neutron stars by relying on relativistic density functional theory. Density functional theory provides a powerful--and perhaps unique--framework for the calculation of both the properties of finite nuclei and neutron stars. Given the enormous densities that may be reached in the core of neutron stars, it is essential that such theoretical framework incorporates from the outset the basic principles of Lorentz covariance and special relativity. After a brief historical perspective, we present the necessary details required to compute the equation of state of dense, neutron-rich matter. As the equation of state is all that is needed to compute the structure of neutron stars, we discuss how nuclear physics--particularly certain kind of laboratory experiments--can provide significant constrains on the behavior of neutron-rich matter.

Piekarewicz, J

2015-01-01T23:59:59.000Z

89

Effective Maxwell equations from time-dependent density functional theory  

E-Print Network [OSTI]

The behavior of interacting electrons in a perfect crystal under macroscopic external electric and magnetic fields is studied. Effective Maxwell equations for the macroscopic electric and magnetic fields are derived starting from time-dependent density functional theory. Effective permittivity and permeability coefficients are obtained.

Weinan E; Jianfeng Lu; Xu Yang

2010-10-23T23:59:59.000Z

90

Density Functional Theory-Based Database Development and CALPHAD Automation  

E-Print Network [OSTI]

Density Functional Theory-Based Database Development and CALPHAD Automation YI WANG,1,2 SHUNLI, the integration of first-principles calculations, CALPHAD modeling, and the automation of phase diagram, and the automated calculation of a phase diagram for the Al- Mg system. INTRODUCTION In thermodynamics, a phase

Chen, Long-Qing

91

Superfluid Local Density Approximation: A Density Functional Theory Approach to the Nuclear Pairing Problem  

E-Print Network [OSTI]

I describe the foundation of a Density Functional Theory approach to include pairing correlations, which was applied to a variety of systems ranging from dilute fermions, to neutron stars and finite nuclei. Ground state properties as well as properties of excited states and time-dependent phenomena can be achieved in this manner within a formalism based on microscopic input.

Aurel Bulgac

2012-04-10T23:59:59.000Z

92

Particle vibrational coupling in covariant density functional theory  

E-Print Network [OSTI]

A consistent combination of covariant density functional theory (CDFT) and Landau-Migdal Theory of Finite Fermi Systems (TFFS) is presented. Both methods are in principle exact, but Landau-Migdal theory cannot describe ground state properties and density functional theory does not take into account the energy dependence of the self-energy and therefore fails to yield proper single-% particle spectra as well as the coupling to complex configurations in the width of giant resonances. Starting from an energy functional, phonons and their vertices are calculated without any further parameters. They form the basis of particle-vibrational coupling leading to an energy dependence of the self-energy and an induced energy-dependent interaction in the response equation. A subtraction procedure avoids double counting. Applications in doubly magic nuclei and in a chain of superfluid nuclei show excellent agreement with experimental data.

P. Ring; E. Litvinova

2010-06-21T23:59:59.000Z

93

Advances in Quantum Chemistry, 43, 95-117 (2003) Differentiability in density-functional theory  

E-Print Network [OSTI]

Advances in Quantum Chemistry, 43, 95-117 (2003) Differentiability in density-functional theory in density-functional theory (DFT) is investigated, and it is shown that the so-called Levy- Lieb functional The differentiability of density functionals is of fundamental importance in Density-Functional Theory (DFT) and forms

Lindgren, Ingvar

94

Time-dependent Density Functional Theory Miguel A. L. Marques and E. K. U. Gross  

E-Print Network [OSTI]

Time-dependent Density Functional Theory Miguel A. L. Marques and E. K. U. Gross 1 Introduction Time-dependent density-functional theory (TDDFT) extends the basic ideas of ground-state density-functional is the one-body electron density, n(r, t). The advantages are clear: The many-body wave-function, a function

Wu, Zhigang

95

SURFACE SYMMETRY ENERGY OF NUCLEAR ENERGY DENSITY FUNCTIONALS  

SciTech Connect (OSTI)

We study the bulk deformation properties of the Skyrme nuclear energy density functionals. Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band-heads in Hg and Pb isotopes, and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nuclei are essential for optimizing future nuclear energy density functionals. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface-symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron-rich matter and description of fission rates for r-process nucleosynthesis.

Nikolov, N; Schunck, N; Nazarewicz, W; Bender, M; Pei, J

2010-12-20T23:59:59.000Z

96

Differentiable but exact formulation of density-functional theory  

SciTech Connect (OSTI)

The universal density functional F of density-functional theory is a complicated and ill-behaved function of the densityin particular, F is not differentiable, making many formal manipulations more complicated. While F has been well characterized in terms of convex analysis as forming a conjugate pair (E, F) with the ground-state energy E via the HohenbergKohn and Lieb variation principles, F is nondifferentiable and subdifferentiable only on a small (but dense) subset of its domain. In this article, we apply a tool from convex analysis, MoreauYosida regularization, to construct, for any ? > 0, pairs of conjugate functionals ({sup ?}E, {sup ?}F) that converge to (E, F) pointwise everywhere as ? ? 0{sup +}, and such that {sup ?}F is (Frchet) differentiable. For technical reasons, we limit our attention to molecular electronic systems in a finite but large box. It is noteworthy that no information is lost in the MoreauYosida regularization: the physical ground-state energy E(v) is exactly recoverable from the regularized ground-state energy {sup ?}E(v) in a simple way. All concepts and results pertaining to the original (E, F) pair have direct counterparts in results for ({sup ?}E, {sup ?}F). The MoreauYosida regularization therefore allows for an exact, differentiable formulation of density-functional theory. In particular, taking advantage of the differentiability of {sup ?}F, a rigorous formulation of KohnSham theory is presented that does not suffer from the noninteracting representability problem in standard KohnSham theory.

Kvaal, Simen, E-mail: simen.kvaal@kjemi.uio.no; Ekstrm, Ulf; Helgaker, Trygve [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway)] [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway); Teale, Andrew M. [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway) [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway); School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

2014-05-14T23:59:59.000Z

97

Time-dependent current density functional theory on a lattice  

E-Print Network [OSTI]

A rigorous formulation of time-dependent current density functional theory (TDCDFT) on a lattice is presented. The density-to-potential mapping and the ${\\cal V}$-representability problems are reduced to a solution of a certain nonlinear lattice Schr\\"odinger equation, to which the standard existence and uniqueness results for nonliner differential equations are applicable. For two versions of the lattice TDCDFT we prove that any continuous in time current density is locally ${\\cal V}$-representable (both interacting and noninteracting), provided in the initial state the local kinetic energy is nonzero everywhere. In most cases of physical interest the ${\\cal V}$-representability should also hold globally in time. These results put the application of TDCDFT to any lattice model on a firm ground, and open a way for studying exact properties of exchange correlation potentials.

I. V. Tokatly

2010-11-11T23:59:59.000Z

98

Phase-space explorations in time-dependent density functional theory A.K. Rajam a  

E-Print Network [OSTI]

Phase-space explorations in time-dependent density functional theory A.K. Rajam a , Paul Hessler b online xxxx Keywords: Time-dependent density functional theory Phase-space Momentum-distributions Density to phase-space densities, discuss some formal aspects of such a ``phase-space density functional theory

99

Excitations and benchmark ensemble density functional theory for two electrons  

SciTech Connect (OSTI)

A new method for extracting ensemble Kohn-Sham potentials from accurate excited state densities is applied to a variety of two-electron systems, exploring the behavior of exact ensemble density functional theory. The issue of separating the Hartree energy and the choice of degenerate eigenstates is explored. A new approximation, spin eigenstate Hartree-exchange, is derived. Exact conditions that are proven include the signs of the correlation energy components and the asymptotic behavior of the potential for small weights of the excited states. Many energy components are given as a function of the weights for two electrons in a one-dimensional flat box, in a box with a large barrier to create charge transfer excitations, in a three-dimensional harmonic well (Hooke's atom), and for the He atom singlet-triplet ensemble, singlet-triplet-singlet ensemble, and triplet bi-ensemble.

Pribram-Jones, Aurora; Burke, Kieron [Department of Chemistry, University of California-Irvine, Irvine, California 92697 (United States)] [Department of Chemistry, University of California-Irvine, Irvine, California 92697 (United States); Yang, Zeng-hui; Ullrich, Carsten A. [Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211 (United States)] [Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211 (United States); Trail, John R.; Needs, Richard J. [Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom)] [Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE (United Kingdom)

2014-05-14T23:59:59.000Z

100

Probability Density Function Method for Langevin Equations with Colored Noise  

SciTech Connect (OSTI)

We present a novel method to derive closed-form, computable PDF equations for Langevin systems with colored noise. The derived equations govern the dynamics of joint or marginal probability density functions (PDFs) of state variables, and rely on a so-called Large-Eddy-Diffusivity (LED) closure. We demonstrate the accuracy of the proposed PDF method for linear and nonlinear Langevin equations, describing the classical Brownian displacement and dispersion in porous media.

Wang, Peng; Tartakovsky, Alexandre M.; Tartakovsky, Daniel M.

2013-04-05T23:59:59.000Z

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While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Atomistic force field for alumina fit to density functional theory  

SciTech Connect (OSTI)

We present a force field for bulk alumina (Al{sub 2}O{sub 3}), which has been parametrized by fitting the energies, forces, and stresses of a large database of reference configurations to those calculated with density functional theory (DFT). We use a functional form that is simpler and computationally more efficient than some existing models of alumina parametrized by a similar technique. Nevertheless, we demonstrate an accuracy of our potential that is comparable to those existing models and to DFT. We present calculations of crystal structures and energies, elastic constants, phonon spectra, thermal expansion, and point defect formation energies.

Sarsam, Joanne [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Finnis, Michael W.; Tangney, Paul, E-mail: p.tangney@imperial.ac.uk [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)

2013-11-28T23:59:59.000Z

102

A long-range-corrected density functional that performs well for both ground-state properties and time-dependent density functional theory  

E-Print Network [OSTI]

and time-dependent density functional theory excitation energies, including charge-transfer excited states energies within time-dependent density functional theory, is systematically evaluated, and optimal values. THEORETICAL BACKGROUND Generalized gradient approximations GGAs in density functional theory DFT are quite

Herbert, John

103

Density functional theory for Baxter's sticky hard spheres in confinement  

E-Print Network [OSTI]

It has recently been shown that a free energy for Baxter's sticky hard sphere fluid is uniquely defined within the framework of fundamental measure theory (FMT) for the inhomogeneous hard sphere fluid, provided that it obeys scaled-particle theory and the Percus-Yevick (PY) result for the direct correlation function [Hansen-Goos and Wettlaufer, J. Chem. Phys. {\\bf 134}, 014506 (2011)]. Here, combining weighted densities from common versions of FMT with a new vectorial weighted density, we derive a regularization of the divergences of the associated strongly confined limit. Moreover, the simple free energy that emerges is exact in the zero-dimensional limit, leaves the underlying equation of state unaffected, and yields a direct correlation function distinct from the PY expression. Comparison with simulation data for both the bulk pair correlation function and the density profiles in confinement shows that the new theory is significantly more accurate than the PY-based results. Finally, the resulting free energy is applicable to a glass of adhesive hard spheres.

Hendrik Hansen-Goos; Mark A. Miller; J. S. Wettlaufer

2011-12-15T23:59:59.000Z

104

Model hamiltonians in density functional theory Paola Gori-Giorgi, Julien Toulouse, and Andreas Savin  

E-Print Network [OSTI]

Model hamiltonians in density functional theory Paola Gori-Giorgi, Julien Toulouse, and Andreas, density functional theory. 1 hal-00981803,version1-22Apr2014 Author manuscript, published in "High (density functional theory [3], and density matrix functional theory [4], that is somehow in between

Paris-Sud XI, Université de

105

Last Name First Name Degree Abookire Susan MD, MPH  

E-Print Network [OSTI]

Frey-Vogel Ariel MD, MAT Garfield Joseph M.D. Gaufberg Elizabeth MD MPH Ghosh Arundhati MBBS, FRCS MD Miller Katherine MD Minehart Rebecca M.D. Mitchell John MD Monaghan Colleen MD Muto Michael MD-Vernaglia Shannon MD Shapiro Jo MD Sharma Niraj MD, MPH Sharp John MD Shields Helen MD Ship Amy MD Simone

Paulsson, Johan

106

Current density partitioning in time-dependent current density functional theory  

SciTech Connect (OSTI)

We adapt time-dependent current density functional theory to allow for a fragment-based solution of the many-electron problem of molecules in the presence of time-dependent electric and magnetic fields. Regarding a molecule as a set of non-interacting subsystems that individually evolve under the influence of an auxiliary external electromagnetic vector-scalar potential pair, the partition 4-potential, we show that there are one-to-one mappings between this auxiliary potential, a sharply-defined set of fragment current densities, and the total current density of the system. The partition electromagnetic (EM) 4-potential is expressed in terms of the real EM 4-potential of the system and a gluing EM 4-potential that accounts for exchange-correlation effects and mutual interaction forces between fragments that are required to yield the correct electron dynamics. We prove the zero-force theorem for the fragmented system, establish a variational formulation in terms of action functionals, and provide a simple illustration for a charged particle in a ring.

Mosquera, Martn A. [Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 (United States)] [Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 (United States); Wasserman, Adam, E-mail: awasser@purdue.edu [Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 (United States) [Department of Chemistry, Purdue University, West Lafayette, Indiana 47907 (United States); Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States)

2014-05-14T23:59:59.000Z

107

Symmetry Projected Density Functional Theory and Neutron Halos  

E-Print Network [OSTI]

The appearance of halo phenomena near the drip line nuclei has challenged our traditional understanding of the nuclei as an incompressible charged liquid drop and extended nuclear physics to low density and inhomogeneous system, where the coupling to the continuum has to be treated in a consistent way. Recently Relativistic Hartree Bogoliubov (RHB) theory in the continuum has been applied successfully to the description of halo phenomena in light and medium heavy nuclei [1, 2, 3]. This theory provides a self-consistent treatment of pairing correlation in the presence of the continuum and allows a microscopic description of halo phenomena in the framework of density functional theory. Essential conditions for the formation of a neutron halo have been found: (a) the Fermi surface of the neutrons has to

unknown authors

108

Subsystem real-time Time Dependent Density Functional Theory  

E-Print Network [OSTI]

We present the extension of Frozen Density Embedding (FDE) theory to real-time Time Dependent Density Functional Theory (rt-TDDFT). FDE a is DFT-in-DFT embedding method that allows to partition a larger Kohn-Sham system into a set of smaller, coupled Kohn-Sham systems. Additional to the computational advantage, FDE provides physical insight into the properties of embedded systems and the coupling interactions between them. The extension to rt-TDDFT is done straightforwardly by evolving the Kohn-Sham subsystems in time simultaneously, while updating the embedding potential between the systems at every time step. Two main applications are presented: the explicit excitation energy transfer in real time between subsystems is demonstrated for the case of the Na$_4$ cluster and the effect of the embedding on optical spectra of coupled chromophores. In particular, the importance of including the full dynamic response in the embedding potential is demonstrated.

Krishtal, Alisa; Pavanello, Michele

2015-01-01T23:59:59.000Z

109

PHYSICAL REVIEW B 89, 155112 (2014) Angular momentum dependent orbital-free density functional theory  

E-Print Network [OSTI]

-free density functional theory (OFDFT) directly solves for the ground-state electron density. It scales of the Hohenberg- Kohn theorems [1], density functional theory (DFT) has gained vast popularity as an extremelyPHYSICAL REVIEW B 89, 155112 (2014) Angular momentum dependent orbital-free density functional

Florian, Libisch

110

Augmented Lagrangian Method for Constrained Nuclear Density Functional Theory  

E-Print Network [OSTI]

The augmented Lagrangiam method (ALM), widely used in quantum chemistry constrained optimization problems, is applied in the context of the nuclear Density Functional Theory (DFT) in the self-consistent constrained Skyrme Hartree-Fock-Bogoliubov (CHFB) variant. The ALM allows precise calculations of multidimensional energy surfaces in the space of collective coordinates that are needed to, e.g., determine fission pathways and saddle points; it improves accuracy of computed derivatives with respect to collective variables that are used to determine collective inertia; and is well adapted to supercomputer applications.

A. Staszczak; M. Stoitsov; A. Baran; W. Nazarewicz

2010-07-21T23:59:59.000Z

111

Deformed one-quasiparticle states in covariant density functional theory  

E-Print Network [OSTI]

Systematic investigation of the accuracy of the description of the energies of deformed one-quasiparticle states has been performed in covariant density functional theory in actinide and rare-earth mass regions. The sources of the discrepancies between theory and experiment are analyzed. Although some improvements in the description of ground state configurations and one-quasiparticle spectra can be achieved by better parametrization of the relativistic mean field Lagrangian, the analysis suggests that spectroscopic quality of their description can be achieved only in theoretical framework which takes into account particle-vibration coupling.

A. V. Afanasjev; S. Shawaqfeh

2012-05-10T23:59:59.000Z

112

Existence of A Rigorous Density-Functional Theory for Open Electronic Systems  

E-Print Network [OSTI]

We prove that the electron density function of a real physical system can be uniquely determined by its values on any finite subsystem. This establishes the existence of a rigorous density-functional theory for any open electronic system. By introducing a new density functional for dissipative interactions between the reduced system and its environment, we subsequently develop a time-dependent density-functional theory which depends in principle only on the electron density of the reduced system.

Xiao Zheng; Fan Wang; GuanHua Chen

2006-05-11T23:59:59.000Z

113

A mathematical perspective on density functional perturbation theory  

E-Print Network [OSTI]

In this article, we provide a mathematical analysis of the perturbation method for extended Kohn-Sham models, in which fractional occupation numbers are allowed. All our results are established in the framework of the reduced Hartree-Fock (rHF) model, but our approach can be used to study other kinds of extended Kohn-Sham models, under some assumptions on the mathematical structure of the exchange-correlation functional. The classical results of Density Functional Perturbation Theory in the non-degenerate case (that is when the Fermi level is not a degenerate eigenvalue of the mean-field Hamiltonian) are formalized, and a proof of Wigner's (2n + 1) rule is provided. We then focus on the situation when the Fermi level is a degenerate eigenvalue of the rHF Hamiltonian, which had not been considered so far.

Eric Cancs; Nahia Mourad

2014-05-06T23:59:59.000Z

114

Daubechies wavelets for linear scaling density functional theory  

SciTech Connect (OSTI)

We demonstrate that Daubechies wavelets can be used to construct a minimal set of optimized localized adaptively contracted basis functions in which the Kohn-Sham orbitals can be represented with an arbitrarily high, controllable precision. Ground state energies and the forces acting on the ions can be calculated in this basis with the same accuracy as if they were calculated directly in a Daubechies wavelets basis, provided that the amplitude of these adaptively contracted basis functions is sufficiently small on the surface of the localization region, which is guaranteed by the optimization procedure described in this work. This approach reduces the computational costs of density functional theory calculations, and can be combined with sparse matrix algebra to obtain linear scaling with respect to the number of electrons in the system. Calculations on systems of 10?000 atoms or more thus become feasible in a systematic basis set with moderate computational resources. Further computational savings can be achieved by exploiting the similarity of the adaptively contracted basis functions for closely related environments, e.g., in geometry optimizations or combined calculations of neutral and charged systems.

Mohr, Stephan [Institut fr Physik, Universitt Basel, Klingelbergstr. 82, 4056 Basel (Switzerland); Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France and CEA, INAC-SP2M, F-38000 Grenoble (France); Ratcliff, Laura E.; Genovese, Luigi; Caliste, Damien; Deutsch, Thierry [Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France and CEA, INAC-SP2M, F-38000 Grenoble (France); Boulanger, Paul [Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France and CEA, INAC-SP2M, F-38000 Grenoble (France); Institut Nel, CNRS and Universit Joseph Fourier, B.P. 166, 38042 Grenoble Cedex 09 (France); Goedecker, Stefan [Institut fr Physik, Universitt Basel, Klingelbergstr. 82, 4056 Basel (Switzerland)

2014-05-28T23:59:59.000Z

115

Particle-vibration coupling within covariant density functional theory  

E-Print Network [OSTI]

Covariant density functional theory, which has so far been applied only within the framework of static and time dependent mean field theory is extended to include Particle-Vibration Coupling (PVC) in a consistent way. Starting from a conventional energy functional we calculate the low-lying collective vibrations in Relativistic Random Phase Approximation (RRPA) and construct an energy dependent self-energy for the Dyson equation. The resulting Bethe-Salpeter equation in the particle-hole ($ph$) channel is solved in the Time Blocking Approximation (TBA). No additional parameters are used and double counting is avoided by a proper subtraction method. The same energy functional, i.e. the same set of coupling constants, generates the Dirac-Hartree single-particle spectrum, the static part of the residual $ph$-interaction and the particle-phonon coupling vertices. Therefore a fully consistent description of nuclear excited states is developed. This method is applied for an investigation of damping phenomena in the spherical nuclei with closed shells $^{208}$Pb and $^{132}$Sn. Since the phonon coupling terms enrich the RRPA spectrum with a multitude of $ph\\otimes$phonon components a noticeable fragmentation of the giant resonances is found, which is in full agreement with experimental data and with results of the semi-phenomenological non-relativistic approach.

E. Litvinova; P. Ring; V. Tselyaev

2007-05-08T23:59:59.000Z

116

Hydrogen adsorption on graphene and coronene: A van der Waals density functional study.  

E-Print Network [OSTI]

??This thesis investigates hydrogen adsorption on graphene and coronene within the framework of density functional theory. The new nonlocal van der Waals density functional (vdW-DF) (more)

Varenius, Eskil

2011-01-01T23:59:59.000Z

117

An Isofactorial Change-of-Scale Model for the Wind Speed Probability Density Function  

Science Journals Connector (OSTI)

The wind speed probability density function (PDF) is used in a variety of applications in meteorology, oceanography, and climatology usually as a dataset comparison tool of a function of a quantity such as momentum flux or wind power density. The ...

Mark L. Morrissey; Angie Albers; J. Scott Greene; Susan Postawko

2010-02-01T23:59:59.000Z

118

Electrons in Dry DNA from Density Functional Calculations  

E-Print Network [OSTI]

The electronic structure of an infinite poly-guanine - poly-cytosine DNA molecule in its dry A-helix structure is studied by means of density-functional calculations. An extensive study of 30 nucleic base pairs is performed to validate the method. The electronic energy bands of DNA close to the Fermi level are then analyzed in order to clarify the electron transport properties in this particularly simple DNA realization, probably the best suited candidate for conduction. The energy scale found for the relevant band widths, as compared with the energy fluctuations of vibrational or genetic-sequence origin, makes highly implausible the coherent transport of electrons in this system. The possibility of diffusive transport with sub-nanometer mean free paths is, however, still open. Information for model Hamiltonians for conduction is provided.

E. Artacho; M. Machado; D. Sanchez-Portal; P. Ordejon; J. M. Soler

2002-09-24T23:59:59.000Z

119

Recent progress in the study of fission barriers in covariant density functional theory  

E-Print Network [OSTI]

Recent progress in the study of fission barriers of actinides and superheavy nuclei within covariant density functional theory is overviewed.

A. V. Afanasjev; H. Abusara; P. Ring

2012-05-10T23:59:59.000Z

120

Alternative separation of exchange and correlation in density-functional theory R. Armiento*  

E-Print Network [OSTI]

Alternative separation of exchange and correlation in density-functional theory R. Armiento.245120 PACS number s : 71.15.Mb, 31.15.Ew Kohn-Sham KS density-functional theory1 DFT is a successful scheme on this approach by creating and deploying a local-density-approximation-type XC functional. Hence, this work

Armiento, Rickard

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

Multicomponent density-functional theory for electrons and nuclei Thomas Kreibich  

E-Print Network [OSTI]

Multicomponent density-functional theory for electrons and nuclei Thomas Kreibich Institut für a general multicomponent density-functional theory in which electrons and nuclei are treated completely , 71.10. w I. INTRODUCTION Density-functional theory DFT is among the most suc- cessful approaches

Gross, E.K.U.

122

Intermolecular forces and nonbonded interactions: Superoperator nonlinear time-dependent density-functional-theory response approach  

E-Print Network [OSTI]

Intermolecular forces and nonbonded interactions: Superoperator nonlinear time-dependent density-functional-theory oscillator (CEO) eigenmodes of linearized time-dependent density-functional theory. Closed expressions response [35­38] with time- dependent density-functional theory (TDDFT) [21,39­43] to develop a systematic

Mukamel, Shaul

123

Density-Functional Theory for Triplet Superconductors K. Capelle E.K.U. Gross  

E-Print Network [OSTI]

Density-Functional Theory for Triplet Superconductors K. Capelle E.K.U. Gross Institut f Introduction The purpose of this work is to generalize the density-functional theory (DFT) for superur Theoretische Physik Universitat Wurzburg Am Hubland D-97074 Wurzburg Germany Abstract The density-functional

Gross, E.K.U.

124

On the Floquet formulation of time-dependent density functional theory  

E-Print Network [OSTI]

On the Floquet formulation of time-dependent density functional theory Neepa T. Maitra *, Kieron by Elsevier Science B.V. Ground-state density functional theory (DFT) [1] has been tremendously successful generalized ground-state density functional theory to time-dependent problems (TDDFT) [4]. TDDFT has become

125

Electronic Structure: Density Functional Theory S. Kurth, M. A. L. Marques, and E. K. U. Gross  

E-Print Network [OSTI]

Electronic Structure: Density Functional Theory S. Kurth, M. A. L. Marques, and E. K. U. Gross: July 5, 2003) PACS numbers: 71.15.Mb, 31.15.Ew 1 #12;I. INTRODUCTION Density functional theory (DFT systems becomes prohibitive. A different approach is taken in density functional theory where, instead

Gross, E.K.U.

126

Spin-Multiplet Energies from Time-Dependent Density-Functional Theory  

E-Print Network [OSTI]

Spin-Multiplet Energies from Time-Dependent Density-Functional Theory M. Petersilka and E, density-functional theory (DFT) [1, 2, 3, 4, 5] has enjoyed increas- ing popularity in the #12;eld energies which is based on time-dependent density- functional theory (TDDFT) [26]. In the linear response

Gross, E.K.U.

127

Current density functional theory of spontaneously magnetised solids H. Ebert and Marco Battocletti  

E-Print Network [OSTI]

Current density functional theory of spontaneously magnetised solids H. Ebert and Marco Battocletti, 1997) The first application of current density functional theory (CDFT) to spontaneously magnetised to a plain calculation done within spin density functional theory (SDFT). Ms number LB6710. PACS numbers: 71

Gross, E.K.U.

128

Supplementary material to "Curvature and frontier orbital energies in density functional theory", by Stein et al.  

E-Print Network [OSTI]

Supplementary material to "Curvature and frontier orbital energies in density functional theory and frontier orbital energies in density functional theory", by Stein et al. 2. Calculation of curvature from: [{ }] [{ }] #12;Supplementary material to "Curvature and frontier orbital energies in density functional theory

Baer, Roi

129

PHYSICAL REVIEW C 77, 064308 (2008) Effective shell model Hamiltonians from density functional theory: Quadrupolar and  

E-Print Network [OSTI]

for mapping a self-consistent mean-field theory (also known as density functional theory) onto a shell-state solution of this density functional theory at the Hartree-Fock plus BCS level, an effective shell-consistent mean-field (SCMF) approximation [1], also known as density functional theory (DFT

Bertsch George F.

130

Non-periodic finite-element formulation of KohnSham density functional theory  

E-Print Network [OSTI]

Non-periodic finite-element formulation of Kohn­Sham density functional theory Phanish-element formulation for Kohn­Sham density functional theory (KS-DFT). We transform the original variational problem, dislocations and crack tips using density functional theory (DFT) at reasonable computational cost by retaining

Ortiz, Michael

131

Weighted density functional theory of the solvophobic effect Sean X. Sun  

E-Print Network [OSTI]

Weighted density functional theory of the solvophobic effect Sean X. Sun Department of Chemistry be obtained from experimental data. Using these elements, we construct a spatial density functional theory naturally be cast in a simple picture based on the density functional theory DFT description of liquids

Sun, Sean

132

Efficient computation of the coupling matrix in Time-Dependent Density Functional Theory  

E-Print Network [OSTI]

Efficient computation of the coupling matrix in Time-Dependent Density Functional Theory Emmanuel arising in time-dependent density functional theory. The two important aspects involved, solution- dopotentials within density functional theory (DFT) [1]. This approach has been used to predict mechanical

Lorin, Emmanuel

133

On the Derivation of a Density Functional Theory for Microphase Separation of Diblock Copolymers  

E-Print Network [OSTI]

On the Derivation of a Density Functional Theory for Microphase Separation of Diblock Copolymers in copolymer melts. The Ohta-Kawasaki density functional theory gives rise to a nonlocal Cahn copolymers, mean field theory, density functional theory. 1 Introduction A diblock copolymer is a linear

Ren, Xiaofeng

134

Range-separated density-functional theory with random phase approximation: Detailed formalism and illustrative applications  

E-Print Network [OSTI]

Range-separated density-functional theory with random phase approximation: Detailed formalism-body theory, we present the details of a formally exact adiabatic-connection fluctuation-dissipation density-functional´an, Phys. Rev. Lett. 102, 096404 (2009). Range-separated density-functional theory approaches combining

Boyer, Edmond

135

Band structures Optical absorption Summary Key concepts in Density Functional Theory (II)  

E-Print Network [OSTI]

Band structures Optical absorption Summary Key concepts in Density Functional Theory (II) Kohn, Belfast Key concepts in Density Functional Theory (II) Silvana Botti #12;Band structures Optical in Density Functional Theory (II) Silvana Botti #12;Band structures Optical absorption Summary Outline 1 From

Botti, Silvana

136

6 Multicomponent Density-Functional Theory R. van Leeuwen and E.K.U. Gross  

E-Print Network [OSTI]

6 Multicomponent Density-Functional Theory R. van Leeuwen and E.K.U. Gross 6.1 Introduction fields. Our goal is to set up a time-dependent multicomponent density-functional theory (TDMCDFT.K.U. Gross: Multicomponent Density-Functional Theory, Lect. Notes Phys. 706, 93­106 (2006) DOI 10

Gross, E.K.U.

137

A mesh-free convex approximation scheme for KohnSham density functional theory  

E-Print Network [OSTI]

A mesh-free convex approximation scheme for Kohn­Sham density functional theory Phanish: Convex approximation scheme Mesh-free methods Kohn­Sham Density functional theory Maximum-entropy a b s t r a c t Density functional theory developed by Hohenberg, Kohn and Sham is a widely accepted

Ortiz, Michael

138

Double-hybrid density-functional theory with meta-generalized-gradient approximations  

E-Print Network [OSTI]

Double-hybrid density-functional theory with meta-generalized-gradient approximations Sidi Ould-parameter double-hybrid density-functional theory [K. Sharkas, J. Toulouse, and A. Savin, J. Chem. Phys. 134 of the most accurate approximations for electronic-structure calculations within density- functional theory

Paris-Sud XI, Université de

139

Metallophilic interactions from dispersion-corrected density-functional theory  

SciTech Connect (OSTI)

In this article, we present the first comprehensive study of metallophilic (aurophilic) interactions using dispersion-corrected density-functional theory. Dispersion interactions (an essential component of metallophilicity) are treated using the exchange-hole dipole moment (XDM) model. By comparing against coupled-cluster benchmark calculations on simple dimers, we show that LC-?PBE-XDM is a viable functional to study interactions between closed-shell transition metals and that it performs uniformly better than second-order Mller-Plesset theory, the basic computational technique used in previous works. We apply LC-?PBE-XDM to address several open questions regarding metallophilicity, such as the interplay between dispersion and relativistic effects, the interaction strength along group 11, the additivity of homo- and hetero-metallophilic effects, the stability of [E(AuPH{sub 3}){sub 4}]{sup +} cations (E = N, P, As, Sb), and the role of metallophilic effects in crystal packing. We find that relativistic effects explain the prevalence of aurophilicity not by stabilizing metal-metal contacts, but by preventing gold from forming ionic structures involving bridge anions (which are otherwise common for Ag and Cu) as a result of the increased electron affinity of the metal. Dispersion effects are less important than previously assumed and their stabilization contribution is relatively independent of the metal.

Otero-de-la-Roza, Alberto, E-mail: aoterodelaroza@ucmerced.edu; Mallory, Joel D.; Johnson, Erin R., E-mail: ejohnson29@ucmerced.edu [Chemistry and Chemical Biology, School of Natural Sciences, University of California, Merced, 5200 North Lake Road, Merced, California 95343 (United States)

2014-05-14T23:59:59.000Z

140

Self-interaction corrections in density functional theory  

SciTech Connect (OSTI)

Self-interaction corrections for Kohn-Sham density functional theory are reviewed for their physical meanings, formulations, and applications. The self-interaction corrections get rid of the self-interaction error, which is the sum of the Coulomb and exchange self-interactions that remains because of the use of an approximate exchange functional. The most frequently used self-interaction correction is the Perdew-Zunger correction. However, this correction leads to instabilities in the electronic state calculations of molecules. To avoid these instabilities, several self-interaction corrections have been developed on the basis of the characteristic behaviors of self-interacting electrons, which have no two-electron interactions. These include the von Weizscker kinetic energy and long-range (far-from-nucleus) asymptotic correction. Applications of self-interaction corrections have shown that the self-interaction error has a serious effect on the states of core electrons, but it has a smaller than expected effect on valence electrons. This finding is supported by the fact that the distribution of self-interacting electrons indicates that they are near atomic nuclei rather than in chemical bonds.

Tsuneda, Takao, E-mail: ttsuneda@yamanashi.ac.jp [Fuel Cell Nanomaterials Center, University of Yamanashi, Kofu 400-0021 (Japan)] [Fuel Cell Nanomaterials Center, University of Yamanashi, Kofu 400-0021 (Japan); Hirao, Kimihiko [Computational Chemistry Unit, RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047 (Japan)] [Computational Chemistry Unit, RIKEN Advanced Institute for Computational Science, Kobe, Hyogo 650-0047 (Japan)

2014-05-14T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Density of the Values Set of the Tau Function  

E-Print Network [OSTI]

It is shown that the density of the values set {Tau(n): n > x/log x. The currently known density is #{Tau(n) : n > x^(1/2+o(1)), and the expected density is #{Tau(n) : n 2, which arises as a singular case of this analysis, is discussed within.

N. A. Carella

2014-04-10T23:59:59.000Z

142

Hybrid Dynamic Density Functional Theory for Polymer Melts and Blends  

E-Print Network [OSTI]

We propose a high-speed and accurate hybrid dynamic density functional theory for the computer simulations of the phase separation processes of polymer melts and blends. The proposed theory is a combination of the dynamic self-consistent field (SCF) theory and a time-dependent Ginzburg-Landau type theory with the random phase approximation (GRPA). The SCF theory is known to be accurate in evaluating the free energy of the polymer systems in both weak and strong segregation regions although it has a disadvantage of the requirement of a considerable amount of computational cost. On the other hand, the GRPA theory has an advantage of much smaller amount of required computational cost than the SCF theory while its applicability is limited to the weak segregation region. To make the accuracy of the SCF theory and the high-performance of the GRPA theory compatible, we adjust the chemical potential of the GRPA theory by using the SCF theory every constant time steps in the dynamic simulations. The performance of the GRPA and the hybrid theories is tested by using several systems composed of an A/B homopolymer, an AB diblock copolymer, or an ABC triblock copolymer. Using the hybrid theory, we succeeded in reproducing the metastable complex phase-separated domain structures of an ABC triblock copolymer observed by experiments.

Takashi Honda; Toshihiro Kawakatsu

2006-09-05T23:59:59.000Z

143

Efficiency issues related to probability density function comparison  

SciTech Connect (OSTI)

The CANDID project (Comparison Algorithm for Navigating Digital Image Databases) employs probability density functions (PDFs) of localized feature information to represent the content of an image for search and retrieval purposes. A similarity measure between PDFs is used to identify database images that are similar to a user-provided query image. Unfortunately, signature comparison involving PDFs is a very time-consuming operation. In this paper, we look into some efficiency considerations when working with PDFS. Since PDFs can take on many forms, we look into tradeoffs between accurate representation and efficiency of manipulation for several data sets. In particular, we typically represent each PDF as a Gaussian mixture (e.g. as a weighted sum of Gaussian kernels) in the feature space. We find that by constraining all Gaussian kernels to have principal axes that are aligned to the natural axes of the feature space, computations involving these PDFs are simplified. We can also constrain the Gaussian kernels to be hyperspherical rather than hyperellipsoidal, simplifying computations even further, and yielding an order of magnitude speedup in signature comparison. This paper illustrates the tradeoffs encountered when using these constraints.

Kelly, P.M.; Cannon, M.; Barros, J.E.

1996-03-01T23:59:59.000Z

144

A Density Functional Theory Study of Hydrogen Adsorption in MOF-5 Tim Mueller and Gerbrand Ceder*  

E-Print Network [OSTI]

A Density Functional Theory Study of Hydrogen Adsorption in MOF-5 Tim Mueller and Gerbrand Ceder initio molecular dynamics in the generalized gradient approximation to density functional theory to store hydrogen with sufficient gravimetric and volumetric densities to be economi- cally practical

Ceder, Gerbrand

145

Tests of second-generation and third-generation density functionals for thermochemical kineticsy  

E-Print Network [OSTI]

Tests of second-generation and third-generation density functionals for thermochemical kineticsy January 2004 We report tests of second- and third-generation density functionals, for pure density of these methods is tested against each other as well as against first- generation methods (BP86, BLYP, PW91, B3PW

Truhlar, Donald G

146

Fundamental measure density functional theory studies on the freezing of binary hard-sphere and Lennard-Jones mixtures  

E-Print Network [OSTI]

Fundamental measure density functional theory studies on the freezing of binary hard are calculated using the fundamental measure density functional theory. Using the thermodynamic perturbation. INTRODUCTION Density functional theory DFT became a practical the- oretical tool for the calculation

Song, Xueyu

147

Non-perturbative calculation of molecular magnetic properties within current-density functional theory  

SciTech Connect (OSTI)

We present a novel implementation of KohnSham density-functional theory utilizing London atomic orbitals as basis functions. External magnetic fields are treated non-perturbatively, which enable the study of both magnetic response properties and the effects of strong fields, using either standard density functionals or current-density functionalsthe implementation is the first fully self-consistent implementation of the latter for molecules. Pilot applications are presented for the finite-field calculation of molecular magnetizabilities, hypermagnetizabilities, and nuclear magnetic resonance shielding constants, focusing on the impact of current-density functionals on the accuracy of the results. Existing current-density functionals based on the gauge-invariant vorticity are tested and found to be sensitive to numerical details of their implementation. Furthermore, when appropriately regularized, the resulting magnetic properties show no improvement over standard density-functional results. An advantage of the present implementation is the ability to apply density-functional theory to molecules in very strong magnetic fields, where the perturbative approach breaks down. Comparison with high accuracy full-configuration-interaction results show that the inadequacies of current-density approximations are exacerbated with increasing magnetic field strength. Standard density-functionals remain well behaved but fail to deliver high accuracy. The need for improved current-dependent density-functionals, and how they may be tested using the presented implementation, is discussed in light of our findings.

Tellgren, E. I., E-mail: erik.tellgren@kjemi.uio.no; Lange, K. K.; Ekstrm, U.; Helgaker, T. [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway)] [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway); Teale, A. M., E-mail: andrew.teale@nottingham.ac.uk [Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway); School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom); Furness, J. W. [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)] [School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

2014-01-21T23:59:59.000Z

148

Complex structure of electron and density functional theory  

E-Print Network [OSTI]

Effective model for electron as two particle system is considered. The first particle in the system is chargeless mass of electron. The second one is massless charge of electron. Based on this model it is shown that density of energy for the particle is proportional to the probability density and the following formula stands $\\rho_E(x)=mc^2\\rho(x)$.

K. Koshelev

2013-01-08T23:59:59.000Z

149

An Improved Method for Estimating the Wind Power Density Distribution Function  

Science Journals Connector (OSTI)

The wind power density (WPD) distribution curve is essential for wind power assessment and wind turbine engineering. The usual practice of estimating this curve from wind speed data is to first estimate the wind speed probability density function ...

Mark L. Morrissey; Werner E. Cook; J. Scott Greene

2010-07-01T23:59:59.000Z

150

Symmetry Energy as a Function of Density and Mass  

E-Print Network [OSTI]

Energy in nuclear matter is, in practice, completely characterized at different densities and asymmetries, when the density dependencies of symmetry energy and of energy of symmetric matter are specified. The density dependence of the symmetry energy at subnormal densities produces mass dependence of nuclear symmetry coefficient and, thus, can be constrained by that latter dependence. We deduce values of the mass dependent symmetry coefficients, by using excitation energies to isobaric analog states. The coefficient systematic, for intermediate and high masses, is well described in terms of the symmetry coefficient values of a_a^V=(31.5-33.5) MeV for the volume coefficient and a_a^S=(9-12) MeV for the surface coefficient. These two further correspond to the parameter values describing density dependence of symmetry energy, of L~95 MeV and K_{sym}~25 MeV.

Pawel Danielewicz; Jenny Lee

2007-08-21T23:59:59.000Z

151

Symmetry Energy as a Function of Density and Mass  

SciTech Connect (OSTI)

Energy in nuclear matter is, in practice, completely characterized at different densities and asymmetries, when the density dependencies of symmetry energy and of energy of symmetric matter are specified. The density dependence of the symmetry energy at subnormal densities produces mass dependence of nuclear symmetry coefficient and, thus, can be constrained by that latter dependence. We deduce values of the mass dependent symmetry coefficients, by using excitation energies to isobaric analog states. The coefficient systematic, for intermediate and high masses, is well described in terms of the symmetry coefficient values of a{sub a}{sup V} = (31.5-33.5) MeV for the volume coefficient and a{sub a}{sup S} = (9-12) MeV for the surface coefficient. These two further correspond to the parameter values describing density dependence of symmetry energy, of L{approx}95 MeV and K{sub sym}{approx}25 MeV.

Danielewicz, Pawel; Lee, Jenny [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824 (United States)

2007-10-26T23:59:59.000Z

152

Symmetry Energy as a Function of Density and Mass  

E-Print Network [OSTI]

Energy in nuclear matter is, in practice, completely characterized at different densities and asymmetries, when the density dependencies of symmetry energy and of energy of symmetric matter are specified. The density dependence of the symmetry energy at subnormal densities produces mass dependence of nuclear symmetry coefficient and, thus, can be constrained by that latter dependence. We deduce values of the mass dependent symmetry coefficients, by using excitation energies to isobaric analog states. The coefficient systematic, for intermediate and high masses, is well described in terms of the symmetry coefficient values of a_a^V=(31.5-33.5) MeV for the volume coefficient and a_a^S=(9-12) MeV for the surface coefficient. These two further correspond to the parameter values describing density dependence of symmetry energy, of L~95 MeV and K_{sym}~25 MeV.

Danielewicz, Pawel

2007-01-01T23:59:59.000Z

153

Understanding the NMR shifts in paramagnetic transition metal oxides using density functional theory calculations  

E-Print Network [OSTI]

obvious. In this paper, we show by means of density functional theory DFT calcula- tions that a rationalUnderstanding the NMR shifts in paramagnetic transition metal oxides using density functional functional theory DFT calculations in the generalized gradient approximation. For each compound, we calculate

Ceder, Gerbrand

154

Ensemble-Density Functional Theory for Excited States L. N. Oliveira  

E-Print Network [OSTI]

Ensemble-Density Functional Theory for Excited States L. N. Oliveira Instituto de F#19;#16;sica e aspects of the ensemble-density functional approach to the calculation of excited state energies Functional Theory to excited states [1]. That approach, proposed originally by Theophilou [2], is analogous

Gross, E.K.U.

155

Density Functional Theory for Baxter's Sticky Hard Spheres in Confinement Hendrik Hansen-Goos,1  

E-Print Network [OSTI]

Density Functional Theory for Baxter's Sticky Hard Spheres in Confinement Hendrik Hansen-Goos,1 that it obeys scaled-particle theory and the Percus-Yevick (PY) result for the direct correlation function [H with simulation data for both the bulk pair-correlation function and the density profiles in confinement shows

Wettlaufer, John S.

156

Pore Size Analysis of Activated Carbons from Argon and Nitrogen Porosimetry Using Density Functional Theory  

E-Print Network [OSTI]

Form: December 28, 1999 We present isotherms calculated from density functional theory. A similar set of density functional theory isotherms, previously reported for nitrogen adsorption on carbon Functional Theory Robert J. Dombrowski, Daniel R. Hyduke, and Christian M. Lastoskie* Department of Chemical

Lastoskie, Christian M.

157

Accelerating the convergence of the total energy evaluation in density functional theory calculations  

E-Print Network [OSTI]

Accelerating the convergence of the total energy evaluation in density functional theory.1063/1.2821101 I. INTRODUCTION Density functional theory DFT ,1,2 one of the most widely used first functional theory OO-DFT B. Zhou and Y. A. Wang, J. Chem. Phys. 124, 081107 2006 is that the second

Wang, Yan Alexander

158

Tractable Analytic Expressions for the Wind Speed Probability Density Functions Using Expansions of Orthogonal Polynomials  

Science Journals Connector (OSTI)

The use of the two-parameter Weibull function as an estimator of the wind speed probability density function (PDF) is known to be problematic when a high accuracy of fit is required, such as in the computation of the wind power density function. ...

Mark L. Morrissey; J. Scott Greene

2012-07-01T23:59:59.000Z

159

Stretched hydrogen molecule from a constrained-search density-functional perspective  

SciTech Connect (OSTI)

Constrained-search density functional theory gives valuable insights into the fundamentals of density functional theory. It provides exact results and bounds on the ground- and excited-state density functionals. An important advantage of the theory is that it gives guidance in the construction of functionals. Here they engage constrained search theory to explore issues associated with the functional behavior of 'stretched bonds' in molecular hydrogen. A constrained search is performed with familiar valence bond wavefunctions ordinarily used to describe molecular hydrogen. The effective, one-electron hamiltonian is computed and compared to the corresponding uncorrelated, Hartree-Fock effective hamiltonian. Analysis of the functional suggests the need to construct different functionals for the same density and to allow a competition among these functions. As a result the correlation energy functional is composed explicitly of energy gaps from the different functionals.

Valone, Steven M [Los Alamos National Laboratory; Levy, Mel [DIKE UNIV.

2009-01-01T23:59:59.000Z

160

On the breaking and restoration of symmetries within the nuclear energy density functional formalism  

E-Print Network [OSTI]

We review the notion of symmetry breaking and restoration within the frame of nuclear energy density functional methods. We focus on key differences between wave-function- and energy-functional-based methods. In particular, we point to difficulties encountered within the energy functional framework and discuss new potential constraints on the underlying energy density functional that could make the restoration of broken symmetries better formulated within such a formalism. We refer to Ref.~\\cite{duguet10a} for details.

T. Duguet; J. Sadoudi

2010-10-19T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Density Functional Theory Calculations of Mass Transport in UO2  

SciTech Connect (OSTI)

In this talk we present results of density functional theory (DFT) calculations of U, O and fission gas diffusion in UO{sub 2}. These processes all impact nuclear fuel performance. For example, the formation and retention of fission gas bubbles induce fuel swelling, which leads to mechanical interaction with the clad thereby increasing the probability for clad breach. Alternatively, fission gas can be released from the fuel to the plenum, which increases the pressure on the clad walls and decreases the gap thermal conductivity. The evolution of fuel microstructure features is strongly coupled to diffusion of U vacancies. Since both U and fission gas transport rates vary strongly with the O stoichiometry, it is also important to understand O diffusion. In order to better understand bulk Xe behavior in UO{sub 2{+-}x} we first calculate the relevant activation energies using DFT techniques. By analyzing a combination of Xe solution thermodynamics, migration barriers and the interaction of dissolved Xe atoms with U, we demonstrate that Xe diffusion predominantly occurs via a vacancy-mediated mechanism. Since Xe transport is closely related to diffusion of U vacancies, we have also studied the activation energy for this process. In order to explain the low value of 2.4 eV found for U migration from independent damage experiments (not thermal equilibrium) the presence of vacancy clusters must be included in the analysis. Next we investigate species transport on the (111) UO{sub 2} surface, which is motivated by the formation of small voids partially filled with fission gas atoms (bubbles) in UO{sub 2} under irradiation. Surface diffusion could be the rate-limiting step for diffusion of such bubbles, which is an alternative mechanism for mass transport in these materials. As expected, the activation energy for surface diffusion is significantly lower than for bulk transport. These results are further discussed in terms of engineering-scale fission gas release models. Finally, oxidation of UO{sub 2} and the importance of cluster formation for understanding thermodynamic and kinetic properties of UO{sub 2+x} are investigated.

Andersson, Anders D. [Los Alamos National Laboratory; Dorado, Boris [CEA; Uberuaga, Blas P. [Los Alamos National Laboratory; Stanek, Christopher R. [Los Alamos National Laboratory

2012-06-26T23:59:59.000Z

162

Comparison of probability density functions for analyzing irradiance statistics due to atmospheric turbulence  

Science Journals Connector (OSTI)

A large number of model probability density functions (PDFs) are used to analyze atmospheric scintillation statistics. We have analyzed scintillation data from two different...

Mclaren, Jason R W; Thomas, John C; Mackintosh, Jessica L; Mudge, Kerry A; Grant, Kenneth J; Clare, Bradley A; Cowley, William G

2012-01-01T23:59:59.000Z

163

Supplementary data for "Relativistic density functional theory modeling of plutonium and  

E-Print Network [OSTI]

Supplementary data for "Relativistic density functional theory modeling of plutonium and americium equilibrium geometries of plutonium and americium oxide molecules (standard .xyz files separated by empty

Titov, Anatoly

164

Density-matrix functionals for pairing in mesoscopic superconductors  

SciTech Connect (OSTI)

A functional theory based on single-particle occupation numbers is developed for pairing. This functional, that generalizes the Bardeen-Cooper-Schrieffer approach, directly incorporates corrections due to particle number conservation. The functional is benchmarked with the pairing Hamiltonian and reproduces perfectly the energy for any particle number and coupling.

Lacroix, Denis; Hupin, Guillaume [GANIL, CEA/DSM-CNRS/IN2P3, BP 55027, 14076 Caen Cedex 5 (France)

2010-10-01T23:59:59.000Z

165

Effects of d-electrons in pseudopotential screened-exchange density functional calculations  

E-Print Network [OSTI]

Effects of d-electrons in pseudopotential screened-exchange density functional calculations-conservation condition on the PP's guarantees that the net electron density in PP calculations inside the core-radius agrees with the electron density in all-electron (AE) calculations and, at the same time

Geddes, Cameron Guy Robinson

166

Effects of d-electrons in pseudopotential screened-exchange density functional calculations  

E-Print Network [OSTI]

Effects of d-electrons in pseudopotential screened-exchange density functional calculations conservation condition on the PP's guarantees that the net electron density in PP calculation inside the core-radius agree with the electron density in the all-electron (AE) calculations and, at the same time

Geddes, Cameron Guy Robinson

167

Time-dependent density functional theory with ultrasoft pseudopotentials: Real-time electron propagation across a molecular junction  

E-Print Network [OSTI]

Time-dependent density functional theory with ultrasoft pseudopotentials: Real-time electron 2006 A practical computational scheme based on time-dependent density functional theory TDDFT density functional theory22 TDDFT . Density functional theory DFT 23 with the Kohn-Sham reference kinetic

Lin, Xi

168

Density functional approaches to collective phenomena in nuclei: Time-dependent density-functional theory for perturbative and non-perturbative nuclear dynamics  

E-Print Network [OSTI]

We present the basic concepts and our recent developments in the density functional approaches with the Skyrme functionals for describing nuclear dynamics at low energy. The time-dependent density-functional theory (TDDFT) is utilized for the exact linear response with an external perturbation. For description of collective dynamics beyond the perturbative regime, we present a theory of a decoupled collective submanifold to describe for a slow motion based on the TDDFT. Selected applications are shown to demonstrate the quality of their performance and feasibility. Advantages and disadvantages in the numerical aspects are also discussed.

Takashi Nakatsukasa

2012-10-01T23:59:59.000Z

169

LES/probability density function approach for the simulation of an ethanol spray flame  

E-Print Network [OSTI]

LES/probability density function approach for the simulation of an ethanol spray flame Colin Heye a an experimental pilot-stabilized ethanol spray flame. In this particular flame, droplet evaporation occurs away: Large-eddy simulation; Probability density function; Flamelet/progress variable approach; Ethanol

Raman, Venkat

170

Density functional simulations of Tebased phase change materials J. Akola 1,2  

E-Print Network [OSTI]

E*PCOS2008 Density functional simulations of Tebased phase change materials J. Akola 1,2 and R. O limitations of the theoretical methods are discussed. Key words: Phase change materials, density functional. This is extremely difficult in practice, and our first calculations on phase change materials were carried out

171

Probability-density function for energy perturbations of isolated optical pulses  

E-Print Network [OSTI]

Probability-density function for energy perturbations of isolated optical pulses C. J. Mc to determine the probability-density function (PDF) for noise-induced energy perturbations of isolated (solitary) optical pulses in fiber communication systems. The analytical formula is consistent

Lakoba, Taras I.

172

Calculations of free energies in liquid and solid phases: Fundamental measure density-functional approach  

E-Print Network [OSTI]

Calculations of free energies in liquid and solid phases: Fundamental measure density energies of liquid and solid phases using a fundamental measure density-functional theory. Namely, we can, a theoretical description of the free energies and correlation functions of hard-sphere (HS) liquid and solid

Song, Xueyu

173

Azobenzene-Functionalized Carbon Nanotubes As High-Energy Density Solar Thermal Fuels  

Science Journals Connector (OSTI)

Azobenzene-Functionalized Carbon Nanotubes As High-Energy Density Solar Thermal Fuels ... Solar thermal fuels, which reversibly store solar energy in molecular bonds, are a tantalizing prospect for clean, renewable, and transportable energy conversion/storage. ... Here we present a novel solar thermal fuel, composed of azobenzene-functionalized carbon nanotubes, with the volumetric energy density of Li-ion batteries. ...

Alexie M. Kolpak; Jeffrey C. Grossman

2011-06-20T23:59:59.000Z

174

Supplemental Material for Angular Momentum Dependent Orbital Free Density Functional Theory  

E-Print Network [OSTI]

)-(2) the general total energy functional of OFDFT can be rewritten as EOF [(r)] = EOF [{NR}, I(r)], (3) where introduce a smooth scaling function f(r) in the energy density of Ts - TKEDF s to make the KE density for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, USA 2 Material Science

Florian, Libisch

175

Xray and neutron diffraction studies and MD simulation of atomic configurations in polyamorphic Y2O3-Al2O3 systems  

Science Journals Connector (OSTI)

...McMillan and David C. Clary X-ray and neutron diffraction studies and MD simulation...new results of structural studies using neutron and high-energy X-ray diffraction...pair-correlation functions obtained from X-ray and neutron scattering data. Unexpectedly large density...

2005-01-01T23:59:59.000Z

176

Joint density-functional theory for electronic structure of solvated systems  

E-Print Network [OSTI]

We introduce a new form of density functional theory for the {\\em ab initio} description of electronic systems in contact with a molecular liquid environment. This theory rigorously joins an electron density-functional for the electrons of a solute with a classical density-functional theory for the liquid into a single variational principle for the free energy of the combined system. A simple approximate functional predicts, without any fitting of parameters to solvation data, solvation energies as well as state-of-the-art quantum-chemical cavity approaches, which require such fitting.

Sahak Petrosyan; Jean-Francois Briere; David Roundy; T. A. Arias

2007-02-09T23:59:59.000Z

177

Luminosity function and density field of the Sloan and Las Campanas Redshift Survey  

E-Print Network [OSTI]

The luminosity function of galaxies of the Early Data Release of the Sloan Digital Sky Survey (SDSS) and the Las Campanas Redshift Survey (LCRS) is calculated. The luminosity function depends on redshift, density of the environment and is different for the Norther and Southern slice of SDSS. Luminosity functions is used to derive the number and luminosity density fields of galaxies of the SDSS and LCRS surveys with a grid size of 1 h^{-1} Mpc for flat cosmological models with \\Omega_m=0.3 and \\Omega_\\Lambda =0.7. We find that the luminosity function depends on the density of the environment: in high-density regions brightest galaxies are more luminous than in low-density regions by a factor up to 5.

G. Htsi; J. Einasto; D. L. Tucker; E. Saar; M. Einasto; V. Mller; P. Heinmki; S. S. Allam

2002-12-13T23:59:59.000Z

178

Communication: Self-interaction correction with unitary invariance in density functional theory  

SciTech Connect (OSTI)

Standard spin-density functionals for the exchange-correlation energy of a many-electron ground state make serious self-interaction errors which can be corrected by the Perdew-Zunger self-interaction correction (SIC). We propose a size-extensive construction of SIC orbitals which, unlike earlier constructions, makes SIC computationally efficient, and a true spin-density functional. The SIC orbitals are constructed from a unitary transformation that is explicitly dependent on the non-interacting one-particle density matrix. When this SIC is applied to the local spin-density approximation, improvements are found for the atomization energies of molecules.

Pederson, Mark R., E-mail: mark.pederson@science.doe.gov [Office of Basic Energy Sciences, SC22.1, U.S. Department of Energy, Washington, DC 20585 (United States); Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Ruzsinszky, Adrienn [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States)] [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Perdew, John P. [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States) [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122 (United States)

2014-03-28T23:59:59.000Z

179

Brief review related to the foundations of time-dependent density functional theory  

E-Print Network [OSTI]

The electron density $n(\\rb,t)$, which is the central tool of time-dependent density functional theory, is presently considered to be derivable from a one-body time-dependent potential $V(\\rb,t)$, via one-electron wave functions satisfying a time- dependent Schr\\"{o}dinger equation. This is here related via a generalized equation of motion to a Dirac density matrix now involving $t$. Linear response theory is then surveyed, with a special emphasis on the question of causality with respect to the density dependence of the potential. Extraction of $V(\\rb,t)$ for solvable models is also proposed.

Thomas A. Niehaus; Norman H. March

2009-04-28T23:59:59.000Z

180

Fundamental-measure density functional theory study of the crystal-melt interface of the hard sphere system  

E-Print Network [OSTI]

Fundamental-measure density functional theory study of the crystal-melt interface of the hard density functional theory. The equilibrium interfacial density profiles and interfacial free energies were value is 0.6 5,10 . For the past two decades a number of density functional theories were developed

Song, Xueyu

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Stability of titanium oxide phases in Kohn-Sham density functional A well known problem in practical Kohn-Sham (KS) density functional theory (DFT) calculations is that it yields the wrong order of  

E-Print Network [OSTI]

Stability of titanium oxide phases in Kohn-Sham density functional theory A well known problem in practical Kohn-Sham (KS) density functional theory (DFT) calculations is that it yields the wrong order-DFT, but with different levels of corrections to the exchange-correlation functional. Kohn-Sham density functional theory

Bjørnstad, Ottar Nordal

182

Revisiting density functionals for the primitive model of electric double layers  

SciTech Connect (OSTI)

Density functional theory (DFT) calculations are typically based on approximate functionals that link the free energy of a multi-body system of interest with the underlying one-body density distributions. Whereas good performance is often proclaimed for new developments, it is difficult to vindicate the theoretical merits relative to alternative versions without extensive comparison with the numerical results from molecular simulations. Besides, approximate functionals may defy statistical-mechanical sum rules and result in thermodynamic inconsistency. Here we compare systematically several versions of density functionals for ionic distributions near a charged surface using the primitive model of electric double layers. We find that the theoretical performance is sensitive not only to the specific forms of the density functional but also to the range of parameter space and the precise properties under consideration. In general, incorporation of the thermodynamic sum rule into the DFT calculations shows significant improvements for both electrochemical properties and ionic distributions.

Jiang, Jian [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States) [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States); Department of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Cao, Dapeng, E-mail: jwu@engr.ucr.edu, E-mail: doug@chem.byu.edu, E-mail: caodp@mail.buct.edu.cn [Department of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)] [Department of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Henderson, Douglas, E-mail: jwu@engr.ucr.edu, E-mail: doug@chem.byu.edu, E-mail: caodp@mail.buct.edu.cn [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States)] [Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602 (United States); Wu, Jianzhong, E-mail: jwu@engr.ucr.edu, E-mail: doug@chem.byu.edu, E-mail: caodp@mail.buct.edu.cn [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States)] [Department of Chemical and Environmental Engineering and Department of Mathematics, University of California, Riverside, California 92521 (United States)

2014-01-28T23:59:59.000Z

183

Excitation energies of molecules within time-independent density functional theory  

SciTech Connect (OSTI)

Recently proposed exchange energy functional for excited-states is tested for obtaining excitation energies of diatomic molecules. The functional is the ground-state counterpart of the local-density approximation, the modified local spin density (MLSD). The MLSD functional is tested for the N{sub 2} and CO diatomic molecules. The excitation energy obtained with the MLSD functional for the N{sub 2} molecule is in close vicinity to that obtained from the exact exchange orbital functional, Krieger, Li and Iafrate (KLI). For the CO molecule, the departure in excitation energy is observed and is due to the overcorrection of self-interaction.

Hemanadhan, M., E-mail: hemanadh@iitk.ac.in; Harbola, Manoj K., E-mail: hemanadh@iitk.ac.in [Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016 (India)

2014-04-24T23:59:59.000Z

184

On the contact values of the density profiles in an electric double layer using density functional theory  

E-Print Network [OSTI]

A recently proposed local second contact value theorem [Henderson D., Boda D., J. Electroanal. Chem., 2005, 582, 16] for the charge profile of an electric double layer is used in conjunction with the existing Monte Carlo data from the literature to assess the contact behavior of the electrode-ion distributions predicted by the density functional theory. The results for the contact values of the co- and counterion distributions and their product are obtained for the symmetric valency, restricted primitive model planar double layer for a range of electrolyte concentrations and temperatures. Overall, the theoretical results satisfy the second contact value theorem reasonably well, the agreement with the simulations being semi-quantitative or better. The product of the co- and counterion contact values as a function of the electrode surface charge density is qualitative with the simulations with increasing deviations at higher concentrations.

L. B. Bhuiyan; D. Henderson; S. Soko?owski

2012-07-13T23:59:59.000Z

185

Recent developments in classical density functional theory: Internal energy functional and diagrammatic structure of fundamental measure theory  

E-Print Network [OSTI]

An overview of several recent developments in density functional theory for classical inhomogeneous liquids is given. We show how Levy's constrained search method can be used to derive the variational principle that underlies density functional theory. An advantage of the method is that the Helmholtz free energy as a functional of a trial one-body density is given as an explicit expression, without reference to an external potential as is the case in the standard Mermin-Evans proof by reductio ad absurdum. We show how to generalize the approach in order to express the internal energy as a functional of the one-body density distribution and of the local entropy distribution. Here the local chemical potential and the bulk temperature play the role of Lagrange multipliers in the Euler-Lagrange equations for minimiziation of the functional. As an explicit approximation for the free-energy functional for hard sphere mixtures, the diagrammatic structure of Rosenfeld's fundamental measure density unctional is laid out. Recent extensions, based on the Kierlik-Rosinberg scalar weight functions, to binary and ternary non-additive hard sphere mixtures are described.

M. Schmidt; M. Burgis; W. S. B. Dwandaru; G. Leithall; P. Hopkins

2012-12-27T23:59:59.000Z

186

Ensemble density variational methods with self- and ghost-interaction-corrected functionals  

SciTech Connect (OSTI)

Ensemble density functional theory (DFT) offers a way of predicting excited-states energies of atomic and molecular systems without referring to a density response function. Despite a significant theoretical work, practical applications of the proposed approximations have been scarce and they do not allow for a fair judgement of the potential usefulness of ensemble DFT with available functionals. In the paper, we investigate two forms of ensemble density functionals formulated within ensemble DFT framework: the Gross, Oliveira, and Kohn (GOK) functional proposed by Gross et al. [Phys. Rev. A 37, 2809 (1988)] alongside the orbital-dependent eDFT form of the functional introduced by Nagy [J. Phys. B 34, 2363 (2001)] (the acronym eDFT proposed in analogy to eHF ensemble Hartree-Fock method). Local and semi-local ground-state density functionals are employed in both approaches. Approximate ensemble density functionals contain not only spurious self-interaction but also the so-called ghost-interaction which has no counterpart in the ground-state DFT. We propose how to correct the GOK functional for both kinds of interactions in approximations that go beyond the exact-exchange functional. Numerical applications lead to a conclusion that functionals free of the ghost-interaction by construction, i.e., eDFT, yield much more reliable results than approximate self- and ghost-interaction-corrected GOK functional. Additionally, local density functional corrected for self-interaction employed in the eDFT framework yields excitations energies of the accuracy comparable to that of the uncorrected semi-local eDFT functional.

Pastorczak, Ewa [Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, ul. Wroblewskiego 15, 93-590 Lodz (Poland)] [Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology, ul. Wroblewskiego 15, 93-590 Lodz (Poland); Pernal, Katarzyna, E-mail: pernalk@gmail.com [Institute of Physics, Lodz University of Technology, ul. Wolczanska 219, 90-924 Lodz (Poland)] [Institute of Physics, Lodz University of Technology, ul. Wolczanska 219, 90-924 Lodz (Poland)

2014-05-14T23:59:59.000Z

187

short course on density-functional theory lectures given at the Fudan University, Shanghai, January 11-15, 2010  

E-Print Network [OSTI]

short course on density-functional theory lectures given at the Fudan University, Shanghai, January transforms Lecture 2: Density-functional theory · the electronic ground state as a functional of the external-order derivatives from (density-functional) perturbation theory · the 2n+1 theorem · lattice dynamics from DFPT

Gong, Xingao

188

Dynamical density functional theory with hydrodynamic interactions and colloids in unstable traps  

E-Print Network [OSTI]

A density functional theory for colloidal dynamics is presented which includes hydrodynamic interactions between the colloidal particles. The theory is applied to the dynamics of colloidal particles in an optical trap which switches periodically in time from a stable to unstable confining potential. In the absence of hydrodynamic interactions, the resulting density breathing mode, exhibits huge oscillations in the trap center which are almost completely damped by hydrodynamic interactions. The predicted dynamical density fields are in good agreement with Brownian dynamics computer simulations.

M. Rex; H. Loewen

2008-03-13T23:59:59.000Z

189

On the existence of effective potentials in time-dependent density functional theory  

E-Print Network [OSTI]

We investigate the existence and properties of effective potentials in time-dependent density functional theory. We outline conditions for a general solution of the corresponding Sturm-Liouville boundary value problems. We define the set of potentials and v-representable densities, give a proof of existence of the effective potentials under certain restrictions, and show the set of v-representable densities to be independent of the interaction.

M. Ruggenthaler; M. Penz; D. Bauer

2009-11-10T23:59:59.000Z

190

ATP Hydrolysis in Water -A Density Functional Study J. Akola and R. O. Jones*  

E-Print Network [OSTI]

ATP Hydrolysis in Water - A Density Functional Study J. Akola and R. O. Jones* Institut fu¨r Festko 5-triphosphate (ATP) is a basic energy carrier in cellular metabolism. As a high-energy intermediate-dependent hydrolysis reaction. Two paths for ATP hydrolysis in water with Mg2+ are studied here using the density

191

Calculation of hyperfine coupling constants of radicals by density-functional theory  

Science Journals Connector (OSTI)

Hyperfine coupling constants for small radicals have been calculated using the density-functional theory with a gradient-corrected (GC) local-spin-density approximation (LSDA). The agreement between the calculated and observed results is fairly good. The GC-LSDA is essential to calculate the isotropic hyperfine coupling constants for ? radicals. For ? radicals, the simple LSDA also leads to relatively good results.

Nobuhiko Ishii and Tatsuo Shimizu

1993-08-01T23:59:59.000Z

192

Nuclear Physics A 770 (2006) 131 Relativistic nuclear energy density functional  

E-Print Network [OSTI]

Nuclear Physics A 770 (2006) 1­31 Relativistic nuclear energy density functional constrained by low-energy 10 February 2006 Available online 3 March 2006 Abstract A relativistic nuclear energy density nuclear physics: the relationship between low-energy, non- perturbative QCD and the rich structure

Weise, Wolfram

193

Charge transport, configuration interaction and Rydberg states under density functional theory  

E-Print Network [OSTI]

Density functional theory (DFT) is a computationally efficient formalism for studying electronic structure and dynamics. In this work, we develop DFT-based excited-state methods to study electron transport, Rydberg excited ...

Cheng, Chiao-Lun

2008-01-01T23:59:59.000Z

194

Double-hybrid density-functional theory with meta-generalized-gradient approximations  

SciTech Connect (OSTI)

We extend the previously proposed one-parameter double-hybrid density-functional theory [K. Sharkas, J. Toulouse, and A. Savin, J. Chem. Phys. 134, 064113 (2011)] to meta-generalized-gradient-approximation (meta-GGA) exchange-correlation density functionals. We construct several variants of one-parameter double-hybrid approximations using the Tao-Perdew-Staroverov-Scuseria (TPSS) meta-GGA functional and test them on test sets of atomization energies and reaction barrier heights. The most accurate variant uses the uniform coordinate scaling of the density and of the kinetic energy density in the correlation functional, and improves over both standard Kohn-Sham TPSS and second-order Mller-Plesset calculations.

Souvi, Sidi M. O., E-mail: sidi.souvi@irsn.fr; Sharkas, Kamal; Toulouse, Julien, E-mail: julien.toulouse@upmc.fr [Sorbonne Universits, UPMC Univ Paris 06, UMR 7616, Laboratoire de Chimie Thorique, F-75005 Paris (France) [Sorbonne Universits, UPMC Univ Paris 06, UMR 7616, Laboratoire de Chimie Thorique, F-75005 Paris (France); CNRS, UMR 7616, Laboratoire de Chimie Thorique, F-75005 Paris (France)

2014-02-28T23:59:59.000Z

195

Geometric and Electronic Structures of Tc and Mn Clusters by Density Functional Calculations  

Science Journals Connector (OSTI)

The geometric structures of Tc2-Tc5 and Mn2-Mn8 clusters were optimized by the Amsterdam density functional method. The trimeric, tetrameric, and pentameric Tc clusters exhibit the equilibrium structures of isosc...

R. Sekine; R. Kondo; T. Yamamoto; J. Onoe

2003-05-01T23:59:59.000Z

196

Calculation of the Green's function from high- and low-density series expansions for disordered transport  

E-Print Network [OSTI]

We investigate density expansions for the configurationally averaged Green's function for a random walk on a (site) disordered lattice. Two-point Pad summation techniques are used in conjunction with scaling arguments to examine behavior near...

Calef, Daniel F.; Friesner, Richard; Korzeniewski, Gregory; Laird, Brian Bostian; Silbey, Robert

1984-05-01T23:59:59.000Z

197

Towards a Microscopic Reaction Description Based on Energy Density Functionals  

SciTech Connect (OSTI)

A microscopic calculation of reaction cross sections for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all particle-hole excitations in the target and one-nucleon pickup channels. The particle-hole states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for {sup 40,48}Ca, {sup 58}Ni, {sup 90}Zr and {sup 144}Sm were described in a random-phase framework using a Skyrme functional. Reaction cross sections obtained agree very well with experimental data and predictions of a state-of-the-art fitted optical potential. Couplings between inelastic states were found to be negligible, while the pickup channels contribute significantly. The effect of resonances from higher-order channels was assessed. Elastic angular distributions were also calculated within the same method, achieving good agreement with experimental data. For the first time observed absorptions are completely accounted for by explicit channel coupling, for incident energies between 10 and 70 MeV, with consistent angular distribution results.

Nobre, G A; DIetrich, F S; Escher, J E; Thompson, I J; Dupuis, M; Terasaki, J; Engel, J

2011-09-26T23:59:59.000Z

198

Electronic density-of-states of amorphous vanadium pentoxide films: Electrochemical data and density functional theory calculations  

SciTech Connect (OSTI)

Thin films of V{sub 2}O{sub 5} were prepared by sputter deposition onto transparent and electrically conducting substrates and were found to be X-ray amorphous. Their electrochemical density of states was determined by chronopotentiometry and displayed a pronounced low-energy peak followed by an almost featureless contribution at higher energies. These results were compared with density functional theory calculations for amorphous V{sub 2}O{sub 5}. Significant similarities were found between measured data and computations; specifically, the experimental low-energy peak corresponds to a split-off part of the conduction band apparent in the computations. Furthermore, the calculations approximately reproduce the experimental band gap observed in optical measurements.

Lykissa, Iliana; Li, Shu-Yi; Granqvist, Claes G.; Niklasson, Gunnar A., E-mail: gunnar.niklasson@angstrom.uu.se [Department of Engineering Sciences, The ngstrm Laboratory, Uppsala University, P.O. Box 534, SE-75121 Uppsala (Sweden); Ramzan, Muhammad [Department of Physics and Astronomy, The ngstrm Laboratory, Uppsala University, P.O. Box 516, SE-75120 Uppsala (Sweden); Chakraborty, Sudip; Ahuja, Rajeev [Department of Physics and Astronomy, The ngstrm Laboratory, Uppsala University, P.O. Box 516, SE-75120 Uppsala (Sweden); Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden)

2014-05-14T23:59:59.000Z

199

Functional approach for pairing in finite systems: How to define restoration of broken symmetries in Energy Density Functional theory ?  

E-Print Network [OSTI]

The Multi-Reference Energy Density Functional (MR-EDF) approach (also called configuration mixing or Generator Coordinate Method), that is commonly used to treat pairing in finite nuclei and project onto particle number, is re-analyzed. It is shown that, under certain conditions, the MR-EDF energy can be interpreted as a functional of the one-body density matrix of the projected state with good particle number. Based on this observation, we propose a new approach, called Symmetry-Conserving EDF (SC-EDF), where the breaking and restoration of symmetry are accounted for simultaneously. We show, that such an approach is free from pathologies recently observed in MR-EDF and can be used with a large flexibility on the density dependence of the functional.

Guillaume Hupin; Denis Lacroix; Michael Bender

2011-05-30T23:59:59.000Z

200

Exact relations of the quasienergy functional and the exchange-correlation potential from the Floquet formulation of time-dependent density functional theory  

E-Print Network [OSTI]

the Floquet formulation of time-dependent density functional theory Dmitry A. Telnov and Shih-I Chu Department-dependent density functional theory we present several exact relations involving different parts of the quasienergy.012514 PACS number s : 71.45.Gm, 71.15.Mb, 31.15.Ew I. INTRODUCTION Time-independent density functional theory

Chu, Shih-I

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Accurate Ground-State Energies of Solids and Molecules from Time-Dependent Density-Functional Theory  

E-Print Network [OSTI]

-dissipation theorem with time-dependent density- functional theory. The key ingredient is a renormalization scheme be obtained from time- dependent density-functional theory (TDDFT) through the Dyson equation ð? ¼ KS ð? þ KS density-functional theory (DFT), one needs a rather involved approximation for the xc energy in order

Thygesen, Kristian

202

PHYSICAL REVIEW A 85, 052510 (2012) Propagation of initially excited states in time-dependent density-functional theory  

E-Print Network [OSTI]

-dependent density-functional theory Peter Elliott and Neepa T. Maitra Department of Physics and Astronomy, Hunter March 2012; published 22 May 2012) Many recent applications of time-dependent density functional theory-dependent density functional theory (TDDFT) is an exact reformulation of the time-dependent quantum mechanics

203

The many-body problem A solution: DFT HK theorems KS scheme Summary Key concepts in Density Functional Theory (I)  

E-Print Network [OSTI]

's University, Belfast Key concepts in Density Functional Theory (I) Silvana Botti #12;The many-body problem concepts in Density Functional Theory (I) Silvana Botti #12;The many-body problem A solution: DFT HK theorems KS scheme Summary Outline 1 The many-body problem 2 A solution: Density Functional Theory 3

Botti, Silvana

204

PHYSICAL REVIEW B 84, 014103 (2011) Screening for high-performance piezoelectrics using high-throughput density functional theory  

E-Print Network [OSTI]

-throughput density functional theory Rickard Armiento,1 Boris Kozinsky,2 Marco Fornari,3 and Gerbrand Ceder1 1-scale density functional theory (DFT) investigation of the ABO3 chemical space in the perovskite crystal-throughput density functional theory19,20 calculations. The last decades have seen a rapid increase of computational

Ceder, Gerbrand

205

Density-functional theory of freezing of quantum liquids at zero temperature using exact liquid-state linear response  

E-Print Network [OSTI]

Density-functional theory of freezing of quantum liquids at zero temperature using exact liquid the shortcomings of the currently popular density-functional approximate theories to describe 3d freezing distances. S0163-1829 97 04310-5 I. INTRODUCTION The modern density-functional theory DFT , which

Likos, Christos N.

206

in: "Density Functional Theory", edited by R.F. Nalewajski, Topics in Current Chemistry, Vol. 181, p. 81  

E-Print Network [OSTI]

in: "Density Functional Theory", edited by R.F. Nalewajski, Topics in Current Chemistry, Vol. 181, p. 81 Springer­Verlag Berlin Heidelberg 1996 Density functional theory of time­dependent phenomena E of density functional theory (DFT) is to describe an interacting many­particle system exclusively

Gross, E.K.U.

207

Quasiparticle band structure and density-functional theory: Single-particle excitations and band gaps in lattice models  

E-Print Network [OSTI]

ARTICLES Quasiparticle band structure and density-functional theory: Single-particle excitations-particle eigenvalues. Without rigorous basis even for the exact density-functional theory , these are often taken, eigenvalues obtained from density-functional theory DFT , and those from a corresponding LDA. Notable among

Hess, Daryl W.

208

Density-functional theory with optimized effective potential and self-interaction correction for ground states and autoionizing resonances  

E-Print Network [OSTI]

Density-functional theory with optimized effective potential and self-interaction correction-interaction-free density-functional theory DFT for the treatment of both the static prop- erties of the ground states and Sham 2 , the density-functional theory DFT has undergone significant theoretical and computational ad

Chu, Shih-I

209

in: "Density Functional Theory", edited by R.F. Nalewajski, Topics in Current Chemistry, Vol. 181, p. 81  

E-Print Network [OSTI]

in: "Density Functional Theory", edited by R.F. Nalewajski, Topics in Current Chemistry, Vol. 181, p. 81 Springer-Verlag Berlin Heidelberg 1996 Density functional theory of time-dependent phenomena E of density functional theory (DFT) is to describe an interacting many-particle system exclusively

Gross, E.K.U.

210

Density Functional Theory with Correct Long-Range Asymptotic Behavior Roi Baer1,* and Daniel Neuhauser2,  

E-Print Network [OSTI]

Density Functional Theory with Correct Long-Range Asymptotic Behavior Roi Baer1,* and Daniel within density functional theory (DFT) which spawns a class of approximations leading to correct long.043002 PACS numbers: 31.15.Ew, 31.15.Ne, 31.25.Eb, 71.15.Mb Density functional theory (DFT) [1,2] is an in

Baer, Roi

211

Electronic Structure: Density Functional Theory S. Kurth, M.A.L. Marques, and E. K. U. Gross  

E-Print Network [OSTI]

Electronic Structure: Density Functional Theory S. Kurth, M.A.L. Marques, and E. K. U. Gross: July 5, 2003) PACS numbers: 71.15.Mb, 31.15.Ew 1 #12; I. INTRODUCTION Density functional theory (DFT systems becomes prohibitive. A di#erent approach is taken in density functional theory where, instead

Gross, E.K.U.

212

Density functional theory and Kohn-Sham scheme for self-bound systems  

E-Print Network [OSTI]

We demonstrate how the separation of the total energy of a self-bound system into a functional of the internal one-body Fermionic density and a function of an arbitrary wave vector describing the center-of-mass kinetic energy can be used to set-up an "internal" Kohn-Sham scheme.

J. Messud; M. Bender; E. Suraud

2009-11-10T23:59:59.000Z

213

Isospin coupling-channel decomposition of nuclear symmetry energy in covariant density functional theory  

E-Print Network [OSTI]

The isospin coupling-channel decomposition of the potential energy density functional is carried out within the covariant density functional theory, and their isospin and density dependence in particular the influence on the symmetry energy is studied. It is found that both isospin-singlet and isospin-triplet components of the potential energy play the dominant role in deciding the symmetry energy, especially when the Fock diagram is introduced. The results illustrate a quite different mechanism to the origin of the symmetry energy from the microscopic Brueckner-Hartree-Fock theory, and demonstrate the importance of the Fork diagram in the CDF theory, especially from the isoscalar mesons, in the isospin properties of the in-medium nuclear force at high density.

Qian Zhao; Bao Yuan Sun; Wen Hui Long

2014-11-23T23:59:59.000Z

214

Isospin coupling-channel decomposition of nuclear symmetry energy in covariant density functional theory  

E-Print Network [OSTI]

The isospin coupling-channel decomposition of the potential energy density functional is carried out within the covariant density functional theory, and their isospin and density dependence in particular the influence on the symmetry energy is studied. It is found that both isospin-singlet and isospin-triplet components of the potential energy play the dominant role in deciding the symmetry energy, especially when the Fock diagram is introduced. The results illustrate a quite different mechanism to the origin of the symmetry energy from the microscopic Brueckner-Hartree-Fock theory, and demonstrate the importance of the Fork diagram in the CDF theory, especially from the isoscalar mesons, in the isospin properties of the in-medium nuclear force at high density.

Zhao, Qian; Long, Wen Hui

2014-01-01T23:59:59.000Z

215

Category:Baltimore, MD | Open Energy Information  

Open Energy Info (EERE)

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216

Density functional theory of freezing for soft interactions in two dimensions  

E-Print Network [OSTI]

A density functional theory of two-dimensional freezing is presented for a soft interaction potential that scales as inverse cube of particle distance. This repulsive potential between parallel, induced dipoles is realized for paramagnetic colloids on an interface, which are additionally exposed to an external magnetic field. An extended modified weighted density approximation which includes correct triplet correlations in the liquid state is used. The theoretical prediction of the freezing transition is in good agreement with experimental and simulation data.

Sven van Teeffelen; Christos N. Likos; Norman Hoffmann; Hartmut Lwen

2006-04-18T23:59:59.000Z

217

Stationary nature of the density-functional free energy: Application to accelerated multiple-scattering calculations  

Science Journals Connector (OSTI)

The number of operations required for conventional density-functional algorithms grows as the cube of the number of atoms, N. For large systems the computing requirements are unattainable. To overcome this limitation it is acceptable to approximate those variables with respect to which the free energy is stationary. We show that the stationarity of the free energy with respect to electron density, one-electron potential, chemical potential, occupation function, and temperature allows for very useful approximations leading to rapid and accurate determination of the free energy. Here we discuss approximations involved in calculating the finite temperature electron density needed to evaluate the Harris-Foulkes free energy. Of particular importance are (1) an electron density at each site that is based on exact solution of the Poisson equation combined with a solution of the multiple-scattering problem in which only scattering from a small cluster of sites surrounding the site in question is retained and (2) an approximate occupation function having a finite number of poles in the complex energy plane. The intention is to develop, within density-functional theory, an O(N) scalable first-principles scheme, based on spatially local multiple-scattering methods, for calculating free energies of large systems.

D. M. C. Nicholson; G. M. Stocks; Y. Wang; W. A. Shelton; Z. Szotek; W. M. Temmerman

1994-11-15T23:59:59.000Z

218

Ultra-nonlocality in density functional theory for photo-emission spectroscopy  

SciTech Connect (OSTI)

We derive an exact expression for the photocurrent of photo-emission spectroscopy using time-dependent current density functional theory (TDCDFT). This expression is given as an integral over the Kohn-Sham spectral function renormalized by effective potentials that depend on the exchange-correlation kernel of current density functional theory. We analyze in detail the physical content of this expression by making a connection between the density-functional expression and the diagrammatic expansion of the photocurrent within many-body perturbation theory. We further demonstrate that the density functional expression does not provide us with information on the kinetic energy distribution of the photo-electrons. Such information can, in principle, be obtained from TDCDFT by exactly modeling the experiment in which the photocurrent is split into energy contributions by means of an external electromagnetic field outside the sample, as is done in standard detectors. We find, however, that this procedure produces very nonlocal correlations between the exchange-correlation fields in the sample and the detector.

Uimonen, A.-M. [Department of Physics, Nanoscience Center, University of Jyvskyl, Survontie 9, 40014 Jyvskyl (Finland)] [Department of Physics, Nanoscience Center, University of Jyvskyl, Survontie 9, 40014 Jyvskyl (Finland); Stefanucci, G. [Dipartimento di Fisica, Universit di Roma Tor Vergata, Via della Ricerca Scientifica, 00133 Rome (Italy) [Dipartimento di Fisica, Universit di Roma Tor Vergata, Via della Ricerca Scientifica, 00133 Rome (Italy); INFN, Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati (Italy); European Theoretical Spectroscopy Facility (ETSF), Louvain-la Neuve (Belgium); Leeuwen, R. van [Department of Physics, Nanoscience Center, University of Jyvskyl, Survontie 9, 40014 Jyvskyl (Finland) [Department of Physics, Nanoscience Center, University of Jyvskyl, Survontie 9, 40014 Jyvskyl (Finland); European Theoretical Spectroscopy Facility (ETSF), Louvain-la Neuve (Belgium)

2014-05-14T23:59:59.000Z

219

Density functional theory for colloidal mixtures of hard platelets, rods, and spheres  

E-Print Network [OSTI]

A geometry-based density functional theory is presented for mixtures of hard spheres, hard needles and hard platelets; both the needles and the platelets are taken to be of vanishing thickness. Geometrical weight functions that are characteristic for each species are given and it is shown how convolutions of pairs of weight functions recover each Mayer bond of the ternary mixture and hence ensure the correct second virial expansion of the excess free energy functional. The case of sphere-platelet overlap relies on the same approximation as does Rosenfeld's functional for strictly two-dimensional hard disks. We explicitly control contributions to the excess free energy that are of third order in density. Analytic expressions relevant for the application of the theory to states with planar translational and cylindrical rotational symmetry, e.g. to describe behavior at planar smooth walls, are given. For binary sphere-platelet mixtures, in the appropriate limit of small platelet densities, the theory differs from that used in a recent treatment [L. Harnau and S. Dietrich, Phys. Rev. E 71, 011504 (2004)]. As a test case of our approach we consider the isotropic-nematic bulk transition of pure hard platelets, which we find to be weakly first order, with values for the coexistence densities and the nematic order parameter that compare well with simulation results.

Ansgar Esztermann; Hendrik Reich; Matthias Schmidt

2005-11-18T23:59:59.000Z

220

Calculation of the Electron Velocity Distribution Function in a Plasma Slab with Large Temperature and Density Gradients  

Science Journals Connector (OSTI)

...velocity. The distribution function for the...calculate the distribution function as a...region of the quiet Sun using several data-sets for temperature and density gradients...high-velocity tail of the distribution function. The...

1990-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Quantum Electrodynamical Density-Functional Theory: Bridging Quantum Optics and Electronic-Structure Theory  

E-Print Network [OSTI]

In this work we give a comprehensive derivation of an exact and numerically feasible method to perform ab-initio calculations of quantum particles interacting with a quantized electromagnetic field. We present a hierachy of density-functional-type theories that describe the interaction of charged particles with photons and introduce the appropriate Kohn-Sham schemes. We show how the evolution of a system described by quantum electrodynamics in Coulomb gauge is uniquely determined by its initial state and two reduced quantities. These two fundamental observables, the polarization of the Dirac field and the vector potential of the photon field, can be calculated by solving two coupled, non-linear evolution equations without the need to explicitly determine the (numerically infeasible) many-body wave function of the coupled quantum system. To find reliable approximations to the implicit functionals we present the according Kohn-Sham construction. In the non-relativistic limit this density-functional-type theory ...

Ruggenthaler, Michael; Pellegrini, Camilla; Appel, Heiko; Tokatly, Ilya V; Rubio, Angel

2014-01-01T23:59:59.000Z

222

Exchange and correlation as a functional of the local density of states  

Science Journals Connector (OSTI)

A functional Exc[?(r,?)] is presented, in which the exchange and correlation energy of an electron gas depends on the local density of occupied states. A simple local parametrization scheme is proposed, entirely from first-principles, based on the decomposition of the exchange-correlation hole in scattering states of different relative energies. In its practical Kohn-Sham-like form, the single-electron orbitals become the independent variables, and an explicit formula for the functional derivative is obtained.

Jos M. Soler

2004-05-04T23:59:59.000Z

223

Orbital-free density functional theory of out-of-plane charge screening in graphene  

E-Print Network [OSTI]

We propose a density functional theory of Thomas-Fermi-Dirac-von Weizs\\"acker type to describe the response of a single layer of graphene resting on a dielectric substrate to a point charge or a collection of point charges some distance away from the layer. We formulate a variational setting in which the proposed energy functional admits minimizers, both in the case of free graphene layers and under back-gating. We further provide conditions under which those minimizers are unique and correspond to configurations consisting of inhomogeneous density profiles of charge carrier of only one type. The associated Euler-Lagrange equation for the charge density is also obtained, and uniqueness, regularity and decay of the minimizers are proved under general conditions. In addition, a bifurcation from zero to non-zero response at a finite threshold value of the external charge is proved.

Jianfeng Lu; Vitaly Moroz; Cyrill B. Muratov

2014-05-20T23:59:59.000Z

224

Configuration mixing within the energy density functional formalism: pathologies and cures  

E-Print Network [OSTI]

Configuration mixing calculations performed in terms of the Skyrme/Gogny Energy Density Functional (EDF) rely on extending the Single-Reference energy functional into non-diagonal EDF kernels. The standard way to do so, based on an analogy with the pure Hamiltonian case and the use of the generalized Wick theorem, is responsible for the recently observed divergences and steps in Multi-Reference calculations. We summarize here the minimal solution to this problem recently proposed [Lacroix et al, arXiv:0809.2041] and applied with success to particle number restoration[Bender et al, arXiv:0809.2045]. Such a regularization method provides suitable corrections of pathologies for EDF depending on integer powers of the density. The specific case of fractional powers of the density[Duguet et al, arXiv:0809.2049] is also discussed.

Denis Lacroix; Michael Bender; Thomas Duguet

2008-11-14T23:59:59.000Z

225

A Framework to Determine the Probability Density Function for the Output Power of Wind Farms  

E-Print Network [OSTI]

A Framework to Determine the Probability Density Function for the Output Power of Wind Farms Sairaj to the power output of a wind farm while factoring in the availability of the wind turbines in the farm availability model for the wind turbines, we propose a method to determine the wind-farm power output pdf

Liberzon, Daniel

226

Generalized dynamical density functional theory for classical fluids and the significance of inertia and hydrodynamic interactions  

E-Print Network [OSTI]

We study the dynamics of a colloidal fluid including inertia and hydrodynamic interactions, two effects which strongly influence the non-equilibrium properties of the system. We derive a general dynamical density functional theory (DDFT) which shows very good agreement with full Langevin dynamics. In suitable limits, we recover existing DDFTs and a Navier-Stokes-like equation with additional non-local terms.

Benjamin D. Goddard; Andreas Nold; Nikos Savva; Grigorios A. Pavliotis; Serafim Kalliadasis

2012-08-08T23:59:59.000Z

227

Density functional study of molecular crystals: Polyethylene and a crystalline analog of bisphenol-A polycarbonate  

E-Print Network [OSTI]

Density functional study of molecular crystals: Polyethylene and a crystalline analog of bisphenol polyethylene comprising covalently bonded parallel chains with weak interchain interactions, and b reaction barriers.8 In a recent study of the interchain interactions in crystalline polyethylene PE ,9 we

228

NONPARAMETRIC FUNCTIONAL DATA ANALYSIS THROUGH BAYESIAN DENSITY ABEL RODRIGUEZ, DAVID B. DUNSON, AND ALAN E. GELFAND  

E-Print Network [OSTI]

1 NONPARAMETRIC FUNCTIONAL DATA ANALYSIS THROUGH BAYESIAN DENSITY ESTIMATION ABEL RODR´IGUEZ, DAVID in the north Atlantic. 1 Abel Rodriguez is Ph.D. candidate, Institute of Statistics and Decision Sciences, Duke@niehs.nih.gov. Alan E. Gelfand is James B. Duke professor, Institute of Statistics and Decision Sciences

West, Mike

229

Application of the velocity-dissipation probability density function model to inhomogeneous turbulent flows  

E-Print Network [OSTI]

Application of the velocity-dissipation probability density function model to inhomogeneous. Fluids A 2, 1437 ( 1990) ] developed a turbulence model based on the one-point Eulerian joint probability were constructed by reference to the known statistics of homogenous turbulence, and the applicability

230

Reactions of Polycarbonate with Cyclohexene Oxide and Phosphites: A Density Functional Study  

E-Print Network [OSTI]

bisphenol A polycarbonate (BPA-PC). We describe density functional (DF) calculations of the reactions of cyclohexene oxide (CHO, cyclohexane epoxide) and phosphites with chain segments of BPA- PC, with the aim to organic molecules and polymers, focusing on bisphenol A polycarbonate (BPA-PC). BPA-PC is an important

231

Density Functional Theory Studies of the Structure Sensitivity of Ethanol Oxidation on Palladium Surfaces  

E-Print Network [OSTI]

Density Functional Theory Studies of the Structure Sensitivity of Ethanol Oxidation on PalladiumVised Manuscript ReceiVed: May 04, 2010 In this work, the adsorption behaviors and oxidation mechanisms of ethanol palladium surfaces, the adsorption behaviors, and the first step dehydrogenation of ethanol, it is found

Zhao, Tianshou

232

Characterization of the nitrogen split interstitial defect in wurtzite aluminum nitride using density functional theory  

SciTech Connect (OSTI)

We carried out Heyd-Scuseria-Ernzerhof hybrid density functional theory plane wave supercell calculations in wurtzite aluminum nitride in order to characterize the geometry, formation energies, transition levels, and hyperfine tensors of the nitrogen split interstitial defect. The calculated hyperfine tensors may provide useful fingerprint of this defect for electron paramagnetic resonance measurement.

Szlls, A., E-mail: szallas.attila@wigner.mta.hu [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Szsz, K. [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Institute of Physics, Etvs University, Pzmny Pter stny 1/A, H-1117 Budapest (Hungary); Trinh, X. T.; Son, N. T.; Janzn, E. [Department of Physics, Chemistry and Biology, Linkping University, SE-581 83 Linkping (Sweden); Gali, A., E-mail: gali.adam@wigner.mta.hu [Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest (Hungary); Department of Atomic Physics, Budapest University of Technology and Economics, Budafoki t 8, H-1111 Budapest (Hungary)

2014-09-21T23:59:59.000Z

233

Relativistic density functional theory modeling of plutonium and americium higher oxide molecules  

E-Print Network [OSTI]

Relativistic density functional theory modeling of plutonium and americium higher oxide molecules of plutonium and americium higher oxide molecules Andréi Zaitsevskii,1,2,a) Nikolai S. Mosyagin,2,3 Anatoly V of plutonium and americium higher oxide molecules (actinide oxidation states VI through VIII) by two

Titov, Anatoly

234

Fluorescence of PRODAN in Water: a Computational QM/MM MD Study  

SciTech Connect (OSTI)

Fluorescent properties of PRODAN (6-propionyl-2-dimethylaminonaphthalene) in water were studied by means of excited state molecular dynamics simulations employing a combined quantum mechanical and molecular mechanical approach with the time-dependent density functional theory (TD-DFT QM/MM MD). The state of the art coupled cluster method was used to benchmark density functional theory calculations. The influence of the water environment on PRODAN emission was investigated by employing several computational schemes with varying description of the solvent. The issue of the molecular geometry of the excited state PRODAN molecule in water was addressed. The experimental emission spectrum was reproduced for the planar excited state conformer of PRODAN in the extended environment of 300 explicit water molecules. The planar conformer was shown to be predominantly responsible for fluorescence. The twisted isomer is strongly stabilized in water, but rapidly evolve towards a conical intersection, and hence the twisted conformer is fluorescently inactive.

Pederzoli, Marek; Sobek, Lukas; Brabec, Jiri; Kowalski, Karol; Cwiklik, Lukasz; Pittner, Jiri

2014-03-28T23:59:59.000Z

235

The 2dF Galaxy Redshift Survey: luminosity functions by density environment and galaxy type  

E-Print Network [OSTI]

We use the 2dF Galaxy Redshift Survey to measure the dependence of the bJ-band galaxy luminosity function on large-scale environment, defined by density contrast in spheres of radius 8h-1Mpc, and on spectral type, determined from principal component analysis. We find that the galaxy populations at both extremes of density differ significantly from that at the mean density. The population in voids is dominated by late types and shows, relative to the mean, a deficit of galaxies that becomes increasingly pronounced at magnitudes brighter than M_bJ-5log10h <-18.5. In contrast, cluster regions have a relative excess of very bright early-type galaxies with M_bJ-5log10h < -21. Differences in the mid to faint-end population between environments are significant: at M_bJ-5log10h=-18 early and late-type cluster galaxies show comparable abundances, whereas in voids the late types dominate by almost an order of magnitude. We find that the luminosity functions measured in all density environments, from voids to clusters, can be approximated by Schechter functions with parameters that vary smoothly with local density, but in a fashion which differs strikingly for early and late-type galaxies. These observed variations, combined with our finding that the faint-end slope of the overall luminosity function depends at most weakly on density environment, may prove to be a significant challenge for models of galaxy formation.

Darren J. Croton; Glennys R. Farrar; Peder Norberg; Matthew Colless; John A. Peacock; I. K. Baldry; C. M. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; S. Cole; C. Collins; W. Couch; G. Dalton; R. De Propris; S. P. Driver; G. Efstathiou; R. S. Ellis; C. S. Frenk; K. Glazebrook; C. Jackson; O. Lahav; I. Lewis; S. Lumsden; S. Maddox; D. Madgwick; B. A. Peterson; W. Sutherland; K. Taylor

2005-02-08T23:59:59.000Z

236

Modifying the variational principle in the action integral functional derivation of time-dependent density functional theory  

E-Print Network [OSTI]

According to a recent paper by G. Vignale [Phys. Rev. A 77, 062511 (2008), arXiv:0803.2727], the problems arising in the original derivation of time-dependent density functional theory (TDDFT) based on the Runge-Gross (RG) action-integral functional (AIF) are due to an incorrect variational principle (VP). This argument and the proposed modification of the VP are critically analyzed. The more fundamental problem, though, is the indefiniteness of the RG AIF. In contrast to a widely held belief, that indefiniteness is not eliminated in the variational procedure, which unwittingly is corroborated by Vignale's initial point.

J. Schirmer

2010-10-20T23:59:59.000Z

237

Fundamental gaps with approximate density functionals: The derivative discontinuity revealed from ensemble considerations  

SciTech Connect (OSTI)

The fundamental gap is a central quantity in the electronic structure of matter. Unfortunately, the fundamental gap is not generally equal to the Kohn-Sham gap of density functional theory (DFT), even in principle. The two gaps differ precisely by the derivative discontinuity, namely, an abrupt change in slope of the exchange-correlation energy as a function of electron number, expected across an integer-electron point. Popular approximate functionals are thought to be devoid of a derivative discontinuity, strongly compromising their performance for prediction of spectroscopic properties. Here we show that, in fact, all exchange-correlation functionals possess a derivative discontinuity, which arises naturally from the application of ensemble considerations within DFT, without any empiricism. This derivative discontinuity can be expressed in closed form using only quantities obtained in the course of a standard DFT calculation of the neutral system. For small, finite systems, addition of this derivative discontinuity indeed results in a greatly improved prediction for the fundamental gap, even when based on the most simple approximate exchange-correlation density functional the local density approximation (LDA). For solids, the same scheme is exact in principle, but when applied to LDA it results in a vanishing derivative discontinuity correction. This failure is shown to be directly related to the failure of LDA in predicting fundamental gaps from total energy differences in extended systems.

Kraisler, Eli; Kronik, Leeor [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100 (Israel)] [Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100 (Israel)

2014-05-14T23:59:59.000Z

238

Effective electron displacements: A tool for time-dependent density functional theory computational spectroscopy  

SciTech Connect (OSTI)

We extend our previous definition of the metric ?r for electronic excitations in the framework of the time-dependent density functional theory [C. A. Guido, P. Cortona, B. Mennucci, and C. Adamo, J. Chem. Theory Comput. 9, 3118 (2013)], by including a measure of the difference of electronic position variances in passing from occupied to virtual orbitals. This new definition, called ?, permits applications in those situations where the ?r-index is not helpful: transitions in centrosymmetric systems and Rydberg excitations. The ?-metric is then extended by using the Natural Transition Orbitals, thus providing an intuitive picture of how locally the electron density changes during the electronic transitions. Furthermore, the ? values give insight about the functional performances in reproducing different type of transitions, and allow one to define a confidence radius for GGA and hybrid functionals.

Guido, Ciro A., E-mail: ciro.guido@ecp.fr; Cortona, Pietro [Laboratoire Structures, Proprits et Modlisation des Solides (SPMS), CNRS UMR 8580, cole Centrale Paris, Grande Voie des Vignes, F-92295 Chtenay-Malabry (France)] [Laboratoire Structures, Proprits et Modlisation des Solides (SPMS), CNRS UMR 8580, cole Centrale Paris, Grande Voie des Vignes, F-92295 Chtenay-Malabry (France); Adamo, Carlo [Laboratoire dlectrochimie, Chimie des Interfaces et Modlisation pour lEnergie, CNRS UMR-7575, Chimie ParisTech, 11 rue P. et M. Curie, F-75231 Paris Cedex 05 (France) [Laboratoire dlectrochimie, Chimie des Interfaces et Modlisation pour lEnergie, CNRS UMR-7575, Chimie ParisTech, 11 rue P. et M. Curie, F-75231 Paris Cedex 05 (France); Institut Universitaire de France, 103 Bd Saint-Michel, F-75005 Paris (France)

2014-03-14T23:59:59.000Z

239

Double-hybrid density-functional theory applied to molecular crystals  

E-Print Network [OSTI]

We test the performance of a number of two- and one-parameter double-hybrid approximations, combining semilocal exchange-correlation density functionals with periodic local second-order M{\\o}ller-Plesset (LMP2) perturbation theory, for calculating lattice energies of a set of molecular crystals: urea, formamide, ammonia, and carbon dioxide. All double-hybrid methods perform better on average than the corresponding Kohn-Sham calculations with the same functionals, but generally not better than standard LMP2. The one-parameter double-hybrid approximations based on the PBEsol density functional gives lattice energies per molecule with an accuracy of about 6 kJ/mol, which is similar to the accuracy of LMP2. This conclusion is further verified on molecular dimers and on the hydrogen cyanide crystal.

Sharkas, Kamal; Maschio, Lorenzo; Civalleri, Bartolomeo

2014-01-01T23:59:59.000Z

240

Density Functional Study of Perovskite Superconductor MgCNi{sub 3}  

SciTech Connect (OSTI)

We here report the first principle density functional study of MgCNi{sub 3} which crystallize in cubic perovskite structure having critical transition temperature of 8 K. The interesting aspect of this compound is that in normal state it is non magnetic in nature despite conduction electrons in it are derived from partially filled Ni d states, which typically lead to ferromagnetism in metallic Ni and many Ni-based binary alloys. To investigate the detailed microscopic origin of the non magnetic nature we have done density functional based calculations on this compound. The lattice constant is calculated using minimum energy criteria from total energy versus lattice constant plot. By taking the calculated values of lattice constant we have done the precise calculations on the compound using Full Potential Linear Augmented Plane Wave (FP-LAPW) method implemented in ELK code. The electronic density of states is found spin degenerate that corresponds to a non-magnetic ground state. The density of states (DOS) at Fermi level, N(E{sub F}) is dominated by Ni-d states. The sharp peak observed just below Fermi level corresponds to van Hove singularity (vHs). The projected density of states (PDOS) suggests a strong hybridization of Ni-3d and C-2p states which is responsible for the observed non magnetic nature of MgCNi{sub 3}.

Kumar, Jagdish [Quantum Phenomena and Application Division, National Physical Laboratory, New Delhi-110012 (India); Department of Physics, Himachal Pradesh University, Shimla-171005 (India); Sharma, Devina [Quantum Phenomena and Application Division, National Physical Laboratory, New Delhi-110012 (India); Department of Physics, Panjab University Chandigarah-160014 (India); Kumar, Ranjan [Department of Physics, Panjab University Chandigarah-160014 (India); Awana, V. P. S. [Quantum Phenomena and Application Division, National Physical Laboratory, New Delhi-110012 (India); Ahluwalia, P. K. [Department of Physics, Himachal Pradesh University, Shimla-171005 (India)

2011-12-12T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Role of exchange in density-functional theory for weakly interacting systems: Quantum Monte Carlo analysis of electron density and interaction energy  

E-Print Network [OSTI]

We analyze the density-functional theory (DFT) description of weak interactions by employing diffusion and reptation quantum Monte Carlo (QMC) calculations, for a set of benzene-molecule complexes. While the binding energies ...

Grossman, Jeffrey C.

242

Why do ultrasoft repulsive particles cluster and crystallize? Analytical results from density functional theory  

E-Print Network [OSTI]

We demonstrate the accuracy of the hypernetted chain closure and of the mean-field approximation for the calculation of the fluid-state properties of systems interacting by means of bounded and positive-definite pair potentials with oscillating Fourier transforms. Subsequently, we prove the validity of a bilinear, random-phase density functional for arbitrary inhomogeneous phases of the same systems. On the basis of this functional, we calculate analytically the freezing parameters of the latter. We demonstrate explicitly that the stable crystals feature a lattice constant that is independent of density and whose value is dictated by the position of the negative minimum of the Fourier transform of the pair potential. This property is equivalent with the existence of clusters, whose population scales proportionally to the density. We establish that regardless of the form of the interaction potential and of the location on the freezing line, all cluster crystals have a universal Lindemann ratio L = 0.189 at freezing. We further make an explicit link between the aforementioned density functional and the harmonic theory of crystals. This allows us to establish an equivalence between the emergence of clusters and the existence of negative Fourier components of the interaction potential. Finally, we make a connection between the class of models at hand and the system of infinite-dimensional hard spheres, when the limits of interaction steepness and space dimension are both taken to infinity in a particularly described fashion.

Christos N. Likos; Bianca M. Mladek; Dieter Gottwald; Gerhard Kahl

2007-02-22T23:59:59.000Z

243

Density-functional electronic structure of PuCoGa5  

Science Journals Connector (OSTI)

Density-functional electronic-structure calculations for PuCoGa5 are performed to address the possibility of magnetic interactions in this high-temperature superconductor. Within an itinerant 5f-electron picture, cohesion and crystallographic parameters compares favorably with experiment, whereas only when spin and orbital interactions are accounted for the calculated electronic density of states agrees with photoemission spectra. This fact suggests that spin and orbital correlations are important for a correct description of the PuCoGa5 electronic structure and may play a role in an unconventional mechanism for superconductivity.

P. Sderlind

2004-09-24T23:59:59.000Z

244

Dynamical density functional theory for the diffusion of injected Brownian particles  

E-Print Network [OSTI]

While the theory of diffusion of a single Brownian particle in confined geometries is well-established by now, we discuss here the theoretical framework necessary to generalize the theory of diffusion to dense suspensions of strongly interacting Brownian particles. Dynamical density functional theory (DDFT) for classical Brownian particles represents an ideal tool for this purpose. After outlining the basic ingredients to DDFT we show that it can be readily applied to flowing suspensions with time-dependent particle sources. Particle interactions lead to considerable layering in the mean density profiles, a feature that is absent in the trivial case of noninteracting, freely diffusing particles. If the particle injection rate varies periodically in time with a suitable frequency, a resonance in the layering of the mean particle density profile is predicted.

H. Lwen; M. Heinen

2014-09-08T23:59:59.000Z

245

Electronic and structural properties of ultrathin tungsten nanowires and nanotubes by density functional theory calculation  

SciTech Connect (OSTI)

The simulated annealing basin-hopping method incorporating the penalty function was used to predict the lowest-energy structures for ultrathin tungsten nanowires and nanotubes of different sizes. These predicted structures indicate that tungsten one-dimensional structures at this small scale do not possess B.C.C. configuration as in bulk tungsten material. In order to analyze the relationship between multi-shell geometries and electronic transfer, the electronic and structural properties of tungsten wires and tubes including partial density of state and band structures which were determined and analyzed by quantum chemistry calculations. In addition, in order to understand the application feasibility of these nanowires and tubes on nano-devices such as field emitters or chemical catalysts, the electronic stability of these ultrathin tungsten nanowires was also investigated by density functional theory calculations.

Sun, Shih-Jye [Department of Applied Physics, National University of Kaohsiung, Kaohsiung 811, Taiwan (China); Lin, Ken-Huang; Li, Jia-Yun [Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Ju, Shin-Pon, E-mail: jushin-pon@mail.nsysu.edu.tw [Department of Mechanical and Electro-Mechanical Engineering, National Sun Yat-Sen University, Kaohsiung 804, Taiwan (China); Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan (China)

2014-10-07T23:59:59.000Z

246

Singlet-Triplet Energy Gaps for Diradicals from Fractional-Spin Density-Functional Theory  

SciTech Connect (OSTI)

Open-shell singlet diradicals are difficult to model accurately within conventional Kohn?Sham (KS) density-functional theory (DFT). These methods are hampered by spin contamination because the KS determinant wave function is neither a pure spin state nor an eigenfunction of the S2 operator. Here we present a theoretical foray for using single-reference closed-shell ground states to describe diradicals by fractional-spin DFT (FS-DFT). This approach allows direct, self-consistent calculation of electronic properties using the electron density corresponding to the proper spin eigenfunction. The resulting FS-DFT approach is benchmarked against diradical singlet?triplet gaps for atoms and small molecules. We have also applied FS-DFT to the singlet?triplet gaps of hydrocarbon polyacenes.

Ess, Daniel H.; Johnson, E R; Hu, Xiangqian; Yang, W T

2011-01-01T23:59:59.000Z

247

Density functional theory for hard-sphere mixtures: the White-Bear version Mark II  

E-Print Network [OSTI]

In the spirit of the White-Bear version of fundamental measure theory we derive a new density functional for hard-sphere mixtures which is based on a recent mixture extension of the Carnahan-Starling equation of state. In addition to the capability to predict inhomogeneous density distributions very accurately, like the original White-Bear version, the new functional improves upon consistency with an exact scaled-particle theory relation in the case of the pure fluid. We examine consistency in detail within the context of morphological thermodynamics. Interestingly, for the pure fluid the degree of consistency of the new version is not only higher than for the original White-Bear version but also higher than for Rosenfeld's original fundamental measure theory.

Hendrik Hansen-Goos; Roland Roth

2006-07-27T23:59:59.000Z

248

Uncertainty Quantification for Nuclear Density Functional Theory and Information Content of New Measurements  

E-Print Network [OSTI]

Statistical tools of uncertainty quantification can be used to assess the information content of measured observables with respect to present-day theoretical models; to estimate model errors and thereby improve predictive capability; to extrapolate beyond the regions reached by experiment; and to provide meaningful input to applications and planned measurements. To showcase new opportunities offered by such tools, we make a rigorous analysis of theoretical statistical uncertainties in nuclear density functional theory using Bayesian inference methods. By considering the recent mass measurements from the Canadian Penning Trap at Argonne National Laboratory, we demonstrate how the Bayesian analysis and a direct least-squares optimization, combined with high-performance computing, can be used to assess the information content of the new data with respect to a model based on the Skyrme energy density functional approach. Employing the posterior probability distribution computed with a Gaussian process emulator, w...

McDonnell, J D; Higdon, D; Sarich, J; Wild, S M; Nazarewicz, W

2015-01-01T23:59:59.000Z

249

Toward understanding the exchange-correlation energy and total-energy density functionals  

Science Journals Connector (OSTI)

If an accurate ground-state electron density ?0 for a system is known, it is shown from calculations on atoms that a strikingly good estimate for the total electronic energy of atoms is provided by the formula E[?0]=tsumi?i-(1-1/N)J[?0], where N is the number of electrons, J[?0] is the classical Coulomb repulsion energy for ?0, and the ?i are the Kohn-Sham orbital energies determined by the Zhao-Morrison-Parr procedure [Phys. Rev. A 50, 2138 (1994)] for implementation of the Levy-constrained search determination of the Kohn-Sham kinetic energy. The surprising accuracy of this formula is attributed to the fact that the exchange-correlation functional is equal to -J/N plus a functional that behaves as if it were approximately homogeneous, of degree 1 in the electron density. A corresponding exact formula is given, and various approximate models are constructed.

Robert G. Parr and Swapan K. Ghosh

1995-05-01T23:59:59.000Z

250

van der Waals forces in density functional theory: The vdW-DF method  

E-Print Network [OSTI]

A density functional theory (DFT) that accounts for van der Waals (vdW) interactions in condensed matter, materials physics, chemistry, and biology is reviewed. The insights that led to the construction of the Rutgers-Chalmers van der Waals Density Functional (vdW-DF) are presented with the aim of giving a historical perspective, while also emphasising more recent efforts which have sought to improve its accuracy. In addition to technical details, we discuss a range of recent applications that illustrate the necessity of including dispersion interactions in DFT. This review highlights the value of the vdW-DF method as a general-purpose method, not only for dispersion bound systems, but also in densely packed systems where these types of interactions are traditionally thought to be negligible.

Berland, Kristian; Lee, Kyuho; Schrder, Elsebeth; Thonhauser, T; Hyldgaard, Per; Lundqvist, Bengt I

2014-01-01T23:59:59.000Z

251

Energy-density-functional calculations including the proton-neutron mixing  

E-Print Network [OSTI]

We present results of calculations based on the Skyrme energy density functional including the arbitrary mixing between protons and neutrons. In this framework, single-particle states are superpositions of proton and neutron components and the energy density functional is fully invariant with respect to three-dimensional rotations in the isospin space. The isospin of the system is controlled by means of the isocranking method, which carries over the standard cranking approach to the isospin space. We show numerical results of the isocranking calculations performed for isobaric analogue states in the A=14 and $A=40-56$ nuclei. We also present such results obtained for high-isospin states in $^{48}$Cr, with constraints on the isospin implemented by using the augmented Lagrange method.

Koichi Sato; Jacek Dobaczewski; Takashi Nakatsukasa; Wojciech Satu?a

2013-08-08T23:59:59.000Z

252

Using the electron localization function to correct for confinement physics in semi-local density functional theory  

SciTech Connect (OSTI)

We have previously proposed that further improved functionals for density functional theory can be constructed based on the Armiento-Mattsson subsystem functional scheme if, in addition to the uniform electron gas and surface models used in the Armiento-Mattsson 2005 functional, a model for the strongly confined electron gas is also added. However, of central importance for this scheme is an index that identifies regions in space where the correction provided by the confined electron gas should be applied. The electron localization function (ELF) is a well-known indicator of strongly localized electrons. We use a model of a confined electron gas based on the harmonic oscillator to show that regions with high ELF directly coincide with regions where common exchange energy functionals have large errors. This suggests that the harmonic oscillator model together with an index based on the ELF provides the crucial ingredients for future improved semi-local functionals. For a practical illustration of how the proposed scheme is intended to work for a physical system we discuss monoclinic cupric oxide, CuO. A thorough discussion of this system leads us to promote the cell geometry of CuO as a useful benchmark for future semi-local functionals. Very high ELF values are found in a shell around the O ions, and take its maximum value along the CuO directions. An estimate of the exchange functional error from the effect of electron confinement in these regions suggests a magnitude and sign that could account for the error in cell geometry.

Hao, Feng, E-mail: hfeng413@gmail.com; Mattsson, Ann E., E-mail: aematts@sandia.gov [Multi-Scale Science MS 1322, Sandia National Laboratories, Albuquerque, New Mexico 87185-1322 (United States); Armiento, Rickard [Department of Physics, Chemistry and Biology (IFM), Linkping University, SE-58183 Linkping (Sweden)] [Department of Physics, Chemistry and Biology (IFM), Linkping University, SE-58183 Linkping (Sweden)

2014-05-14T23:59:59.000Z

253

Nuclear energy density functionals: what we can learn about/from their global performance?  

E-Print Network [OSTI]

A short review of recent results on the global performance of covariant energy density functionals is presented. It is focused on the analysis of the accuracy of the description of physical observables of ground and excited states as well as to related theoretical uncertainties. In addition, a global analysis of pairing properties is presented and the impact of pairing on the position of two-neutron drip line is discussed.

Afanasjev, A V; Ray, D; Ring, P

2015-01-01T23:59:59.000Z

254

Structure of a liquid crystalline fluid around a macroparticle: Density functional theory study  

E-Print Network [OSTI]

The structure of a molecular liquid, in both the nematic liquid crystalline and isotropic phases, around a cylindrical macroparticle, is studied using density functional theory. In the nematic phase the structure of the fluid is highly anisotropic with respect to the director, in agreement with results from simulation and phenomenological theories. On going into the isotropic phase the structure becomes rotationally invariant around the macroparticle with an oriented layer at the surface.

David L. Cheung; Michael P. Allen

2006-04-10T23:59:59.000Z

255

Reformulation of nonperturbative density-functional theories of classical nonuniform systems  

Science Journals Connector (OSTI)

It is shown that most nonperturbative density-functional theories of classical systems can be reformulated as second-order truncations of exact perturbative expansions, thus eliminating the ad hoc nature of such theories. This reformulation is used as a basis for discussion as to why some theories work better than others when applied to hard spheres, why most theories perform poorly for continuous potentials, and in what direction they might be modified so as to improve their performance.

J. F. Lutsko

1991-04-15T23:59:59.000Z

256

Steam Reforming on Transition-metal Carbides from Density-functional Theory  

SciTech Connect (OSTI)

A screening study of the steam reforming reaction on clean and oxygen covered early transition-metal carbides surfaces is performed by means of density-functional theory calculations. It is found that carbides provide a wide spectrum of reactivities, from too reactive via suitable to too inert. Several molybdenum-based systems are identified as possible steam reforming catalysts. The findings suggest that carbides provide a playground for reactivity tuning, comparable to the one for pure metals.

Vojvodic, Aleksandra

2012-05-11T23:59:59.000Z

257

Linear-response calculation in the time-dependent density functional theory  

SciTech Connect (OSTI)

Linear response calculations based on the time-dependent density-functional theory are presented. Especially, we report results of the finite amplitude method which we have recently proposed as an alternative and feasible approach to the (quasiparticle-)random-phase approximation. Calculated properties of the giant resonances and low-energy E1 modes are discussed. We found a universal linear correlation between the low-energy E1 strength and the neutron skin thickness.

Nakatsukasa, Takashi; Inakura, Tsunenori; Avogadro, Paolo; Ebata, Shuichiro; Sato, Koichi; Yabana, Kazuhiro [RIKEN Nishina Center, Wako-shi 351-0198, Japan and Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); RIKEN Nishina Center, Wako-shi 351-0198 (Japan); Departimento di Fisica, Universita degli Studi di Milano, via Celoria 16, 20133 Milan (Italy) and RIKEN Nishina Center, Wako-shi 351-0198 (Japan); Center for Nuclear Study, University of Tokyo, Bunkyo-ku, 113-0033, Japan and RIKEN Nishina Center, Wako-shi 351-0198 (Japan); RIKEN Nishina Center, Wako-shi 351-0198 (Japan); Center for Computational Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan) and RIKEN Nishina Center, Wako-shi 351-0198 (Japan)

2012-11-12T23:59:59.000Z

258

Covariance analysis of finite temperature density functional theory: symmetric nuclear matter  

E-Print Network [OSTI]

We study symmetric nuclear matter at finite temperature, with particular emphasis on the liquid-gas phase transition. We use a standard covariance analysis to propagate statistical uncertainties from the density functional to the thermodynamic properties. We use four functionals with known covariance matrices to obtain as wide a set of results as possible. Our findings suggest that thermodynamical properties are very well constrained by fitting data at zero temperature. The propagated statistical errors in the liquid-gas phase transition parameters are relatively small.

A. Rios; X. Roca-Maza

2014-08-21T23:59:59.000Z

259

Coarse-grained spin density-functional theory: infinite-volume limit via the hyperfinite  

E-Print Network [OSTI]

Coarse-grained spin density functional theory (SDFT) is a version of SDFT which works with number/spin densities specified to a limited resolution --- averages over cells of a regular spatial partition --- and external potentials constant on the cells. This coarse-grained setting facilitates a rigorous investigation of the mathematical foundations which goes well beyond what is currently possible in the conventional formualation. Problems of existence, uniqueness and regularity of representing potentials in the coarse-grained SDFT setting are here studied using techniques of (Robinsonian) nonstandard analysis. Every density which is nowhere spin-saturated is V-representable, and the set of representing potentials is the functional derivative, in an appropriate generalized sense, of the Lieb interal energy functional. Quasi-continuity and closure properties of the set-valued representing potentials map are also established. The extent of possible non-uniqueness is similar to that found in non-rigorous studies of the conventional theory, namely non-uniqueness can occur for states of collinear magnetization which are eigenstates of $S_z$.

Paul E. Lammert

2015-02-09T23:59:59.000Z

260

Real-time linear response for time-dependent density-functional theory Department of Physical Chemistry and the Lise Meitner Minerva-Center for Quantum Chemistry,  

E-Print Network [OSTI]

Real-time linear response for time-dependent density-functional theory Roi Baer Department a linear-response approach for time-dependent density-functional theories using time-adiabatic functionals ground state. This ground state can be treated using density-functional theory, where the density n0(r) 2

Baer, Roi

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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261

Density Functional Calculations of ATP Systems. 2. ATP Hydrolysis at the Active Site of J. Akola and R. O. Jones*  

E-Print Network [OSTI]

Density Functional Calculations of ATP Systems. 2. ATP Hydrolysis at the Active Site of Actin J-triphosphate (ATP) at the active site of actin has been studied using density functional calculations. The active site is modeled by the triphosphate tail of ATP, an Mg cation, surrounding water molecules

262

Kohn-Sham Kinetic Energy Density in the Nuclear and Asymptotic Regions: Deviations from the Von Weizs\\"acker Behavior and Applications to Density Functionals  

E-Print Network [OSTI]

We show that the Kohn-Sham positive-definite kinetic energy (KE) density significantly differs from the von Weizs\\"acker (VW) one at the nuclear cusp as well as in the asymptotic region. At the nuclear cusp, the VW functional is shown to be linear and the contribution of p-type orbitals to the KE density is theoretically derived and numerically demonstrated in the limit of infinite nuclear charge, as well in the semiclassical limit of neutral large atoms. In the latter case, it reaches 12 of the KE density. In the asymptotic region we find new exact constraints for meta Generalized Gradient Approximation (meta-GGA) exchange functionals: with an exchange enhancement factor proportional to $\\sqrt{\\alpha}$, where $\\alpha$ is the common meta-GGA ingredient, both the exchange energy density and the potential are proportional to the exact ones. In addition, this describes exactly the large-gradient limit of quasi-two dimensional systems.

Della Sala, F; Constantin, L A

2014-01-01T23:59:59.000Z

263

Localized form of Fock terms in nuclear covariant density functional theory  

E-Print Network [OSTI]

In most of the successful versions of covariant density functional theory in nuclei, the Fock terms are not included explicitly, which leads to local functionals and forms the basis of their widespread applicability at present. However, it has serious consequences for the description of Gamow-Teller resonances (GTR) and spin-dipole resonances (SDR) which can only be cured by adding further phenomenological parameters. Relativistic Hartree-Fock models do not suffer from these problems. They can successfully describe the GTR and SDR as well as the isovector part of the Dirac effective mass without any additional parameters. However, they are non-local and require considerable numerical efforts. By the zero-range reduction and the Fierz transformation, a new method is proposed to take into account the Fock terms in local functionals, which retains the simplicity of conventional models and provides proper descriptions of the spin-isospin channels and the Dirac masses.

Haozhao Liang; Pengwei Zhao; Peter Ring; Xavier Roca-Maza; Jie Meng

2012-07-26T23:59:59.000Z

264

Correlated density-dependent chiral forces for infinite-matter calculations within the Green's function approach  

Science Journals Connector (OSTI)

The properties of symmetric nuclear and pure neutron matter are investigated within an extended self-consistent Green's function method that includes the effects of three-body forces. We use the ladder approximation for the study of infinite nuclear matter and incorporate the three-body interaction by means of a density-dependent two-body force. This force is obtained via a correlated average over the third particle, with an in-medium propagator consistent with the many-body calculation we perform. We analyze different prescriptions in the construction of the average and conclude that correlations provide small modifications at the level of the density-dependent force. Microscopic as well as bulk properties are studied, focusing on the changes introduced by the density-dependent two-body force. The total energy of the system is obtained by means of a modified Galitskii-Migdal-Koltun sum rule. Our results validate previously used uncorrelated averages and extend the availability of chirally motivated forces to a larger density regime.

Arianna Carbone; Arnau Rios; Artur Polls

2014-11-18T23:59:59.000Z

265

Correlated density-dependent chiral forces for infinite matter calculations within the Green's function approach  

E-Print Network [OSTI]

The properties of symmetric nuclear and pure neutron matter are investigated within an extended self-consistent Green's function method that includes the effects of three-body forces. We use the ladder approximation for the study of infinite nuclear matter and incorporate the three-body interaction by means of a density-dependent two-body force. This force is obtained via a correlated average over the third particle, with an in-medium propagator consistent with the many-body calculation we perform. We analyze different prescriptions in the construction of the average and conclude that correlations provide small modifications at the level of the density-dependent force. Microscopic as well as bulk properties are studied, focusing on the changes introduced by the density dependent two-body force. The total energy of the system is obtained by means of a modified Galitskii-Migdal-Koltun sum rule. Our results validate previously used uncorrelated averages and extend the availability of chirally motivated forces to a larger density regime.

Arianna Carbone; Arnau Rios; Artur Polls

2014-08-04T23:59:59.000Z

266

Thermally-assisted-occupation density functional theory with generalized-gradient approximations  

SciTech Connect (OSTI)

We extend the recently proposed thermally-assisted-occupation density functional theory (TAO-DFT) [J.-D. Chai, J. Chem. Phys. 136, 154104 (2012)] to generalized-gradient approximation (GGA) exchange-correlation density functionals. Relative to our previous TAO-LDA (i.e., the local density approximation to TAO-DFT), the resulting TAO-GGAs are significantly superior for a wide range of applications, such as thermochemistry, kinetics, and reaction energies. For noncovalent interactions, TAO-GGAs with empirical dispersion corrections are shown to yield excellent performance. Due to their computational efficiency for systems with strong static correlation effects, TAO-LDA and TAO-GGAs are applied to study the electronic properties (e.g., the singlet-triplet energy gaps, vertical ionization potentials, vertical electron affinities, fundamental gaps, and symmetrized von Neumann entropy) of acenes with different number of linearly fused benzene rings (up to 100), which is very challenging for conventional electronic structure methods. The ground states of acenes are shown to be singlets for all the chain lengths studied here. With the increase of acene length, the singlet-triplet energy gaps, vertical ionization potentials, and fundamental gaps decrease monotonically, while the vertical electron affinities and symmetrized von Neumann entropy (i.e., a measure of polyradical character) increase monotonically.

Chai, Jeng-Da, E-mail: jdchai@phys.ntu.edu.tw [Department of Physics, Center for Theoretical Sciences, and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)] [Department of Physics, Center for Theoretical Sciences, and Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

2014-05-14T23:59:59.000Z

267

Enhanced von Weizscker Wang-Govind-Carter kinetic energy density functional for semiconductors  

SciTech Connect (OSTI)

We propose a new form of orbital-free (OF) kinetic energy density functional (KEDF) for semiconductors that is based on the Wang-Govind-Carter (WGC99) nonlocal KEDF. We enhance within the latter the semi-local von Weizscker KEDF term, which is exact for a single orbital. The enhancement factor we introduce is related to the extent to which the electron density is localized. The accuracy of the new KEDF is benchmarked against Kohn-Sham density functional theory (KSDFT) by comparing predicted energy differences between phases, equilibrium volumes, and bulk moduli for various semiconductors, along with metal-insulator phase transition pressures. We also compare point defect and (100) surface energies in silicon for a broad test of its applicability. This new KEDF accurately reproduces the exact non-interacting kinetic energy of KSDFT with only one additional adjustable parameter beyond the three parameters in the WGC99 KEDF; it exhibits good transferability between semiconducting to metallic silicon phases and between various III-V semiconductors without parameter adjustment. Overall, this KEDF is more accurate than previously proposed OF KEDFs (e.g., the Huang-Carter (HC) KEDF) for semiconductors, while the computational efficiency remains at the level of the WGC99 KEDF (several hundred times faster than the HC KEDF). This accurate, fast, and transferable new KEDF holds considerable promise for large-scale OFDFT simulations of metallic through semiconducting materials.

Shin, Ilgyou [Department of Chemistry, Princeton University, Princeton, New Jersey 08544-1009 (United States)] [Department of Chemistry, Princeton University, Princeton, New Jersey 08544-1009 (United States); Carter, Emily A., E-mail: eac@princeton.edu [Department of Mechanical and Aerospace Engineering, Program in Applied and Computational Mathematics, and Andlinger Center for Energy and the Environment, Princeton University, Princeton, New Jersey 08544-5263 (United States)

2014-05-14T23:59:59.000Z

268

Testing time-dependent density functional theory with depopulated molecular orbitals for predicting electronic excitation energies of valence, Rydberg, and charge-transfer  

E-Print Network [OSTI]

Testing time-dependent density functional theory with depopulated molecular orbitals for predicting functionals for time-dependent density functional theory calculations of valence and Rydberg electronic functional that performs well for both ground-state properties and time-dependent density functional theory

Truhlar, Donald G

269

DENSITY-FUNCTIONAL STUDY OF U-Mo AND U-Zr ALLOYS  

SciTech Connect (OSTI)

Density-functional theory previously used to describe phase equilibria in U-Zr alloys [A. Landa, P. Soederlind, P.E.A. Turchi, J. Alloys Comp. 478 (2009) 103-110] is extended to investigate the ground-state properties of U-Mo solid solutions. We discuss how the heat of formation in both alloys correlates with the charge transfer between the alloy components, and how the specific behavior of the density of states in the vicinity of the Fermi level promotes the stabilization of the U{sub 2}Mo compound. Our calculations prove that, due to the existence of a single {gamma}-phase over the typical fuel operation temperatures, {gamma}-U-Mo alloys should indeed have much lower constituent redistribution than {gamma}-U-Zr alloys for which binodal decomposition causes a high degree of constituent redistribution.

Landa, A; Soderlind, P; Turchi, P A

2010-11-01T23:59:59.000Z

270

Density Functional Study of the Structure, Stability and Oxygen Reduction Activity of Ultrathin Platinum Nanowires  

SciTech Connect (OSTI)

We used density functional theory to study the difference in the structure, stability and catalytic reactivity between ultrathin, 0.51.0 nm diameter, platinum nanotubes and nanowires. Model nanowires were formed by inserting an inner chain of platinum atoms in small diameter nanotubes. In this way more stable, non-hollow structures were formed. The difference in the electronic structure of platinum nanotubes and nanowires was examined by inspecting the density of surface states and band structure. Furthermore, reactivity toward the oxygen reduction reaction of platinum nanowires was assessed by studying the change in the chemisorption energies of oxygen, hydroxyl, and hydroperoxyl groups, induced by converting the nanotube models to nanowires. Both ultrathin platinum nanotubes and nanowires show distinct properties compared to bulk platinum. Single-wall nanotubes and platinum nanowires with diameters larger than 1 nm show promise for use as oxygen reduction catalysts.

Matanovic, Ivana; Kent, Paul; Garzon, Fernando; Henson, Neil J.

2013-03-14T23:59:59.000Z

271

G-centers in irradiated silicon revisited: A screened hybrid density functional theory approach  

SciTech Connect (OSTI)

Electronic structure calculations employing screened hybrid density functional theory are used to gain fundamental insight into the interaction of carbon interstitial (C{sub i}) and substitutional (C{sub s}) atoms forming the C{sub i}C{sub s} defect known as G-center in silicon (Si). The G-center is one of the most important radiation related defects in Czochralski grown Si. We systematically investigate the density of states and formation energy for different types of C{sub i}C{sub s} defects with respect to the Fermi energy for all possible charge states. Prevalence of the neutral state for the C-type defect is established.

Wang, H.; Schwingenschlgl, U., E-mail: Udo.Schwingenschlogl@kaust.edu.sa [PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia); Chroneos, A., E-mail: Alex.Chroneos@open.ac.uk [Engineering and Innovation, The Open University, Milton Keynes MK7 6AA (United Kingdom); Department of Materials, Imperial College, London SW7 2AZ (United Kingdom); Londos, C. A.; Sgourou, E. N. [University of Athens, Solid State Physics Section, Panepistimiopolis Zografos, Athens 157 84 (Greece)

2014-05-14T23:59:59.000Z

272

Ground state properties and high pressure behavior of plutonium dioxide: Systematic density functional calculations  

E-Print Network [OSTI]

Plutonium dioxide is of high technological importance in nuclear fuel cycle and is particularly crucial in long-term storage of Pu-based radioactive waste. Using first-principles density-functional theory, in this paper we systematically study the structural, electronic, mechanical, thermodynamic properties, and pressure induced structural transition of PuO$_{2}$. To properly describe the strong correlation in the Pu $5f$ electrons, the local density approximation$+U$ and the generalized gradient approximation$+U$ theoretical formalisms have been employed. We optimize the $U$ parameter in calculating the total energy, lattice parameters, and bulk modulus at the nonmagnetic, ferromagnetic, and antiferromagnetic configurations for both ground state fluorite structure and high pressure cotunnite structure. The best agreement with experiments is obtained by tuning the effective Hubbard parameter $U$ at around 4 eV within the LDA$+U$ approach. After carefully testing the validity of the ground state, we further in...

Zhang, Ping; Zhao, Xian-Geng

2010-01-01T23:59:59.000Z

273

Density-functional study of water adsorption on the PuO2(110) surface  

Science Journals Connector (OSTI)

Water adsorption on a PuO2(110) surface is studied using a periodic model with both the local-density approximation (LDA) and the generalized gradient approximation (GGA) of density-functional theory. The 60 core electrons of the Pu atom are represented by a relativistic effective core potential, and scalar relativistic effects have been incorporated into the valence orbitals. Both molecular and dissociative configurations of the adsorbate H2O are considered at one molecular layer coverage. For molecular water adsorption, LDA calculations indicate binding only at the top site, whereas the GGA indicates no binding for any site. Dissociative adsorption is found to be energetically more favorable than molecular adsorption, in agreement with experimental observations. The effects on the geometric and electronic structures influenced by water adsorption are investigated.

Xueyuan Wu and Asok K. Ray

2002-01-30T23:59:59.000Z

274

Exact exchange in relativistic spin-density-functional theory: Exchange splitting versus spin-orbit coupling  

Science Journals Connector (OSTI)

Recently, the concept of the exact orbital-dependent exchange was introduced into relativistic spin-density-functional theory (RSDFT) within the collinear limit [D. Kdderitzsch et al., Phys. Rev. B 77, 045101 (2008)]. In this contribution we further expand this exact exchange (EXX) formalism by (i) extending the basic equations to the general noncollinear form of RSDFT and (ii) discussing in detail the solution of the coupled integral equations resulting from orbital-dependent functionals in the framework of RSDFT. The EXX scheme is then applied to open-shell atoms in order to study (i) the relative importance of exchange splitting and spin-orbit coupling, (ii) the consequences of the exact exchange for atomic hyperfine constants, and (iii) the relative stability of the 3dn?14s2 and 3dn4s1 configurations in case of the 3d transition-metal elements. In particular, it is demonstrated that the exact exchange, when combined with the orbital-dependent random-phase approximation for correlation, yields s-d-transfer energies which are clearly superior to the values obtained with conventional density functionals.

E. Engel, D. Kdderitzsch, and H. Ebert

2008-12-30T23:59:59.000Z

275

Calculation of the Micellar Structure of Polymer Surfactant Based on the Density Functional Theory  

E-Print Network [OSTI]

Amphiphilic block copolymer solutions form various micellar structures including micelles and vesicles. We applied the density functional theory for block copolymers which we have proposed to amphiphilic block copolymer systems. The 3 dimensional simulation for AB diblock copolymer solutions and AB diblock copolymer / A homopolymer blends has been done and it is shown that the spherical micelles, cylindrical micelles and spherical vesicles are formed. It is also shown that the phase diagram for AB diblock copolymer / A homopolymer blends qualitatively agrees with the phase diagram obtained by the experiment.

Takashi Uneyama; Masao Doi

2005-04-26T23:59:59.000Z

276

Tuning Range-Separated Density Functional Theory for Photocatalytic Water Splitting Systems  

E-Print Network [OSTI]

We discuss the applicability of long-range separated density functional theory (DFT) to the prediction of electronic transitions of a particular photocatalytic system based on an Ir(III) photosensitizer (IrPS). Special attention is paid to the charge-transfer properties which are of key importance for the photoexcitation dynamics, but and cannot be correctly described by means of conventional DFT. The optimization of the range-separation parameter is discussed for IrPS including its complexes with electron donors and acceptors used in photocatalysis. Particular attention is paid to the problems arising for a description of medium effects by a polarizable continuum model.

Bokareva, Olga S; Bokarev, Sergey I; Khn, Oliver

2015-01-01T23:59:59.000Z

277

Growth mechanism of atomic layer deposition of zinc oxide: A density functional theory approach  

SciTech Connect (OSTI)

Atomic layer deposition of zinc oxide (ZnO) using diethylzinc (DEZ) and water is studied using density functional theory. The reaction pathways between the precursors and ZnO surface sites are discussed. Both reactions proceed by the formation of intermediate complexes on the surface. The Gibbs free energy of the formation of these complexes is positive at temperatures above ?120?C and ?200?C for DEZ and water half-reactions, respectively. Spectroscopic ellipsometry results show that the growth per cycle changes at approximately the same temperatures.

Afshar, Amir; Cadien, Kenneth C., E-mail: kcadien@ualberta.ca [Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4 (Canada)

2013-12-16T23:59:59.000Z

278

Anisotropic exchange coupling in diluted magnetic semiconductors: Ab initio spin-density functional theory  

Science Journals Connector (OSTI)

A different scheme to calculate the exchange tensor J?ij describing in a phenomenological way the anisotropic exchange coupling of two moments in a magnetically ordered system is presented. The ab initio approach is based on spin-polarized relativistic multiple-scattering theory within the framework of spin-density functional theory. The scheme is applied to ferromagnetic CrTe as well as the diluted magnetic semiconductor system Ga1?xMnxAs. In the latter case the results show that there is a noticeable anisotropy in the exchange coupling present, although not as pronounced as those suggested in recent theoretical investigations.

H. Ebert and S. Mankovsky

2009-01-26T23:59:59.000Z

279

Oxidation of stepped Pt(111) studied by x-ray photoelectron spectroscopy and density functional theory  

SciTech Connect (OSTI)

In this comparative density functional theory and x-ray photoelectron spectroscopy study on the interaction of oxygen with stepped Pt(111) surfaces, we show that both the initial adsorption and oxidation occur at the steps rather than terraces. An equivalent behavior was observed for the oxide formation at higher chemical potentials, where, after the formation of a one-dimensional PtO{sub 2}-type oxide at the steps, similar oxide chains form on the (111) terraces, indicating the initial stages of bulk oxide formation.

Bandlow, Jochen; Kaghazchi, Payam; Jacob, Timo [Institut fuer Elektrochemie, Universitaet Ulm, Albert-Einstein-Allee 47, D-89069 Ulm (Germany); Papp, C.; Traenkenschuh, B.; Streber, R.; Lorenz, M. P. A.; Fuhrmann, T.; Steinrueck, H.-P. [Lehrstuhl fuer Physikalische Chemie II, Universitaet Erlangen-Nuernberg, Egerlandstr. 3, D-91058 Erlangen (Germany); Denecke, R. [Wilhelm-Ostwald-Institut fuer Physikalische und Theoretische Chemie, Universitaet Leipzig, Linnestr. 2, D-04103 Leipzig (Germany)

2011-05-01T23:59:59.000Z

280

Mean-Field Calculation Based on Proton-Neutron Mixed Energy Density Functionals  

E-Print Network [OSTI]

We have performed calculations based on the Skyrme energy density functional (EDF) that includes arbitrary mixing between protons and neutrons. In this framework, single-particle states are generalized as mixtures of proton and neutron components. The model assumes that the Skyrme EDF is invariant under the rotation in isospin space and the Coulomb force is the only source of the isospin symmetry breaking. To control the isospin of the system, we employ the isocranking method, which is analogous to the standard cranking approach used for describing high-spin states. Here, we present results of the isocranking calculations performed for the isobaric analog states in $A = 40$ and $A = 54$ nuclei.

Koichi Sato; Jacek Dobaczewski; Takashi Nakatsukasa; Wojciech Satu?a

2014-10-10T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Mean-Field Calculation Based on Proton-Neutron Mixed Energy Density Functionals  

E-Print Network [OSTI]

We have performed calculations based on the Skyrme energy density functional (EDF) that includes arbitrary mixing between protons and neutrons. In this framework, single-particle states are generalized as mixtures of proton and neutron components. The model assumes that the Skyrme EDF is invariant under the rotation in isospin space and the Coulomb force is the only source of the isospin symmetry breaking. To control the isospin of the system, we employ the isocranking method, which is analogous to the standard cranking approach used for describing high-spin states. Here, we present results of the isocranking calculations performed for the isobaric analog states in $A = 40$ and $A = 54$ nuclei.

Sato, Koichi; Nakatsukasa, Takashi; Satu?a, Wojciech

2014-01-01T23:59:59.000Z

282

Tunneling density of states as a function of thickness in superconductor/ strong ferromagnet bilayers  

SciTech Connect (OSTI)

We have made an experimental study of the tunneling density of states (DOS) in strong ferromagnetic thin films (CoFe) in proximity with a thick superconducting film (Nb) as a function of d{sub F}, the ferromagnetic thickness. Remarkably, we find that as d{sub F} increases, the superconducting DOS exhibits a scaling behavior in which the deviations from the normal-state conductance have a universal shape that decreases exponentially in amplitude with characteristic length d* {approx} 0.4 nm. We do not see oscillations in the DOS as a function of d{sub F}, as expected from predictions based on the Usadel equations, although an oscillation in T{sub c}(d{sub F}) has been seen in the same materials.

Reymond, S.

2010-04-29T23:59:59.000Z

283

Density Functional Investigation of Melamine-Formaldehyde Crosslinking Agents Part 1: Partially Substituted Melamine  

SciTech Connect (OSTI)

Computational modeling has been performed on the cross-linking mechanism of partially substituted melamine reacting with poly(vinyl alcohol). Ab initio calculations were performed with density functional theory employing the BLYP functional and double numerical DND basis set. The mechanism, general acid catalysis, has been modeled with respect to structures, protonation, and reaction with a polymer. Protonation of the oxygen is required initially, followed by liberation of methanol. The reaction can take one of two pathways after methanol liberation. The conjugate base of the weak acid can abstract a proton, generating a Schiff-base intermediate. The O-H on the polymer then adds to the C-N double bond, producing the polymer-melamine bond. The alternative is that the polymer adds to the charged melamine, using the specific acid catalysis mechanism. After polymer addition, the proton is abstracted, producing the product.

Benson, Michael Timothy

2003-07-01T23:59:59.000Z

284

Density functional theory and evolution algorithm calculations of elastic properties of AlON  

SciTech Connect (OSTI)

Different models for aluminum oxynitride (AlON) were calculated using density functional theory and optimized using an evolutionary algorithm. Evolutionary algorithm and density functional theory (DFT) calculations starting from several models of AlON with different Al or O vacancy locations and different positions for the N atoms relative to the vacancy were carried out. The results show that the constant anion model [McCauley et al., J. Eur. Ceram. Soc. 29(2), 223 (2009)] with a random distribution of N atoms not adjacent to the Al vacancy has the lowest energy configuration. The lowest energy structure is in a reasonable agreement with experimental X-ray diffraction spectra. The optimized structure of a 55 atom unit cell was used to construct 220 and 440 atom models for simulation cells using DFT with a Gaussian basis set. Cubic elastic constant predictions were found to approach the experimentally determined AlON single crystal elastic constants as the model size increased from 55 to 440 atoms. The pressure dependence of the elastic constants found from simulated stress-strain relations were in overall agreement with experimental measurements of polycrystalline and single crystal AlON. Calculated IR intensity and Raman spectra are compared with available experimental data.

Batyrev, I. G.; Taylor, D. E.; Gazonas, G. A.; McCauley, J. W. [U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States)

2014-01-14T23:59:59.000Z

285

Accurate and systematically improvable density functional theory embedding for correlated wavefunctions  

SciTech Connect (OSTI)

We analyze the sources of error in quantum embedding calculations in which an active subsystem is treated using wavefunction methods, and the remainder using density functional theory. We show that the embedding potential felt by the electrons in the active subsystem makes only a small contribution to the error of the method, whereas the error in the nonadditive exchange-correlation energy dominates. We test an MP2 correction for this term and demonstrate that the corrected embedding scheme accurately reproduces wavefunction calculations for a series of chemical reactions. Our projector-based embedding method uses localized occupied orbitals to partition the system; as with other local correlation methods, abrupt changes in the character of the localized orbitals along a reaction coordinate can lead to discontinuities in the embedded energy, but we show that these discontinuities are small and can be systematically reduced by increasing the size of the active region. Convergence of reaction energies with respect to the size of the active subsystem is shown to be rapid for all cases where the density functional treatment is able to capture the polarization of the environment, even in conjugated systems, and even when the partition cuts across a double bond.

Goodpaster, Jason D.; Barnes, Taylor A.; Miller, Thomas F., E-mail: tfm@caltech.edu [Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125 (United States); Manby, Frederick R., E-mail: fred.manby@bristol.ac.uk [Centre for Computational Chemistry, School of Chemistry, University of Bristol, Bristol BS8 ITS (United Kingdom)

2014-05-14T23:59:59.000Z

286

Ionic Asymmetry and Solvent Excluded Volume Effects on Spherical Electric Double Layers: A Density Functional Approach  

SciTech Connect (OSTI)

In this article we present a classical density functional theory for electrical double layers of spherical macroions that extends the capabilities of conventional approaches by accounting for electrostatic ion correlations, size asymmetry and excluded volume effects. The approach is based on a recent approximation introduced by Hansen-Goos and Roth for the hard sphere excess free energy of inhomogeneous fluids (J. Chem. Phys. 124, 154506). It accounts for the proper and efficient description of the effects of ionic asymmetry and solvent excluded volume, especially at high ion concentrations and size asymmetry ratios including those observed in experimental studies. Additionally, we utilize a leading functional Taylor expansion approximation of the ion density profiles. In addition, we use the Mean Spherical Approximation for multi-component charged hard sphere fluids to account for the electrostatic ion correlation effects. These approximations are implemented in our theoretical formulation into a suitable decomposition of the excess free energy which plays a key role in capturing the complex interplay between charge correlations and excluded volume effects. We perform Monte Carlo simulations in various scenarios to validate the proposed approach, obtaining a good compromise between accuracy and computational cost. We use the proposed computational approach to study the effects of ion size, ion size asymmetry and solvent excluded volume on the ion profiles, integrated charge, mean electrostatic potential, and ionic coordination number around spherical macroions in various electrolyte mixtures. Our results show that both solvent hard sphere diameter and density play a dominant role in the distribution of ions around spherical macroions, mainly for experimental water molarity and size values where the counterion distribution is characterized by a tight binding to the macroion, similar to that predicted by the Stern model.

Medasani, Bharat; Ovanesyan, Zaven; Thomas, Dennis G.; Sushko, Maria L.; Marucho, Marcelo

2014-05-29T23:59:59.000Z

287

Toward a Non-Born-Oppenheimer Density Functional Theory in the Context of Local-Scaling Transformations  

Science Journals Connector (OSTI)

The N- and v-representable formulation of density functional theory given in terms of local-scaling transformations is extended here to the case of moving nuclei. The effect of these transformations on both wavef...

Eugene S. Kryachko; Eduardo V. Ludea; Vladimiro Mujica

1991-01-01T23:59:59.000Z

288

Isovector Giant Dipole Resonance from the 3D Time-Dependent Density Functional Theory for Superfluid Nuclei  

SciTech Connect (OSTI)

A fully symmetry unrestricted Time-Dependent Density Functional Theory extended to include pairing correlations is used to calculate properties of the isovector giant dipole resonances of the deformed open-shell nuclei 172Yb, 188Os, and 238U, and to demonstrate good agreement with experimental data on nuclear photo-absorption cross-sections for two different Skyrme force parameterizations of the energy density functional: SkP and SLy4.

Stetcu, Ionel; Bulgac, Aurel; Magierski, Piotr; Roche, Kenneth J.

2011-11-21T23:59:59.000Z

289

Perspective: Fifty years of density-functional theory in chemical physics  

SciTech Connect (OSTI)

Since its formal inception in 19641965, Kohn-Sham density-functional theory (KS-DFT) has become the most popular electronic structure method in computational physics and chemistry. Its popularity stems from its beautifully simple conceptual framework and computational elegance. The rise of KS-DFT in chemical physics began in earnest in the mid 1980s, when crucial developments in its exchange-correlation term gave the theory predictive power competitive with well-developed wave-function methods. Today KS-DFT finds itself under increasing pressure to deliver higher and higher accuracy and to adapt to ever more challenging problems. If we are not mindful, however, these pressures may submerge the theory in the wave-function sea. KS-DFT might be lost. I am hopeful the Kohn-Sham philosophical, theoretical, and computational framework can be preserved. This Perspective outlines the history, basic concepts, and present status of KS-DFT in chemical physics, and offers suggestions for its future development.

Becke, Axel D., E-mail: axel.becke@dal.ca [Department of Chemistry, Dalhousie University, 6274 Coburg Rd., P.O. Box 15000, Halifax, Nova Scotia B3H 4R2 (Canada)

2014-05-14T23:59:59.000Z

290

Dynamic density functional theory of protein adsorption on polymer-coated nanoparticles  

E-Print Network [OSTI]

We present a theoretical model for the description of the adsorption kinetics of globular proteins onto charged core-shell microgel particles based on Dynamic Density Functional Theory (DDFT). This model builds on a previous description of protein adsorption thermodynamics [Yigit \\textit{et al}, Langmuir 28 (2012)], shown to well interpret the available calorimetric experimental data of binding isotherms. In practice, a spatially-dependent free-energy functional including the same physical interactions is built, and used to study the kinetics via a generalised diffusion equation. To test this model, we apply it to the case study of Lysozyme adsorption on PNIPAM coated nanoparticles, and show that the dynamics obtained within DDFT is consistent with that extrapolated from experiments. We also perform a systematic study of the effect of various parameters in our model, and investigate the loading dynamics as a function of proteins' valence and hydrophobic adsorption energy, as well as their concentration and that of the nanoparticles. Although we concentrated here on the case of adsorption for a single protein type, the model's generality allows to study multi-component system, providing a reliable instrument for future studies of competitive and cooperative adsorption effects often encountered in protein adsorption experiments.

Stefano Angioletti-Uberti; Matthias Ballauff; Joachim Dzubiella

2014-06-11T23:59:59.000Z

291

Computational Complexity of interacting electrons and fundamental limitations of Density Functional Theory  

E-Print Network [OSTI]

One of the central problems in quantum mechanics is to determine the ground state properties of a system of electrons interacting via the Coulomb potential. Since its introduction by Hohenberg, Kohn, and Sham, Density Functional Theory (DFT) has become the most widely used and successful method for simulating systems of interacting electrons, making their original work one of the most cited in physics. In this letter, we show that the field of computational complexity imposes fundamental limitations on DFT, as an efficient description of the associated universal functional would allow to solve any problem in the class QMA (the quantum version of NP) and thus particularly any problem in NP in polynomial time. This follows from the fact that finding the ground state energy of the Hubbard model in an external magnetic field is a hard problem even for a quantum computer, while given the universal functional it can be computed efficiently using DFT. This provides a clear illustration how the field of quantum computing is useful even if quantum computers would never be built.

Norbert Schuch; Frank Verstraete

2007-12-04T23:59:59.000Z

292

Bulk phase behaviour of binary hard platelet mixtures from density functional theory  

E-Print Network [OSTI]

We investigate isotropic-isotropic, isotropic-nematic and nematic-nematic phase coexistence in binary mixtures of circular platelets with vanishing thickness, continuous rotational degrees of freedom and radial size ratios $\\lambda$ up to 5. A fundamental measure density functional theory, previously used for the one-component model, is proposed and results are compared against those from Onsager theory as a benchmark. For $\\lambda \\leq 1.7$ the system displays isotropic-nematic phase coexistence with a widening of the biphasic region for increasing values of $\\lambda$. For size ratios $\\lambda \\geq 2$, we find demixing into two nematic states becomes stable and an isotropic-nematic-nematic triple point can occur. Fundamental measure theory gives a smaller isotropic-nematic biphasic region than Onsager theory and locates the transition at lower densities. Furthermore, nematic-nematic demixing occurs over a larger range of compositions at a given value of $\\lambda$ than found in Onsager theory. Both theories predict the same topologies of the phase diagrams. The partial nematic order parameters vary strongly with composition and indicate that the larger particles are more strongly ordered than the smaller particles.

Jonathan Phillips; Matthias Schmidt

2010-01-29T23:59:59.000Z

293

Radical Coupling Reactions in Lignin Synthesis: A Density Functional Theory Study  

SciTech Connect (OSTI)

Lignin is a complex, heterogeneous polymer in plant cell walls that provides mechanical strength to the plant stem and confers resistance to degrading microbes, enzymes, and chemicals. Lignin synthesis initiates through oxidative radical-radical coupling of monolignols, the most common of which are p-coumaryl, coniferyl, and sinapyl alcohols. Here, we use density functional theory to characterize radical-radical coupling reactions involved in monolignol dimerization. We compute reaction enthalpies for the initial self- and cross-coupling reactions of these monolignol radicals to form dimeric intermediates via six major linkages observed in natural lignin. The 8-O-4, 8-8, and 8-5 coupling are computed to be the most favorable, whereas the 5-O-4, 5-5, and 8-1 linkages are less favorable. Overall, p-coumaryl self- and cross-coupling reactions are calculated to be the most favorable. For cross-coupling reactions, in which each radical can couple via either of the two sites involved in dimer formation, the more reactive of the two radicals is found to undergo coupling at its site with the highest spin density.

Sangha, A. K.; Parks, J. M.; Standaert, R. F.; Ziebell, A.; Davis, M.; Smith, J. C.

2012-04-26T23:59:59.000Z

294

Thermodynamics of baryonic matter with strangeness within non-relativistic energy density functional model  

E-Print Network [OSTI]

We study the thermodynamical properties of compressed baryonic matter with strangeness within non-relativistic energy density functional models with a particular emphasis on possible phase transitions found earlier for a simple $n,p,e,\\Lambda$-mixture. The aim of the paper is twofold: I) examining the phase structure of the complete system, including the full baryonic octet and II) testing the sensitivity of the results to the model parameters. We find that, associated to the onset of the different hyperonic families, up to three separate strangeness-driven phase transitions may occur. Consequently, a large fraction of the baryonic density domain is covered by phase coexistence with potential relevance for (proto)-neutron star evolution. It is shown that the presence of a phase transition is compatible both with the observational constraint on the maximal neutron star mass, and with the present experimental information on hypernuclei. In particular we show that two solar mass neutron stars are compatible with important hyperon content. Still, the parameter space is too large to give a definitive conclusion of the possible occurrence of a strangeness driven phase transition, and further constraints from multiple-hyperon nuclei and/or hyperon diffusion data are needed.

Ad. R. Raduta; F. Gulminelli; M. Oertel

2014-06-02T23:59:59.000Z

295

Mixing of equations of state for xenon-deuterium using density functional theory  

SciTech Connect (OSTI)

We report on a theoretical study of equation of state (EOS) properties of fluid and dense plasma mixtures of xenon and deuterium to explore and illustrate the basic physics of the mixing of a light element with a heavy element. Accurate EOS models are crucial to achieve high-fidelity hydrodynamics simulations of many high-energy-density phenomena, for example inertial confinement fusion and strong shock waves. While the EOS is often tabulated for separate species, the equation of state for arbitrary mixtures is generally not available, requiring properties of the mixture to be approximated by combining physical properties of the pure systems. Density functional theory (DFT) at elevated-temperature is used to assess the thermodynamics of the xenon-deuterium mixture at different mass ratios. The DFT simulations are unbiased as to elemental species and therefore provide comparable accuracy when describing total energies, pressures, and other physical properties of mixtures as they do for pure systems. The study focuses on addressing the accuracy of different mixing rules in the temperature range 1000-40 000 K for pressures between 100 and 600 GPa (1-6 Mbar), thus, including the challenging warm dense matter regime of the phase diagram. We find that a mix rule taking into account pressure equilibration between the two species performs very well over the investigated range.

Magyar, Rudolph J.; Mattsson, Thomas R. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

2013-03-15T23:59:59.000Z

296

Hydration of Clays at the Molecular Scale: The Promising Perspective of Classical Density Functional Theory  

E-Print Network [OSTI]

We report here how the hydration of complex surfaces can be efficiently studied thanks to recent advances in classical molecular density functional theory. This is illustrated on the example of the pyrophylite clay. After presenting the most recent advances, we show that the strength of this implicit method is that (i) it is in quantitative or semi-quantitative agreement with reference all-atoms simulations (molecular dynamics here) for both the solvation structure and energetics, and that (ii) the computational cost is two to three orders of magnitude less than in explicit methods. The method remains imperfect, in that it locally overestimates the polarization of water close to hydrophylic sites of the clay. The high numerical efficiency of the method is illustrated and exploited to carry a systematic study of the electrostatic and van der Waals components of the surface-solvant interactions within the most popular force field for clays, CLAYFF. Hydration structure and energetics are found to weakly depend u...

Jeanmairet, Guillaume; Levesque, Maximilien; Rotenberg, Benjamin; Borgis, Daniel

2014-01-01T23:59:59.000Z

297

Analytic cubic and quartic force fields using density-functional theory  

SciTech Connect (OSTI)

We present the first analytic implementation of cubic and quartic force constants at the level of KohnSham density-functional theory. The implementation is based on an open-ended formalism for the evaluation of energy derivatives in an atomic-orbital basis. The implementation relies on the availability of open-ended codes for evaluation of one- and two-electron integrals differentiated with respect to nuclear displacements as well as automatic differentiation of the exchangecorrelation kernels. We use generalized second-order vibrational perturbation theory to calculate the fundamental frequencies of methane, ethane, benzene, and aniline, comparing B3LYP, BLYP, and HartreeFock results. The HartreeFock anharmonic corrections agree well with the B3LYP corrections when calculated at the B3LYP geometry and from B3LYP normal coordinates, suggesting that the inclusion of electron correlation is not essential for the reliable calculation of cubic and quartic force constants.

Ringholm, Magnus; Gao, Bin; Thorvaldsen, Andreas J.; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of TromsThe Arctic University of Norway, 9037 Troms (Norway)] [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of TromsThe Arctic University of Norway, 9037 Troms (Norway); Jonsson, Dan [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of TromsThe Arctic University of Norway, 9037 Troms (Norway) [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of TromsThe Arctic University of Norway, 9037 Troms (Norway); High Performance Computing Group, University of TromsThe Arctic University of Norway, 9037 Troms (Norway); Bast, Radovan [Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, S-10691 Stockholm, Sweden and PDC Center for High Performance Computing, Royal Institute of Technology, S-10044 Stockholm (Sweden)] [Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, S-10691 Stockholm, Sweden and PDC Center for High Performance Computing, Royal Institute of Technology, S-10044 Stockholm (Sweden); Ekstrm, Ulf; Helgaker, Trygve [Center for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo (Norway)] [Center for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo (Norway)

2014-01-21T23:59:59.000Z

298

Octupole deformation and Ra puzzle in reflection asymmetric covariant density functional theory  

E-Print Network [OSTI]

Reflection asymmetric covariant density functional theory(CDFT) based on the point-coupling interaction is established on a two-center harmonic-oscillator basis and applied to investigate the Ra puzzle, i.e., the anomalous enhancement of the residual proton-neutron interactions for Ra isotopes around N=135. The octupole deformation and shape evolution in the Ra and Rn isotopes are examined in the potential energy surfaces in(beta2, beta3) plane by the constrained reflection asymmetric calculations. The residual proton-neutron interactions extracted from the double difference of the binding energies for Ra isotopes are compared with the data as well as the axial and the triaxial calculations. It is found that the octupole deformation is responsible for the Ra puzzle in the microscopic CDFT.

L. F. Yu; P. W. Zhao; S. Q. Zhang; J. Meng

2012-11-03T23:59:59.000Z

299

Magnetic rotations in 198Pb and 199Pb within covariant density functional theory  

E-Print Network [OSTI]

Well-known examples of shears bands in the nuclei 198Pb and 199Pb are investigated within tilted axis cranking relativistic mean-field theory. Energy spectra, the relation between spin and rotational frequency, deformation parameters and reduced $M1$ and $E2$ transition probabilities are calculated. The results are in good agreement with available data and with calculations based on the phenomenological pairing plus-quadrupole-quadrupole tilted-axis cranking model. It is shown that covariant density functional theory provides a successful microscopic and fully self-consistent description of magnetic rotation in the Pb region showing the characteristic properties as the shears mechanism and relatively large B(M1) transitions decreasing with increasing spin.

L. F. Yu; P. W. Zhao; S. Q. Zhang; P. Ring; J. Meng

2012-02-28T23:59:59.000Z

300

Global Minimum Determination of the Born-Oppenheimer Surface within Density Functional Theory  

SciTech Connect (OSTI)

We present a novel method, which we refer to as the dual minima hopping method, that allows us to find the global minimum of the potential energy surface (PES) within density functional theory for systems where a fast but less accurate calculation of the PES is possible. This method can rapidly find the ground state configuration of clusters and other complex systems with present day computer power by performing a systematic search. We apply the new method to silicon clusters. Even though these systems have already been extensively studied by other methods, we find new global minimum candidates for Si{sub 16} and Si{sub 19}, as well as new low-lying isomers for Si{sub 16}, Si{sub 17}, and Si{sub 18}.

Goedecker, Stefan; Hellmann, Waldemar; Lenosky, Thomas [Institut fuer Physik, Universitaet Basel, Klingelbergstrasse 82, 4056 Basel (Switzerland); Physics Department, Ohio State University, 1040 Physics Research Building, 191 West Woodruff Avenue, Columbus, Ohio 43210-1117 (United States)

2005-07-29T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
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to obtain the most current and comprehensive results.


301

Nuclear matrix elements in neutrinoless double beta decay: beyond mean-field covariant density functional theory  

E-Print Network [OSTI]

We report a systematic study of nuclear matrix elements (NMEs) in neutrinoless double-beta decays with state-of-the-art beyond mean-field covariant density functional theory. The dynamic effects of particle-number and angular-momentum conservations as well as quadrupole shape fluctuations are taken into account with projections and generator coordinate method for both initial and final nuclei. The full relativistic transition operator is adopted to calculate the NMEs which are found to be consistent with the results of previous beyond non-relativistic mean-field calculation based on a Gogny force with the exception of $^{150}$Nd. Our study shows that the total NMEs can be well approximated by the pure axial-vector coupling term, the calculation of which is computationally much cheaper than that of full terms.

J. M. Yao; L. S. Song; K. Hagino; P. Ring; J. Meng

2014-10-23T23:59:59.000Z

302

Hydrogen-bridge bonding on semiconductor surfaces:?Density-functional calculations  

Science Journals Connector (OSTI)

The relative stabilities of hydrogen bridge bonds on diamond C(001), Si(001), Ge(001), and GaAs(001) surfaces have been studied within the framework of density functional theory. Hydrogen-bridge bonds are found to be stable on cation terminated GaAs(001) and almost stable on p-type doped Si(001) surfaces with an excess energy of 0.08eV per bridge. Bridge bonds are unstable on n-type doped Si(001) and anion terminated GaAs(001). H-bridges are metastable on intrinsic group IV surfaces, and the excess energy cost diminishes monotonically across the C-Si-Ge series. In stark contrast with group IV semiconductors, the (21) monohydride dimer structure is not stable on GaAs(001).

J. M. Ripalda; J. D. Gale; T. S. Jones

2004-12-16T23:59:59.000Z

303

Impact ionization in GaAs: A screened exchange density-functional approach  

SciTech Connect (OSTI)

Results are presented of a fully ab initio calculation of impact ionization rates in GaAs within the density functional theory framework, using a screened-exchange formalism and the highly precise all-electron full-potential linearized augmented plane wave method. The calculated impact ionization rates show a marked orientation dependence in k space, indicating the strong restrictions imposed by the conservation of energy and momentum. This anisotropy diminishes as the impacting electron energy increases. A Keldysh type fit performed on the energy-dependent rate shows a rather soft edge and a threshold energy greater than the direct band gap. The consistency with available Monte Carlo and empirical pseudopotential calculations shows the reliability of our approach and paves the way to ab initio calculations of pair production rates in new and more complex materials.

Picozzi, S., Asahi, R., Geller, C.B., Continenza, A., and Freeman, A.J.

2001-08-13T23:59:59.000Z

304

A density functional study of phosphorus-doped clusters (n=18)  

Science Journals Connector (OSTI)

We have designed numerous models of C n P 3 + (n=18) using molecular graphics software. The geometry optimization and calculation of vibrational frequency were carried out by the B3LYP density functional method. The ground-state structures are straight carbon chains with a P2C ring connected at one end and a phosphorus atom at the other. The bond length features of the straight chains suggest a polyacetylene-like structure for even n and cumulenic-like structure for odd n. The C n P 3 + (n=18) with even number of carbon atoms are more stable than those with odd number. The odd/even alternation trend can be explained according to the variation of bonding characters, ionization potentials, and incremental binding energies.

M.D. Chen; X.B. Li; L. Dang; H. Liang; Q.E. Zhang; C.T. Au

2005-01-01T23:59:59.000Z

305

Steam reforming on transition-metal carbides from density-functional theory  

E-Print Network [OSTI]

A screening study of the steam reforming reaction (CH_4 + H_2O -> CO + 3H_2) on early transition-metal carbides (TMC's) is performed by means of density-functional theory calculations. The set of considered surfaces includes the alpha-Mo_2C(100) surfaces, the low-index (111) and (100) surfaces of TiC, VC, and delta-MoC, and the oxygenated alpha-Mo_2C(100) and TMC(111) surfaces. It is found that carbides provide a wide spectrum of reactivities towards the steam reforming reaction, from too reactive via suitable to too inert. The reactivity is discussed in terms of the electronic structure of the clean surfaces. Two surfaces, the delta-MoC(100) and the oxygen passivated alpha-Mo_2C(100) surfaces, are identified as promising steam reforming catalysts. These findings suggest that carbides provide a playground for reactivity tuning, comparable to the one for pure metals.

Vojvodic, Aleksandra

2009-01-01T23:59:59.000Z

306

Nuclear matrix elements in neutrinoless double beta decay: beyond mean-field covariant density functional theory  

E-Print Network [OSTI]

We report a systematic study of nuclear matrix elements (NMEs) in neutrinoless double-beta decays with state-of-the-art beyond mean-field covariant density functional theory. The dynamic effects of particle-number and angular-momentum conservations as well as quadrupole shape fluctuations are taken into account with projections and generator coordinate method for both initial and final nuclei. The full relativistic transition operator is adopted to calculate the NMEs which are found to be consistent with the results of previous beyond non-relativistic mean-field calculation based on a Gogny force with the exception of $^{150}$Nd. Our study shows that the total NMEs can be well approximated by the pure axial-vector coupling term, the calculation of which is computationally much cheaper than that of full terms.

Yao, J M; Hagino, K; Ring, P; Meng, J

2014-01-01T23:59:59.000Z

307

Modeling the doubly excited state with time-dependent HartreeFock and density functional theories  

Science Journals Connector (OSTI)

Multielectron excited states have become a hot topic in many cutting-edge research fields such as the photophysics of polyenes and in the possibility of multiexciton generation in quantum dots for the purpose of increasing solar cell efficiency. However obtaining multielectron excited states has been a major obstacle as it is often done with multiconfigurational methods which involve formidable computational cost for large systems. Although they are computationally much cheaper than multiconfigurational wave function based methods linear response adiabatic time-dependent HartreeFock (TDHF) and density functional theory (TDDFT) are generally considered incapable of obtaining multielectron excited states. We have developed a real-time TDHF and adiabatic TDDFT approach that is beyond the perturbative regime. We show that TDHF/TDDFT is able to simultaneously excite two electrons from the ground state to the doubly excited state and that the real-time TDHF/TDDFT implicitly includes double excitation within a superposition state. We also present a multireference linear response theory to show that the real-time electron density response corresponds to a superposition of perturbative linear responses of the S 0 and S 2 states. As a result the energy of the two-electron doubly excited state can be obtained with several different approaches. This is done within the adiabatic approximation of TDDFT a realm in which the doubly excited state has been deemed missing. We report results on simple two-electron systems including the energies and dipole moments for the two-electron excited states of H 2 and He H + . These results are compared to those obtained with the full configuration interaction method.

Christine M. Isborn; Xiaosong Li

2008-01-01T23:59:59.000Z

308

Applications of Skyrme energy-density functional to fusion reactions for synthesis of superheavy nuclei  

SciTech Connect (OSTI)

The Skyrme energy-density functional approach has been extended to study massive heavy-ion fusion reactions. Based on the potential barrier obtained and the parametrized barrier distribution the fusion (capture) excitation functions of a lot of heavy-ion fusion reactions are studied systematically. The average deviations of fusion cross sections at energies near and above the barriers from experimental data are less than 0.05 for 92% of 76 fusion reactions with Z{sub 1}Z{sub 2}<1200. For the massive fusion reactions, for example, the {sup 238}U-induced reactions and {sup 48}Ca+{sup 208}Pb, the capture excitation functions have been reproduced remarkably well. The influence of structure effects in the reaction partners on the capture cross sections is studied with our parametrized barrier distribution. By comparing the reactions induced by double-magic nucleus {sup 48}Ca and by {sup 32}S and {sup 35}Cl, the ''threshold-like'' behavior in the capture excitation function for {sup 48}Ca-induced reactions is explored and an optimal balance between the capture cross section and the excitation energy of the compound nucleus is studied. Finally, the fusion reactions with {sup 36}S, {sup 37}Cl, {sup 48}Ca, and {sup 50}Ti bombarding {sup 248}Cm, {sup 247,249}Bk, {sup 250,252,254}Cf, and {sup 252,254}Es, as well as the reactions leading to the same compound nucleus with Z=120 and N=182, are studied further. The calculation results for these reactions are useful for searching for the optimal fusion configuration and suitable incident energy in the synthesis of superheavy nuclei.

Wang Ning; Scheid, Werner [Institute for Theoretical Physics at Justus-Liebig-University, D-35392 Giessen (Germany); Wu Xizhen; Liu Min [China Institute of Atomic Energy, Beijing 102413 (China); Li Zhuxia [China Institute of Atomic Energy, Beijing 102413 (China); Institute of Theoretical Physics, Chinese Academic of Science, Beijing 100080 (China); Nuclear Theory Center of National Laboratory of Heavy Ion Accelerator, Lanzhou 730000 (China)

2006-10-15T23:59:59.000Z

309

Relativistic density-functional theory with the optimized effective potential and self-interaction correction: Application to atomic structure calculations ,,Z 2106...  

E-Print Network [OSTI]

Relativistic density-functional theory with the optimized effective potential and self, Lawrence, Kansas 66045 Received 30 July 1997 We present a self-interaction-free relativistic density-functional-2947 98 06201-5 PACS number s : 31.15.Ew, 32.10.Hq, 71.15.Rf I. INTRODUCTION In recent years, the density-functional

Chu, Shih-I

310

A high-throughput infrastructure for density functional theory calculations Anubhav Jain, Geoffroy Hautier, Charles J. Moore, Shyue Ping Ong, Christopher C. Fischer,  

E-Print Network [OSTI]

A high-throughput infrastructure for density functional theory calculations Anubhav Jain, Geoffroy-throughput computation Density functional theory Materials screening GGA Formation enthalpies a b s t r a c t The use of high-throughput density functional theory (DFT) calculations to screen for new materials and conduct

Ceder, Gerbrand

311

1318 Brazilian Journal of Physics, vol. 36, no. 4A, December, 2006 A Bird's-Eye View of Density-Functional Theory  

E-Print Network [OSTI]

of the Brazilian Physical Society. It is an attempt to introduce density-functional theory (DFT) in a language of the many excellent more technical reviews available in the literature. Keywords: Density-functional theory of the Brazilian Physical So- ciety [1]. The main text is a description of density-functional theory (DFT

Wu, Zhigang

312

Hardness of FeB{sub 4}: Density functional theory investigation  

SciTech Connect (OSTI)

A recent experimental study reported the successful synthesis of an orthorhombic FeB{sub 4} with a high hardness of 62(5) GPa [H. Gou et al., Phys. Rev. Lett. 111, 157002 (2013)], which has reignited extensive interests on whether transition-metal borides compounds will become superhard materials. However, it is contradicted with some theoretical studies suggesting transition-metal boron compounds are unlikely to become superhard materials. Here, we examined structural and electronic properties of FeB{sub 4} using density functional theory. The electronic calculations show the good metallicity and covalent FeB bonding. Meanwhile, we extensively investigated stress-strain relations of FeB{sub 4} under various tensile and shear loading directions. The calculated weakest tensile and shear stresses are 40 GPa and 25 GPa, respectively. Further simulations (e.g., electron localization function and bond length along the weakest loading direction) on FeB{sub 4} show the weak FeB bonding is responsible for this low hardness. Moreover, these results are consistent with the value of Vickers hardness (11.732.3 GPa) by employing different empirical hardness models and below the superhardness threshold of 40 GPa. Our current results suggest FeB{sub 4} is a hard material and unlikely to become superhard (>40 GPa)

Zhang, Miao; Du, Yonghui; Gao, Lili [Department of Physics, Beihua University, Jilin 132013 (China)] [Department of Physics, Beihua University, Jilin 132013 (China); Lu, Mingchun [Department of Aeronautical Engineering Professional Technology, Jilin Institute of Chemical Technology, Jilin 132102 (China)] [Department of Aeronautical Engineering Professional Technology, Jilin Institute of Chemical Technology, Jilin 132102 (China); Lu, Cheng [Department of Physics, Nanyang Normal University, Nanyang 473061 (China)] [Department of Physics, Nanyang Normal University, Nanyang 473061 (China); Liu, Hanyu, E-mail: hal420@mail.usask.ca [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)] [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2 (Canada)

2014-05-07T23:59:59.000Z

313

Density-Functional-Theory Calculations of Matter in Strong Magnetic Fields: I. Atoms and Molecules  

E-Print Network [OSTI]

We present new ab initio calculations of the electronic structure of various atoms and molecules in strong magnetic fields ranging from B=10^12 G to 2x10^15 G, appropriate for radio pulsars and magnetars. For these field strengths, the magnetic forces on the electrons dominate over the Coulomb forces, and to a good approximation the electrons are confined to the ground Landau level. Our calculations are based on the density functional theory, and use a local magnetic exchange-correlation function which is tested to be reliable in the strong field regime. Numerical results of the ground-state energies are given for H_N (up to N=10), He_N (up to N=8), C_N (up to N=5) and Fe_N (up to N=3), as well as for various ionized atoms. Fitting formulae for the B-dependence of the energies are also given. In general, as N increases, the binding energy per atom in a molecule, |E_N|/N, increases and approaches a constant value. For all the field strengths considered in this paper, hydrogen, helium, and carbon molecules are found to be bound relative to individual atoms (although for B less than a few x 10^12 G, the relative binding between C and C_2 is small). Iron molecules are not bound at B<10^13 G, but become energetically more favorable than individual atoms at larger field strengths.

Zach Medin; Dong Lai

2007-01-05T23:59:59.000Z

314

A Mixed Basis Density Functional Approach for Low Dimensional Systems with B-splines  

E-Print Network [OSTI]

A mixed basis approach based on density functional theory is employed for low dimensional systems. The basis functions are taken to be plane waves for the periodic direction multiplied by B-spline polynomials in the non-periodic direction. B-splines have the following advantages:(1) the associated matrix elements are sparse, (2) B-splines possess a superior treatment of derivatives, (3) B-splines are not associated with atomic positions when the geometry structure is optimized, making the geometry optimization easy to implement. With this mixed basis set we can directly calculate the total energy of the system instead of using the conventional supercell model with a slab sandwiched between vacuum regions. A generalized Lanczos-Krylov iterative method is implemented for the diagonalization of the Hamiltonian matrix. To demonstrate the present approach, we apply it to study the C(001)-(2x1) surface with the norm-conserving pseudopotential, the n-type delta-doped graphene, and graphene nanoribbon with Vanderbilt...

Ren, Chung-Yuan; Chang, Yia-Chung

2014-01-01T23:59:59.000Z

315

Building a Universal Nuclear Energy Density Functional (UNEDF): SciDAC-2 Project  

SciTech Connect (OSTI)

An understanding of the properties of atomic nuclei is crucial for a complete nuclear theory, for element formation, for properties of stars, and for present and future energy and defense applications. During the period of Dec. 1, 2006 - Jun. 30, 2012, the UNEDF collaboration carried out a comprehensive study of all nuclei based on the most accurate knowledge of the strong nuclear interaction, the most reliable theoretical approaches, the most advanced algorithms, and extensive computational resources, with a view towards scaling to the petaflop platforms and beyond. The long-term vision initiated with UNEDF is to arrive at a comprehensive, quantitative, and unified description of nuclei and their reactions, grounded in the fundamental interactions between the constituent nucleons. We seek to replace current phenomenological models of nuclear structure and reactions with a well-founded microscopic theory that delivers maximum predictive power with well-quantified uncertainties. Specifically, the mission of this project has been three-fold: first, to find an optimal energy density functional (EDF) using all our knowledge of the nucleonic Hamiltonian and basic nuclear properties; second, to apply the EDF theory and its extensions to validate the functional using all the available relevant nuclear structure and reaction data; and third, to apply the validated theory to properties of interest that cannot be measured, in particular the properties needed for reaction theory.

Carlson, Joe; Furnstahl, Dick; Lusk, Rusty; Nazarewicz, Witek; Ng, Esmond; Thompson, Ian; Vary, James

2012-06-30T23:59:59.000Z

316

A density functional theory model of mechanically activated silyl ester hydrolysis  

SciTech Connect (OSTI)

To elucidate the mechanism of the mechanically activated dissociation of chemical bonds between carboxymethylated amylose (CMA) and silane functionalized silicon dioxide, we have investigated the dissociation kinetics of the bonds connecting CMA to silicon oxide surfaces with density functional calculations including the effects of force, solvent polarizability, and pH. We have determined the activation energies, the pre-exponential factors, and the reaction rate constants of candidate reactions. The weakest bond was found to be the silyl ester bond between the silicon and the alkoxy oxygen atom. Under acidic conditions, spontaneous proton addition occurs close to the silyl ester such that neutral reactions become insignificant. Upon proton addition at the most favored position, the activation energy for bond hydrolysis becomes 31 kJ?mol{sup ?1}, which agrees very well with experimental observation. Heterolytic bond scission in the protonated molecule has a much higher activation energy. The experimentally observed bi-exponential rupture kinetics can be explained by different side groups attached to the silicon atom of the silyl ester. The fact that different side groups lead to different dissociation kinetics provides an opportunity to deliberately modify and tune the kinetic parameters of mechanically activated bond dissociation of silyl esters.

Pill, Michael F.; Schmidt, Sebastian W. [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany) [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany); Institut fr Physikalische Chemie, Christian-Albrechts-Universitt zu Kiel, Olshausenstrae 40, 24098 Kiel (Germany); Center for Nanoscience (CeNS), Geschwister-Scholl-Platz 1, 80539 Munich (Germany); Beyer, Martin K. [Institut fr Physikalische Chemie, Christian-Albrechts-Universitt zu Kiel, Olshausenstrae 40, 24098 Kiel (Germany) [Institut fr Physikalische Chemie, Christian-Albrechts-Universitt zu Kiel, Olshausenstrae 40, 24098 Kiel (Germany); Institut fr Ionenphysik und Angewandte Physik, Leopold-Franzens-Universitt Innsbruck, Technikerstrae 25, 6020 Innsbruck (Austria); Clausen-Schaumann, Hauke [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany) [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany); Center for Nanoscience (CeNS), Geschwister-Scholl-Platz 1, 80539 Munich (Germany); Kersch, Alfred, E-mail: akersch@hm.edu [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany)] [Department of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany)

2014-01-28T23:59:59.000Z

317

Interatomic potentials for ionic systems with density functional accuracy based on charge densities obtained by a neural network  

E-Print Network [OSTI]

Based on an analysis of the short range chemical environment of each atom in a system, standard machine learning based approaches to the construction of interatomic potentials aim at determining directly the central quantity which is the total energy. This prevents for instance an accurate description of the energetics of systems where long range charge transfer is important as well as of ionized systems. We propose therefore not to target directly with machine learning methods the total energy but an intermediate physical quantity namely the charge density, which then in turn allows to determine the total energy. By allowing the electronic charge to distribute itself in an optimal way over the system, we can describe not only neutral but also ionized systems with unprecedented accuracy. We demonstrate the power of our approach for both neutral and ionized NaCl clusters where charge redistribution plays a decisive role for the energetics. We are able to obtain chemical accuracy, i.e. errors of less than a mil...

Ghasemi, S Alireza; Saha, Santanu; Goedecker, Stefan

2015-01-01T23:59:59.000Z

318

Ground-state properties and high-pressure behavior of plutonium dioxide: Density functional theory calculations  

Science Journals Connector (OSTI)

Plutonium dioxide is of high technological importance in nuclear fuel cycle and is particularly crucial in long-term storage of Pu-based radioactive waste. Using first-principles density-functional theory, in this paper we systematically study the structural, electronic, mechanical, thermodynamic properties, and pressure-induced structural transition of PuO2. To properly describe the strong correlation in Pu?5f electrons, the local-density approximation (LDA)+U and the generalized gradient approximation+U theoretical formalisms have been employed. We optimize U parameter in calculating the total energy, lattice parameters, and bulk modulus at nonmagnetic, ferromagnetic, and antiferromagnetic configurations for both ground-state fluorite structure and high-pressure cotunnite structure. Best agreement with experiments is obtained by tuning the effective Hubbard parameter U at around 4 eV within LDA+U approach. After carefully testing the validity of the ground-state calculation, we further investigate the bonding nature, elastic constants, various moduli, Debye temperature, hardness, ideal tensile strength, and phonon dispersion for fluorite PuO2. Some thermodynamic properties, e.g., Gibbs free energy, volume thermal expansion, and specific heat are also calculated. As for cotunnite phase, besides elastic constants, various moduli, and Debye temperature at 0 GPa, we have further presented our calculated electronic, structural, and magnetic properties for PuO2 under pressure up to 280 GPa. A metallic transition at around 133 GPa and an isostructural transition in pressure range of 75133 GPa are predicted. Additionally, as an illustration on the valency trend and subsequent effect on the mechanical properties, the calculated results for other actinide metal dioxides (ThO2, UO2, and NpO2) are also presented.

Ping Zhang; Bao-Tian Wang; Xian-Geng Zhao

2010-10-19T23:59:59.000Z

319

Near quantitative agreement of model free DFT- MD predictions...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Near quantitative agreement of model free DFT- MD predictions with XAFS observations of the hydration structure of highly Near quantitative agreement of model free DFT- MD...

320

Editorial John Hickner, MD, MSc Editor-in-Chief  

E-Print Network [OSTI]

Health Care, Overland Park, Kan kEVin PEtErSon, MD, MPH University of Minnesota, St. Paul goutHAM rAo, MD

Alford, Simon

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321

Spontaneous Fission Modes and Lifetimes of Superheavy Elements in the Nuclear Density Functional Theory  

SciTech Connect (OSTI)

Background: The reactions with the neutron-rich 48Ca beam and actinide targets resulted in the detection of new superheavy (SH) nuclides with Z=104 118. The unambiguous identification of the new isotopes, however, still poses a problem because their -decay chains terminate by spontaneous fission (SF) before reaching the known region of the nuclear chart. The understanding of the competition between -decay and SF channels in SH nuclei is, therefore, of crucial importance for our ability to map the SH region and to assess its extent.

Purpose: We perform self-consistent calculations of the competing decay modes of even-even SH isotopes with 108 Z 126 and 148 N 188.

Methods: We use the state-of-the-art computational framework based on self-consistent symmetry-unrestricted nuclear density functional theory capable of describing the competition between nuclear attraction and electrostatic repulsion. We apply the SkM* Skyrme energy density functional. The collective mass tensor of the fissioning superfluid nucleus is computed by means of the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov (HFB) approach. This paper constitutes a systematic self-consistent study of spontaneous fission in the SH region, carried out at a full HFB level, that simultaneously takes into account both triaxiality and reflection asymmetry.

Results: Breaking axial symmetry and parity turns out to be crucial for a realistic estimate of collective action; it results in lowering SF lifetimes by more than 7 orders of magnitude in some cases. We predict two competing SF modes: reflection symmetric modes and reflection asymmetric modes.

Conclusions: The shortest-lived SH isotopes decay by SF; they are expected to lie in a narrow corridor formed by 280Hs, 284Fl, and 118284Uuo that separates the regions of SH nuclei synthesized in cold-fusion and hot-fusion reactions. The region of long-lived SH nuclei is expected to be centered on 294Ds with a total half-life of 1.5 days. Our survey provides a solid benchmark for the future improvements of self-consistent SF calculations in the region of SH nuclei.

Staszczak, A, [UTK/ORNL/Inst. Physics, Maria Curie-Sklodowska University, Poland; Baran, A. [UTK/ORNL/Inst. Physics, Maria Curie-Sklodowska University, Poland; Nazarewicz, Witold [UTK/ORNL/University of Warsaw

2013-01-01T23:59:59.000Z

322

Energy Density Functionals From the Strong-Coupling Limit Applied to the Anions of the He Isoelectronic Series  

E-Print Network [OSTI]

Anions and radicals are important for many applications including environmental chemistry, semiconductors, and charge transfer, but are poorly described by the available approximate energy density functionals. Here we test an approximate exchange-correlation functional based on the exact strong-coupling limit of the Hohenberg-Kohn functional on the prototypical case of the He isoelectronic series with varying nuclear charge $Z$, which includes weakly bound negative ions and a quantum phase transition at a critical value of $Z$, representing a big challenge for density functional theory. We use accurate calculations to validate our results, comparing energies and Kohn-Sham potentials. We show that our functional is able to bind H$^-$ and to capture in general the physics of loosely bound anions, with a tendency to overbind that can be proven mathematically. We also include corrections based on the uniform electron gas which largely improve the results.

Mirtschink, Andr; Morgan, John D; Gori-Giorgi, Paola

2014-01-01T23:59:59.000Z

323

DOCTOR'S HEART George Stetten, M.D.  

E-Print Network [OSTI]

1 DOCTOR'S HEART George Stetten, M.D. "Resident Forum," Journal of the American Medical Association War --- soldier's heart. We should not be surprised or ashamed to find such reactions in ourselves

Stetten, George

324

David Brick, MD, FAAP, FACC Image credit  

E-Print Network [OSTI]

#12;David Brick, MD, FAAP, FACC #12;Image credit: www.imagewisely.org #12;1) Understand why Adolescent medicine 12-24 years Brain scans show unique features. Adult congenital Brand new natural

325

Density Functional Theory Study of Oxygen Reduction Activity on Ultrathin Platinum Nanotubes  

SciTech Connect (OSTI)

The structure, stability, and catalytic activity of a number of single- and double-wall platinum (n,m) nanotubes ranging in diameter from 0.3 to 2.0 nm were studied using plane-wave based density functional theory in the gas phase and water environment. The change in the catalytic activity toward the oxygen reduction reaction (ORR) with the size and chirality of the nanotube was studied by calculating equilibrium adsorption potentials for ORR intermediates and by constructing free energy diagrams in the ORR dissociative mechanism network. In addition, the stability of the platinum nanotubes is investigated in terms of electrochemical dissolution potentials and by determining the most stable state of the material as a function of pH and potential, as represented in Pourbaix diagrams. Our results show that the catalytic activity and the stability toward electrochemical dissolution depend greatly on the diameter and chirality of the nanotube. On the basis of the estimated overpotentials for ORR, we conclude that smaller, approximately 0.5 nm in diameter single-wall platinum nanotubes consistently show a huge, up to 400 mV larger overpotential than platinum, indicating very poor catalytic activity toward ORR. This is the result of substantial structural changes induced by the adsorption of any chemical species on these tubes. Single-wall n = m platinum nanotubes with a diameter larger than 1 nm have smaller ORR overpotentials than bulk platinum for up to 180 mV and thus show improved catalytic activity relative to bulk. We also predict that these nanotubes can endure the highest cell potentials but dissolution potentials are still for 110 mV lower than for the bulk, indicating a possible corrosion problem.

Matanovic, Ivana; Kent, Paul; Garzon, Fernando; Henson, Neil J.

2012-07-13T23:59:59.000Z

326

Uranium (VI)Bis(imido) chalcogenate complexes:synthesis and density functional theory analysis  

SciTech Connect (OSTI)

Bis(imido) uranium(VI) trans- and cis-dichalcogenate complexes with the general formula U(NtBu)2(EAr)2(OPPh3)2 (EAr = O-2-tBuC6H4, SPh, SePh, TePh) and U(NtBu)2(EAr)2(R2bpy) (EAr = SPh, SePh, TePh) (R2bpy = 4,4'-disubstituted-2,2'-bipyridyl, R = Me, tBu) have been prepared. This family of complexes includes the first reported monodentate selenolate and tellurolate complexes of uranium(VI). Density functional theory calculations show that covalent interactions in the U-E bond increase in the trans-dichalcogenate series U(NtBu)2(EAr)2(OPPh3)2 as the size of the chalcogenate donor increases and that both 5f and 6d orbital participation is important in the M-E bonds of U-S, U-Se, and U-Te complexes.

Spencer, Liam P [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory; Boncella, James M [Los Alamos National Laboratory; Yang, Ping [Los Alamos National Laboratory; Scott, Brian L [Los Alamos National Laboratory

2009-01-01T23:59:59.000Z

327

Spontaneous fission modes and lifetimes of super-heavy elements in the nuclear density functional theory  

E-Print Network [OSTI]

Lifetimes of super-heavy (SH) nuclei are primarily governed by alpha decay and spontaneous fission (SF). Here we study the competing decay modes of even-even SH isotopes with 108 density functional theory framework capable of describing the competition between nuclear attraction and electrostatic repulsion. The collective mass tensor of the fissioning superfluid nucleus is computed by means of the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov approach. Along the path to fission, our calculations allow for the simultaneous breaking of axial and space inversion symmetries; this may result in lowering SF lifetimes by more than seven orders of magnitude in some cases. We predict two competing SF modes: reflection-symmetric and reflection-asymmetric.The shortest-lived SH isotopes decay by SF; they are expected to lie in a narrow corridor formed by $^{280}$Hs, $^{284}$Fl, and $^{284}_{118}$Uuo that separates the regions of SH nuclei synthesized in "cold fusion" and "hot fusion" reactions. The region of long-lived SH nuclei is expected to be centered on $^{294}$Ds with a total half-life of ?1.5 days.

A. Staszczak; A. Baran; W. Nazarewicz

2012-08-06T23:59:59.000Z

328

Describing long-range charge-separation processes with subsystem density-functional theory  

SciTech Connect (OSTI)

Long-range charge-transfer processes in extended systems are difficult to describe with quantum chemical methods. In particular, cost-effective (non-hybrid) approximations within time-dependent density functional theory (DFT) are not applicable unless special precautions are taken. Here, we show that the efficient subsystem DFT can be employed as a constrained DFT variant to describe the energetics of long-range charge-separation processes. A formal analysis of the energy components in subsystem DFT for such excitation energies is presented, which demonstrates that both the distance dependence and the long-range limit are correctly described. In addition, electronic couplings for these processes as needed for rate constants in Marcus theory can be obtained from this method. It is shown that the electronic structure of charge-separated states constructed by a positively charged subsystem interacting with a negatively charged one is difficult to converge charge leaking from the negative subsystem to the positive one can occur. This problem is related to the delocalization error in DFT and can be overcome with asymptotically correct exchangecorrelation (XC) potentials or XC potentials including a sufficiently large amount of exact exchange. We also outline an approximate way to obtain charge-transfer couplings between locally excited and charge-separated states.

Solovyeva, Alisa; Neugebauer, Johannes, E-mail: j.neugebauer@uni-muenster.de [Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Simulation, Westflische Wilhelms-Universitt Mnster, Corrensstrae 40, 48149 Mnster (Germany)] [Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Simulation, Westflische Wilhelms-Universitt Mnster, Corrensstrae 40, 48149 Mnster (Germany); Pavanello, Michele, E-mail: m.pavanello@rutgers.edu [Department of Chemistry, Rutgers University, 73 Warren St., Newark, New Jersey 07102 (United States)] [Department of Chemistry, Rutgers University, 73 Warren St., Newark, New Jersey 07102 (United States)

2014-04-28T23:59:59.000Z

329

Microscopic description of fission in Uranium isotopes with the Gogny energy density functional  

E-Print Network [OSTI]

The most recent parametrizations D1S, D1N and D1M of the Gogny energy density functional are used to describe fission in the isotopes $^{232-280}$ U. Fission paths, collective masses and zero point quantum corrections, obtained within the constrained Hartree-Fock-Bogoliubov approximation, are used to compute the systematics of the spontaneous fission half-lives $t_\\mathrm{SF}$, the masses and charges of the fission fragments as well as their intrinsic shapes. The Gogny-D1M parametrization has been benchmarked against available experimental data on inner and second barrier heights, excitation energies of the fission isomers and half-lives in a selected set of Pu, Cm, Cf, Fm, No, Rf, Sg, Hs and Fl nuclei. It is concluded that D1M represents a reasonable starting point to describe fission in heavy and superheavy nuclei. Special attention is also paid to understand the uncertainties in the predicted $t_\\mathrm{SF}$ values arising from the different building blocks entering the standard semi-classical Wentzel-Kramers-Brillouin formula. Although the uncertainties are large, the trend with mass or neutron numbers are well reproduced and therefore the theory still has predictive power. In this respect, it is also shown that modifications of a few per cent in the pairing strength can have a significant impact on the collective masses leading to uncertainties in the $t_\\mathrm{SF}$ values of several orders of magnitude.

R. Rodriguez-Guzman; L. M. Robledo

2014-05-25T23:59:59.000Z

330

Hydrogen storage capacities of nanoporous carbon calculated by density functional and Mller-Plesset methods  

Science Journals Connector (OSTI)

The hydrogen storage capacities of nanoporous carbons, simulated as flat graphene slit pores, have been calculated using a quantum-thermodynamical model. The model is applied for several interaction potentials between the hydrogen molecules and the graphitic walls that have been generated from density functional theory (DFT) and second-order Mller-Plesset (MP2) calculations. The hydrogen storage properties of the pores can be correlated with the features of the potential. It is shown that the storage capacity increases with the depth of the potential, De. Moreover, the optimal pore widths, yielding the maximum hydrogen storage capacities, are close to twice the equilibrium distance of the hydrogen molecule to one graphene layer. The experimental hydrogen storage capacities of several nanoporous carbons such as activated carbons (ACs) and carbide-derived carbons (CDCs) are well reproduced within the slit pore model considering pore widths of about 4.95.1? for the DFT potential and slightly larger pore widths (5.35.9?) for the MP2 potentials. The calculations predict that nanoporous carbons made of slit pores with average widths of 5.86.5? would yield the highest hydrogen storage capacities at 300 K and 10 MPa.

I. Cabria; M. J. Lpez; J. A. Alonso

2008-08-13T23:59:59.000Z

331

Density functional study of CaN mono and bilayer on Cu(001)  

SciTech Connect (OSTI)

Density functional - pseudopotential calculations are performed to provide first-principles insights into magnetic behaviour of bulk CaN and CaN monolayers on Cu(001) in the rock-salt (RS) and zinc-blende (ZB) structures. Our results indicate that both RS- and ZB-CaN exhibit half-metallic ferromagnetism originated from the incomplete 2p shell of the nitrogen ion. In contrast to the bulk CaN, the CaN monolayers on Cu(001) generally favor ZB structure. We argue that the more stable ZB-CaN thin films on Cu(001) are nonmagnetic, because of strong Cu-N bonding at the interface, while the less stable Ca terminated ZB-CaN thin films exhibit half-metallic ferromagnetism. The transition path between the high energy ferromagnetic and the stable nonmagnetic configurations of the ZB-CaN monolayer on Cu(001) are studied by using the nudged elastic band method. We observe a two stages transition and an activation barrier of about 1.18 eV in the minimum energy path of this transition.

Zahedifar, Maedeh; Hashemifar, S. Javad, E-mail: hashemifar@cc.iut.ac.ir; Akbarzadeh, Hadi [Department of Physics, Isfahan University of Technology, Isfahan, 84156-83111 (Iran, Islamic Republic of)] [Department of Physics, Isfahan University of Technology, Isfahan, 84156-83111 (Iran, Islamic Republic of)

2014-01-15T23:59:59.000Z

332

Development and evaluation of probability density functions for a set of human exposure factors  

SciTech Connect (OSTI)

The purpose of this report is to describe efforts carried out during 1998 and 1999 at the Lawrence Berkeley National Laboratory to assist the U.S. EPA in developing and ranking the robustness of a set of default probability distributions for exposure assessment factors. Among the current needs of the exposure-assessment community is the need to provide data for linking exposure, dose, and health information in ways that improve environmental surveillance, improve predictive models, and enhance risk assessment and risk management (NAS, 1994). The U.S. Environmental Protection Agency (EPA) Office of Emergency and Remedial Response (OERR) plays a lead role in developing national guidance and planning future activities that support the EPA Superfund Program. OERR is in the process of updating its 1989 Risk Assessment Guidance for Superfund (RAGS) as part of the EPA Superfund reform activities. Volume III of RAGS, when completed in 1999 will provide guidance for conducting probabilistic risk assessments. This revised document will contain technical information including probability density functions (PDFs) and methods used to develop and evaluate these PDFs. The PDFs provided in this EPA document are limited to those relating to exposure factors.

Maddalena, R.L.; McKone, T.E.; Bodnar, A.; Jacobson, J.

1999-06-01T23:59:59.000Z

333

Introducing constricted variational density functional theory in its relaxed self-consistent formulation (RSCF-CV-DFT) as an alternative to adiabatic time dependent density functional theory for studies of charge transfer transitions  

SciTech Connect (OSTI)

We have applied the relaxed and self-consistent extension of constricted variational density functional theory (RSCF-CV-DFT) for the calculation of the lowest charge transfer transitions in the molecular complex X-TCNE between X = benzene and TCNE = tetracyanoethylene. Use was made of functionals with a fixed fraction (?) of Hartree-Fock exchange ranging from ? = 0 to ? = 0.5 as well as functionals with a long range correction (LC) that introduces Hartree-Fock exchange for longer inter-electronic distances. A detailed comparison and analysis is given for each functional between the performance of RSCF-CV-DFT and adiabatic time-dependent density functional theory (TDDFT) within the Tamm-Dancoff approximation. It is shown that in this particular case, all functionals afford the same reasonable agreement with experiment for RSCF-CV-DFT whereas only the LC-functionals afford a fair agreement with experiment using TDDFT. We have in addition calculated the CT transition energy for X-TCNE with X = toluene, o-xylene, and naphthalene employing the same functionals as for X = benzene. It is shown that the calculated charge transfer excitation energies are in as good agreement with experiment as those obtained from highly optimized LC-functionals using adiabatic TDDFT. We finally discuss the relation between the optimization of length separation parameters and orbital relaxation in the RSCF-CV-DFT scheme.

Krykunov, Mykhaylo; Seth, Mike; Ziegler, Tom [Department of Chemistry, University of Calgary, University Drive 2500, Calgary, Alberta T2N 1N4 (Canada)] [Department of Chemistry, University of Calgary, University Drive 2500, Calgary, Alberta T2N 1N4 (Canada)

2014-05-14T23:59:59.000Z

334

E-Print Network 3.0 - analytic density functional Sample Search...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Physics 17 Maximization of No-Load Flux Density in Surface Mounted Permanent Magnet Motors Frdric DUBAS, Christophe ESPANET & Abdellatif MIRAOUI. Summary:...

335

van der Waals density functionals built upon the electron-gas tradition: Facing the challenge of competing interactions  

SciTech Connect (OSTI)

The theoretical description of sparse matter attracts much interest, in particular for those ground-state properties that can be described by density functional theory. One proposed approach, the van der Waals density functional (vdW-DF) method, rests on strong physical foundations and offers simple yet accurate and robust functionals. A very recent functional within this method called vdW-DF-cx [K. Berland and P. Hyldgaard, Phys. Rev. B 89, 035412 (2014)] stands out in its attempt to use an exchange energy derived from the same plasmon-based theory from which the nonlocal correlation energy was derived. Encouraged by its good performance for solids, layered materials, and aromatic molecules, we apply it to several systems that are characterized by competing interactions. These include the ferroelectric response in PbTiO{sub 3}, the adsorption of small molecules within metal-organic frameworks, the graphite/diamond phase transition, and the adsorption of an aromatic-molecule on the Ag(111) surface. Our results indicate that vdW-DF-cx is overall well suited to tackle these challenging systems. In addition to being a competitive density functional for sparse matter, the vdW-DF-cx construction presents a more robust general-purpose functional that could be applied to a range of materials problems with a variety of competing interactions.

Berland, Kristian [Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Gteborg (Sweden) [Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Gteborg (Sweden); Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Arter, Calvin A.; Thonhauser, T. [Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109 (United States)] [Department of Physics, Wake Forest University, Winston-Salem, North Carolina 27109 (United States); Cooper, Valentino R. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6114 (United States)] [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6114 (United States); Lee, Kyuho [Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States) [Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720 (United States); Lundqvist, Bengt I. [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gteborg (Sweden)] [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Gteborg (Sweden); Schrder, Elsebeth; Hyldgaard, Per [Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Gteborg (Sweden)] [Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Gteborg (Sweden)

2014-05-14T23:59:59.000Z

336

Excited states properties of organic molecules: from density functional theory to the GW and BetheSalpeter Green's function formalisms  

Science Journals Connector (OSTI)

...quasi-particle Green's function approaches...accurate electronic energy levels (ionization...The many-body Green's function GW formalism...expression of the self-energy within many-body...the poles in the energy representation of...time-ordered G(1,2) Green's function which...

2014-01-01T23:59:59.000Z

337

Magnetism in undoped ZnS studied from density functional theory  

SciTech Connect (OSTI)

The magnetic property induced by the native defects in ZnS bulk, thin film, and quantum dots are investigated comprehensively based on density functional theory within the generalized gradient approximation + Hubbard U (GGA?+?U) approach. We find the origin of magnetism is closely related to the introduction of hole into ZnS systems. The relative localization of S-3p orbitals is another key to resulting in unpaired p-electron, due to Hund's rule. For almost all the ZnS systems under study, the magnetic moment arises from the S-dangling bonds generated by Zn vacancies. The charge-neutral Zn vacancy, Zn vacancy in 1? charge sate, and S vacancy in the 1+ charge sate produce a local magnetic moment of 2.0, 1.0, and 1.0??{sub B}, respectively. The Zn vacancy in the neutral and 1? charge sates are the important cause for the ferromagnetism in ZnS bulk, with a Curie temperature (T{sub C}) above room temperature. For ZnS thin film with clean (111) surfaces, the spins on each surface are ferromagnetically coupled but antiferromagnetically coupled between two surfaces, which is attributable to the internal electric field between the two polar (111) surfaces of the thin film. Only surface Zn vacancies can yield local magnetic moment for ZnS thin film and quantum dot, which is ascribed to the surface effect. Interactions between magnetic moments on S-3p states induced by hole-doping are responsible for the ferromagnetism observed experimentally in various ZnS samples.

Xiao, Wen-Zhi, E-mail: xiaowenzhi@hnu.edu.cn, E-mail: llwang@hun.edu.cn; Rong, Qing-Yan; Xiao, Gang [Department of Physics and Mathematics, Hunan Institute of Engineering, Xiangtan 411104 (China); Wang, Ling-ling, E-mail: xiaowenzhi@hnu.edu.cn, E-mail: llwang@hun.edu.cn [School of Physics and Microelectronics and Key Lab for Micro-Nano Physics and Technology of Hunan Province, Hunan University, Changsha 410082 (China); Meng, Bo [College of Physics and Electronic Engineering, Caili University, Kaili 556011 (China)

2014-06-07T23:59:59.000Z

338

Higher-order adaptive finite-element methods for KohnSham density functional theory  

SciTech Connect (OSTI)

We present an efficient computational approach to perform real-space electronic structure calculations using an adaptive higher-order finite-element discretization of KohnSham density-functional theory (DFT). To this end, we develop an a priori mesh-adaption technique to construct a close to optimal finite-element discretization of the problem. We further propose an efficient solution strategy for solving the discrete eigenvalue problem by using spectral finite-elements in conjunction with GaussLobatto quadrature, and a Chebyshev acceleration technique for computing the occupied eigenspace. The proposed approach has been observed to provide a staggering 100200-fold computational advantage over the solution of a generalized eigenvalue problem. Using the proposed solution procedure, we investigate the computational efficiency afforded by higher-order finite-element discretizations of the KohnSham DFT problem. Our studies suggest that staggering computational savingsof the order of 1000-foldrelative to linear finite-elements can be realized, for both all-electron and local pseudopotential calculations, by using higher-order finite-element discretizations. On all the benchmark systems studied, we observe diminishing returns in computational savings beyond the sixth-order for accuracies commensurate with chemical accuracy, suggesting that the hexic spectral-element may be an optimal choice for the finite-element discretization of the KohnSham DFT problem. A comparative study of the computational efficiency of the proposed higher-order finite-element discretizations suggests that the performance of finite-element basis is competing with the plane-wave discretization for non-periodic local pseudopotential calculations, and compares to the Gaussian basis for all-electron calculations to within an order of magnitude. Further, we demonstrate the capability of the proposed approach to compute the electronic structure of a metallic system containing 1688 atoms using modest computational resources, and good scalability of the present implementation up to 192 processors.

Motamarri, P. [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)] [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Nowak, M.R. [Department of Electrical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)] [Department of Electrical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Leiter, K.; Knap, J. [U.S. Army Research Labs, Aberdeen Proving Ground, Aberdeen, MD 21001 (United States)] [U.S. Army Research Labs, Aberdeen Proving Ground, Aberdeen, MD 21001 (United States); Gavini, V., E-mail: vikramg@umich.edu [Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI 48109 (United States)

2013-11-15T23:59:59.000Z

339

Interaction of TiO{sub 2}{sup ?} with water: Photoelectron spectroscopy and density functional calculations  

SciTech Connect (OSTI)

The interactions of titania with water molecules were studied via photoelectron spectroscopy and density functional calculations of TiO(OH){sub 2}{sup ?} and Ti(OH){sub 4}(H{sub 2}O){sub n}{sup ?} (n = 05) clusters which are corresponding to the TiO{sub 2}(H{sub 2}O){sup ?} and TiO{sub 2}(H{sub 2}O){sub n+2}{sup ?} (n = 05) systems, respectively. Experimental observation and theoretical calculations confirmed that TiO(OH){sub 2}{sup ?} was produced when TiO{sub 2}{sup ?} interacts with one water molecule, and Ti(OH){sub 4}(H{sub 2}O){sub n}{sup ?} (n = 05) were produced successively when TiO{sub 2}{sup ?} interacts with two or more water molecules. The structures of Ti(OH){sub 4}(H{sub 2}O){sub n}{sup ?} with n = 4, 5 are slightly different from those of n = 13. The structures of Ti(OH){sub 4}(H{sub 2}O){sub 1-3}{sup ?} can be viewed as the water molecules interacting with the Ti(OH){sub 4}{sup ?} core through hydrogen bonds; however, in Ti(OH){sub 4}(H{sub 2}O){sub 4,5}{sup ?}, one of the water molecules interacts directly with the Ti atom via its oxygen atom instead of a hydrogen bond and distorted the Ti(OH){sub 4}{sup ?} core.

Li, Ren-Zhong [College of Electronics and Information, Xi'an Polytechnic University, Xi'an 710048 (China) [College of Electronics and Information, Xi'an Polytechnic University, Xi'an 710048 (China); Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China); Xu, Hong-Guang; Cao, Guo-Jin; Xu, Xi-Ling; Zheng, Wei-Jun, E-mail: zhengwj@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)] [Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (China)

2013-11-14T23:59:59.000Z

340

Understanding of Ethanol Decomposition on Rh(111) From Density Functional Theory and Kinetic Monte Carlo Simulations  

SciTech Connect (OSTI)

Reaction mechanisms of ethanol decomposition on Rh(1 1 1) were elucidated by means of periodic density functional theory (DFT) calculations and kinetic Monte Carlo (KMC) simulations. We propose that the most probable reaction pathway is via CH{sub 3}CH{sub 2}O* on the basis of our mechanistic study: CH{sub 3}CH{sub 2}OH* {yields} CH{sub 3}CH{sub 2}O* {yields} CH{sub 2}CH{sub 2}O* {yields} CH{sub 2}CHO* {yields} CH{sub 2}CO* {yields} CHCO* {yields} CH* + CO* {yields} C* + CO*. In contrast, the contribution from the pathway via CH{sub 3}CHOH* is relatively small, CH{sub 3}CH{sub 2}OH* {yields} CH{sub 3}CHOH* {yields} CH{sub 3}CHO* {yields} CH{sub 3}CO* {yields} CH{sub 2}CO* {yields} CHCO* {yields} CH* + CO* {yields} C* + CO*. According to our calculations, one of the slow steps is the formation of the oxametallacycle CH{sub 2}CH{sub 2}O* species, which leads to the production of CHCO*, the precursor for C-C bond breaking. Finally, the decomposition of ethanol leads to the production of C and CO. Our calculations, for ethanol combustion on Rh, the major obstacle is not C-C bond cleavage, but the C contamination on Rh(1 1 1). The strong C-Rh interaction may deactivate the Rh catalyst. The formation of Rh alloys with Pt and Pd weakens the C-Rh interaction, easing the removal of C, and, as expected, in accordance with the experimental findings, facilitating ethanol combustion.

Liu, P.; Choi, Y.M.

2011-05-16T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Nonaxial-octupole Y_{32} correlations in N = 150 isotones from multidimensional constrained covariant density functional theories  

E-Print Network [OSTI]

The non-axial reflection-asymmetric $\\beta_{32}$ shape in some transfermium nuclei with N=150, namely $^{246}$Cm, $^{248}$Cf, $^{250}$Fm, and $^{252}$No are investigated with multidimensional constrained covariant density functional theories. By using the density-dependent point coupling covariant density functional theory with the parameter set DD-PC1 in the particle-hole channel, it is found that, for the ground states of $^{248}$Cf and $^{250}$Fm, the non-axial octupole deformation parameter $\\beta_{32} > 0.03$ and the energy gain due to the $\\beta_{32}$ distortion is larger than 300 keV. In $^{246}$Cm and $^{252}$No, shallow $\\beta_{32}$ minima are found. The occurrence of the non-axial octupole $\\beta_{32}$ correlations is mainly from a pair of neutron orbitals $[734]9/2$ ($\

Jie Zhao; Bing-Nan Lu; En-Guang Zhao; Shan-Gui Zhou

2012-09-28T23:59:59.000Z

342

Vacancy diffusion in colloidal crystals as determined by dynamical density-functional theory and the phase-field-crystal model  

E-Print Network [OSTI]

A two-dimensional crystal of repulsive dipolar particles is studied in the vicinity of its melting transition by using Brownian dynamics computer simulation, dynamical density functional theory and phase-field crystal modelling. A vacancy is created by taking out a particle from an equilibrated crystal and the relaxation dynamics of the vacancy is followed by monitoring the time-dependent one-particle density. We find that the vacancy is quickly filled up by diffusive hopping of neighbouring particles towards the vacancy center. We examine the temperature dependence of the diffusion constant and find that it decreases with decreasing temperature in the simulations. This trend is reproduced by the dynamical density functional theory. Conversely, the phase field crystal calculations predict the opposite trend. Therefore, the phase-field model needs a temperature-dependent expression for the mobility to predict trends correctly.

Sven van Teeffelen; Cristian Vasile Achim; Hartmut Lwen

2013-02-05T23:59:59.000Z

343

A density-functional theory investigation of cluster formation in an effective-potential model of dendrimers  

E-Print Network [OSTI]

We consider a system of particles interacting via a purely repulsive, soft-core potential recently introduced to model effective pair interactions between dendrimers, which is expected to lead to the formation of crystals with multiple occupancy of the lattice sites. The phase diagram is investigated by density-functional theory (DFT) without making any a priori assumption on the functional form of the density profile or on the type of crystal lattice. As the average density $\\rho$ is increased, the system displays first a transition from a fluid to a bcc phase, and subsequently to hcp and fcc phases. In the inhomogeneous region, the behavior is that found in previous investigations of this class of cluster-forming potentials. Specifically, the particles arrange into clusters strongly localized at the lattice sites, and the lattice constant depends very weakly on $\\rho$, leading to an occupancy number of the sites which is a nearly linear function of $\\rho$. These results are compared to those predicted by the more widespread approach, in which the DFT minimization is carried out by representing the density profile by a given functional form depending on few variational parameters. We find that for the model potential studied here, the latter approach recovers most of the predictions of the unconstrained minimization.

Davide Pini

2014-07-04T23:59:59.000Z

344

Linear Relationship Between Weighted-Average Madelung and Density Functional Theory Energies for MgO Nanotubes  

E-Print Network [OSTI]

Energies for MgO Nanotubes Journal: The Journal of Physical Chemistry Manuscript ID: jp-2012-08041d.R1 Constants and Density Functional Theory Energies for MgO Nanotubes Mark D. Baker,*1 A. David Baker2 , Jane-average Madelung constants of MgO nanotubes correlate in an essentially perfectly linear way with cohesive energies

Hanusa, Christopher

345

A computable evolution equation for the joint response-excitation probability density function of stochastic dynamical systems  

Science Journals Connector (OSTI)

...on the extended probability space consisting...response-excitation statistics. In particular...in the extended probability space consisting...response-excitation statistics, the standard...of the response probability density function...The relevant statistics, i.e. the mean...

2012-01-01T23:59:59.000Z

346

Large-eddy simulation/probability density function modeling of a non-premixed CO/H2  

E-Print Network [OSTI]

;applicable to practical devices such as gas turbine combustors and internal combustion engines [2­ 4]. In LES September 2012 Abstract We report a large-eddy simulation (LES)/probability density function (PDF) study/PDF modeling approach, recent progress of LES of tur- bulent combustion is reviewed in [10]. In the modeling

347

E-Print Network 3.0 - allen byrnes md Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

, M.D., 1975 Sue K. Anderson, M.D., 1977 Terry Allen Boulware, M.D., 1977 William E. Stricker, M.D... BAMD program. We also accept students into MD-only and MDoral surgery...

348

Density functional theory for the description of spherical non-associating monomers in confined media using the SAFT-VR equation of state and weighted density approximations  

SciTech Connect (OSTI)

As a first step of an ongoing study of thermodynamic properties and adsorption of complex fluids in confined media, we present a new theoretical description for spherical monomers using the Statistical Associating Fluid Theory for potential of Variable Range (SAFT-VR) and a Non-Local Density Functional Theory (NLDFT) with Weighted Density Approximations (WDA). The well-known Modified Fundamental Measure Theory is used to describe the inhomogeneous hard-sphere contribution as a reference for the monomer and two WDA approaches are developed for the dispersive terms from the high-temperature Barker and Henderson perturbation expansion. The first approach extends the dispersive contributions using the scalar and vector weighted densities introduced in the Fundamental Measure Theory (FMT) and the second one uses a coarse-grained (CG) approach with a unique weighted density. To test the accuracy of this new NLDFT/SAFT-VR coupling, the two versions of the theoretical model are compared with Grand Canonical Monte Carlo (GCMC) molecular simulations using the same molecular model. Only the version with the CG approach for the dispersive terms provides results in excellent agreement with GCMC calculations in a wide range of conditions while the FMT extension version gives a good representation solely at low pressures. Hence, the CG version of the theoretical model is used to reproduce methane adsorption isotherms in a Carbon Molecular Sieve and compared with experimental data after a characterization of the material. The whole results show an excellent agreement between modeling and experiments. Thus, through a complete and consistent comparison both with molecular simulations and with experimental data, the NLDFT/SAFT-VR theory has been validated for the description of monomers.

Malheiro, Carine; Mendiboure, Bruno; Plantier, Frdric; Miqueu, Christelle [Universit Pau et Pays Adour, CNRS, TOTAL - UMR 5150 LFC-R Laboratoire des Fluides Complexes et leurs Rservoirs, BP 1155 PAU, F-64013 (France)] [Universit Pau et Pays Adour, CNRS, TOTAL - UMR 5150 LFC-R Laboratoire des Fluides Complexes et leurs Rservoirs, BP 1155 PAU, F-64013 (France); Blas, Felipe J. [Departamento de Fsica Aplicada, and Centro de Fsica Terica y Matemtica FIMAT, Universidad de Huelva, 21071 Huelva (Spain)] [Departamento de Fsica Aplicada, and Centro de Fsica Terica y Matemtica FIMAT, Universidad de Huelva, 21071 Huelva (Spain)

2014-04-07T23:59:59.000Z

349

Exploring the limit of accuracy for density functionals based on the generalized gradient approximation: Local, global hybrid, and range-separated hybrid functionals with and without dispersion corrections  

SciTech Connect (OSTI)

The limit of accuracy for semi-empirical generalized gradient approximation (GGA) density functionals is explored by parameterizing a variety of local, global hybrid, and range-separated hybrid functionals. The training methodology employed differs from conventional approaches in 2 main ways: (1) Instead of uniformly truncating the exchange, same-spin correlation, and opposite-spin correlation functional inhomogeneity correction factors, all possible fits up to fourth order are considered, and (2) Instead of selecting the optimal functionals based solely on their training set performance, the fits are validated on an independent test set and ranked based on their overall performance on the training and test sets. The 3 different methods of accounting for exchange are trained both with and without dispersion corrections (DFT-D2 and VV10), resulting in a total of 491508 candidate functionals. For each of the 9 functional classes considered, the results illustrate the trade-off between improved training set performance and diminished transferability. Since all 491508 functionals are uniformly trained and tested, this methodology allows the relative strengths of each type of functional to be consistently compared and contrasted. The range-separated hybrid GGA functional paired with the VV10 nonlocal correlation functional emerges as the most accurate form for the present training and test sets, which span thermochemical energy differences, reaction barriers, and intermolecular interactions involving lighter main group elements.

Mardirossian, Narbe; Head-Gordon, Martin, E-mail: mhg@cchem.berkeley.edu [Department of Chemistry, University of California, Berkeley and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)] [Department of Chemistry, University of California, Berkeley and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2014-05-14T23:59:59.000Z

350

Structural and electronic properties of poly(vinyl alcohol) using density functional theory  

SciTech Connect (OSTI)

The first principles calculations have been carried out to investigate the structural, electronic band structure density of states along with the projected density of states for poly(vinyl alcohol). Our structural calculation suggests that the poly(vinyl alcohol) exhibits monoclinic structure. The calculated structural lattice parameters are in excellent agreement with available experimental values. The band structure calculations reveal that the direct and indirect band gaps are 5.55 eV and 5.363 eV respectively in accordance with experimental values.

Dabhi, Shweta, E-mail: shwetadabhi1190@gmail.com; Jha, Prafulla K., E-mail: shwetadabhi1190@gmail.com [Department of Physics, Maharaja Krishnakumasinhji Bhavnagar University, Bhavnagar-364001 (India)

2014-04-24T23:59:59.000Z

351

Comparison of Small Polaron Migration and Phase Separation in Olivine LiMnPO? and LiFePO? using Hybrid Density Functional Theory  

E-Print Network [OSTI]

Using hybrid density functional theory based on the Heyd-Scuseria-Ernzerhof (HSE06) functional, we compared polaron migration and phase separation in olivine LiMnPO? to LiFePO?. The barriers for free hole and electron ...

Ong, Shyue Ping

352

Electronic responses of long chains to electrostatic fields: Hartree-Fock vs. density-functional theory: A model study  

SciTech Connect (OSTI)

The response to an electrostatic field is determined through simple model calculations, within both the restricted Hartree-Fock and density functional theory methods, for long, finite as well as infinite, periodic chains. The permanent dipole moment, ?{sub 0}, the polarizability, ?, and the hyperpolarizabilities ? and ?, calculated using a finite-field approach, are extensively analyzed. Our simple model allows for treatment of large systems and for separation of the properties into atomic and unit-cell contributions. That part of the response properties attributable to the terminations of the finite system change into delocalized current contributions in the corresponding infinite periodic system. Special emphasis is placed on analyzing the reasons behind the dramatic overestimation of the response properties found with density functional theory methods presently in common use.

Vargas, Jorge, E-mail: j.vargas@mx.uni-saarland.de [Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrcken (Germany)] [Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrcken (Germany); Springborg, Michael, E-mail: m.springborg@mx.uni-saarland.de [Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrcken (Germany) [Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrcken (Germany); School of Materials Science and Engineering, Tianjin University, Tianjin 300072 (China); Kirtman, Bernard [Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 (United States)] [Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106 (United States)

2014-02-07T23:59:59.000Z

353

Derivation of a three-dimensional phase-field-crystal model for liquid crystals from density functional theory  

E-Print Network [OSTI]

Using a generalized order parameter gradient expansion within density functional theory, we derive a phase-field-crystal model for liquid crystals composed by apolar particles in three spatial dimensions. Both the translational density and the orientational direction and ordering are included as order parameters. Different terms involving gradients in the order parameters in the resulting free energy functional are compared to the macroscopic Ginzburg-Landau approach as well as to the hydrodynamic description for liquid crystals. Our approach provides microscopic expressions for all prefactors in terms of the particle interactions. Our phase-field-crystal model generalizes the conventional phase-field-crystal model of spherical particles to orientational degrees of freedom and can be used as a starting point to explore phase transitions and interfaces for various liquid-crystalline phases.

Raphael Wittkowski; Hartmut Lwen; Helmut R. Brand

2010-07-09T23:59:59.000Z

354

Improved analytical representation of combinations of Fermi-Dirac integrals for finite-temperature density functional calculations  

E-Print Network [OSTI]

Smooth, highly accurate analytical representations of Fermi-Dirac (FD) integral combinations important in free-energy density functional calculations are presented. Specific forms include those that occur in the local density approximation (LDA), generalized gradient approximation (GGA), and fourth-order gradient expansion of the non-interacting free energy as well as in the LDA and second-order gradient expansion for exchange. By construction, all the representations and their derivatives of any order are continuous on the full domains of their independent variables. The same type of technique provides an analytical representation of the function inverse to the FD integral of order $1/2$. It plays an important role in physical problems related to the electron gas at finite temperature. From direct evaluation, the quality of these improved representations is shown to be substantially superior to existing ones, many of which were developed before the era of large-scale computation or early in the era.

Karasiev, Valentin V; Trickey, S B

2014-01-01T23:59:59.000Z

355

Searching for 4$?$ linear-chain structure in excited states of $^{16}$O with a covariant density functional theory  

E-Print Network [OSTI]

A study of 4$\\alpha$ linear-chain structure in high-lying collective excitation states of $^{16}$O with a covariant density functional theory is presented. The low-spin states are obtained by configuration mixing of particle-number and angular-momentum projected quadrupole deformed mean-field states with generator coordinate method. The high-spin states are determined by cranking calculations. These two calculations are based on the same energy density functional PC-PK1. We have found a rotational band at low-spin with the dominated intrinsic configuration considered to be the one that 4$\\alpha$ clusters stay along a common axis. The strongly deformed rod shape also appears in the high-spin region with the angular momentum $13-18\\hbar$; however whether the state is pure $4\\alpha$ linear chain or not is less obvious than that in the low-spin states.

J. M. Yao; N. Itagaki; J. Meng

2014-03-31T23:59:59.000Z

356

Community Academic Profile Jon D. Fuller, MD  

E-Print Network [OSTI]

-1987 University of Utah School of Medicine MD Salt Lake City, Utah 1979-1983 University of Wyoming BS with honors-2001 Education & Community Professional Education Fellowship, Charles A. Dana. Foundation Fellowship Laramie, Wyoming Zoology/Physiology PROFESSIONAL TRAINING 1992-1993 Stanford University Charles A. Dana

Ford, James

357

Community Academic Profile Mina Charon, MD  

E-Print Network [OSTI]

.S., University of California, Davis, CA, 1992 Community & International Work RotaCare Free Clinic in Mountain View, CA Scientific Focus Publications Charon, M. Chapter on Yucca roots. In: Rotblatt MD, Ziment I Treadmill Testing · Medical staff scheduling VOLUNTEER: · RotaCare Free Clinic in Mountain View, California

Ford, James

358

Heart Valve Disease James S. Gammie, MD  

E-Print Network [OSTI]

Heart Valve Disease James S. Gammie, MD Professor and Chief Division of Cardiac Surgery University USA Source: CDC #12;#12;CARDIOTHORACIC SURGEON: A SURGEON THAT TREATS HEART AND LUNG DISEASE #12;Valvular Heart Disease: Common and Under-diagnosed 0 2 4 6 8 10 12 14 18 - 44 45 - 54 55 - 64 65 - 74 > 75

Weber, David J.

359

Strategic Plan Update Lydia Pleotis Howell MD  

E-Print Network [OSTI]

diagnostic testing that is tailored to the prevention and management of disease. 4. Develop a culture....where are we at and what have we accomplished?? #12; Maximized resources, efficiency and effectiveness CultureStrategic Plan Update 2014-2015 Lydia Pleotis Howell MD Professor and Chair Pathology

Leistikow, Bruce N.

360

Strategic Plan Update Lydia Pleotis Howell MD  

E-Print Network [OSTI]

diagnostic testing that is tailored to the prevention and management of disease. 4. Develop a culture....where are we at and what have we accomplished?? #12; Maximized resources, efficiency and effectiveness CultureStrategic Plan Update 2013-2014 Lydia Pleotis Howell MD Professor and Chair Pathology

Leistikow, Bruce N.

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Marylee M. Rothschild, MD Louisville, Kentucky  

E-Print Network [OSTI]

, which results in respiratory problems from indoor air pollution as well as burns. HELPS has installed Brookfield, Wisconsin Daniel L. Wegg, MD Winchester, Indiana Brett A. Wyrick, DO Hilo, Hawaii Solomon Adu the health effects of the stove program through a comparison of medical diagnoses before and after

362

Density Functional Calculations of ATP Systems. 1. Crystalline ATP Hydrates and Related J. Akola and R. O. Jones*  

E-Print Network [OSTI]

Density Functional Calculations of ATP Systems. 1. Crystalline ATP Hydrates and Related Molecules J¨lich, Germany ReceiVed: August 31, 2005; In Final Form: February 8, 2006 Adenosine 5-triphosphate (ATP ) 1, 4-7), the crystalline pyrophosphates Mg2P2O7,6H2O and R-CaNa2P2O7,4H2O, and crystalline Na2ATP,3H

363

Modeling with Hybrid Density Functional Theory the Electronic Band Alignment at the Zinc OxideAnatase Interface  

Science Journals Connector (OSTI)

Modeling with Hybrid Density Functional Theory the Electronic Band Alignment at the Zinc OxideAnatase Interface ... This work was pursued with financial help from national project FOTOMAT (Grant No. MAT2009-14625), regional project NUMANCIA-2 (Grant No. S2009ENE-1477), and COST action 540 PHONASUM and used the CTI computing infrastructure of the CSIC; to all of them thanks are given here. ...

Jos C. Conesa

2012-08-13T23:59:59.000Z

364

Surface Area and Microporosity of a Pillared Interlayered Clay (PILC) from a Hybrid Density Functional Theory (DFT) Method  

Science Journals Connector (OSTI)

Surface Area and Microporosity of a Pillared Interlayered Clay (PILC) from a Hybrid Density Functional Theory (DFT) Method ... Using these models and the experimental isotherm data, the integral equation of adsorption was inverted by a regularization method to yield the micropore and mesopore size distribution of a pillared interlayered clay (PILC). ... In this paper we show how such a deconvolution method can be used for estimating the pore size distribution of a pillared interlayered clay (PILC). ...

James P. Olivier; Mario L. Occelli

2000-12-23T23:59:59.000Z

365

Density functional theory study of oxygen and water adsorption on SrTiO3(001)  

E-Print Network [OSTI]

effortlessly leading to the formation of a pair of hydroxyl groups. For the titanium dioxide termina- tionDensity functional theory study of oxygen and water adsorption on SrTiO3(001) D I S S E R TAT I O N and they are computationally feasible. For the oxygen and water adsorption the binding energy is controlled by long-range sur

366

The structure of mixed {sup 3}He-{sup 4}He droplets doped with OCS: A density functional approach  

SciTech Connect (OSTI)

We have investigated the structure and energetics of mixed {sup 3}He-{sup 4}He droplets doped with a carbonyl sulfide molecule within a density functional approach considering a small but finite temperature of 0.1 K. The molecule is treated as an external field to which the helium droplet is attached. The energetics and appearance of these droplets are discussed for selected numbers of helium atoms, identifying the first magic numbers of the fermionic component.

Leal, Antonio; Mateo, David; Pi, Mart; Barranco, Manuel [Departament ECM, Facultat de Fsica and IN2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain)] [Departament ECM, Facultat de Fsica and IN2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Navarro, Jess [IFIC (CSIC-Universidad de Valencia), P.O. Box 22085, E-46071 Valencia (Spain)] [IFIC (CSIC-Universidad de Valencia), P.O. Box 22085, E-46071 Valencia (Spain)

2013-11-07T23:59:59.000Z

367

Generalization of internal Density Functional Theory and Kohn-Sham scheme to multicomponent systems, and link with traditional DFT  

E-Print Network [OSTI]

We generalize the recently developped "internal" Density Functional Theory (DFT) and Kohn-Sham scheme to multicomponent systems. We obtain a general formalism, applicable for the description of multicomponent self-bound systems (as molecules where the nuclei are treated explicitely, atomic nuclei and mix of 3He and 4He droplets), where the fundamental translational symmetry has been treated correctly. The main difference with traditional DFT is the explicit inclusion of center-of-mass correlations in the functional. A large part of the paper is dedicated to the application to molecules, which permits among other to clarify the approximations that underly traditional DFT.

Jeremie Messud

2011-11-21T23:59:59.000Z

368

Energy density functionals from the strong-coupling limit applied to the anions of the He isoelectronic series  

SciTech Connect (OSTI)

Anions and radicals are important for many applications including environmental chemistry, semiconductors, and charge transfer, but are poorly described by the available approximate energy density functionals. Here we test an approximate exchange-correlation functional based on the exact strong-coupling limit of the Hohenberg-Kohn functional on the prototypical case of the He isoelectronic series with varying nuclear charge Z < 2, which includes weakly bound negative ions and a quantum phase transition at a critical value of Z, representing a big challenge for density functional theory. We use accurate wavefunction calculations to validate our results, comparing energies and Kohn-Sham potentials, thus also providing useful reference data close to and at the quantum phase transition. We show that our functional is able to bind H{sup ?} and to capture in general the physics of loosely bound anions, with a tendency to strongly overbind that can be proven mathematically. We also include corrections based on the uniform electron gas which improve the results.

Mirtschink, Andr; Gori-Giorgi, Paola [Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, FEW, Vrije Universiteit, De Boelelaan 1083, 1081HV Amsterdam (Netherlands)] [Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, FEW, Vrije Universiteit, De Boelelaan 1083, 1081HV Amsterdam (Netherlands); Umrigar, C. J. [Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853 (United States)] [Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853 (United States); Morgan, John D. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)] [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States)

2014-05-14T23:59:59.000Z

369

Density Functional Theory for Protein Transfer Free Energy Eric A. Mills and Steven S. Plotkin*  

E-Print Network [OSTI]

-solvation" repulsive force at larger distances. 1. INTRODUCTION Proteins fold and function in the crowded environment different that the conditions for protein folding are generally mutually exclusive between the two milieu environment on protein folding, stability, and function. Accurately accounting for the effects of the cell

Plotkin, Steven S.

370

Density functional simulations of phase change materials: disordered phases of Ge8Sb2Te11 and Ag/In/Sb/Te alloys  

E-Print Network [OSTI]

E*PCOS2009 Density functional simulations of phase change materials: disordered phases of Ge8Sb2Te75.0Te17.7 (AIST). These represent two families used widely as phase change materials: pseudobinary and more flexible than those of Ag. Key words: Phase change materials, density functional calculations

371

Weighted-density functionals for cavity formation and dispersion energies in continuum solvation models  

E-Print Network [OSTI]

Continuum solvation models enable efficient first principles calculations of chemical reactions in solution, but require extensive parametrization and fitting for each solvent and class of solute systems. Here, we examine the assumptions of continuum solvation models in detail and replace empirical terms with physical models in order to construct a minimally-empirical solvation model. Specifically, we derive solvent radii from the nonlocal dielectric response of the solvent from ab initio calculations, construct a closed-form and parameter-free weighted-density approximation for the free energy of the cavity formation, and employ a pair-potential approximation for the dispersion energy. We show that the resulting model with a single solvent-independent parameter: the electron density threshold ($n_c$), and a single solvent-dependent parameter: the dispersion scale factor ($s_6$), reproduces solvation energies of organic molecules in water, chloroform and carbon tetrachloride with RMS errors of 1.1, 0.6 and 0....

Sundararaman, Ravishankar; Arias, T A

2014-01-01T23:59:59.000Z

372

Isospin-invariant Skyrme energy-density-functional approach with axial symmetry  

E-Print Network [OSTI]

We develop the isospin-invariant Skyrme-EDF method by considering local densities in all possible isospin channels and proton-neutron (p-n) mixing terms as mandated by the isospin symmetry. The EDF employed has the most general form that depends quadratically on the isoscalar and isovector densities. We test and benchmark the resulting p-n EDF approach, and study the general properties of the new scheme by means of the cranking in the isospin space. We extend the existing axial DFT solver HFBTHO to the case of isospin-invariant EDF approach with all possible p-n mixing terms. Explicit expressions have been derived for all the densities and potentials that appear in the isospin representation. In practical tests, we consider the Skyrme EDF SkM* and, as a first application, concentrate on Hartree-Fock aspects of the problem, i.e., pairing has been disregarded. Calculations have been performed for the (A=78, T~11), (A=40, T~8), and (A=48, T~4) isobaric analog chains. Isospin structure of self-consistent p-n mixed solutions has been investigated with and without the Coulomb interaction, which is the sole source of isospin symmetry breaking in our approach. The extended axial HFBTHO solver has been benchmarked against the symmetry-unrestricted HFODD code for deformed and spherical states. We developed and tested a general isospin-invariant Skyrme-EDF framework. The new approach permits spin-isospin densities that may give rise to, hitherto, unexplored modes in the excitation spectrum. The new formalism has been tested in the Hartree-Fock limit. A systematic comparison between HFODD and HFBTHO results show a maximum deviation of about 10 keV on the total binding energy for deformed nuclei when the Coulomb term is included. Without this term, the results of both solvers agree down to a ~10 eV level.

J. A. Sheikh; N. Hinohara; J. Dobaczewski; T. Nakatsukasa; W. Nazarewicz; K. Sato

2014-05-20T23:59:59.000Z

373

DOE - Office of Legacy Management -- Johns Hopkins University - MD 02  

Office of Legacy Management (LM)

Johns Hopkins University - MD 02 Johns Hopkins University - MD 02 FUSRAP Considered Sites Site: JOHNS HOPKINS UNIVERSITY (MD.02 ) Eliminated from further consideration under FUSRAP Designated Name: Not Designated Alternate Name: None Location: Baltimore , Maryland MD.02-1 Evaluation Year: 1987 MD.02-2 Site Operations: Conducted spectroscopic studies under contract number AT(49-1)-309. MD.02-1 Site Disposition: Eliminated - Potential for contamination considered remote based on limited quantities of material used in a controlled environment MD.02-2 Radioactive Materials Handled: Yes Primary Radioactive Materials Handled: Tritium MD.02-1 Radiological Survey(s): None Indicated Site Status: Eliminated from further consideration under FUSRAP Also see Documents Related to JOHNS HOPKINS UNIVERSITY

374

E-Print Network 3.0 - alan menter md Sample Search Results  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

MD (Chair) Psychiatry Psychiatry Marie Acierno, MD Ophthalmology... Ophthalmology David Smith, MD ... Source: Louisiana State University Health Sciences Center in New...

375

The effects of gaps between bridge foils and PETN as a function of PETN density and specific surface area  

SciTech Connect (OSTI)

X-ray computer tomography scans of artificially aged PETN seem to indicate shrinkage of material and, by extension, an increased high explosive density, resulting in potential separation of the HE from the header/bridge foil. We have investigated these phenomena by mimicking this shrinkage of material (load density). Thus, we have evaluated various induced gaps between the exploding bridge foil and the PETN in our custom detonators by changing both specific surface area - recognizing crystal morphology changes - and load density. Analyses for these data include absolute function time relative to bridge burst and careful evaluation of the detonation wave breakout curvature, using an electronic streak camera for wave capture, in cases where the bridge foil (exploding bridge wire - EBW style) initiation successfully traverses the gap (a 'go' condition). In addition, a fireset with subnanosecond trigger jitter was used for these tests allowing easy comparison of relative 'go' function times. Using the same test matrix and fine-tuning the induced gap, a second, smaller subset of these experiments were performed to provide additional insight as to what conditions we might expect detonator anomalies/failure.

Phillips, D; Roeske, F; Burnham, A

2007-06-26T23:59:59.000Z

376

Electronic and optical properties of nanocrystalline WO3 thin films studied by optical spectroscopy and density functional calculations  

Science Journals Connector (OSTI)

The optical and electronic properties of nanocrystalline WO3 thin films prepared by reactive dc magnetron sputtering at different total pressures (Ptot) were studied by optical spectroscopy and density functional theory (DFT) calculations. Monoclinic films prepared at low Ptot show absorption in the near infrared due to polarons, which is attributed to a strained film structure. Analysis of the optical data yields band-gap energies Eg?3.1eV, which increase with increasing Ptotby 0.1eV, and correlate with the structural modifications of the films. The electronic structures of triclinic ?-WO3, and monoclinic ?- and ?-WO3 were calculated using the Green function with screened Coulomb interaction (GW approach), and the local density approximation. The ?-WO3 and ?-WO3 phases are found to have very similar electronic properties, with weak dispersion of the valence and conduction bands, consistent with a direct band-gap. Analysis of the joint density of states shows that the optical absorption around the band edge is composed of contributions from forbidden transitions (>3eV) and allowed transitions (>3.8eV). The calculations show that Eg in ?-WO3 is higher than in the ?-WO3 and ?-WO3 phases, which provides an explanation for the Ptot dependence of the optical data.

Malin B Johansson; Gustavo Baldissera; Iryna Valyukh; Clas Persson; Hans Arwin; Gunnar A Niklasson; Lars sterlund

2013-01-01T23:59:59.000Z

377

Transverse exchange energy in relativistic density-functional calculations: An alternative approximation  

Science Journals Connector (OSTI)

The large error of the local-density approximation for the transverse photon-electron or Breit interaction is analyzed, transforming the Breit interaction into a sum of terms suitable to be handled in a nonrelativistic formalism: the local approximation for each of these terms is built up and an alternative expression for the relativistic exchange energy is proposed. Calculations using this expression are made for atoms ranging throughout the periodic table and the results show a sharp improvement when compared to those obtained by the previous approximation.

Mauro Boero and Pietro Cortona

1994-02-01T23:59:59.000Z

378

Density-functional theory of macroscopic stress: Gradient-corrected calculations for crystalline Se  

Science Journals Connector (OSTI)

We generalize the Nielsen-Martin stress theorem beyond the local-density approximation (LDA) and present an alternative derivation of the whole theorem. We show that the exchange-correlation stress becomes anisotropic in the most general case: its explicit form is given within a gradient-corrected (GC) scheme. As a test implementation, we use the generalized theorem to achieve fast structural optimization in crystalline Se. In this material LDA predicts a rather poor structure period. Our GC calculation is in much better agreement with the experiment.

Andrea Dal Corso and Raffaele Resta

1994-08-15T23:59:59.000Z

379

Near and Above Ionization Electronic Excitations with Non-Hermitian Real-Time Time-Dependent Density Functional Theory  

SciTech Connect (OSTI)

We present a real-time time-dependent density functional theory (RT-TDDFT) prescription for capturing near and post-ionization excitations based on non-Hermitian von Neumann density matrix propagation with atom-centered basis sets, tuned range-separated DFT, and a phenomenological imaginary molecular orbital-based absorbing potential to mimic coupling to the continuum. The computed extreme ultraviolet absorption spectra for acetylene (C2H2), water (H2O), and Freon 12 (CF2Cl2) agree well with electron energy loss spectroscopy (EELS) data over the range 0 to 50 eV. The absorbing potential removes spurious high energy finite basis artifacts, yielding correct bound to bound transitions, metastable (autoionizing) resonance states, and consistent overall absorption shapes.

Lopata, Kenneth A.; Govind, Niranjan

2013-11-12T23:59:59.000Z

380

Tools for incorporating a D-wave contribution in Skyrme energy density functionals  

E-Print Network [OSTI]

The possibility of adding a D-wave term to the standard Skyrme effective interaction has been widely considered in the past. Such a term has been shown to appear in the next-to-next-to-leading order of the Skyrme pseudo-potential. The aim of the present article is to provide the necessary tools to incorporate this term in a fitting procedure: first, a mean-field equation written in spherical symmetry in order to describe spherical nuclei and second, the response function to detect unphysical instabilities. With these tools it will be possible to build a new fitting procedure to determine the coupling constants of the new functional.

P. Becker; D. Davesne; J. Meyer; A. Pastore; J. Navarro

2014-06-02T23:59:59.000Z

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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Charged-Particle Thermonuclear Reaction Rates: II. Tables and Graphs of Reaction Rates and Probability Density Functions  

E-Print Network [OSTI]

Numerical values of charged-particle thermonuclear reaction rates for nuclei in the A=14 to 40 region are tabulated. The results are obtained using a method, based on Monte Carlo techniques, that has been described in the preceding paper of this series (Paper I). We present a low rate, median rate and high rate which correspond to the 0.16, 0.50 and 0.84 quantiles, respectively, of the cumulative reaction rate distribution. The meaning of these quantities is in general different from the commonly reported, but statistically meaningless expressions, "lower limit", "nominal value" and "upper limit" of the total reaction rate. In addition, we approximate the Monte Carlo probability density function of the total reaction rate by a lognormal distribution and tabulate the lognormal parameters {\\mu} and {\\sigma} at each temperature. We also provide a quantitative measure (Anderson-Darling test statistic) for the reliability of the lognormal approximation. The user can implement the approximate lognormal reaction rate probability density functions directly in a stellar model code for studies of stellar energy generation and nucleosynthesis. For each reaction, the Monte Carlo reaction rate probability density functions, together with their lognormal approximations, are displayed graphically for selected temperatures in order to provide a visual impression. Our new reaction rates are appropriate for bare nuclei in the laboratory. The nuclear physics input used to derive our reaction rates is presented in the subsequent paper of this series (Paper III). In the fourth paper of this series (Paper IV) we compare our new reaction rates to previous results.

Christian Iliadis; Richard Longland; Art Champagne; Alain Coc; Ryan Fitzgerald

2010-04-23T23:59:59.000Z

382

Core and Valence Excitations in Resonant X-ray Spectroscopy using Restricted Excitation Window Time-dependent Density Functional Theory  

SciTech Connect (OSTI)

We report simulations of X-ray absorption near edge structure (XANES), resonant inelastic X-ray scattering (RIXS) and 1D stimulated X-ray Raman spectroscopy (SXRS) signals of cysteine at the oxygen, nitrogen and sulfur K and L2,3 edges. The simulated XANES signals from the restricted window time-dependent density functional theory (REW-TDDFT) and the static exchange (STEX) method are compared with experiments, showing that REW-TDDFT is more accurate and computationally less expensive than STEX. Simulated RIXS and 1D SXRS signals from REW-TDDFT give some insights on the correlation of different excitations in the molecule.

Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul

2012-11-21T23:59:59.000Z

383

Description of interfaces of fluid-tethered chains: advances in density functional theories and off-lattice computer simulations  

E-Print Network [OSTI]

Many objects of nanoscopic dimensions involve fluid-tethered chain interfaces. These systems are of interest for basic science and for several applications, in particular for design of nanodevices for specific purposes. We review recent developments of theoretical methods in this area of research and in particular of density functional (DF) approaches, which provide important insights into microscopic properties of such interfaces. The theories permit to describe the dependence of adsorption, wettability, solvation forces and electric interfacial phenomena on thermodynamic states and on characteristics of tethered chains. Computer simulations for the problems in question are overviewed as well. Theoretical results are discussed in relation to simulation results and to some experimental observations.

S. Soko?owski; J. Ilnytskyi; O. Pizio

2014-03-06T23:59:59.000Z

384

BiFeO3 Domain Wall Energies and Structures: A Combined Experimental and Density Functional Theory+U Study  

DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

We determined the atomic structures and energies of 109, 180, and 71 domain walls in BiFeO3, combining density functional theory+U calculations and aberration-corrected transmission electron microscopy images. We find a substantial Bi sublattice shift and a rather uniform Fe sublattice across the walls. The calculated wall energies (?) follow the sequence ?109 180 71 for the 109, 180, and 71 walls. We attribute the high 71 wall energy to an opposite tilting rotation of the oxygen octahedra and the low 109 wall energy to the opposite twisting rotation of the oxygen octahedra across the domain walls.

Wang, Yi; Nelson, Chris; Melville, Alexander; Winchester, Benjamin; Shang, Shunli; Liu, Zi-Kui; Schlom, Darrell G.; Pan, Xiaoqing; Chen, Long-Qing

2013-06-01T23:59:59.000Z

385

Localized Orbital Corrections for the Barrier Heights in Density Functional Theory  

Science Journals Connector (OSTI)

In these cases, we have had to make decisions concerning which data to employ, and the choices are described below. ... Therefore, we must decide upon one resonance structure for each in order to successfully apply the LOC scheme. ... From an assessment of G2 and d. functional theories (DFT) on this test set G2 theory is the most reliable method both in terms of av. ...

Michelle Lynn Hall; Dahlia A. Goldfeld; Arteum D. Bochevarov; Richard A. Friesner

2009-10-27T23:59:59.000Z

386

DOE - Office of Legacy Management -- Maryland Disposal Site - MD 05  

Office of Legacy Management (LM)

Maryland Disposal Site - MD 05 Maryland Disposal Site - MD 05 FUSRAP Considered Sites Site: MARYLAND DISPOSAL SITE (MD.05 ) Eliminated from consideration under FUSRAP Designated Name: Not Designated Alternate Name: None Location: Baltimore - Vicinity , Maryland MD.05-1 Evaluation Year: 1989 MD.05-1 Site Operations: Proposed disposal site - never developed. MD.05-1 Site Disposition: Eliminated Radioactive Materials Handled: None Indicated Primary Radioactive Materials Handled: None Indicated Radiological Survey(s): None Indicated Site Status: Eliminated from consideration under FUSRAP Also see Documents Related to MARYLAND DISPOSAL SITE MD.05-1 - Report (DOE/OR/20722-131 Revision 0); Site Plan for the Maryland Disposal Site; April 1989 Historical documents may contain links which are no longer valid or to

387

Study of the interaction of solutes with ?5 (013) tilt grain boundaries in iron using density-functional theory  

SciTech Connect (OSTI)

Substitutional alloying elements significantly affect the recrystallization and austenite-ferrite phase transformation rates in steels. The atomistic mechanisms of their interaction with the interfaces are still largely unexplored. Using density functional theory, we determine the segregation energies between commonly used alloying elements and the ?5 (013) tilt grain boundary in bcc iron. We find a strong solute-grain boundary interaction for Nb, Mo, and Ti that is consistent with experimental observations of the effects of these alloying elements on delaying recrystallization and the austenite-to-ferrite transformation in low-carbon steels. In addition, we compute the solute-solute interactions as a function of solute pair distance in the grain boundary, which suggest co-segregation for these large solutes at intermediate distances in striking contrast to the bulk.

Jin, Hao; Militzer, Matthias [Centre for Metallurgical Process Engineering, The University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada); Elfimov, Ilya [Quantum Matter Institute, The University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada)

2014-03-07T23:59:59.000Z

388

Calculation of metallic and insulating phases of V{sub 2}O{sub 3} by hybrid density functionals  

SciTech Connect (OSTI)

The electronic structure of vanadium sesquioxide V{sub 2}O{sub 3} in its different phases has been calculated using the screened exchange hybrid density functional. The hybrid functional accurately reproduces the experimental electronic properties of all three phases, the paramagnetic metal (PM) phase, the anti-ferromagnetic insulating phase, and the Cr-doped paramagnetic insulating (PI) phase. We find that a fully relaxed supercell model of the Cr-doped PI phase based on the corundum structure has a monoclinic-like local strain around the substitutional Cr atoms. This is found to drive the PI-PM transition, consistent with a Peierls-Mott transition. The PI phase has a calculated band gap of 0.15 eV, in good agreement with experiment.

Guo, Yuzheng; Robertson, John, E-mail: jr@eng.cam.ac.uk [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom)] [Department of Engineering, University of Cambridge, Cambridge CB3 0FA (United Kingdom); Clark, Stewart J. [Department of Physics, University of Durham, Durham DH1 3LE (United Kingdom)] [Department of Physics, University of Durham, Durham DH1 3LE (United Kingdom)

2014-02-07T23:59:59.000Z

389

Heterogeneous nucleation of/on nanoparticles: a density functional study using the phase-field crystal model  

E-Print Network [OSTI]

Crystallization of supersaturated liquids usually starts by heterogeneous nucleation. Mounting evidence shows that even homogeneous nucleation in simple liquids takes place in two steps; first a dense amorphous precursor forms, and the crystalline phase appears via heterogeneous nucleation in/on the precursor cluster. Herein, we review recent results by a simple dynamical density functional theory, the phase-field crystal model, for (precursor-mediated) homogeneous and heterogeneous nucleation of nanocrystals. It will be shown that the mismatch between the lattice constants of the nucleating crystal and the substrate plays a decisive role in determining the contact angle and nucleation barrier, which were found to be non-monotonic functions of the lattice mismatch. Time dependent studies are essential as investigations based on equilibrium properties often cannot identify the preferred nucleation pathways. Modeling of these phenomena is essential for designing materials on the basis of controlled nucleation and/or nano-patterning.

Lszl Grnsy; Frigyes Podmaniczky; Gyula I. Tth; Gyrgy Tegze; Tams Pusztai

2014-07-14T23:59:59.000Z

390

Density Functional Theory Simulations Predict New Materials for Magnesium-Ion Batteries (Fact Sheet), NREL Highlights, Science  

SciTech Connect (OSTI)

Multivalence is identified in the light element, B, through structure morphology. Boron sheets exhibit highly versatile valence, and the layered boron materials may hold the promise of a high-energy-density magnesium-ion battery. Practically, boron is superior to previously known multivalence materials, especially transition metal compounds, which are heavy, expensive, and often not benign. Based on density functional theory simulations, researchers at the National Renewable Energy Laboratory (NREL) have predicted a series of stable magnesium borides, MgB{sub x}, with a broad range of stoichiometries, 2 < x < 16, by removing magnesium atoms from MgB{sub 2}. The layered boron structures are preserved through an in-plane topological transformation between the hexagonal lattice domains and the triangular domains. The process can be reversibly switched as the charge transfer changes with Mg insertion/extraction. The mechanism of such a charge-driven transformation originates from the versatile valence state of boron in its planar form. The discovery of these new physical phenomena suggests the design of a high-capacity magnesium-boron battery with theoretical energy density 876 mAh/g and 1550 Wh/L.

Not Available

2011-10-01T23:59:59.000Z

391

Deliquescence of NaBH4 from Density Functional Theory and Experiments  

Science Journals Connector (OSTI)

Ping Li , Lin Yu , Michael A. Matthews , Wissam A. Saidi , and J. Karl Johnson * ... We have used the DFT-TS approach as implemented within VASP by Al-Saidi et al.(43, 44) We have computed adsorption energies and geometries for several H2O/NaBH4(100) configurations using each of these functionals. ... Al-Saidi, W. A.; Voora, V. K.; Jordan, K. D.An Assessment of the vdW-TS Method for Extended Systems J. Chem. ...

Ping Li; Lin Yu; Michael A. Matthews; Wissam A. Saidi; J. Karl Johnson

2013-09-10T23:59:59.000Z

392

Ab initio density functional studies of stepped TaC surfaces V. B. Shenoy and C. V. Ciobanu  

E-Print Network [OSTI]

RevB.67.081402 PACS number s : 68.35.Bs, 68.35.Md, 73.20.At The stepped surfaces of transition-metal carbides TiC, TaC, etc. are technologically important due to their applica- tions as surface catalysts as they provide a rich ground for studying faceting transitions that involve single- and multiple-height steps

Ciobanu, Cristian

393

Comparison of several classical density functional theories for the adsorption of flexible chain molecules into cylindrical nanopores  

SciTech Connect (OSTI)

Adsorption of flexible oligomers into narrow cylindrical pores has been studied by means of several versions of classical density functional theory (CDFT) and Monte Carlo simulation. The adsorption process is interesting to study due to the competition between the entropic depletion of oligomers from the pores and the walloligomer attraction. It is also challenging to describe using current CDFTs, which tend to overestimate the amount of the adsorbed fluid. From a comparison of several different CDFT approaches, we find that this is due to the assumption of ideal or freely jointed chain conformations. Moreover, it is demonstrated that it is impossible to obtain a reasonable description of the adsorption isotherms without taking into account accurate contact values in the distribution functions describing the structure of the reference monomer fluid. At low densities, more accurate result are obtained in comparison with Monte Carlo simulation data when accurate contact values are incorporated into the theory rather than the more commonly used hard-sphere contact value. However, even the CDFT with accurate contact values still overestimates the amount of the adsorbed fluid due to the ideal or freely jointed chain approximation, used for the description of chain conformations in most CDFT approaches. We find that significant improvement can achieved by employing self-consistent field theory, which samples self-avoiding chain conformations and decreases the number of possible chain conformations, and, consequently, the amount of the adsorbed fluid.

Hlushak, S. P., E-mail: stepan.hlushak@gmail.com [Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States); Institute for Condensed Matter Physics, Svientsitskoho 1, 79011 Lviv (Ukraine); Cummings, P. T. [Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States) [Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States); Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); McCabe, C. [Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States) [Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States); Department of Chemistry, Vanderbilt University, Nashville 37235 (United States)

2013-12-21T23:59:59.000Z

394

Electronic structure and reactivity in water splitting of the iron oxide dimers and their hexacarbonyls: A density functional study  

SciTech Connect (OSTI)

The iron oxide dimers (FeO){sub 2} and their peroxide isomers are studied with the B3LYP density functional as bare clusters and as hexacarbonyls. Among the bare clusters the planar four-member ring structures are more stable than the non-planar ones and the rhombic dioxide Fe{sub 2}O{sub 2} with antiferromagnetically ordered electrons on iron centers is the global minimum. Water adsorption on the bare diiron dioxide is exothermic, but dissociation does not occur. Carbonylation favors a non-planar Fe{sub 2}O{sub 2} ring for both the dioxides and the peroxides and high electron density at the Fe centers is induced, evidenced by the natural charge distribution, the high proton affinity, and the values of global electronegativity and hardness. The iron dioxide hexacarbonyl Fe{sub 2}O{sub 2}(CO){sub 6} is diamagnetic in the state of the global minimum. It is separated from the next low-lying triplet state by a small energy gap of 0.22 eV. Time-dependent density functional theory methods were applied to examine electron excitations from the ground state to the low-lying triplet states in the hexacarbonyls and their adsorption complexes with water. Singlet-to-triplet state excitations occur via ligand-to-metal charge transfer in the hexacarbonyls; in the adsorption complexes excitations from the oxygen lone pairs to the adsorption center also occur and they appear in the IR-visible region. The lowest energy singlet and triplet state reaction paths for water splitting were followed. On the singlet potential energy surface (PES), water splitting is spontaneous, while for the triplet PES an activation barrier of 14.1 kJ mol{sup ?1} was determined.

Uzunova, Ellie L., E-mail: ellie@svr.igic.bas.bg [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia 1113 (Bulgaria); Mikosch, Hans [Institute for Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/E164-EC, 1060 Vienna (Austria)] [Institute for Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/E164-EC, 1060 Vienna (Austria)

2014-01-14T23:59:59.000Z

395

Triplet state photochemistry and the three-state crossing of acetophenone within time-dependent density-functional theory  

SciTech Connect (OSTI)

Even though time-dependent density-functional theory (TDDFT) works generally well for describing excited states energies and properties in the Franck-Condon region, it can dramatically fail in predicting photochemistry, notably when electronic state crossings occur. Here, we assess the ability of TDDFT to describe the photochemistry of an important class of triplet sensitizers, namely, aromatic ketones. We take acetophenone as a test molecule, for which accurate ab initio results exist in the literature. Triplet acetophenone is generated thanks to an exotic three-state crossing involving one singlet and two triplets states (i.e., a simultaneous intersystem crossing and triplet conical intersection), thus being a stringent test for approximate TDDFT. We show that most exchange-correlation functionals can only give a semi-qualitative picture of the overall photochemistry, in which the three-state crossing is rather represented as a triplet conical intersection separated from the intersystem crossing. The best result overall is given by the double hybrid functional mPW2PLYP, which is even able to reproduce quantitatively the three-state crossing region. We rationalize this results by noting that double hybrid functionals include a larger portion of double excitation character to the excited states.

Huix-Rotllant, Miquel, E-mail: miquel.huix@gmail.com; Ferr, Nicolas, E-mail: nicolas.ferre@univ-amu.fr [Institut de Chimie Radicalaire (UMR-7273), Aix-Marseille Universit, CNRS, 13397 Marseille Cedex 20 (France)] [Institut de Chimie Radicalaire (UMR-7273), Aix-Marseille Universit, CNRS, 13397 Marseille Cedex 20 (France)

2014-04-07T23:59:59.000Z

396

New density functional theory approaches for enabling prediction of chemical and physical properties of plutonium and other actinides.  

SciTech Connect (OSTI)

Density Functional Theory (DFT) based Equation of State (EOS) construction is a prominent part of Sandia's capabilities to support engineering sciences. This capability is based on amending experimental data with information gained from computational investigations, in parts of the phase space where experimental data is hard, dangerous, or expensive to obtain. A prominent materials area where such computational investigations are hard to perform today because of limited accuracy is actinide and lanthanide materials. The Science of Extreme Environment Lab Directed Research and Development project described in this Report has had the aim to cure this accuracy problem. We have focused on the two major factors which would allow for accurate computational investigations of actinide and lanthanide materials: (1) The fully relativistic treatment needed for materials containing heavy atoms, and (2) the needed improved performance of DFT exchange-correlation functionals. We have implemented a fully relativistic treatment based on the Dirac Equation into the LANL code RSPt and we have shown that such a treatment is imperative when calculating properties of materials containing actinides and/or lanthanides. The present standard treatment that only includes some of the relativistic terms is not accurate enough and can even give misleading results. Compared to calculations previously considered state of the art, the Dirac treatment gives a substantial change in equilibrium volume predictions for materials with large spin-orbit coupling. For actinide and lanthanide materials, a Dirac treatment is thus a fundamental requirement in any computational investigation, including those for DFT-based EOS construction. For a full capability, a DFT functional capable of describing strongly correlated systems such as actinide materials need to be developed. Using the previously successful subsystem functional scheme developed by Mattsson et.al., we have created such a functional. In this functional the Harmonic Oscillator Gas is providing the necessary reference system for the strong correlation and localization occurring in actinides. Preliminary testing shows that the new Hao-Armiento-Mattsson (HAM) functional gives a trend towards improved results for the crystalline copper oxide test system we have chosen. This test system exhibits the same exchange-correlation physics as the actinide systems do, but without the relativistic effects, giving access to a pure testing ground for functionals. During the work important insights have been gained. An example is that currently available functionals, contrary to common belief, make large errors in so called hybridization regions where electrons from different ions interact and form new states. Together with the new understanding of functional issues, the Dirac implementation into the RSPt code will permit us to gain more fundamental understanding, both quantitatively and qualitatively, of materials of importance for Sandia and the rest of the Nuclear Weapons complex.

Mattsson, Ann Elisabet

2012-01-01T23:59:59.000Z

397

Towards a specific reaction parameter density functional for reactive scattering of H{sub 2} from Pd(111)  

SciTech Connect (OSTI)

Recently, an implementation of the specific reaction parameter (SRP) approach to density functional theory (DFT) was used to study several reactive scattering experiments of H{sub 2} on Cu(111). It was possible to obtain chemical accuracy (1 kcal/mol ? 4.2 kJ/mol), and therefore, accurately model this paradigmatic example of activated H{sub 2} dissociation on a metal surface. In this work, the SRP-DFT methodology is applied to the dissociation of hydrogen on a Pd(111) surface, in order to test whether the SRP-DFT approach is also applicable to non-activated H{sub 2}-metal systems. In the calculations, the BornOppenheimer static surface approximations are used. A comparison to molecular beam sticking experiments, performed at incidence energies ?125 meV, on H{sub 2} + Pd(111) suggested the PBE-vdW [where the Perdew, Burke, and Ernzerhof (PBE) correlation is replaced by van der Waals correlation] functional as a candidate SRP density functional describing the reactive scattering of H{sub 2} on Pd(111). Unfortunately, quantum dynamics calculations are not able to reproduce the molecular beam sticking results for incidence energies <125 meV. From a comparison to initial state-resolved (degeneracy averaged) sticking probabilities it seems clear that for H{sub 2} + Pd(111) dynamic trapping and steering effects are important, and that these effects are not yet well modeled with the potential energy surfaces considered here. Applying the SRP-DFT method to systems where H{sub 2} dissociation is non-activated remains difficult. It is suggested that a density functional that yields a broader barrier distribution and has more non-activated pathways than PBE-vdW (i.e., non-activated dissociation at some sites but similarly high barriers at the high energy end of the spectrum) should allow a more accurate description of the available experiments. Finally, it is suggested that new and better characterized molecular beam sticking experiments be done on H{sub 2} + Pd(111), to facilitate the development of a more accurate theoretical description of this system.

Boereboom, J. M.; Wijzenbroek, M.; Somers, M. F.; Kroes, G. J. [Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands)] [Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands)

2013-12-28T23:59:59.000Z

398

Weighted?density?functional theory calculation of elastic constants for face?centered?cubic and body?centered?cubic hard?sphere crystals  

E-Print Network [OSTI]

The isothermal elastic constants for the face?centered?cubic (fcc) and body?centered?cubic (bcc) hard?sphere crystal are calculated for a range of densities using the modified weighted?density functional of Denton and Ashcroft [Phys. Rev. A 3 9...

Laird, Brian Bostian

1992-06-01T23:59:59.000Z

399

Intrinsic point-defect equilibria in tetragonal ZrO[subscript 2]: Density functional theory analysis with finite-temperature effects  

E-Print Network [OSTI]

We present a density functional theory (DFT) framework taking into account the finite temperature effects to quantitatively understand and predict charged defect equilibria in a metal oxide. Demonstration of this approach ...

Youssef, Mostafa Youssef Mahm

400

Texture classification based on comparison of second-order statistics. I. Two-point probability density function estimation and distance measure  

Science Journals Connector (OSTI)

The two-point probability density function (2P-PDF) gives a full description of the first- and second-order statistics of a random process. We propose a framework for texture...

Goon, Alexei A; Rolland, Jannick P

1999-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

Density Functional Theory Analysis of Metal/Graphene Systems As a Filter Membrane to Prevent CO Poisoning in Hydrogen Fuel Cells  

Science Journals Connector (OSTI)

Density Functional Theory Analysis of Metal/Graphene Systems As a Filter Membrane to Prevent CO Poisoning in Hydrogen Fuel Cells ... Fuel cells: principles, types, fuels, and applications ... Components for PEM fuel cell systems using hydrogen and CO containing fuels ...

Deborah J. D. Durbin; Cecile Malardier-Jugroot

2010-12-21T23:59:59.000Z

402

Templating Effects on the Mineralization of Layered Inorganic Compounds:? (1) Density Functional Calculations of the Formation of Single-Layered Magnesium Hydroxide as a Brucite Model  

Science Journals Connector (OSTI)

Templating Effects on the Mineralization of Layered Inorganic Compounds:? (1) Density Functional Calculations of the Formation of Single-Layered Magnesium Hydroxide as a Brucite Model ... This work aims at understanding the formation and stability of a layered structure of brucite mineral [Mg(OH)2] via density functional calculations. ... It has been confirmed that this polymerization reaction leads spontaneously to a planar cluster, which is regarded as a part of the brucite layer. ...

Hisako Sato; Akihiro Morita; Kanta Ono; Haruyuki Nakano; Noboru Wakabayashi; Akihiko Yamagishi

2003-07-12T23:59:59.000Z

403

Complex-energy approach to sum rules within nuclear density functional theory  

E-Print Network [OSTI]

The linear response of the nucleus to an external field contains unique information about the effective interaction, correlations, and properties of its excited states. To characterize the response, it is useful to use its energy-weighted moments, or sum rules. By comparing computed sum rules with experimental values, the information content of the response can be utilized in the optimization process of the nuclear Hamiltonian or EDF. But the additional information comes at a price: compared to the ground state, computation of excited states is more demanding. To establish an efficient framework to compute sum rules of the response that is adaptable to the optimization of the nuclear EDF and large-scale surveys of collective strength, we have developed a new technique within the complex-energy FAM based on the QRPA. To compute sum rules, we carry out contour integration of the response function in the complex-energy plane. We benchmark our results against the conventional matrix formulation of the QRPA theory...

Hinohara, Nobuo; Nazarewicz, Witold; Olsen, Erik

2015-01-01T23:59:59.000Z

404

Phenomenology of Psychogenic Movement Disorders in Children Joseph Ferrara, MD and Joseph Jankovic, MD  

E-Print Network [OSTI]

Phenomenology of Psychogenic Movement Disorders in Children Joseph Ferrara, MD and Joseph Jankovic little has been published regarding the frequency and phenomenology of PMDs in children. We reviewed (61) 14 (26) 7 (13) Objective: To assess the frequency and phenomenology of psychogenic movement

Lichtarge, Olivier

405

The Structure of Hydrated Electron. Part 1. Magnetic Resonance of Internally Trapping Water Anions: A Density Functional Theory Study  

E-Print Network [OSTI]

Density functional theory (DFT) is used to rationalize magnetic parameters of hydrated electron trapped in alkaline glasses as observed using Electron Paramagnetic Resonance (EPR) and Electron Spin Echo Envelope Modulation (ESEEM) spectroscopies. To this end, model water cluster anions (n=4-8 and n=20,24) that localize the electron internally are examined. It is shown that EPR parameters of such water anions (such as hyperfine coupling tensors of H/D nuclei in the water molecules) are defined mainly by the cavity size and the coordination number of the electron; the water molecules in the second solvation shell play a relatively minor role. An idealized model of hydrated electron (that is usually attributed to L. Kevan) in which six hydroxyl groups arranged in an octahedral pattern point towards the common center is shown to provide the closest match to the experimental parameters, such as isotropic and anisotropic hyperfine coupling constants for the protons (estimated from ESEEM), the second moment of the EPR spectra, and the radius of gyration. The salient feature of these DFT models is the significant transfer (10-20%) of spin density into the frontal O 2p orbitals of water molecules. Spin bond polarization involving these oxygen orbitals accounts for small, negative hyperfine coupling constants for protons in hydroxyl groups that form the electron-trapping cavity. In Part 2, these results are generalized for more realistic geometries of core anions obtained using a dynamic one-electron mixed qunatum/classical molecular dynamics model.

I. A. Shkrob

2006-07-25T23:59:59.000Z

406

Water-gas Shift Reaction on oxide/Cu(111): Rational Catalyst Screening from Density Functional Theory  

SciTech Connect (OSTI)

Developing improved catalysts based on a fundamental understanding of reaction mechanism has become one of the grand challenges in catalysis. A theoretical understanding and screening the metal-oxide composite catalysts for the water-gas shift (WGS) reaction is presented here. Density functional theory was employed to identify the key step for the WGS reaction on the Au, Cu-oxide catalysts, where the calculated reaction energy for water dissociation correlates well with the experimental measured WGS activity. Accordingly, the calculated reaction energy for water dissociation was used as the scaling descriptor to screen the inverse model catalysts, oxide/Cu(111), for the better WGS activity. Our calculations predict that the WGS activity increases in a sequence: Cu(111), ZnO/Cu(111) < TiO{sub 2}/Cu(111), ZrO{sub 2}/Cu(111) < MoO{sub 3}/Cu(111). Our results imply that the high performances of Au, Cu-oxide nanocatalysts in the WGS reaction rely heavily on the direct participation of both oxide and metal sites. The degree that the oxide is reduced by Cu plays an important role in determining the WGS activity of oxide/Cu catalysts. The reducible oxide can be transformed from the fully oxidized form to the reduced form due to the interaction with Cu and, therefore, the transfer of electron density from Cu, which helps in releasing the bottleneck water dissociation and, therefore, facilitating the WGS reaction on copper.

Liu, P.

2010-11-28T23:59:59.000Z

407

Helium under high pressure: A comparative study of all-electron and pseudopotential methods within density functional theory  

E-Print Network [OSTI]

We have calculated the ground state electronic structure of He under pressure from 0 to 1500 GPa using both all-electron full-potential and pseudopotential methods based on the density functional theory (DFT). We find that throughout this pressure range, pseudopotentials yield essentially the same energy-volume curve for all of bcc, fcc, and hcp configurations as does the full-potential method, a strong indication that pseudopotential approximation works well for He both as the common element in some giant planets and as detrimental impurities in fusion reactor materials. The hcp lattice is always the most stable structure and bcc the least stable one. Since the energy preference of hcp over fcc and bcc is within 0.01 eV below 100 GPa and about 0.1 eV at 1500 GPa, on the same order of the error bar in local or semi-local density approximations in DFT, phase transitions can only be discussed with more precise description of electron correlation in Quantum Monte Carlo or DFT-based GW methods.

Xiao, W; Geng, W T

2012-01-01T23:59:59.000Z

408

Crucial test for covariant density functional theory with new and accurate mass measurements from Sn to Pa  

E-Print Network [OSTI]

The covariant density functional theory with the point-coupling interaction PC-PK1 is compared with new and accurate experimental masses in the element range from 50 to 91. The experimental data are from a mass measurement performed with the storage ring mass spectrometry at GSI [Chen et al., Nucl. Phys. A 882, 71 (2012)]. Although the microscopic theory contains only 11 parameters, it agrees well with the experimental data. The comparison is characterized by a rms deviation of 0.859 MeV. For even-even nuclei, the theory agrees within about 600 keV. Larger deviations are observed in this comparison for the odd-A and odd-odd nuclei. Improvements and possible reasons for the deviations are discussed in this contribution as well.

P. W. Zhao; L. S. Song; B. Sun; H. Geissel; J. Meng

2012-12-31T23:59:59.000Z

409

Elastic constants and Fermi surface topology change in Calaverite AuTe{sub 2}: A density functional study  

SciTech Connect (OSTI)

Structural, elastic, electronic and Fermi surface studies of AuTe{sub 2} have been carried out by means of first principles calculations based on density functional theory. The calculated ground state properties agree well with the experiment. Fermi surface and elastic constants are predicted for the first time and from the calculated elastic constants we find the compound to be mechanically stable satisfying the stability criteria of monoclinic structure. In addition, we also find the c-axis to be more compressible than the other two which is also speculated from the present work. The metallic behaviour of this compound is confirmed from the electronic band structure calculation as we find the bands to cross the Fermi level (E{sub F}). In addition, we also observe a FS topology change under pressure which is also explained in the present work.

Gudelli, Vijay Kumar, E-mail: kanchana@iith.ac.in; Kanchana, V., E-mail: kanchana@iith.ac.in [Department of Physics, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram-502205, Andhra Pradesh (India)

2014-04-24T23:59:59.000Z

410

UV-vis spectra of singlet state cationic polycyclic aromatic hydrocarbons: Time-dependent density functional theory study  

SciTech Connect (OSTI)

A theoretical study of singlet state cations of polycyclic aromatic hydrocarbons is performed. Appropriate symmetry suitable for further calculations is chosen for each of the systems studied. The excitation states of such species are obtained by the time dependent density functional theory (TD-DFT) method. The computations are performed using both Pople and electronic response properties basis sets. The results obtained with the use of different basis sets are compared. The electronic transitions are described and the relationships for the lowest-lying transitions states of different species are found. The properties of in-plane and out-of-plane transitions are also delineated. The TD-DFT results are compared with the experimental data available.

Dominikowska, Justyna, E-mail: justyna@uni.lodz.pl; Domagala, Malgorzata; Palusiak, Marcin [Department of Theoretical and Structural Chemistry, University of ?d?, Pomorska 163/165, 90-236 ?d? (Poland)] [Department of Theoretical and Structural Chemistry, University of ?d?, Pomorska 163/165, 90-236 ?d? (Poland)

2014-01-28T23:59:59.000Z

411

Density Functional Theory for Fractional Particle Number: Derivative Discontinuity of the Energy at the Maximum Number of Bound Electrons  

E-Print Network [OSTI]

The derivative discontinuity in the exact exchange-correlation potential of ensemble Density Functional Theory (DFT) is investigated at the specific integer number that corresponds to the maximum number of bound electrons, $J_{max}$. A recently developed complex-scaled analog of DFT is extended to fractional particle numbers and used to study ensembles of both bound and metastable states. It is found that the exact exchange-correlation potential experiences discontinuous jumps at integer particle numbers including $J_{max}$. For integers below $J_{max}$ the jump is purely real because of the real shift in the chemical potential. At $J_{max}$, the jump has a non-zero imaginary component reflecting the finite lifetime of the $(J_{max}+1)$ state.

Daniel L. Whitenack; Yu Zhang; Adam Wasserman

2011-11-08T23:59:59.000Z

412

Permeation of low-Z atoms through carbon sheets: Density functional theory study on energy barriers and deformation effects  

SciTech Connect (OSTI)

Energetic and geometric aspects of the permeation of the atoms hydrogen to neon neutral atoms through graphene sheets are investigated by investigating the associated energy barriers and sheet deformations. Density functional theory calculations on cluster models, where graphene is modeled by planar polycyclic aromatic hydrocarbons (PAHs), provide the energies and geometries. Particularities of our systems, such as convergence of both energy barriers and deformation curves with increasing size of the PAHs, are discussed. Three different interaction regimes, adiabatic, planar and vertical, are investigated by enforcing different geometrical constraints. The adiabatic energy barriers range from 5 eV for hydrogen to 20 eV for neon. We find that the permeation of oxygen and carbon into graphene is facilitated by temporary chemical bonding while for other, in principle reactive atoms, it is not. We discuss implications of our results for modeling chemical sputtering of graphite.

Huber, Stefan E., E-mail: s.huber@uibk.ac.at, E-mail: Michael.probst@uibk.ac.at; Mauracher, Andreas; Probst, Michael, E-mail: s.huber@uibk.ac.at, E-mail: Michael.probst@uibk.ac.at [Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstrae 25, 6020 Innsbruck (Austria)] [Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstrae 25, 6020 Innsbruck (Austria)

2013-12-15T23:59:59.000Z

413

Density Functional Theory and Reaction Kinetics Studies of the WaterGas Shift Reaction on PtRe Catalysts  

SciTech Connect (OSTI)

Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the watergas shift (WGS) reaction over Pt and PtRe catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the PtRe alloy catalyst likely contain partially oxidized metal ensembles.

Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

2013-12-01T23:59:59.000Z

414

Electronic and optical properties of Co-doped 3C-SiC from density functional calculations  

Science Journals Connector (OSTI)

Abstract Structural properties along with the electronic and optical properties of intrinsic 3C-SiC and Co doped 3C-SiC are calculated using the first principles method based on the density functional theory. The calculated results show that the Fermi level locates at the valence band maximum in the pure 3C-SiC, while it shifts to the conduction band and exhibits metal-like characteristic after Co atoms are introduced into the SiC supercell. The calculated electronic structures indicate that the number of the energy levels in upper valence band substantially increased after Co doping, which is attributed to the Co-3d states. The optical property calculation suggests that the intensity of the photoluminescence (PL) spectrum is determined by the bandgap and the location of PL peak is associated with the optical absorption.

P.L. Zhou; S.K. Zheng; Lei Ma; Jingfang He; Yan Tian; Ruqian Shi

2014-01-01T23:59:59.000Z

415

Crucial test for covariant density functional theory with new and accurate mass measurements from Sn to Pa  

Science Journals Connector (OSTI)

The covariant density functional theory with the point-coupling interaction PC-PK1 is compared with new and accurate experimental masses in the element range from 50 to 91. The experimental data are from a mass measurement performed with the storage ring mass spectrometry at Gesellschaft fr Schwerionenforschung (GSI) [Chen et al., Nucl. Phys. A 882, 71 (2012)]. Although the microscopic theory contains only 11 parameters, it agrees well with the experimental data. The comparison is characterized by a rms deviation of 0.859 MeV. For even-even nuclei, the theory agrees within about 600 keV. Larger deviations are observed in this comparison for the odd-A and odd-odd nuclei. Improvements and possible reasons for the deviations are discussed in this contribution as well.

P. W. Zhao (???); L. S. Song (???); B. Sun (???); H. Geissel; J. Meng (??)

2012-12-28T23:59:59.000Z

416

A posteriori inclusion of parton density functions in NLO QCD final-state calculations at hadron colliders: The APPLGRID Project  

E-Print Network [OSTI]

A method to facilitate the consistent inclusion of cross-section measurements based on complex final-states from HERA, TEVATRON and the LHC in proton parton density function (PDF) fits has been developed. This can be used to increase the sensitivity of LHC data to deviations from Standard Model predictions. The method stores perturbative coefficients of NLO QCD calculations of final-state observables measured in hadron colliders in look-up tables. This allows the posteriori inclusion of parton density functions (PDFs), and of the strong coupling, as well as the a posteriori variation of the renormalisation and factorisation scales in cross-section calculations. The main novelties in comparison to original work on the subject are the use of higher-order interpolation, which substantially improves the trade-off between accuracy and memory use, and a CPU and computer memory optimised way to construct and store the look-up table using modern software tools. It is demonstrated that a sufficient accuracy on the cross-section calculation can be achieved with reasonably small look-up table size by using the examples of jet production and electro-weak boson (Z, W) production in proton-proton collisions at a center-of-mass energy of 14 TeV at the LHC. The use of this technique in PDF fitting is demonstrated in a PDF-fit to HERA data and simulated LHC jet cross-sections as well as in a study of the jet cross-section uncertainties at various centre-of-mass energies.

Tancredi Carli; Dan Clements; Amanda Cooper-Sarkar; Claire Gwenlan; Gavin P. Salam; Frank Siegert; Pavel Starovoitov; Mark Sutton

2009-11-16T23:59:59.000Z

417

Electron dynamics in complex environments with real-time time dependent density functional theory in a QM-MM framework  

SciTech Connect (OSTI)

This article presents a time dependent density functional theory (TDDFT) implementation to propagate the Kohn-Sham equations in real time, including the effects of a molecular environment through a Quantum-Mechanics Molecular-Mechanics (QM-MM) hamiltonian. The code delivers an all-electron description employing Gaussian basis functions, and incorporates the Amber force-field in the QM-MM treatment. The most expensive parts of the computation, comprising the commutators between the hamiltonian and the density matrixrequired to propagate the electron dynamics, and the evaluation of the exchange-correlation energy, were migrated to the CUDA platform to run on graphics processing units, which remarkably accelerates the performance of the code. The method was validated by reproducing linear-response TDDFT results for the absorption spectra of several molecular species. Two different schemes were tested to propagate the quantum dynamics: (i) a leap-frog Verlet algorithm, and (ii) the Magnus expansion to first-order. These two approaches were confronted, to find that the Magnus scheme is more efficient by a factor of six in small molecules. Interestingly, the presence of iron was found to seriously limitate the length of the integration time step, due to the high frequencies associated with the core-electrons. This highlights the importance of pseudopotentials to alleviate the cost of the propagation of the inner states when heavy nuclei are present. Finally, the methodology was applied to investigate the shifts induced by the chemical environment on the most intense UV absorption bands of two model systems of general relevance: the formamide molecule in water solution, and the carboxy-heme group in Flavohemoglobin. In both cases, shifts of several nanometers are observed, consistently with the available experimental data.

Morzan, Uriel N.; Ramrez, Francisco F.; Scherlis, Damin A., E-mail: damian@qi.fcen.uba.ar, E-mail: mcgl@qb.ffyb.uba.ar [Departamento de Qumica Inorgnica, Analtica y Qumica Fsica/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Buenos Aires (C1428EHA) (Argentina); Oviedo, M. Beln; Snchez, Cristin G. [Departamento de Matemtica y Fsica, Facultad de Ciencias Qumicas, INFIQC, Universidad Nacional de Crdoba, Ciudad Universitaria, X5000HUA Crdoba (Argentina)] [Departamento de Matemtica y Fsica, Facultad de Ciencias Qumicas, INFIQC, Universidad Nacional de Crdoba, Ciudad Universitaria, X5000HUA Crdoba (Argentina); Lebrero, Mariano C. Gonzlez, E-mail: damian@qi.fcen.uba.ar, E-mail: mcgl@qb.ffyb.uba.ar [Instituto de Qumica y Fisicoqumica Biolgicas, IQUIFIB, CONICET (Argentina)] [Instituto de Qumica y Fisicoqumica Biolgicas, IQUIFIB, CONICET (Argentina)

2014-04-28T23:59:59.000Z

418

DOE - Office of Legacy Management -- Max Zuckerman and Sons Inc - MD 04  

Office of Legacy Management (LM)

Inc - MD 04 Inc - MD 04 FUSRAP Considered Sites Site: MAX ZUCKERMAN & SONS, INC. (MD.04 ) Eliminated from consideration under FUSRAP Designated Name: Not Designated Alternate Name: Maryland Alloys Corporation MD.04-1 Location: 5245 Fairlawn Avenue , Baltimore , Maryland MD.04-2 Evaluation Year: 1994 MD.04-1 MD.04-3 Site Operations: Scrap metals broker that arranged purchases of materials for third party buyers. MD.04-2 MD.04-4 Site Disposition: Eliminated - Potential for contamination remote MD.04-3 Radioactive Materials Handled: Yes Primary Radioactive Materials Handled: Uranium (Q-11) Oxide/Residue MD.04-2 MD.04-4 Radiological Survey(s): Yes MD.04-1 Site Status: Eliminated from consideration under FUSRAP MD.04-3 Also see Documents Related to MAX ZUCKERMAN & SONS, INC.

419

Self-interaction-free time-dependent density-functional theory for molecular processes in strong fields: High-order harmonic generation of H2 in intense laser fields  

E-Print Network [OSTI]

Self-interaction-free time-dependent density-functional theory for molecular processes in strong work of Hohenberg and Kohn 1 and Kohn and Sham 2 , the steady-state density-functional theory DFT has-electron systems, within the density-functional theory, is much less developed. The central theme of the modern

Chu, Shih-I

420

The 2dF Galaxy Redshift Survey: correlation functions, peculiar velocities and the matter density of the Universe  

E-Print Network [OSTI]

We present a detailed analysis of the two-point correlation function, from the 2dF Galaxy Redshift Survey (2dFGRS). We estimate the redshift-space correlation function, xi(s), from which we measure the redshift-space clustering length, s_0=6.82+/-0.28 Mpc/h. We also estimate the projected correlation function, Xi(sigma), and the real-space correlation function, xi(r), which can be fit by a power-law, with r_0=5.05+/-0.26Mpc/h, gamma_r=1.67+/-0.03. For r>20Mpc/h, xi drops below a power-law as is expected in the popular LCDM model. The ratio of amplitudes of the real and redshift-space correlation functions on scales of 8-30Mpc/h gives an estimate of the redshift-space distortion parameter beta. The quadrupole moment of xi on scales 30-40Mpc/h provides another estimate of beta. We also estimate the distribution function of pairwise peculiar velocities, f(v), including rigorously the effect of infall velocities, and find that it is well fit by an exponential. The accuracy of our xi measurement is sufficient to constrain a model, which simultaneously fits the shape and amplitude of xi(r) and the two redshift-space distortion effects parameterized by beta and velocity dispersion, a. We find beta=0.49+/-0.09 and a=506+/-52km/s, though the best fit values are strongly correlated. We measure the variation of the peculiar velocity dispersion with projected separation, a(sigma), and find that the shape is consistent with models and simulations. Using the constraints on bias from recent estimates, and taking account of redshift evolution, we conclude that beta(L=L*,z=0)=0.47+/-0.08, and that the present day matter density of the Universe is 0.3, consistent with other 2dFGRS estimates and independent analyses.

E. Hawkins; S. Maddox; S. Cole; O. Lahav; D. Madgwick; P. Norberg; J. Peacock; I. Baldry; C. Baugh; J. Bland-Hawthorn; T. Bridges; R. Cannon; M. Colless; C. Collins; W. Couch; G. Dalton; R. De Propris; S. Driver; G. Efstathiou; R. Ellis; C. Frenk; K. Glazebrook; C. Jackson; B. Jones; I. Lewis; S. Lumsden; W. Percival; B. Peterson; W. Sutherland; K. Taylor

2003-08-05T23:59:59.000Z

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

"Kohn-Shamification" of the classical density-functional theory of inhomogeneous polar molecular liquids with application to liquid hydrogen chloride  

E-Print Network [OSTI]

The Gordian knot of density-functional theories for classical molecular liquids remains finding an accurate free-energy functional in terms of the densities of the atomic sites of the molecules. Following Kohn and Sham, we show how to solve this problem by considering noninteracting molecules in a set of effective potentials. This shift in perspective leads to an accurate and computationally tractable description in terms of simple three-dimensional functions. We also treat both the linear- and saturation- dielectric responses of polar systems, presenting liquid hydrogen chloride as a case study.

Johannes Lischner; T. A. Arias

2008-06-27T23:59:59.000Z

422

Increasing the applicability of density functional theory. IV. Consequences of ionization-potential improved exchange-correlation potentials  

SciTech Connect (OSTI)

This paper's objective is to create a consistent mean-field based Kohn-Sham (KS) density functional theory (DFT) meaning the functional should not only provide good total energy properties, but also the corresponding KS eigenvalues should be accurate approximations to the vertical ionization potentials (VIPs) of the molecule, as the latter condition attests to the viability of the exchange-correlation potential (V{sub XC}). None of the prominently used DFT approaches show these properties: the optimized effective potential V{sub XC} based ab initio dft does. A local, range-separated hybrid potential cam-QTP-00 is introduced as the basis for a consistent KS DFT approach. The computed VIPs as the negative of KS eigenvalue have a mean absolute error of 0.8 eV for an extensive set of molecule's electron ionizations, including the core. Barrier heights, equilibrium geometries, and magnetic properties obtained from the potential are in good agreement with experiment. A similar accuracy with less computational efforts can be achieved by using a non-variational global hybrid variant of the QTP-00 approach.

Verma, Prakash; Bartlett, Rodney J., E-mail: bartlett@ufl.edu [Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)

2014-05-14T23:59:59.000Z

423

Assessing the density functional theory-based multireference configuration interaction (DFT/MRCI) method for transition metal complexes  

SciTech Connect (OSTI)

We report an assessment of the performance of density functional theory-based multireference configuration interaction (DFT/MRCI) calculations for a set of 3d- and 4d-transition metal (TM) complexes. The DFT/MRCI results are compared to published reference data from reliable high-level multi-configurational ab initio studies. The assessment covers the relative energies of different ground-state minima of the highly correlated CrF{sub 6} complex, the singlet and triplet electronically excited states of seven typical TM complexes (MnO{sub 4}{sup ?}, Cr(CO){sub 6}, [Fe(CN){sub 6}]{sup 4?}, four larger Fe and Ru complexes), and the corresponding electronic spectra (vertical excitation energies and oscillator strengths). It includes comparisons with results from different flavors of time-dependent DFT (TD-DFT) calculations using pure, hybrid, and long-range corrected functionals. The DFT/MRCI method is found to be superior to the tested TD-DFT approaches and is thus recommended for exploring the excited-state properties of TM complexes.

Escudero, Daniel, E-mail: escudero@kofo.mpg.de, E-mail: thiel@kofo.mpg.de; Thiel, Walter, E-mail: escudero@kofo.mpg.de, E-mail: thiel@kofo.mpg.de [Max-Planck-Institut fr Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mlheim an der Ruhr (Germany)] [Max-Planck-Institut fr Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mlheim an der Ruhr (Germany)

2014-05-21T23:59:59.000Z

424

Density functional theory study of chemical sensing on surfaces of single-layer MoS{sub 2} and graphene  

SciTech Connect (OSTI)

In this work, density functional theory (DFT) calculations have been used to investigate chemical sensing on surfaces of single-layer MoS{sub 2} and graphene, considering the adsorption of the chemical compounds triethylamine, acetone, tetrahydrofuran, methanol, 2,4,6-trinitrotoluene, o-nitrotoluene, o-dichlorobenzene, and 1,5-dicholoropentane. Physisorption of the adsorbates on free-standing surfaces was analyzed in detail for optimized material structures, considering various possible adsorption sites. Similar adsorption characteristics for the two surface types were demonstrated, where inclusion of a correction to the DFT functional for London dispersion was shown to be important to capture interactions at the interface of molecular adsorbate and surface. Charge transfer analyses for adsorbed free-standing surfaces generally demonstrated very small effects. However, charge transfer upon inclusion of the underlying SiO{sub 2} substrate rationalized experimental observations for some of the adsorbates considered. A larger intrinsic response for the electron-donor triethylamine adsorbed on MoS{sub 2} as compared to graphene was demonstrated, which may assist in devising chemical sensors for improved sensitivity.

Mehmood, F.; Pachter, R., E-mail: ruth.pachter@us.af.mil [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States)

2014-04-28T23:59:59.000Z

425

Ecto-F1-ATPase/P2Y pathways in metabolic and vascular functions of high density lipoproteins  

Science Journals Connector (OSTI)

Abstract The atheroprotective property of High Density Lipoprotein (HDL) is supported by many epidemiological studies and cellular and invivo approaches on animal models. While the anti-atherogenic effects of HDL are thought to derive primarily from its role in reverse cholesterol transport, together with anti-inflammatory, anti-oxidant, anti-thrombotic and cytoprotective properties, the mechanisms that support these effects are still not completely understood. However, many advances in identifying the cellular partners involved in HDL functions have been made over the last two decades. This review highlights the diverse roles of the HDL receptor ecto-F1-ATPase coupled to purinergic P2Y receptors in the modulation of important metabolic and vascular functions of HDL. On hepatocytes, the ecto-F1-ATPase is coupled to P2Y13 receptor and contributes to HDL holoparticle endocytosis. On endothelial cells, ecto-F1-ATPase/P2Ys pathway is involved in HDL-mediated endothelial protection and HDL transcytosis. The clinical relevance of this F1-ATPase/P2Ys axis in humans has recently been supported by the identification of serum F1-ATPase inhibitor (IF1) as an independent determinant of HDL-Cholesterol (HDL-C) and coronary heart disease risk. Therapeutic strategies targeting F1-ATPase/P2Y pathways for the treatment of atherosclerosis are currently being explored.

Laurent O. Martinez; Souad Najib; Bertrand Perret; Cendrine Cabou; Laeticia Lichtenstein

2015-01-01T23:59:59.000Z

426

Diffractive parton density functions  

E-Print Network [OSTI]

We discuss the perturbative QCD description of diffractive deep-inelastic scattering, and extract diffractive parton distributions from recent HERA data. The asymptotic collinear factorisation theorem has important modifications in the sub-asymptotic HERA regime. In addition to the usual resolved Pomeron contribution, the direct interaction of the Pomeron must also be accounted for. The diffractive parton distributions are shown to satisfy an inhomogeneous evolution equation, analogous to the parton distributions of the photon.

Watt, G

2005-01-01T23:59:59.000Z

427

Diffractive parton density functions  

E-Print Network [OSTI]

We discuss the perturbative QCD description of diffractive deep-inelastic scattering, and extract diffractive parton distributions from recent HERA data. The asymptotic collinear factorisation theorem has important modifications in the sub-asymptotic HERA regime. In addition to the usual resolved Pomeron contribution, the direct interaction of the Pomeron must also be accounted for. The diffractive parton distributions are shown to satisfy an inhomogeneous evolution equation, analogous to the parton distributions of the photon.

G. Watt

2005-11-29T23:59:59.000Z

428

Density-Functional-Theory Calculations of Matter in Strong Magnetic Fields: II. Infinite Chains and Condensed Matter  

E-Print Network [OSTI]

We present new, ab initio calculations of the electronic structure of one-dimensional infinite chains and three-dimensional condensed matter in strong magnetic fields ranging from B=10^12 G to 2x10^15 G, appropriate for observed magnetic neutron stars. At these field strengths, the magnetic forces on the electrons dominate over the Coulomb forces, and to a good approximation the electrons are confined to the ground Landau level. Our calculations are based on the density functional theory, and use a local magnetic exchange-correlation function appropriate in the strong field regime. The band structures of electrons in different Landau orbitals are computed self-consistently. Numerical results of the ground-state energies and electron work functions are given for one-dimensional chains of H, He, C, and Fe. Fitting formulae for the B-dependence of the energies are also provided. For all the field strengths considered in this paper, hydrogen, helium, and carbon chains are found to be bound relative to individual atoms (although for B less than a few x 10^12 G, the relative binding between C and C_infinity is small). Iron chains are significantly bound for B>10^14 G and are weakly bound if at all at B<10^13 G. We also study the cohesive property of three-dimensional condensed matter of H, He, C, and Fe at zero pressure, constructed from interacting chains in a body-centered tetragonal lattice. Such three-dimensional condensed matter is found to be bound relative to individual atoms, with the cohesive energy increasing rapidly with increasing B.

Zach Medin; Dong Lai

2007-01-05T23:59:59.000Z

429

Use of functionalized metallocene copolymers from ethylene and polar olefins as compatibilizers for low-density-polyethylene/starch and low-density-polyethylene/dextran blends .  

E-Print Network [OSTI]

??Functionalized metallocene copolymers synthesized from ethylene with 5-hexen-1-ol and ethylene with 10-undecen-1-ol were used as compatibilizers in LDPE/starch and LDPE/dextran blends in order to improve (more)

Domnguez Barcel, Ana Mara

2006-01-01T23:59:59.000Z

430

Probing Ligand Effects on the Redox Energies of [4Fe-4S] Clusters Using Broken-Symmetry Density Functional Theory  

SciTech Connect (OSTI)

A central issue in understanding redox properties of iron-sulfur proteins is determining the factors that tune the reduction potentials of the Fe-S clusters. Recently, Solomon and coworkers have shown that the Fe-S bond covalency of protein analogs measured by %L, the percent ligand character of the Fe 3d orbitals, from ligand K-edge X-ray absorption spectroscopy (XAS) correlates with the electrochemical redox potentials. Also, Wang and coworkers have measured electron detachment energies for iron-sulfur clusters without environmental perturbations by gas-phase photoelectron spectroscopy (PES). Here the correlations of the ligand character with redox energy and %L character are examined in [Fe?S?L?]2? clusters with different ligands by broken symmetry density functional theory (BS-DFT) calculations using the B3LYP functional together with PES and XAS experimental results. These gas-phase studies assess ligand effects independently of environmental perturbations and thus provide essential information for computational studies of iron-sulfur proteins. The B3LYP oxidation energies agree well with PES data, and the %L character obtained from natural bond orbital analysis correlates with XAS values, although it systematically underestimates them because of basis set effects. The results show that stronger electron-donating terminal ligands increase %Lt, the percent ligand character from terminal ligands, but decrease %Sb, the percent ligand character from the bridging sulfurs. Because the oxidized orbital has significant Fe-Lt antibonding character, the oxidation energy correlates well with %Lt. However, because the reduced orbital has varying contributions of both Fe-Lt and Fe-Sb antibonding character, the reduction energy does not correlate with either %Lt or %Sb. Overall, BSDFT calculations together with XAS and PES experiments can unravel the complex underlying factors in the redox energy and chemical bonding of the [4Fe-4S] clusters in iron-sulfur proteins.

Niu, Shuqiang; Ichiye, Toshiko

2009-05-14T23:59:59.000Z

431

Mixed valency and site-preference chemistry for cerium and its compounds: A predictive density-functional theory study  

SciTech Connect (OSTI)

Cerium and its technologically relevant compounds are examples of anomalous mixed valency, originating from two competing oxidation statesitinerant Ce4+ and localized Ce3+. Under applied stress, anomalous transitions are observed but not well understood. Here we treat mixed valency as an alloy problem involving two valences with competing and numerous site-occupancy configurations. We use density-functional theory with Hubbard U (i.e., DFT+U) to evaluate the effective valence and predict properties, including controlling the valence by pseudoternary alloying. For Ce and its compounds, such as (Ce,La)2(Fe,Co)14B permanent magnets, we find a stable mixed-valent ? state near the spectroscopic value of ?s=3.53. Ce valency in compounds depends on its steric volume and local chemistry. For La doping, Ce valency shifts towards ?-like Ce3+, as expected from steric volume; for Co doping, valency depends on local Ce-site chemistry and steric volume. Our approach captures the key origins of anomalous valency and site-preference chemistry in complex compounds.

Alam, Aftab [Ames Laboratory; Johnson, Duane D. [Ames Laboratory

2014-06-01T23:59:59.000Z

432

Thermal decomposition of 1,3,3-trinitroazetidine (TNAZ): A density functional theory and ab initio study  

SciTech Connect (OSTI)

Density functional theory and ab initio methods are employed to investigate decomposition pathways of 1,3,3-trinitroazetidine initiated by unimolecular loss of NO{sub 2} or HONO. Geometry optimizations are performed using M06/cc-pVTZ and coupled-cluster (CC) theory with single, double, and perturbative triple excitations, CCSD(T), is used to calculate accurate single-point energies for those geometries. The CCSD(T)/cc-pVTZ energies for NO{sub 2} elimination by NN and CN bond fission are, including zero-point energy (ZPE) corrections, 43.21 kcal/mol and 50.46 kcal/mol, respectively. The decomposition initiated by trans-HONO elimination can occur by a concerted H-atom and nitramine NO{sub 2} group elimination or by a concerted H-atom and nitroalkyl NO{sub 2} group elimination via barriers (at the CCSD(T)/cc-pVTZ level with ZPE corrections) of 47.00 kcal/mol and 48.27 kcal/mol, respectively. Thus, at the CCSD(T)/cc-pVTZ level, the ordering of these four decomposition steps from energetically most favored to least favored is: NO{sub 2} elimination by NN bond fission, HONO elimination involving the nitramine NO{sub 2} group, HONO elimination involving a nitroalkyl NO{sub 2} group, and finally NO{sub 2} elimination by CN bond fission.

Veals, Jeffrey D.; Thompson, Donald L. [Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211 (United States)] [Department of Chemistry, University of Missouri-Columbia, Columbia, Missouri 65211 (United States)

2014-04-21T23:59:59.000Z

433

Density functional study of structural and electronic properties of Al{sub n}@C{sub 60}  

SciTech Connect (OSTI)

Fullerene derivatives have been shown to make contributions in many types of applications. Ab initio investigation of structural and electronic properties of aluminum doped endohedral fullerene has been performed using numerical atomic orbital density functional theory. We have obtained ground state structures for Al{sub n}@C{sub 60} (n=110). Which shows that C{sub 60} molecule can accommodate maximum of nine aluminum atoms, for n > 9 the cage eventually break. Encapsulated large number of aluminum atoms leads to deformation of cage with diameter varies from 7.16 to 7.95. Binding energy/Al atom is found to increase till n = 4 and after that it decreases with the number of Al atoms with a sudden increase for n=10 due to breakage of C{sub 60} cage and electronic affinity first increases till n=4 then it decreases up to n=9 with a sharp increase for n=10. Ionization potential also first increases and then decreases. Homo-Lumo gap decreases till n=3 with a sharp increase for n=4, after that it shows an oscillatory nature. The results obtained are consistent with available theoretical and experimental results. The ab-initio calculations were performed using SIESTA code with generalized gradient approximation (GGA)

Dhiman, Shobhna, E-mail: s-dhiman@hotmail.com [Department of Applied Science, PEC, University of Technology, Chandigarh-160012 (India); Kumar, Ranjan; Dharamvir, Keya [Department of Physics, Panjab University, Chandigarh-160014 (India)

2014-04-24T23:59:59.000Z

434

DOE - Office of Legacy Management -- Armco-Rustless Iron and Steel - MD 03  

Office of Legacy Management (LM)

Armco-Rustless Iron and Steel - MD Armco-Rustless Iron and Steel - MD 03 FUSRAP Considered Sites Site: Armco-Rustless Iron & Steel (MD.03 ) Eliminated from consideration under FUSRAP Designated Name: Not Designated Alternate Name: ARMCO Baltimore Works MD.03-1 Location: Baltimore , Maryland MD.03-2 Evaluation Year: 1987 MD.03-1 Site Operations: Test rolling of uranium billets. MD.03-2 MD.03-3 Site Disposition: Eliminated - Potential for contamination remote due to limited quantity of material and duration of test MD.03-1 Radioactive Materials Handled: Yes Primary Radioactive Materials Handled: Uranium MD.03-2 Radiological Survey(s): Health and safety monitoring conducted during operations MD.03-2 Site Status: Eliminated from consideration under FUSRAP MD.03-1 Also see

435

Serial Intraoperative MR Imaging of Brain Shift Arya Nabavi, M.D.1  

E-Print Network [OSTI]

Serial Intraoperative MR Imaging of Brain Shift Arya Nabavi, M.D.1 , Peter McL. Black, M.D. Ph.D.1 , David T. Gering, M.S.4 , Carl-Fredrik Westin, Ph.D3 , Vivek Mehta, M.D.1 , Richard S. Pergolizzi Jr., M, M.D., Ph.D.2 , William M. Wells III, Ph.D4 ., Ron Kikinis, M.D.3 , Ferenc A. Jolesz, M.D.3 1

436

Rotational properties of nuclei around $^{254}$No investigated using a spectroscopic-quality Skyrme energy density functional  

E-Print Network [OSTI]

Nuclei in the $Z\\approx100$ mass region represent the heaviest systems where detailed spectroscopic information is experimentally available. Although microscopic-macroscopic and self-consistent models have achieved great success in describing the data in this mass region, a fully satisfying precise theoretical description is still missing. By using fine-tuned parametrizations of the energy density functionals, the present work aims at an improved description of the single-particle properties and rotational bands in the nobelium region. Such locally optimized parameterizations may have better properties when extrapolating towards the superheavy region. Skyrme-Hartree-Fock-Bogolyubov and Lipkin-Nogami methods were used to calculate the quasiparticle energies and rotational bands of nuclei in the nobelium region. Starting from the most recent Skyrme parametrization, UNEDF1, the spin-orbit coupling constants and pairing strengths have been tuned, so as to achieve a better agreement with the excitation spectra and odd-even mass differences in $^{251}$Cf and $^{249}$Bk. The quasiparticle properties of $^{251}$Cf and $^{249}$Bk were very well reproduced. At the same time, crucial deformed neutron and proton shell gaps open up at $N=152$ and $Z=100$, respectively. Rotational bands in Fm, No, and Rf isotopes, where experimental data are available, were also fairly well described. To help future improvements towards a more precise description, small deficiencies of the approach were carefully identified. In the $Z\\approx100$ mass region, larger spin-orbit strengths than those from global adjustments lead to improved agreement with data. Puzzling effects of particle-number restoration on the calculated moment of inertia, at odds with the experimental behaviour, require further scrutiny.

Yue Shi; J. Dobaczewski; P. T. Greenlees

2013-12-16T23:59:59.000Z

437

L-asparagine crystals with wide gap semiconductor features: Optical absorption measurements and density functional theory computations  

SciTech Connect (OSTI)

Results of optical absorption measurements are presented together with calculated structural, electronic, and optical properties for the anhydrous monoclinic L-asparagine crystal. Density functional theory (DFT) within the generalized gradient approximation (GGA) including dispersion effects (TS, Grimme) was employed to perform the calculations. The optical absorption measurements revealed that the anhydrous monoclinic L-asparagine crystal is a wide band gap material with 4.95 eV main gap energy. DFT-GGA+TS simulations, on the other hand, produced structural parameters in very good agreement with X-ray data. The lattice parameter differences ?a, ?b, ?c between theory and experiment were as small as 0.020, 0.051, and 0.022, respectively. The calculated band gap energy is smaller than the experimental data by about 15%, with a 4.23 eV indirect band gap corresponding to Z???? and Z???? transitions. Three other indirect band gaps of 4.30 eV, 4.32 eV, and 4.36 eV are assigned to ?3 ???, ?1 ???, and ?2 ??? transitions, respectively. ?-sol computations, on the other hand, predict a main band gap of 5.00 eV, just 50 meV above the experimental value. Electronic wavefunctions mainly originating from O 2pcarboxyl, C 2pside chain, and C 2pcarboxyl orbitals contribute most significantly to the highest valence and lowest conduction energy bands, respectively. By varying the lattice parameters from their converged equilibrium values, we show that the unit cell is less stiff along the b direction than for the a and c directions. Effective mass calculations suggest that hole transport behavior is more anisotropic than electron transport, but the mass values allow for some charge mobility except along a direction perpendicular to the molecular layers of L-asparagine which form the crystal, so anhydrous monoclinic L-asparagine crystals could behave as wide gap semiconductors. Finally, the calculations point to a high degree of optical anisotropy for the absorption and complex dielectric function, with more structured curves for incident light polarized along the 100 and 101 directions.

Zanatta, G.; Gottfried, C. [Departamento de Bioqumica, Universidade Federal do Rio Grande do Sul, 90035-003 Porto Alegre-RS (Brazil)] [Departamento de Bioqumica, Universidade Federal do Rio Grande do Sul, 90035-003 Porto Alegre-RS (Brazil); Silva, A. M. [Universidade Estadual do Piau, 64260-000 Piripiri-Pi (Brazil)] [Universidade Estadual do Piau, 64260-000 Piripiri-Pi (Brazil); Caetano, E. W. S., E-mail: ewcaetano@gmail.com [Instituto de Educao, Cincia e Tecnologia do Cear, 60040-531 Fortaleza-CE (Brazil)] [Instituto de Educao, Cincia e Tecnologia do Cear, 60040-531 Fortaleza-CE (Brazil); Sales, F. A. M.; Freire, V. N. [Departamento de Fsica, Universidade Federal do Cear, Caixa Postal 6030, 60455-760 Fortaleza-CE (Brazil)] [Departamento de Fsica, Universidade Federal do Cear, Caixa Postal 6030, 60455-760 Fortaleza-CE (Brazil)

2014-03-28T23:59:59.000Z

438

Excitation energies with linear response density matrix functional theory along the dissociation coordinate of an electron-pair bond in N-electron systems  

SciTech Connect (OSTI)

Time dependent density matrix functional theory in its adiabatic linear response formulation delivers exact excitation energies ?{sub ?} and oscillator strengths f{sub ?} for two-electron systems if extended to the so-called phase including natural orbital (PINO) theory. The Lwdin-Shull expression for the energy of two-electron systems in terms of the natural orbitals and their phases affords in this case an exact phase-including natural orbital functional (PILS), which is non-primitive (contains other than just J and K integrals). In this paper, the extension of the PILS functional to N-electron systems is investigated. With the example of an elementary primitive NO functional (BBC1) it is shown that current density matrix functional theory ground state functionals, which were designed to produce decent approximations to the total energy, fail to deliver a qualitatively correct structure of the (inverse) response function, due to essential deficiencies in the reconstruction of the two-body reduced density matrix (2RDM). We now deduce essential features of an N-electron functional from a wavefunction Ansatz: The extension of the two-electron Lwdin-Shull wavefunction to the N-electron case informs about the phase information. In this paper, applications of this extended Lwdin-Shull (ELS) functional are considered for the simplest case, ELS(1): one (dissociating) two-electron bond in the field of occupied (including core) orbitals. ELS(1) produces high quality ?{sub ?}(R) curves along the bond dissociation coordinate R for the molecules LiH, Li{sub 2}, and BH with the two outer valence electrons correlated. All of these results indicate that response properties are much more sensitive to deficiencies in the reconstruction of the 2RDM than the ground state energy, since derivatives of the functional with respect to both the NOs and the occupation numbers need to be accurate.

Meer, R. van; Gritsenko, O. V. [Faculty of Exact Sciences, Theoretical Chemistry, VU University, Amsterdam (Netherlands) [Faculty of Exact Sciences, Theoretical Chemistry, VU University, Amsterdam (Netherlands); WCU Program, Dep. of Chemistry, Pohang Univ. of Science and Techn., Pohang (Korea, Republic of); Baerends, E. J. [Faculty of Exact Sciences, Theoretical Chemistry, VU University, Amsterdam (Netherlands) [Faculty of Exact Sciences, Theoretical Chemistry, VU University, Amsterdam (Netherlands); WCU Program, Dep. of Chemistry, Pohang Univ. of Science and Techn., Pohang (Korea, Republic of); Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah 21589 (Saudi Arabia)

2014-01-14T23:59:59.000Z

439

Effects of Oxygen-Containing Functional Groups on Supercapacitor...  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Oxygen-Containing Functional Groups on Supercapacitor Performance. Effects of Oxygen-Containing Functional Groups on Supercapacitor Performance. Abstract: Molecular dynamics (MD)...

440

Diffusion of Te vacancy and interstitials of Te, Cl, O, S, P and Sb in CdTe: A density functional theory study  

E-Print Network [OSTI]

Diffusion of Te vacancy and interstitials of Te, Cl, O, S, P and Sb in CdTe: A density functional profiles in CdTe of native, Te adatom and vacancy, and anionic non-native interstitial adatoms P, Sb, O, S B.V. All rights reserved. 1. Introduction Cadmium telluride (CdTe) based thin films have emerged

Khare, Sanjay V.

Note: This page contains sample records for the topic "md density functional" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Why are MD simulated protein folding times wrong? Dmitry Nerukh  

E-Print Network [OSTI]

Why are MD simulated protein folding times wrong? Dmitry Nerukh Unilever Centre for Molecular.ac.uk The question of significant deviations of protein folding times simulated using molecular dynamics from

Nerukh, Dmitry

442

Nature of the Transition Structure for Alkene Epoxidation by Peroxyformic Acid, Dioxirane, and Dimethyldioxirane: A Comparison of B3LYP Density Functional Theory  

E-Print Network [OSTI]

calcula- tions of the prototype ion-molecule gas-phase SN2 reactions, CH3Cl + Cl- and CH3Br + Cl-, have of the B3LYP density functional theory calculations has been studied for the epoxidation reactions the activation barriers for the epoxidation reactions calculated at the B3LYP/6-31G* and B3LYP/6- 31+G* levels

Schlegel, H. Bernhard

443

Structural and electronic properties of cobalt carbide Co2C and its surface stability: Density functional theory study  

E-Print Network [OSTI]

.V. All rights reserved. 1. Introduction Transition metal carbides (TMCs), typically including all 3 d ele- ments and 4 d/5 d elements of groups 3­6 early transition metals, possess unique physical and chemicalStructural and electronic properties of cobalt carbide Co2C and its surface stability: Density

Li, Weixue

444

MD Simulation Study of the Influence of Branch Content on Relaxation and Crystallization of Branched Polyethylene Chains with Uniform Branch Distribution  

E-Print Network [OSTI]

of Branched Polyethylene Chains with Uniform Branch Distribution I. A. HUSSEIN, B. F. ABU-SHARKH* Department-density polyethylene (LLDPE) chains with different levels of branch content (BC), ranging from 10 to 80 branches/1000 C words: MD simulation, Polyethylene, branch content, chain conformation, radius of gyration

Hussein, Ibnelwaleed A.

445

TO J. A. QuigUy, M.D. NATIONALLPADCW~  

Office of Legacy Management (LM)

J. A. QuigUy, M.D. J. A. QuigUy, M.D. NATIONALLPADCW~ OF oliI0 Cincbnati 39, Ohio September 23, 1960 TRIP RBPCRT TO PIONRBR DIVISION, BENDIX AVI4TIONC~ ION, DAVBNPQRT, SOWA,oNSEPTEMBR6-9,196O F. J. Klein CENTRAL FILE The purpose of this trip was tot (1) determine if a Bendix ronic energy cleaning system can clean uranium-contaminated drums to the extent of rcduciug the @ha ccmtazuinatiou level belav that required for sale as %oa-contaminatecl** by AEC Manual Chapter 5182-0s UOOO a dMlOO& average and at peak not more than 25,OOO a d~lOOcm2, and (2) observe . the health and safety aspects of the wotk and insure the adequate decontauimtiou of the machinery, tools, equi~t, aud teat area. This waa a wet operation Md the tauk waa not ventilated; hawever, should

446

Numerical simulation of the transient photoconductivity in a-Si:H as a function of excitation density  

SciTech Connect (OSTI)

The dependence of the transient photoconductivity induced by pulsed excitation (TPC) on the excitation density is discussed with the help of numerical simulations. It is shown that recombination between excess mobile electrons and all excess holes (mainly localized) can explain the excitation density dependence of the TPC amplitude of standard a-Si:H at room temperature using a rate parameter k{sub BB} of 10{sup {minus}8} cm{sup 3}/s. This model leads to a decay faster than experimentally observed in the time range from 40 ns to 1 {micro}s. A variation of the recombination model is presented that gives short time range. Moreover comparison of the simulations with experimental data yields limits for the parameters of the conduction band tail. In particular, the time necessary to establish a dynamic equilibrium of excess electrons between delocalized states in the conduction band and localized states in the tail appears to be very informative.

Feist, H.; Kunst, M.

1997-07-01T23:59:59.000Z

447

DOE - Office of Legacy Management -- Bendix Corp Frieze Division - MD 0-01  

Office of Legacy Management (LM)

Bendix Corp Frieze Division - MD Bendix Corp Frieze Division - MD 0-01 FUSRAP Considered Sites Site: BENDIX CORP., FRIEZE DIVISION (MD.0-01 ) Eliminated from further consideration under FUSRAP Designated Name: Not Designated Alternate Name: None Location: Baltimore , Maryland MD.0-01-1 Evaluation Year: 1987 MD.0-01-3 Site Operations: Produced "classified units" believed to be electronics components - no radioactive materials involved. MD.0-01-1 MD.0-01-3 Site Disposition: Eliminated - No radioactive materials handled at this site MD.0-01-3 Radioactive Materials Handled: No Primary Radioactive Materials Handled: None MD.0-01-3 Radiological Survey(s): No Site Status: Eliminated from further consideration under FUSRAP Also see Documents Related to BENDIX CORP., FRIEZE DIVISION

448

DOE - Office of Legacy Management -- Naval Ordnance Laboratory - MD 0-03  

Office of Legacy Management (LM)

Ordnance Laboratory - MD 0-03 Ordnance Laboratory - MD 0-03 FUSRAP Considered Sites Site: NAVAL ORDNANCE LABORATORY (MD.0-03 ) Eliminated from further consideration under FUSRAP - Referred to DOD Designated Name: Not Designated Alternate Name: Naval Ordnance Laboratory - White Oak Location: White Oak Area , Silver Spring , Maryland MD.0-03-1 MD.0-03-2 Evaluation Year: 1987 MD.0-03-2 Site Operations: Research and development - may have involved radioactive materials because the site was identified on a 1955 Accountability Station List. MD.0-03-1 Site Disposition: Eliminated - NRC licensed MD.0-03-2 Radioactive Materials Handled: None Specifically Identified Primary Radioactive Materials Handled: None specifically indicated Radiological Survey(s): None Indicated Site Status: Eliminated from further consideration under FUSRAP - Referred to DOD MD.0-03-2

449

A time-dependent momentum-space density functional theoretical approach for electron transport dynamics in molecular devices  

E-Print Network [OSTI]

the Fermi energy. The eigen- value equation for the eigenfunctions is obtained by setting t= 0 in eq. (3) and replacing the term on the left-hand side of eq. (3) with E?(0). Note that VD(t) = 0 when t= 0. Applying the second-order split-operator method [31...), central (C), and right (R) zones [814]. The C zone is chosen to include the molecule and some atomic layers of the electrodes so that the Hamiltonian and the electron density of the L and R zones (the semi-infinite electrodes) are accurately described...

Chu, Shih-I; Zhou, Zhongyuan

2009-10-27T23:59:59.000Z

450

MD6151-8-10 Murdoch Counselling Service  

E-Print Network [OSTI]

MD6151-8-10 Murdoch Counselling Service Stress management What is stress? Stress is the way your to gather physical and emotional energy which helps you deal with changes and challenges in your daily life which drains you of emotional and physical energy. How is university stressful? University life can

451

GRANT AWARDS Justin Annes, MD, PhD  

E-Print Network [OSTI]

Therapy POSTDOCS AWARDS Joseph Cheng, PhD, MEng, BS Postdoctoral fellow, Radiology Pediatric Radiology, Pediatrics Gastroenterology Project: Translational Studies using Immune and Microbiota markers in Vancomycin-treated Children with GI disease Adam Frymoyer, MD Instructor, Pediatrics General Pediatrics & Neonatal

Bejerano, Gill

452

Joseph P. Vacanti, MD Chief of Pediatric Surgery  

E-Print Network [OSTI]

, neurosurgery, radiology, pediatric intensive care, genetic counseling, social work and palliative careJoseph P. Vacanti, MD Chief of Pediatric Surgery and Surgeon-in-Chief MassGeneral Hospital Pediatrics Debra Burke, RN, MSN, MBA Associate Chief Nurse Chiefs' Notes To provide optimal support

Mootha, Vamsi K.

453

Including screening in van der Waals corrected density functional theory calculations: The case of atoms and small molecules physisorbed on graphene  

SciTech Connect (OSTI)

The Density Functional Theory (DFT)/van der Waals-Quantum Harmonic Oscillator-Wannier function (vdW-QHO-WF) method, recently developed to include the vdW interactions in approximated DFT by combining the quantum harmonic oscillator model with the maximally localized Wannier function technique, is applied to the cases of atoms and small molecules (X=Ar, CO, H{sub 2}, H{sub 2}O) weakly interacting with benzene and with the ideal planar graphene surface. Comparison is also presented with the results obtained by other DFT vdW-corrected schemes, including PBE+D, vdW-DF, vdW-DF2, rVV10, and by the simpler Local Density Approximation (LDA) and semilocal generalized gradient approximation approaches. While for the X-benzene systems all the considered vdW-corrected schemes perform reasonably well, it turns out that an accurate description of the X-graphene interaction requires a proper treatment of many-body contributions and of short-range screening effects, as demonstrated by adopting an improved version of the DFT/vdW-QHO-WF method. We also comment on the widespread attitude of relying on LDA to get a rough description of weakly interacting systems.

Silvestrelli, Pier Luigi; Ambrosetti, Alberto [Dipartimento di Fisica e Astronomia, Universit di Padova, via Marzolo 8, I35131 Padova, Italy and DEMOCRITOS National Simulation Center of the Italian Istituto Officina dei Materiali (IOM) of the Italian National Research Council (CNR), Trieste (Italy)] [Dipartimento di Fisica e Astronomia, Universit di Padova, via Marzolo 8, I35131 Padova, Italy and DEMOCRITOS National Simulation Center of the Italian Istituto Officina dei Materiali (IOM) of the Italian National Research Council (CNR), Trieste (Italy)

2014-03-28T23:59:59.000Z

454

Ab initio density functional theory investigation of the structural, electronic and optical properties of Ca{sub 3}Sb{sub 2} in hexagonal and cubic phases  

SciTech Connect (OSTI)

A density functional theory study of structural, electronical and optical properties of Ca{sub 3}Sb{sub 2} compound in hexagonal and cubic phases is presented. In the exchangecorrelation potential, generalized gradient approximation (PBE-GGA) has been used to calculate lattice parameters, bulk modulus, cohesive energy, dielectric function and energy loss spectra. The electronic band structure of this compound has been calculated using the above two approximations as well as another form of PBE-GGA, proposed by Engle and Vosko (EV-GGA). It is found that the hexagonal phase of Ca{sub 3}Sb{sub 2} has an indirect gap in the ??N direction; while in the cubic phase there is a direct-gap at the ? point in the PBE-GGA and EV-GGA. Effects of applying pressure on the band structure of the system studied and optical properties of these systems were calculated. - Graphical abstract: A density functional theory study of structural, electronic and optical properties of Ca{sub 3}Sb{sub 2} compound in hexagonal and cubic phases is presented. Display Omitted - Highlights: Physical properties of Ca{sub 3}Sb{sub 2} in hexagonal and cubic phases are investigated. It is found that the hexagonal phase is an indirect gap semiconductor. Ca{sub 3}Sb{sub 2} is a direct-gap semiconductor at the ? point in the cubic phase. By increasing pressure the semiconducting band gap and anti-symmetry gap are decreased.

Arghavani Nia, Borhan, E-mail: b.arghavani@gmail.com [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Sedighi, Matin [Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Shahrokhi, Masoud [Young Researchers and Elite Club, Kermanshah Branch, Islamic Azad University, Kermanshah (Iran, Islamic Republic of); Moradian, Rostam [Nano-Science and Nano-Technology Research Center, Razi University, Kermanshah (Iran, Islamic Republic of); Computational Physics Science Research Laboratory, Department of Nano-Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-1795, Tehran (Iran, Islamic Republic of)

2013-11-15T23:59:59.000Z

455

Electronic band structure of LiInSe2: A first-principles study using the Tran-Blaha density functional and GW approximation  

Science Journals Connector (OSTI)

Abstract Using first-principles theoretical techniques within density functional theory and many-body perturbation theory we investigated the structural and electronic properties of two LiInSe2 crystal modifications, orthorhombic (?-NaFeO2-type) and tetragonal (CuFeS2-type), focusing on the interband transitions and band gaps. It is found that the Tran-Blaha (TB09) functional predicts LiInSe2 to be a direct-gap semiconductor with a significantly larger band gap as compared with that from common local-density and gradient-corrected functionals. The most accurate values of the fundamental energy gaps are calculated within quasiparticle GW approximation and found to be 2.95eV for the orthorhombic phase and 2.85eV for the tetragonal one, with equal pressure coefficients of 63meV/GPa. Our theoretical results eliminate the uncertainty in the band gap of LiInSe2. Moreover, the data obtained define the upper limit of the band gap of solid solutions (Cu,Li)InSe2 and (Ag,Li)InSe2, which can be of interest for applications in optoelectronics.

A.V. Kosobutsky; Yu.M. Basalaev

2014-01-01T23:59:59.000Z

456

Isospin-breaking corrections to superallowed Fermi beta-decay in isospin- and angular-momentum-projected nuclear Density Functional Theory  

E-Print Network [OSTI]

Background: The superallowed beta-decay rates provide stringent constraints on physics beyond the Standard Model of particle physics. To extract crucial information about the electroweak force, small isospin-breaking corrections to the Fermi matrix element of superallowed transitions must be applied. Purpose: We perform systematic calculations of isospin-breaking corrections to superallowed beta-decays and estimate theoretical uncertainties related to the basis truncation, time-odd polarization effects related to the intrinsic symmetry of the underlying Slater determinants, and to the functional parametrization. Methods: We use the self-consistent isospin- and angular-momentum-projected nuclear density functional theory employing two density functionals derived from the density independent Skyrme interaction. Pairing correlations are ignored. Our framework can simultaneously describe various effects that impact matrix elements of the Fermi decay: symmetry breaking, configuration mixing, and long-range Coulomb polarization. Results: The isospin-breaking corrections to the I=0+,T=1 --> I=0+,T=1 pure Fermi transitions are computed for nuclei from A=10 to A=98 and, for the first time, to the Fermi branch of the I,T=1/2 --> I,T=1/2 transitions in mirror nuclei from A=11 to A=49. We carefully analyze various model assumptions impacting theoretical uncertainties of our calculations and provide theoretical error bars on our predictions. Conclusions: The overall agreement with empirical isospin-breaking corrections is very satisfactory. Using computed isospin-breaking corrections we show that the unitarity of the CKM matrix is satisfied with a precision better than 0.1%.

W. Satula; J. Dobaczewski; W. Nazarewicz; T. R. Werner

2012-10-25T23:59:59.000Z

457

The adsorption of h-BN monolayer on the Ni(111) surface studied by density functional theory calculations with a semiempirical long-range dispersion correction  

SciTech Connect (OSTI)

The geometric and spin-resolved electronic structure of a h-BN adsorbed Ni(111) surface has been investigated by density functional theory calculations. Two energy minima (physisorption and chemisorption) are obtained when the dispersive van der Waals correction is included. The geometry of N atom on top site and B atom on fcc site is the most energetically favorable. Strong hybridization with the ferromagnetic Ni substrate induces considerable gap states in the h-BN monolayer. The induced ?* states are spin-polarized.

Sun, X., E-mail: sunx@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Pratt, A. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); York Institute for Materials Research, Department of Physics, University of York, York YO10 5DD (United Kingdom); Li, Z. Y. [Hefei National Laboratory for Physical Sciences at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026 (China); Ohtomo, M.; Sakai, S. [Advanced Science Research Center, Japan Atomic Energy Agency, 2-4 Shirakata-Shirane, Ibaraki 319-1195 (Japan); Yamauchi, Y. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

2014-05-07T23:59:59.000Z

458

Nuclear energy density optimization: Shell structure  

Science Journals Connector (OSTI)

Background: Nuclear density functional theory is the only microscopical theory that can be applied throughout the entire nuclear landscape. Its key ingredient is the energy density functional.

M. Kortelainen; J. McDonnell; W. Nazarewicz; E. Olsen; P.-G. Reinhard; J. Sarich; N. Schunck; S. M. Wild; D. Davesne; J. Erler; A. Pastore

2014-05-15T23:59:59.000Z

459

Development of multicomponent hybrid density functional theory with polarizable continuum model for the analysis of nuclear quantum effect and solvent effect on NMR chemical shift  

SciTech Connect (OSTI)

We have developed the multicomponent hybrid density functional theory [MC-(HF+DFT)] method with polarizable continuum model (PCM) for the analysis of molecular properties including both nuclear quantum effect and solvent effect. The chemical shifts and H/D isotope shifts of the picolinic acid N-oxide (PANO) molecule in chloroform and acetonitrile solvents are applied by B3LYP electron exchange-correlation functional for our MC-(HF+DFT) method with PCM (MC-B3LYP/PCM). Our MC-B3LYP/PCM results for PANO are in reasonable agreement with the corresponding experimental chemical shifts and isotope shifts. We further investigated the applicability of our method for acetylacetone in several solvents.

Kanematsu, Yusuke; Tachikawa, Masanori [Quantum Chemistry Division, Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027 (Japan)] [Quantum Chemistry Division, Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027 (Japan)

2014-04-28T23:59:59.000Z

460

Thermodynamic stability of LaMnO3 and its competing oxides: A hybrid density functional study of an alkaline fuel cell catalyst  

Science Journals Connector (OSTI)

The phase stability of LaMnO3 with respect to its competing oxides is studied using hybrid-exchange density functional theory (DFT) as implemented in crystal09. The underpinning DFT total-energy calculations are embedded in a thermodynamic framework that takes optimal advantage of error cancellation within DFT. It has been found that by using the ab initio thermodynamic techniques described here, the standard Gibbs formation energies can be calculated to a significantly greater accuracy than was previously reported (a mean error of 1.6% with a maximum individual error of ?3.0%). This is attributed to both the methodology for isolating the chemical potentials of the reference states, as well as the use of the Becke, three-parameter, Lee-Yang-Parr (B3LYP) functional to thoroughly investigate the ground-state energetics of the competing oxides.

E. A. Ahmad; L. Liborio; D. Kramer; G. Mallia; A. R. Kucernak; N. M. Harrison

2011-08-30T23:59:59.000Z

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461

Spin and orbital magnetism of coinage metal trimers (Cu{sub 3}, Ag{sub 3}, Au{sub 3}): A relativistic density functional theory study  

SciTech Connect (OSTI)

We have demonstrated electronic structure and magnetic properties of Cu{sub 3}, Ag{sub 3} and Au{sub 3} trimers using a full potential local orbital method in the framework of relativistic density functional theory. We have also shown that the non-relativistic generalized gradient approximation for the exchange-correlation energy functional gives reliable magnetic properties in coinage metal trimers compared to experiment. In addition we have indicated that the spin-orbit coupling changes the structure and magnetic properties of gold trimer while the structure and magnetic properties of copper and silver trimers are marginally affected. A significant orbital moment of 0.21?{sub B} was found for most stable geometry of the gold trimer whereas orbital magnetism is almost quenched in the copper and silver trimers.

Afshar, Mahdi [Department of Physics, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of)] [Department of Physics, Iran University of Science and Technology, Tehran (Iran, Islamic Republic of); Sargolzaei, Mohsen [Department of Chemistry, Shahrood University of Technology, Shahrood (Iran, Islamic Republic of)] [Department of Chemistry, Shahrood University of Technology, Shahrood (Iran, Islamic Republic of)

2013-11-15T23:59:59.000Z

462

STELLAR POPULATIONS IN THE CENTRAL 0.5 pc OF THE GALAXY. I. A NEW METHOD FOR CONSTRUCTING LUMINOSITY FUNCTIONS AND SURFACE-DENSITY PROFILES  

SciTech Connect (OSTI)

We present new high angular resolution near-infrared spectroscopic observations of the nuclear star cluster surrounding the Milky Way's central supermassive black hole. Using the integral-field spectrograph OSIRIS on Keck II behind the laser-guide-star adaptive optics system, this spectroscopic survey enables us to separate early-type (young, 4-6 Myr) and late-type (old, >1 Gyr) stars with a completeness of 50% down to K' = 15.5 mag, which corresponds to {approx}10 M {sub Sun} for the early-type stars. This work increases the radial extent of reported OSIRIS/Keck measurements by more than a factor of three from 4'' to 14'' (0.16 to 0.56 pc), along the projected disk of young stars. For our analysis, we implement a new method of completeness correction using a combination of star-planting simulations and Bayesian inference. We assign probabilities for the spectral type of every source detected in deep imaging down to K' = 15.5 mag using information from spectra, simulations, number counts, and the distribution of stars. The inferred radial surface-density profiles, {Sigma}(R){proportional_to}R {sup -{Gamma}}, for the young stars and late-type giants are consistent with earlier results ({Gamma}{sub early} = 0.93 {+-} 0.09, {Gamma}{sub late} = 0.16 {+-} 0.07). The late-type surface-density profile is approximately flat out to the edge of the survey. While the late-type stellar luminosity function is consistent with the Galactic bulge, the completeness-corrected luminosity function of the early-type stars has significantly more young stars at faint magnitudes compared with previous surveys with similar depth. This luminosity function indicates that the corresponding mass function of the young stars is likely less top-heavy than that inferred from previous surveys.

Do, T.; Martinez, G. D. [Physics and Astronomy Department, University of California, Irvine, CA 92697 (United States)] [Physics and Astronomy Department, Unive