Pair densities in density functional theory
Chen, Huajie
2015-01-01T23:59:59.000Z
The exact interaction energy of a many-electron system is determined by the electron pair density, which is not well-approximated in standard Kohn-Sham density functional models. Here we study the (complicated but well-defined) exact universal map from density to pair density. We show that many common functionals, including the most basic version of the LDA (Dirac exchange with no correlation contribution), arise from particular approximations of this map. We develop an algorithm to compute the map numerically, and apply it to one-parameter families {a*rho(a*x)} of one-dimensional homogeneous and inhomogeneous single-particle densities. We observe that the pair density develops remarkable multiscale patterns which strongly depend on both the particle number and the "width" 1/a of the single-particle density. The simulation results are confirmed by rigorous asymptotic results in the limiting regimes a>>1 and a<<1. For one-dimensional homogeneous systems, we show that the whole spectrum of patterns is rep...
Density-dependent covariant energy density functionals
Lalazissis, G. A. [Physics Department, Aristotle University of Thessaloniki, GR-54124 (Greece)
2012-10-20T23:59:59.000Z
Relativistic nuclear energy density functionals are applied to the description of a variety of nuclear structure phenomena at and away fromstability line. Isoscalar monopole, isovector dipole and isoscalar quadrupole giant resonances are calculated using fully self-consistent relativistic quasiparticle randomphase approximation, based on the relativistic Hartree-Bogoliubovmodel. The impact of pairing correlations on the fission barriers in heavy and superheavy nuclei is examined. The role of pion in constructing desnity functionals is also investigated.
Phenomenological Relativistic Energy Density Functionals
Lalazissis, G. A.; Kartzikos, S. [Physics Department, Aristotle University of Thessaloniki (Greece); Niksic, T.; Paar, N.; Vretenar, D. [Physics Department, University of Zagreb (Croatia); Ring, P. [Physics Department, TU Muenchen, Garching (Germany)
2009-08-26T23:59:59.000Z
The framework of relativistic nuclear energy density functionals is applied to the description of a variety of nuclear structure phenomena, not only in spherical and deformed nuclei along the valley of beta-stability, but also in exotic systems with extreme isospin values and close to the particle drip-lines. Dynamical aspects of exotic nuclear structure is explored using the fully consistent quasiparticle random-phase approximation based on the relativistic Hartree-Bogoliubov model. Recent applications of energy density functionals with explicit density dependence of the meson-nucleon couplings are presented.
Path Integral Monte Carlo and Density Functional Molecular Dynamics Simulations of Hot, Dense Helium
Militzer, Burkhard
Path Integral Monte Carlo and Density Functional Molecular Dynamics Simulations of Hot, Dense integral Monte Carlo (PIMC) and density func- tional molecular dynamics (DFT-MD), are applied to study hot excitation mecha- nisms that determine their behavior at high temperature. The helium atom has two ionization
Jacek Dobaczewski Density functional theory and energy
Dobaczewski, Jacek
in Poland per voivodship Energy density functional 245 647 Price voivodship functional 654 763 295 580Jacek Dobaczewski Density functional theory and energy density functionals in nuclear physics Jacek://www.fuw.edu.pl/~dobaczew/Stellenbosch/dobaczewski_lecture.pdf Home page: http://www.fuw.edu.pl/~dobaczew/ #12;Jacek Dobaczewski Nuclear Structure Energy scales
Quantum critical benchmark for density functional theory
Paul E. Grabowski; Kieron Burke
2014-08-09T23:59:59.000Z
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.
Magnetic fields and density functional theory
Salsbury Jr., Freddie
1999-02-01T23:59:59.000Z
A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.
Density functional theory for carbon dioxide crystal
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
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.
Instabilities in the Nuclear Energy Density Functional
M. Kortelainen; T. Lesinski
2010-02-05T23:59:59.000Z
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.
Periodic subsystem density-functional theory
Genova, Alessandro; Pavanello, Michele, E-mail: m.pavanello@rutgers.edu [Department of Chemistry, Rutgers University, Newark, New Jersey 07102 (United States); Ceresoli, Davide [Department of Chemistry, Rutgers University, Newark, New Jersey 07102 (United States); CNR-ISTM, Institute of Molecular Sciences and Technologies, Milano (Italy)
2014-11-07T23:59:59.000Z
By partitioning the electron density into subsystem contributions, the Frozen Density Embedding (FDE) formulation of subsystem Density Functional Theory (DFT) has recently emerged as a powerful tool for reducing the computational scaling of Kohn–Sham DFT. To date, however, FDE has been employed to molecular systems only. Periodic systems, such as metals, semiconductors, and other crystalline solids have been outside the applicability of FDE, mostly because of the lack of a periodic FDE implementation. To fill this gap, in this work we aim at extending FDE to treat subsystems of molecular and periodic character. This goal is achieved by a dual approach. On one side, the development of a theoretical framework for periodic subsystem DFT. On the other, the realization of the method into a parallel computer code. We find that periodic FDE is capable of reproducing total electron densities and (to a lesser extent) also interaction energies of molecular systems weakly interacting with metallic surfaces. In the pilot calculations considered, we find that FDE fails in those cases where there is appreciable density overlap between the subsystems. Conversely, we find FDE to be in semiquantitative agreement with Kohn–Sham DFT when the inter-subsystem density overlap is low. We also conclude that to make FDE a suitable method for describing molecular adsorption at surfaces, kinetic energy density functionals that go beyond the GGA level must be employed.
Error Analysis in Nuclear Density Functional Theory
Nicolas Schunck; Jordan D. McDonnell; Jason Sarich; Stefan M. Wild; Dave Higdon
2014-07-11T23:59:59.000Z
Nuclear density functional theory (DFT) is the only microscopic, global approach to the structure of atomic nuclei. It is used in numerous applications, from determining the limits of stability to gaining a deep understanding of the formation of elements in the universe or the mechanisms that power stars and reactors. The predictive power of the theory depends on the amount of physics embedded in the energy density functional as well as on efficient ways to determine a small number of free parameters and solve the DFT equations. In this article, we discuss the various sources of uncertainties and errors encountered in DFT and possible methods to quantify these uncertainties in a rigorous manner.
Density Functional Theory Models for Radiation Damage
Density Functional Theory Models for Radiation Damage S.L. Dudarev EURATOM/CCFE Fusion Association and informative as the most advanced experimental techniques developed for the observation of radiation damage investigation and assessment of radiation damage effects, offering new insight into the origin of temperature
A Density Functional Theory Study of Formaldehyde Adsorption...
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Density Functional Theory Study of Formaldehyde Adsorption on Ceria. A Density Functional Theory Study of Formaldehyde Adsorption on Ceria. Abstract: Molecular adsorption of...
Effects of van der Waals Density Functional Corrections on Trends...
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van der Waals Density Functional Corrections on Trends in Furfural Adsorption and Hydrogenation on Close-Packed Effects of van der Waals Density Functional Corrections on Trends in...
Density Functional Theory Study of Oxygen Reduction Activity...
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Density Functional Theory Study of Oxygen Reduction Activity on Ultrathin Platinum Nanotubes. Density Functional Theory Study of Oxygen Reduction Activity on Ultrathin Platinum...
Configuration Interactions Constrained by Energy Density Functionals
B. Alex Brown; Angelo Signoracci; Morten Hjorth-Jensen
2010-09-24T23:59:59.000Z
A new method for constructing a Hamiltonian for configuration interaction calculations with constraints to energies of spherical configurations obtained with energy-density-functional (EDF) methods is presented. This results in a unified model that reproduced the EDF binding-energy in the limit of single-Slater determinants, but can also be used for obtaining energy spectra and correlation energies with renormalized nucleon-nucleon interactions. The three-body and/or density-dependent terms that are necessary for good nuclear saturation properties are contained in the EDF. Applications to binding energies and spectra of nuclei in the region above 208Pb are given.
Nuclear fission in covariant density functional theory
A. V. Afanasjev; H. Abusara; P. Ring
2013-09-12T23:59:59.000Z
The current status of the application of covariant density functional theory to microscopic description of nuclear fission with main emphasis on superheavy nuclei (SHN) is reviewed. The softness of SHN in the triaxial plane leads to an emergence of several competing fission pathes in the region of the inner fission barrier in some of these nuclei. The outer fission barriers of SHN are considerably affected both by triaxiality and octupole deformation.
Fast plane wave density functional theory molecular dynamics calculations on multi-GPU machines
Jia, Weile, E-mail: jiawl@sccas.cn [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China) [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing (China); Fu, Jiyun, E-mail: fujy@sccas.cn [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China) [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China); University of Chinese Academy of Sciences, Beijing (China); Cao, Zongyan, E-mail: zycao@sccas.cn [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China)] [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China); Wang, Long, E-mail: wangl@sccas.cn [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China)] [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China); Chi, Xuebin, E-mail: chi@sccas.cn [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China)] [Supercomputing Center, Computer Network Information Center, Chinese Academy of Sciences, No. 4 South 4th Street, ZhongGuanCun, Beijing 100190 (China); Gao, Weiguo, E-mail: wggao@fudan.edu.cn [School of Mathematical Sciences, Fudan University, 220 Handan Road, Shanghai 200433 (China) [School of Mathematical Sciences, Fudan University, 220 Handan Road, Shanghai 200433 (China); MOE Key Laboratory of Computational Physical Sciences, Fudan University, Shanghai (China); Wang, Lin-Wang, E-mail: lwwang@lbl.gov [Material Science Division, Lawrence Berkeley National Laboratory, One Cyclotron Road Mail Stop 50F Berkeley, CA 94720 (United States)] [Material Science Division, Lawrence Berkeley National Laboratory, One Cyclotron Road Mail Stop 50F Berkeley, CA 94720 (United States)
2013-10-15T23:59:59.000Z
Plane wave pseudopotential (PWP) density functional theory (DFT) calculation is the most widely used method for material simulations, but its absolute speed stagnated due to the inability to use large scale CPU based computers. By a drastic redesign of the algorithm, and moving all the major computation parts into GPU, we have reached a speed of 12 s per molecular dynamics (MD) step for a 512 atom system using 256 GPU cards. This is about 20 times faster than the CPU version of the code regardless of the number of CPU cores used. Our tests and analysis on different GPU platforms and configurations shed lights on the optimal GPU deployments for PWP-DFT calculations. An 1800 step MD simulation is used to study the liquid phase properties of GaInP.
Symmetry energy in nuclear density functional theory
W. Nazarewicz; P. -G. Reinhard; W. Satula; D. Vretenar
2013-07-22T23:59:59.000Z
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.
Band terminations in density functional theory
A. V. Afanasjev
2009-02-01T23:59:59.000Z
The analysis of the terminating bands has been performed in the relativistic mean field framework. It was shown that nuclear magnetism provides an additional binding to the energies of the specific configuration and this additional binding increases with spin and has its {\\it maximum} exactly at the terminating state. This suggests that the terminating states can be an interesting probe of the time-odd mean fields {\\it provided that other effects can be reliably isolated.} Unfortunately, a reliable isolation of these effects is not that simple: many terms of the density functional theories contribute into the energies of the terminating states and the deficiencies in the description of those terms affect the result. The recent suggestion \\cite{ZSW.05} that the relative energies of the terminating states in the $N \
Building a Universal Nuclear Energy Density Functional
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
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.
Constrained Density-Functional Theory--Configuration Interaction
Kaduk, Benjamin James
2012-01-01T23:59:59.000Z
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 ...
Density Functional Study of the Structure, Stability and Oxygen...
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Study of the Structure, Stability and Oxygen Reduction Activity of Ultrathin Platinum Nanowires. Density Functional Study of the Structure, Stability and Oxygen Reduction Activity...
Density Functional Theory Studies of the Electronic Structure...
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Theory Studies of the Electronic Structure of Solid State Actinide Oxides. Density Functional Theory Studies of the Electronic Structure of Solid State Actinide Oxides. Abstract:...
Density-Functional Theory for Complex Fluids
Wu, Jianzhong
. This generic methodology is built upon a mathematical theorem that states, for an equilibrium system at a given modeling of the microscopic struc- tures and phase behavior of soft-condensed matter. The methodol- ogy to the one-body density profile Grand potential: the free energy of an open system at fixed volume
Nuclear Energy Density Functionals Constrained by Low-Energy QCD
Dario Vretenar
2008-02-06T23:59:59.000Z
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.
Energy density functional for nuclei and neutron stars
J. Erler; C. J. Horowitz; W. Nazarewicz; M. Rafalski; P. -G. Reinhard
2012-11-27T23:59:59.000Z
We aim to develop a nuclear energy density functional that can be simultaneously applied to finite nuclei and neutron stars. 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. The new functional TOV-min yields results for nuclear bulk properties (energy, r.m.s. radius, diffraction radius, 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 $^{208}$Pb and the neutron star radius. 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.
Recovering Risk-Neutral Probability Density Functions from Options ...
density function (pdf) of the future prices of an underlying asset from the prices of ...... options prices: An application to crude oil during theI² ulfcw risis. © o£ rd¨.
Real time density functional simulations of quantum scale conductance
Evans, Jeremy Scott
2009-01-01T23:59:59.000Z
We study electronic conductance through single molecules by subjecting a molecular junction to a time dependent potential and propagating the electronic state in real time using time-dependent density functional theory ...
Density Functional Theory with Dissipation: Transport through Single Molecules
Kieron Burke
2012-04-30T23:59:59.000Z
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.
Preface: Special Topic on Advances in Density Functional Theory
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
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.
Monte Carlo tests of Orbital-Free Density Functional Theory
D. I. Palade
2014-12-12T23:59:59.000Z
The relationship between the exact kinetic energy density in a quantum system in the frame of Density Functional Theory and the semiclassical functional expression for the same quantity is investigated. The analysis is performed with Monte Carlo simulations of the Kohn-Sham potentials. We find that the semiclassical form represents the statistical expectation value of the quantum nature. Based on the numerical results, we propose an empirical correction to the existing functional and an associated method to improve the Orbital-Free results.
Nuclear Energy Density Functionals: What do we really know?
Bulgac, Aurel; Jin, Shi
2015-01-01T23:59:59.000Z
We present the simplest nuclear energy density functional (NEDF) to date, determined by only 4 significant phenomenological parameters, yet capable of fitting measured nuclear masses with better accuracy than the Bethe-Weizs\\"acker mass formula, while also describing density structures (charge radii, neutron skins etc.) and time-dependent phenomena (induced fission, giant resonances, low energy nuclear collisions, etc.). The 4 significant parameters are necessary to describe bulk nuclear properties (binding energies and charge radii); an additional 2 to 3 parameters have little influence on the bulk nuclear properties, but allow independent control of the density dependence of the symmetry energy and isovector excitations, in particular the Thomas-Reiche-Kuhn sum rule. This Hohenberg-Kohn-style of density functional theory successfully realizes Weizs\\"acker's ideas and provides a computationally tractable model for a variety of static nuclear properties and dynamics, from finite nuclei to neutron stars, where...
Probability distribution functions in the finite density lattice QCD
S. Ejiri; Y. Nakagawa; S. Aoki; K. Kanaya; H. Saito; T. Hatsuda; H. Ohno; T. Umeda
2012-12-04T23:59:59.000Z
We study the phase structure of QCD at high temperature and density by lattice QCD simulations adopting a histogram method. We try to solve the problems which arise in the numerical study of the finite density QCD, focusing on the probability distribution function (histogram). As a first step, we investigate the quark mass dependence and the chemical potential dependence of the probability distribution function as a function of the Polyakov loop when all quark masses are sufficiently large, and study the properties of the distribution function. The effect from the complex phase of the quark determinant is estimated explicitly. The shape of the distribution function changes with the quark mass and the chemical potential. Through the shape of the distribution, the critical surface which separates the first order transition and crossover regions in the heavy quark region is determined for the 2+1-flavor case.
Density Functional Theory Studies of Magnetically Confined Fermi Gas
Chen, Y J; Chen, Yu-Jun
2001-01-01T23:59:59.000Z
A theory is developed for magnetically confined Fermi gas at low temperature based on the density functional theory. The theory is illustrated by numerical calculation of density distributions of Fermi atoms $^{40}$K with parameters according to DeMarco and Jin's experiment[Science, 285(1999)1703]. Our results are in good agreement with the experiment. To check the theory, we also performed calculations using our theory at high temperature and compared very well to the result of classical limit.
Addressing spectroscopic quality of covariant density functional theory
A. V. Afanasjev
2014-09-17T23:59:59.000Z
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.
Relativistic Nuclear Energy Density Functionals: adjusting parameters to binding energies
T. Niksic; D. Vretenar; P. Ring
2008-09-08T23:59:59.000Z
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.
Practical Attacks on Digital Signatures Using MD5 Message Digest
schemes based on MD5 message digest on an example using GPG. Keywords: collision, hash function, MD5 1 on digital signatures on an example using GPG (section 5) and finally an exam- ple of real-world attack
Binding Energies in Benzene Dimers: Nonlocal Density Functional Calculations
Aaron Puzder; Maxime Dion; David C. Langreth
2005-09-15T23:59:59.000Z
The interaction energy and minimum energy structure for different geometries of the benzene dimer has been calculated using the recently developed nonlocal correlation energy functional for calculating dispersion interactions. The comparison of this straightforward and relatively quick density functional based method with recent calculations can elucidate how the former, quicker method might be exploited in larger more complicated biological, organic, aromatic, and even infinite systems such as molecules physisorbed on surfaces, and van der Waals crystals.
Density matrix renormalization group and wave function factorization for nuclei
T. Papenbrock; D. J. Dean
2005-07-15T23:59:59.000Z
We employ the density matrix renormalization group (DMRG) and the wave function factorization method for the numerical solution of large scale nuclear structure problems. The DMRG exhibits an improved convergence for problems with realistic interactions due to the implementation of the finite algorithm. The wave function factorization of fpg-shell nuclei yields rapidly converging approximations that are at the present frontier for large-scale shell model calculations.
Density Functional Resonance Theory of Unbound Electronic Systems
Daniel L. Whitenack; Adam Wasserman
2011-06-20T23:59:59.000Z
Density Functional Resonance Theory (DFRT) is a complex-scaled version of ground-state Density Functional Theory (DFT) that allows one to calculate the resonance energies and lifetimes of metastable anions. In this formalism, the exact energy and lifetime of the lowest-energy resonance of unbound systems is encoded into a complex "density" that can be obtained via complex-coordinate scaling. This complex density is used as the primary variable in a DFRT calculation just as the ground-state density would be used as the primary variable in DFT. As in DFT, there exists a mapping of the N-electron interacting system to a Kohn-Sham system of N non-interacting particles in DFRT. This mapping facilitates self consistent calculations with an initial guess for the complex density, as illustrated with an exactly-solvable model system. Whereas DFRT yields in principle the exact resonance energy and lifetime of the interacting system, we find that neglecting the complex-correlation contribution leads to errors of similar magnitude to those of standard scattering close-coupling calculations under the bound-state approximation.
Relativistic density functional theory for finite nuclei and neutron stars
J. Piekarewicz
2015-02-05T23:59:59.000Z
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.
Density Functional Theory-Based Database Development and CALPHAD Automation
Chen, Long-Qing
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
Calibrating Speed-Density Functions for ff SMesoscopic Traffic Simulation
Bertini, Robert L.
. (1999), Tavana & Mahmassani (2000), Wang & Papageorgiou (2005), Antoniou et al. (2007) #12;Case Studies) supply #12;Case Studies (contd.) · DynaMIT speed-density function form · Performance measures ( )= - S i pointsdataofnumber speed)(count,simulated : : S iy #12;Case Studies (contd.) · Methodology Large
Classical density functional theory to tackle solvation in molecular liquids
Jeanmairet, Guillaume; Sergiievskyi, Volodymyr; Borgis, Daniel
2015-01-01T23:59:59.000Z
We present a brief review of the classical density functional theory of atomic and molecular fluids. We focus on the application of the theory to the determination of the solvation properties of arbitrary molecular solutes in arbitrary molecular solvent. This includes the prediction of the solvation free energies, as well as the characterization of the microscopic, three-dimensional solvent structure.
SURFACE SYMMETRY ENERGY OF NUCLEAR ENERGY DENSITY FUNCTIONALS
Nikolov, N; Schunck, N; Nazarewicz, W; Bender, M; Pei, J
2010-12-20T23:59:59.000Z
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.
Measuring the entanglement of analogue Hawking radiation by the density-density correlation function
Steinhauer, Jeff
2015-01-01T23:59:59.000Z
We theoretically study the entanglement of Hawking radiation emitted by an analogue black hole. We find that this entanglement can be measured by the experimentally accessible density-density correlation function, which only requires standard imaging techniques. It is seen that the high energy tail of the distribution of Hawking radiation should be entangled, whereas the low energy part is not. This confirms a previous numerical study. The full Peres-Horodecki criterion is considered, but a significant simplification is found in the stationary, homogeneous case. Our method applies to systems which are sufficiently cold that the thermal phonons can be neglected.
Excitations and benchmark ensemble density functional theory for two electrons
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
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.
Finite-size instabilities in nuclear energy density functionals
Hellemans, V.; Heenen, P.-H.; Bender, M. [Universite Libre de Bruxelles, PNTPM, CP229, 1050 Bruxelles (Belgium); Univ. Bordeaux, CENBG, UMR5797, F-33170 Gradignan (France) and CNRS/IN2P3, CENBG, UMR5797, F-33170 Gradignan (France)
2012-10-20T23:59:59.000Z
The systematic lack of convergence of self-consistent mean-field calculations with certain parameterizations of the Skyrme energy density functional has been attributed to the appearance of finite-size instabilities. In this contribution, we investigate what happens at the instability associated with the C{sub 0}{sup {Delta}s}s{sub 0} Dot-Operator {Delta}s{sub 0} term in a high-spin state of the superdeformed band in {sup 194}Hg.
Measuring the Density Fluctuation From the Cluster Gas Mass Function
Kazuhiro Shimasaku
1997-01-27T23:59:59.000Z
We investigate the gas mass function of clusters of galaxies to measure the density fluctuation spectrum on cluster scales. The baryon abundance confined in rich clusters is computed from the gas mass function and compared with the mean baryon density in the universe which is predicted by the Big Bang Nucleosynthesis. This baryon fraction and the slope of the gas mass function put constraints on $\\sigma_8$, the rms linear fluctuation on scales of $8h^{-1}\\Mpc$, and the slope of the fluctuation spectrum, where $h$ is the Hubble constant in units of 100 $\\kms \\oMpc$. We find $\\sigma_8 = 0.80 \\pm 0.15$ and $n \\sim -1.5$ for $0.5 \\le h \\le 0.8$, where we assume that the density spectrum is approximated by a power law on cluster scales: $\\sigma(r) \\propto r^{-{3+n\\over{2}}}$. Our value of $\\sigma_8$ is independent of the density parameter, $\\Omega_0$, and thus we can estimate $\\Omega_0$ by combining $\\sigma_8$ obtained in this study with those from $\\Omega_0$-dependent analyses to date. We find that $\\sigma_8(\\Omega_0)$ derived from the cluster abundance such as the temperature function gives $\\Omega_0 \\sim 0.5$ while $\\sigma_8(\\Omega_0)$ measured from the peculiar velocity field of galaxies gives $\\Omega_0 \\sim 0.2-1$, depending on the technique used to analyze peculiar velocity data. Constraints are also derived for open, spatially flat, and tilted Cold Dark Matter models and for Cold + Hot Dark Matter models.
A Wigner Monte Carlo approach to density functional theory
Sellier, J.M., E-mail: jeanmichel.sellier@gmail.com; Dimov, I.
2014-08-01T23:59:59.000Z
In order to simulate quantum N-body systems, stationary and time-dependent density functional theories rely on the capacity of calculating the single-electron wave-functions of a system from which one obtains the total electron density (Kohn–Sham systems). In this paper, we introduce the use of the Wigner Monte Carlo method in ab-initio calculations. This approach allows time-dependent simulations of chemical systems in the presence of reflective and absorbing boundary conditions. It also enables an intuitive comprehension of chemical systems in terms of the Wigner formalism based on the concept of phase-space. Finally, being based on a Monte Carlo method, it scales very well on parallel machines paving the way towards the time-dependent simulation of very complex molecules. A validation is performed by studying the electron distribution of three different systems, a Lithium atom, a Boron atom and a hydrogenic molecule. For the sake of simplicity, we start from initial conditions not too far from equilibrium and show that the systems reach a stationary regime, as expected (despite no restriction is imposed in the choice of the initial conditions). We also show a good agreement with the standard density functional theory for the hydrogenic molecule. These results demonstrate that the combination of the Wigner Monte Carlo method and Kohn–Sham systems provides a reliable computational tool which could, eventually, be applied to more sophisticated problems.
Progress at the interface of wave-function and density-functional theories
Gidopoulos, Nikitas I. [ISIS, Rutherford Appleton Laboratory, STFC, Didcot, OX11 0QX, Oxon (United Kingdom)
2011-04-15T23:59:59.000Z
The Kohn-Sham (KS) potential of density-functional theory (DFT) emerges as the minimizing effective potential in a variational scheme that does not involve fixing the unknown single-electron density. Using Rayleigh Schroedinger (RS) perturbation theory (PT), we construct ab initio approximations for the energy difference, the minimization of which determines the KS potential directly - thereby bypassing DFT's traditional algorithm to search for the density that minimizes the total energy. From second-order RS PT, we obtain variationally stable energy differences to be minimized, solving the severe problem of variational collapse of orbital-dependent exchange-correlation functionals based on second-order RS PT.
Subsystem real-time Time Dependent Density Functional Theory
Krishtal, Alisa; Pavanello, Michele
2015-01-01T23:59:59.000Z
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.
Symmetry Projected Density Functional Theory and Neutron Halo’s
unknown authors
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
Density functional theory study of mercury adsorption on metal surfaces
Steckel, J.A.
2008-01-01T23:59:59.000Z
Density functional theory #1;DFT#2; calculations are used to characterize the interaction of mercury with copper, nickel, palladium, platinum, silver, and gold surfaces. Mercury binds relatively strongly to all the metal surfaces studied, with binding energies up to #3;1 eV for Pt and Pd. DFT calculations underestimate the energy of adsorption with respect to available experimental data. Plane-wave DFT results using the local density approximation and the Perdew-Wang 1991 and Perdew-Burke-Ernzerhof parametrizations of the generalized gradient approximation indicate that binding of mercury at hollow sites is preferred over binding at top or bridge sites. The interaction with mercury in order of increasing reactivity over the six metals studied is Ag #1;Au#1;Cu#1;Ni#1;Pt#1;Pd. Binding is stronger on the #1;001#2; faces of the metal surfaces, where mercury is situated in fourfold hollow sites as opposed to the threefold hollow sites on #1;111#2; faces. In general, mercury adsorption leads to decreases in the work function; adsorbate-induced work function changes are particularly dramatic on Pt.
Quantification of Uncertainties in Nuclear Density Functional theory
N. Schunck; J. D. McDonnell; D. Higdon; J. Sarich; S. Wild
2014-09-17T23:59:59.000Z
Reliable predictions of nuclear properties are needed as much to answer fundamental science questions as in applications such as reactor physics or data evaluation. Nuclear density functional theory is currently the only microscopic, global approach to nuclear structure that is applicable throughout the nuclear chart. In the past few years, a lot of effort has been devoted to setting up a general methodology to assess theoretical uncertainties in nuclear DFT calculations. In this paper, we summarize some of the recent progress in this direction. Most of the new material discussed here will be be published in separate articles.
Fayer, Michael D.
(CO2) as a function of density from low density (well below the critical density) to high density ethane, carbon dioxide, and fluoroform as a function of density at two temperatures are presented of input information on the SCF properties obtained from the fluids' equations of state and other tabulated
Towards the island of stability with relativistic energy density functionals
Prassa, V.; Niksic, T.; Lalazissis, G. A.; Vretenar, D. [Physics Department, University of Jyvaeskylae, P.O. Box 35 (YFL) FI-40014, Finland and Department of Theoretical Physics, Aristotle University Thessaloniki, GR-54124 (Finland); Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Department of Theoretical Physics, Aristotle University Thessaloniki, GR-54124 (Greece); Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia)
2012-10-20T23:59:59.000Z
Relativistic energy density functionals (REDF) provide a complete and accurate, global description of nuclear structure phenomena. Modern semi-empirical functionals, adjusted to the nuclear matter equation of state and to empirical masses of deformed nuclei, are applied to studies of shapes of superheavy nuclei. The theoretical framework is tested in a comparison to empirical masses, quadrupole deformations, and energy barriers of actinide nuclei. The model is used in a self-consistent mean-field calculation of spherical, axial and triaxial shapes of superheavy nuclei, alpha-decay energies and lifetimes. The effect of explicit treatment of collective correlations is analyzed in calculations that consistently use a collective Hamiltonian model based on REDFs.
BUILDING A UNIVERSAL NUCLEAR ENERGY DENSITY FUNCTIONAL (UNEDF)
Nazarewicz, Witold
2012-07-01T23:59:59.000Z
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.
Uncertainty Quantification and Propagation in Nuclear Density Functional Theory
N. Schunck; J. D. McDonnell; D. Higdon; J. Sarich; S. M. Wild
2015-03-19T23:59:59.000Z
Nuclear density functional theory (DFT) is one of the main theoretical tools used to study the properties of heavy and superheavy elements, or to describe the structure of nuclei far from stability. While on-going efforts seek to better root nuclear DFT in the theory of nuclear forces [see Duguet et al., this issue], energy functionals remain semi-phenomenological constructions that depend on a set of parameters adjusted to experimental data in finite nuclei. In this paper, we review recent efforts to quantify the related uncertainties, and propagate them to model predictions. In particular, we cover the topics of parameter estimation for inverse problems, statistical analysis of model uncertainties and Bayesian inference methods. Illustrative examples are taken from the literature.
Power-law tails in probability density functions of molecular cloud column density
Brunt, Chris
2015-01-01T23:59:59.000Z
Power-law tails are often seen in probability density functions (PDFs) of molecular cloud column densities, and have been attributed to the effect of gravity. We show that extinction PDFs of a sample of five molecular clouds obtained at a few tenths of a parsec resolution, probing extinctions up to A$_{{\\mathrm{V}}}$ $\\sim$ 10 magnitudes, are very well described by lognormal functions provided that the field selection is tightly constrained to the cold, molecular zone and that noise and foreground contamination are appropriately accounted for. In general, field selections that incorporate warm, diffuse material in addition to the cold, molecular material will display apparent core+tail PDFs. The apparent tail, however, is best understood as the high extinction part of a lognormal PDF arising from the cold, molecular part of the cloud. We also describe the effects of noise and foreground/background contamination on the PDF structure, and show that these can, if not appropriately accounted for, induce spurious ...
Correll, S.
1988-04-01T23:59:59.000Z
MD is the S-1 Mark IIA machine debugger. It is the hardware equivalent of a software symbolic debugger. It consists of a user-level program which executes on a VAX computer running Berkeley UNIX and a device driver which resides within the UNIX kernel. It communicates with the S-1 Mark IIA through a front-end interface attached to the UNIBUS of the VAX. The first section of this report describes MD's user interface and command set. The second section describes the virtual machine interface through which MD and the UNIX device driver communicate.
Density functional theory based generalized effective fragment potential method
Nguyen, Kiet A., E-mail: kiet.nguyen@wpafb.af.mil, E-mail: ruth.pachter@wpafb.af.mil [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States); UES, Inc., Dayton, Ohio 45432 (United States); Pachter, Ruth, E-mail: kiet.nguyen@wpafb.af.mil, E-mail: ruth.pachter@wpafb.af.mil [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States); Day, Paul N. [Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States); General Dynamics Information Technology, Inc., Dayton, Ohio 45431 (United States)
2014-06-28T23:59:59.000Z
We present a generalized Kohn-Sham (KS) density functional theory (DFT) based effective fragment potential (EFP2-DFT) method for the treatment of solvent effects. Similar to the original Hartree-Fock (HF) based potential with fitted parameters for water (EFP1) and the generalized HF based potential (EFP2-HF), EFP2-DFT includes electrostatic, exchange-repulsion, polarization, and dispersion potentials, which are generated for a chosen DFT functional for a given isolated molecule. The method does not have fitted parameters, except for implicit parameters within a chosen functional and the dispersion correction to the potential. The electrostatic potential is modeled with a multipolar expansion at each atomic center and bond midpoint using Stone's distributed multipolar analysis. The exchange-repulsion potential between two fragments is composed of the overlap and kinetic energy integrals and the nondiagonal KS matrices in the localized molecular orbital basis. The polarization potential is derived from the static molecular polarizability. The dispersion potential includes the intermolecular D3 dispersion correction of Grimme et al. [J. Chem. Phys. 132, 154104 (2010)]. The potential generated from the CAMB3LYP functional has mean unsigned errors (MUEs) with respect to results from coupled cluster singles, doubles, and perturbative triples with a complete basis set limit (CCSD(T)/CBS) extrapolation, of 1.7, 2.2, 2.0, and 0.5 kcal/mol, for the S22, water-benzene clusters, water clusters, and n-alkane dimers benchmark sets, respectively. The corresponding EFP2-HF errors for the respective benchmarks are 2.41, 3.1, 1.8, and 2.5 kcal/mol. Thus, the new EFP2-DFT-D3 method with the CAMB3LYP functional provides comparable or improved results at lower computational cost and, therefore, extends the range of applicability of EFP2 to larger system sizes.
Building A Universal Nuclear Energy Density Functional (UNEDF)
Carlson, Joe, Los Alamos National Laboratory, Los Alamos, NM; Furnstahl, Dick, Ohio State University, Columbus, OH; Horoi, Mihai, Central Michigan University, Mount Pleasant, MI; Lusk, Rusty, Argonne National Laboratory, Argonne, IL; Nazarewicz, Witek, University of Tennessee, Knoxville, TN; Ng, Esmond, Berkeley National Laboratory, Berkeley, CA; Thompson, Ian, Lawrence Livermore National Laboratory, Livermore, CA; Vary, James, Iowa State University, Ames, Iowa
2012-09-30T23:59:59.000Z
During the period of Dec. 1 2006 â?? 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. The main physics areas of UNEDF, defined at the beginning of the project, were: ab initio structure; ab initio functionals; DFT applications; DFT extensions; reactions.
Dipole polarizability of 120Sn and nuclear energy density functionals
Hashimoto, T; Reinhard, P -G; Tamii, A; von Neumann-Cosel, P; Adachi, T; Aoi, N; Bertulani, C A; Fujita, H; Fujita, Y; Ganio?lu, E; Hatanaka, K; Iwamoto, C; Kawabata, T; Khai, N T; Krugmann, A; Martin, D; Matsubara, H; Miki, K; Neveling, R; Okamura, H; Ong, H J; Poltoratska, I; Ponomarev, V Yu; Richter, A; Sakaguchi, H; Shimbara, Y; Shimizu, Y; Simonis, J; Smit, F D; Süsoy, G; Thies, J H; Suzuki, T; Yosoi, M; Zenihiro, J
2015-01-01T23:59:59.000Z
The electric dipole strength distribution in 120Sn between 5 and 22 MeV has been determined at RCNP Osaka from a polarization transfer analysis of proton inelastic scattering at E_0 = 295 MeV and forward angles including 0{\\deg}. Combined with photoabsorption data an electric dipole polarizability alpha_D(120Sn) = 8.93(36) fm^3 is extracted. The correlation of this value with alpha_D for 208Pb serves as a test of energy density functionals (EDFs). The majority of models based on Skyrme interactions can describe the data while relativistic approaches fail. The accuracy of the experimental results provides important constraints on the static isovector properties of EDFs used to predict symmetry energy parameters and the neutron skin thickness of nuclei.
Descriptions of carbon isotopes within the energy density functional theory
Ismail, Atef [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak, Malaysia and Department of Physics, Al-Azhar University, 71524 Assiut (Egypt); Cheong, Lee Yen; Yahya, Noorhana [Fundamental and Applied Sciences Department, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia); Tammam, M. [Department of Physics, Al-Azhar University, 71524 Assiut (Egypt)
2014-10-24T23:59:59.000Z
Within the energy density functional (EDF) theory, the structure properties of Carbon isotopes are systematically studied. The shell model calculations are done for both even-A and odd-A nuclei, to study the structure of rich-neutron Carbon isotopes. The EDF theory indicates the single-neutron halo structures in {sup 15}C, {sup 17}C and {sup 19}C, and the two-neutron halo structures in {sup 16}C and {sup 22}C nuclei. It is also found that close to the neutron drip-line, there exist amazing increase in the neutron radii and decrease on the binding energies BE, which are tightly related with the blocking effect and correspondingly the blocking effect plays a significant role in the shell model configurations.
George, Steven C.
Short Communication Automated computation of functional vascular density using laser speckle Laser Institute and Medical Clinic, University of California, Irvine, CA 92697, USA c Edwards: Laser speckle imaging Functional vascular density Dorsal window chamber Blood flow We report
A Self-Consistent Hubbard U Density-Functional Theory Approach...
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Self-Consistent Hubbard U Density-Functional Theory Approach to the Addition-Elimination Reactions of Hydrocarbons on Bare FeO A Self-Consistent Hubbard U Density-Functional Theory...
Self-interaction corrections in density functional theory
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
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 Weizsäcker 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.
Moyal's Characteristic Function, the Density Matrix and von Neumann's Idempotent
Basil J. Hiley
2014-08-25T23:59:59.000Z
In the Wigner-Moyal approach to quantum mechanics, we show that Moyal's starting point, the characteristic function $M(\\tau,\\theta)=\\int \\psi^{*}(x)e^{i(\\tau {\\hat p}+\\theta{\\hat x})}\\psi(x)dx$, is essentially the primitive idempotent used by von Neumann in his classic paper "Die Eindeutigkeit der Schr\\"odingerschen Operatoren". This paper provides the original proof of the Stone-von Neumann equation. Thus the mathematical structure Moyal develops is simply a re-expression of what is at the heart of quantum mechanics and reproduces exactly the results of the quantum formalism. The "distribution function" $F(X,P,t)$ is simply the quantum mechanical density matrix expressed in an $( X,P)$-representation, where $X$ and $P$ are the mean co-ordinates of a cell structure in phase space. The whole approach therefore clearly has little to do with classical statistical theories but is a consequence of a non-commutative nature of the theory.
Parameterizing deep convection using the assumed probability density function method
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Storer, R. L.; Griffin, B. M.; Höft, J.; Weber, J. K.; Raut, E.; Larson, V. E.; Wang, M.; Rasch, P. J.
2015-01-01T23:59:59.000Z
Due to their coarse horizontal resolution, present-day climate models must parameterize deep convection. This paper presents single-column simulations of deep convection using a probability density function (PDF) parameterization. The PDF parameterization predicts the PDF of subgrid variability of turbulence, clouds, and hydrometeors. That variability is interfaced to a prognostic microphysics scheme using a Monte Carlo sampling method.The PDF parameterization is used to simulate tropical deep convection, the transition from shallow to deep convection over land, and midlatitude deep convection. These parameterized single-column simulations are compared with 3-D reference simulations. The agreement is satisfactory except when the convective forcing is weak.more »The same PDF parameterization is also used to simulate shallow cumulus and stratocumulus layers. The PDF method is sufficiently general to adequately simulate these five deep, shallow, and stratiform cloud cases with a single equation set. This raises hopes that it may be possible in the future, with further refinements at coarse time step and grid spacing, to parameterize all cloud types in a large-scale model in a unified way.« less
Density functional and neutron diffraction studies of lithium polymer electrolytes.
Baboul, A. G.
1998-06-26T23:59:59.000Z
The structure of PEO doped with lithium perchlorate has been determined using neutron diffraction on protonated and deuterated samples. The experiments were done in the liquid state. Preliminary analysis indicates the Li-O distance is about 2.0 {angstrom}. The geometries of a series of gas phase lithium salts [LiCF{sub 3}SO{sub 3}, Li(CF{sub 3}SO{sub 2}){sub 2}N, Li(CF{sub 3}SO{sub 2}){sub 2}CH, LiClO{sub 4}, LiPF{sub 6}, LiAsF{sub 6}] used in polymer electrolytes have been optimized at B3LYP/6-31G(d) density functional level of theory. All local minima have been identified. For the triflate, imide, methanide, and perchlorate anions, the lithium cation is coordinated to two oxygens and have binding energies of ca 141 kcal/mol at the B3LYP/6-311+G(3df,2p)/B3LYP/6-31G* level of theory. For the hexafluoroarsenate and hexafluorophosphate the lithium cation is coordinated to three oxygens and have binding energies of ca. 136 kcal/mol.
Simple regularization scheme for multi-reference density functional theories
Wojciech Satula; Jacek Dobaczewski
2014-07-03T23:59:59.000Z
Background: Extensions of single-reference (SR) energy-density-functionals (EDFs) to multi-reference (MR) applications involve using the generalized Wick theorem (GWT), which leads to singular energy kernels that cannot be properly integrated to restore symmetries, unless the EDFs are generated by true interactions. Purpose: We propose a new method to regularize the MR EDFs, which is based on using auxiliary quantities obtained by multiplying the kernels with appropriate powers of overlaps. Methods: Regularized matrix elements of two-body interactions are obtained by integrating the auxiliary quantities and then solving simple linear equations. Results: We implement the new regularization method within the self-consistent Skyrme-Hartree-Fock approach and we perform a proof-of-principle angular-momentum projection (AMP) of states in odd-odd nucleus 26Al. We show that for EDFs generated by true interactions, our regularization method gives results identical to those obtained within the standard AMP procedure. We also show that for EDFs that do not correspond to true interactions, it gives stable and converging results that are different than unstable and non-converging standard AMP values. Conclusions: The new regularization method proposed in this work may provide us with a relatively inexpensive and efficient tool to generalize SR EDFs to MR applications, thus allowing for symmetry restoration and configuration mixing performed for typical nuclear EDFs, which most often do not correspond to true interactions.
Desjarlais, Michael Paul; Mattsson, Thomas Kjell Rene
2006-03-01T23:59:59.000Z
Knowledge of the properties of water is essential for correctly describing the physics of shock waves in water as well as the behavior of giant planets. By using finite temperature density functional theory (DFT), we have investigated the structure and electronic conductivity of water across three phase transitions (molecular liquid/ ionic liquid/super-ionic/electronic liquid). There is a rapid transition to ionic conduction at 2000 K and 2 g/cm{sup 3} while electronic conduction dominates at temperatures above 6000 K. We predict that the fluid bordering the super-ionic phase is conducting above 4000 K and 100 GPa. Earlier work instead has the super-ionic phase bordering an insulating fluid, with a transition to metallic fluid not until 7000 K and 250 GPa. The tools and expertise developed during the project can be applied to other molecular systems, for example, methane, ammonia, and CH foam. We are now well positioned to treat also complex molecular systems in the HEDP regime of phase-space.
Maps of current density using density-functional methods A. Soncini,1,a
Helgaker, Trygve
, University of Durham, South Road, Durham DH1 3LE, United Kingdom Received 22 May 2008; accepted 17 July 2008 are compared and integration of the current densities to yield shielding constants is performed. In general of induced current density in molecules. © 2008 American Institute of Physics. DOI: 10.1063/1.2969104 I
Stretched hydrogen molecule from a constrained-search density-functional perspective
Valone, Steven M [Los Alamos National Laboratory; Levy, Mel [DIKE UNIV.
2009-01-01T23:59:59.000Z
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.
On the breaking and restoration of symmetries within the nuclear energy density functional formalism
T. Duguet; J. Sadoudi
2010-10-19T23:59:59.000Z
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.
Density-matrix functionals for pairing in mesoscopic superconductors
Denis Lacroix; Guillaume Hupin
2010-09-03T23:59:59.000Z
A functional theory based on single-particle occupation numbers is developed for pairing. This functional, that generalizes the BCS 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.
Supplementary data for "Relativistic density functional theory modeling of plutonium and
Titov, Anatoly
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
Ceder, Gerbrand
We compare the accuracy of conventional semilocal density functional theory (DFT), the DFT+U method, and the Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional for structural parameters, redox reaction energies, and formation ...
A proximal gradient method for ensemble density functional theory
Michael Ulbrich
2015-04-23T23:59:59.000Z
Apr 23, 2015 ... Although the widely used self-consistent field iteration method can be extended to solve the minimization of the total energy functional with ...
Element orbitals for Kohn-Sham density functional theory
Lin, Lin; Ying, Lexing
2012-05-08T23:59:59.000Z
We present a method to discretize the Kohn-Sham Hamiltonian matrix in the pseudopotential framework by a small set of basis functions automatically contracted from a uniform basis set such as planewaves. Each basis function is localized around an element, which is a small part of the global domain containing multiple atoms. We demonstrate that the resulting basis set achieves meV accuracy for 3D densely packed systems with a small number of basis functions per atom. The procedure is applicable to insulating and metallic systems.
Density functional simulations of Tebased phase change materials J. Akola 1,2
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
Statistical Image Modeling with the Magnitude Probability Density Function of Complex Wavelet
Oraintara, Soontorn
Statistical Image Modeling with the Magnitude Probability Density Function of Complex Wavelet the probability density function (pdf) of the magnitude of complex wavelet coefficients with the assump- tion Statistical image modeling in the wavelet domain is of inter- est in recent years due to the ability
Accurate Energies and Structures for Large Water Clusters Using the X3LYP Hybrid Density Functional
Goddard III, William A.
Accurate Energies and Structures for Large Water Clusters Using the X3LYP Hybrid Density FunctionalVed: June 9, 2004; In Final Form: August 10, 2004 We predict structures and energies of water clusters containing up to 19 waters with X3LYP, an extended hybrid density functional designed to describe
Reactions of Polycarbonate with Cyclohexene Oxide and Phosphites: A Density Functional Study
Reactions of Polycarbonate with Cyclohexene Oxide and Phosphites: A Density Functional Study J bisphenol A polycarbonate (BPA-PC). We describe density functional (DF) calculations of the reactions to organic molecules and polymers, focusing on bisphenol A polycarbonate (BPA-PC). BPA-PC is an important
Electronvibration coupling in time-dependent density-functional theory: Application to benzene
Bertsch George F.
Electronvibration coupling in time-dependent density-functional theory: Application to benzene G://jcp.aip.org/about/rights_and_permissions #12;Electronvibration coupling in time-dependent density-functional theory: Application to benzene G for electronvibration coupling, we apply it to the optical properties of the * transitions in benzene
LES/probability density function approach for the simulation of an ethanol spray flame
Raman, Venkat
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
Applications of Skyrme energy-density functional to fusion reactions spanning the fusion barriers
Min Liu; Ning Wang; Zhuxia Li; Xizhen Wu; Enguang Zhao
2006-01-25T23:59:59.000Z
The Skyrme energy density functional has been applied to the study of heavy-ion fusion reactions. The barriers for fusion reactions are calculated by the Skyrme energy density functional with proton and neutron density distributions determined by using restricted density variational (RDV) method within the same energy density functional together with semi-classical approach known as the extended semi-classical Thomas-Fermi method. Based on the fusion barrier obtained, we propose a parametrization of the empirical barrier distribution to take into account the multi-dimensional character of real barrier and then apply it to calculate the fusion excitation functions in terms of barrier penetration concept. A large number of measured fusion excitation functions spanning the fusion barriers can be reproduced well. The competition between suppression and enhancement effects on sub-barrier fusion caused by neutron-shell-closure and excess neutron effects is studied.
Roberto Peverati; Donald G. Truhlar
2013-09-06T23:59:59.000Z
Kohn-Sham density functional theory is in principle an exact formulation of quantum mechanical electronic structure theory, but in practice we have to rely on approximate exchange-correlation (xc) functionals. The objective of our work has been to design an xc functional with broad accuracy across as wide an expanse of chemistry and physics as possible, leading-as a long-range goal-to a functional with good accuracy for all problems, i.e., a universal functional. To guide our path toward that goal and to measure our progress, we have developed-building on earlier work in our group-a set of databases of reference data for a variety of energetic and structural properties in chemistry and physics. These databases include energies of molecular processes such as atomization, complexation, proton addition, and ionization; they also include molecular geometries and solid-state lattice constants, chemical reaction barrier heights, and cohesive energies and band gaps of solids. For the present paper we gather many of these databases into four comprehensive databases, two with 384 energetic data for chemistry and solid-state physics and another two with 68 structural data for chemistry and solid-state physics, and we test 2 wave function methods and 77 density functionals (12 Minnesota meta functionals and 65 others) in a consistent way across this same broad set of data. We especially highlight the Minnesota density functionals, but the results have broader implications in that one may see the successes and failures of many kinds of density functionals when they are all applied to the same data. Therefore the results provide a status report on the quest for a universal functional.
M. Oettel; S. Goerig; A. Haertel; H. Loewen; M. Radu; T. Schilling
2010-09-03T23:59:59.000Z
We perform a comparative study of the free energies and the density distributions in hard sphere crystals using Monte Carlo simulations and density functional theory (employing Fundamental Measure functionals). Using a recently introduced technique (Schilling and Schmid, J. Chem. Phys 131, 231102 (2009)) we obtain crystal free energies to a high precision. The free energies from Fundamental Measure theory are in good agreement with the simulation results and demonstrate the applicability of these functionals to the treatment of other problems involving crystallization. The agreement between FMT and simulations on the level of the free energies is also reflected in the density distributions around single lattice sites. Overall, the peak widths and anisotropy signs for different lattice directions agree, however, it is found that Fundamental Measure theory gives slightly narrower peaks with more anisotropy than seen in the simulations. Among the three types of Fundamental Measure functionals studied, only the White Bear II functional (Hansen-Goos and Roth, J. Phys.: Condens. Matter 18, 8413 (2006)) exhibits sensible results for the equilibrium vacancy concentration and a physical behavior of the chemical potential in crystals constrained by a fixed vacancy concentration.
Nonequilibrium thermodynamics of interfaces using classical density functional theory
Kjelstrup, Signe
resistivities. The interfacial resistivities for heat transfer, for mass transfer, and for the coupling of heat and condensation.5,6 This description finds that the thermodynamic driving forces are linear functions of the heat the measurable heat fluxes differ on both sides. It is important to take the coupling between the heat and mass
Solovyeva, Alisa [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany); Pavanello, Michele [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Neugebauer, Johannes [Technical University Braunschweig, Institute for Physical and Theoretical Chemistry, Hans-Sommer-Str. 10, 38106 Braunschweig (Germany)
2012-05-21T23:59:59.000Z
Subsystem density-functional theory (DFT) is a powerful and efficient alternative to Kohn-Sham DFT for large systems composed of several weakly interacting subunits. Here, we provide a systematic investigation of the spin-density distributions obtained in subsystem DFT calculations for radicals in explicit environments. This includes a small radical in a solvent shell, a {pi}-stacked guanine-thymine radical cation, and a benchmark application to a model for the special pair radical cation, which is a dimer of bacteriochlorophyll pigments, from the photosynthetic reaction center of purple bacteria. We investigate the differences in the spin densities resulting from subsystem DFT and Kohn-Sham DFT calculations. In these comparisons, we focus on the problem of overdelocalization of spin densities due to the self-interaction error in DFT. It is demonstrated that subsystem DFT can reduce this problem, while it still allows to describe spin-polarization effects crossing the boundaries of the subsystems. In practical calculations of spin densities for radicals in a given environment, it may thus be a pragmatic alternative to Kohn-Sham DFT calculations. In our calculation on the special pair radical cation, we show that the coordinating histidine residues reduce the spin-density asymmetry between the two halves of this system, while inclusion of a larger binding pocket model increases this asymmetry. The unidirectional energy transfer in photosynthetic reaction centers is related to the asymmetry introduced by the protein environment.
Communication: Self-interaction correction with unitary invariance in density functional theory
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
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.
Ensemble density variational methods with self- and ghost-interaction-corrected functionals
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
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.
Towards a Microscopic Reaction Description Based on Energy Density Functionals
Nobre, G A; DIetrich, F S; Escher, J E; Thompson, I J; Dupuis, M; Terasaki, J; Engel, J
2011-09-26T23:59:59.000Z
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.
Jain, Anubhav, Ph.D. Massachusetts Institute of Technology
2011-01-01T23:59:59.000Z
This thesis relates to the emerging field of high-throughput density functional theory (DFT) computation for materials design and optimization. Although highthroughput DFT is a promising new method for materials discovery, ...
Screening for high-performance piezoelectrics using high-throughput density functional theory
Armiento, Rickard R.
We present a large-scale density functional theory (DFT) investigation of the ABO3 chemical space in the perovskite crystal structure, with the aim of identifying those that are relevant for forming piezoelectric materials. ...
Washington at Seattle, University of - Department of Physics, Electroweak Interaction Research Group
Nuclear Structure and Reactions (Quantum Monte Carlo, Lanczos Methods, Density Functional Methods systems: nuclei and the unitary Fermi gas" Thursday, June 9 10:00 am Stefano Gandolfi "Ab
Nuclear Physics A 770 (2006) 131 Relativistic nuclear energy density functional
Weise, Wolfram
Nuclear Physics A 770 (2006) 1Â31 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
Susan P. Taylor, MD Shorewood, Wisconsin
Noxapater, Mississippi Corey W. Gilliland, MD Mesa, Arizona Jeanne V. Hamel, MD Elk Grove, California Steven Manhattan, Kansas Dean Afif Shoucair, DO Frankfort, Illinois John Mitchell Simson, MD Albuquerque, New
On oscillator-bath system: Exact propagator, Reduced density matrix and Green's function
A. Refaei; F. Kheirandish
2014-07-27T23:59:59.000Z
The exact form of quantum propagator of a quantum oscillator interacting with a bosonic bath consisting of $N$ distinguished quantum oscillators with different frequencies is obtained in the Heisenberg picture. Reduced density matrix for oscillator is obtained. The kernel or Green's function connecting the initial density matrix of the oscillator to the density matrix in an arbitrary time is obtained and its connection to Feynman-Vernon influence functional is discussed. Weak coupling regime and squared mean values for position, momentum and energy of the oscillator are obtained in equilibrium.
Lutsker, Vitalij; Niehaus, Thomas A
2015-01-01T23:59:59.000Z
Bridging the gap between first principles methods and empirical schemes, the density functional based tight-binding method (DFTB) has become a versatile tool in predictive atomistic simulations over the past years. One of the major restrictions of this method is the limitation to local or gradient corrected exchange-correlation functionals. This excludes the important class of hybrid or long-range corrected functionals, which are advantageous in thermochemistry, as well as in the computation of vibrational, photoelectron and optical spectra. The present work provides a detailed account of the implementation of DFTB for a long-range corrected functional in generalized Kohn-Sham theory. We apply the method to a set of organic molecules and compare ionization potentials and electron affinities with the original DFTB method and higher level theory. The new scheme cures the significant overpolarization in electric fields found for local DFTB, which parallels the functional dependence in first principles density fu...
Telnov, Dmitry A.; Chu, Shih-I
2000-12-13T23:59:59.000Z
In the framework of the Floquet formulation of time-dependent density functional theory we present several exact relations involving different parts of the quasienergy functional. These relations hold when the exact densities ...
Phonons and related crystal properties from density-functional perturbation theory
Wu, Zhigang
-Functional Perturbation Theory 516 A. Lattice dynamics from electronic-structure theory 516 B. Density-functional theory July 2001) This article reviews the current status of lattice-dynamical calculations in crystals, using specialized topics are treated, including the implementation for metals, the calculation of the response
Klaas J. H. Giesbertz
2015-06-16T23:59:59.000Z
A theorem for the invertibility of arbitrary response functions is presented under the following conditions: the time-dependence of the potentials should be Laplace transformable and the initial state should be a ground state, though it might be degenerate. This theorem provides a rigorous foundation for all density-functional-like theories in the time-dependent linear response regime. Especially for time-dependent one-body reduced density matrix (1RDM) functional theory this is an important step forward, since a solid foundation has currently been lacking. The theorem is equally valid for static response functions in the non-degenerate case, so can be used to characterize the uniqueness of the potential in the ground state version of the corresponding density-functional-like theory. Such a classification of the uniqueness of the non-local potential in ground state 1RDM functional theory has been lacking for decades. With the aid of presented invertibility theorem presented here, a complete classification of the non-uniqueness of the non-local potential in 1RDM functional theory can be given for the first time.
Molecular Density Functional Theory for water with liquid-gas coexistence and correct pressure
Jeanmairet, Guillaume; Sergiievskyi, Volodymyr; Borgis, Daniel
2015-01-01T23:59:59.000Z
The solvation of hydrophobic solutes in water is special because liquid and gas are almost at coexistence. In the common hypernetted chain approximation to integral equations, or equivalently in the homogenous reference fluid of molecular density functional theory, coexistence is not taken into account. Hydration structures and energies of nanometer-scale hydrophobic solutes are thus incorrect. In this article, we propose a bridge functional that corrects this thermodynamic inconsistency by introducing a metastable gas phase for the homogeneous solvent. We show how this can be done by a third order expansion of the functional around the bulk liquid density that imposes the right pressure and the correct second order derivatives. Although this theory is not limited to water, we apply it to study hydrophobic solvation in water at room temperature and pressure and compare the results to all-atom simulations. With this correction, molecular density functional theory gives, at a modest computational cost, quantita...
Moustakidis, Ch. C.; Lalazissis, G. A. [Department of Theoretical Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Niksic, T. [Physics Department, Faculty of Science, University of Zagreb, HR-10000 Zagreb (Croatia); Vretenar, D. [Physics Department, Faculty of Science, University of Zagreb, HR-10000 Zagreb (Croatia); Physik-Department der Technischen Universitaet Muenchen, D-85748 Garching (Germany); Ring, P. [Physik-Department der Technischen Universitaet Muenchen, D-85748 Garching (Germany)
2010-06-15T23:59:59.000Z
The transition density n{sub t} and pressure P{sub t} at the inner edge between the liquid core and the solid crust of a neutron star are analyzed using the thermodynamical method and the framework of relativistic nuclear energy density functionals. Starting from a functional that has been carefully adjusted to experimental binding energies of finite nuclei, and varying the density dependence of the corresponding symmetry energy within the limits determined by isovector properties of finite nuclei, we estimate the constraints on the core-crust transition density and pressure of neutron stars: 0.086 fm{sup -3}<=n{sub t}<0.090 fm{sup -3} and 0.3 MeV fm{sup -3}
Qian Zhao; Bao Yuan Sun; Wen Hui Long
2014-11-23T23:59:59.000Z
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.
Interaction energies of monosubstituted benzene dimers via nonlocal density functional theory
T. Thonhauser; Aaron Puzder; David C. Langreth
2005-09-15T23:59:59.000Z
We present density-functional calculations for the interaction energy of monosubstituted benzene dimers. Our approach utilizes a recently developed fully nonlocal correlation energy functional, which has been applied to the pure benzene dimer and several other systems with promising results. The interaction energy as a function of monomer distance was calculated for four different substituents in a sandwich and two T-shaped configurations. In addition, we considered two methods for dealing with exchange, namely using the revPBE generalized gradient functional as well as full Hartree-Fock. Our results are compared with other methods, such as Moller-Plesset and coupled-cluster calculations, thereby establishing the usefulness of our approach. Since our density-functional based method is considerably faster than other standard methods, it provides a computational inexpensive alternative, which is of particular interest for larger systems where standard calculations are too expensive or infeasible.
Computationally efficient double hybrid density functional theory using dual basis methods
Byrd, Jason N
2015-01-01T23:59:59.000Z
We examine the application of the recently developed dual basis methods of Head-Gordon and co-workers to double hybrid density functional computations. Using the B2-PLYP, B2GP-PLYP, DSD-BLYP and DSD-PBEP86 density functionals, we assess the performance of dual basis methods for the calculation of conformational energy changes in C$_4$-C$_7$ alkanes and for the S22 set of noncovalent interaction energies. The dual basis methods, combined with resolution-of-the-identity second-order M{\\o}ller-Plesset theory, are shown to give results in excellent agreement with conventional methods at a much reduced computational cost.
Peverati, Roberto
2012-01-01T23:59:59.000Z
Kohn-Sham density functional theory is in principle an exact formulation of quantum mechanical electronic structure theory, but in practice we have to rely on approximate exchange-correlation (xc) functionals. The objective of our work has been to design an xc functional with broad accuracy across as wide an expanse of chemistry and physics as possible, leading-as a long-range goal-to a functional with good accuracy for all problems, i.e., a universal functional. To guide our path toward that goal and to measure our progress, we have developed-building on earlier work in our group-a set of databases of reference data for a variety of energetic and structural properties in chemistry and physics. These databases include energies of molecular processes such as atomization, complexation, proton addition, and ionization; they also include molecular geometries and solid-state lattice constants, chemical reaction barrier heights, and cohesive energies and band gaps of solids. For the present paper we gather many of ...
Orbital-free density functional theory of out-of-plane charge screening in graphene
Jianfeng Lu; Vitaly Moroz; Cyrill B. Muratov
2015-06-30T23:59:59.000Z
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 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.
Orbital-free density functional theory of out-of-plane charge screening in graphene
Jianfeng Lu; Vitaly Moroz; Cyrill B. Muratov
2014-05-20T23:59:59.000Z
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.
Configuration mixing within the energy density functional formalism: pathologies and cures
Denis Lacroix; Michael Bender; Thomas Duguet
2008-11-17T23:59:59.000Z
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.
Energy density functional analysis of shape coexistence in {sup 44}S
Li, Z. P.; Yao, J. M.; Vretenar, D.; Niksic, T.; Meng, J. [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Physics Department, Faculty of Science, University of Zagreb (Croatia); State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China)
2012-10-20T23:59:59.000Z
The structure of low-energy collective states in the neutron-rich nucleus {sup 44}S is analyzed using a microscopic collective Hamiltonian model based on energy density functionals (EDFs). The calculated triaxial energy map, low-energy spectrum and corresponding probability distributions indicate a coexistence of prolate and oblate shapes in this nucleus.
Bochevarov, Arteum D.
We report the performance of eight density functionals (B3LYP, BPW91, OLYP, O3LYP, M06, M06-2X, PBE, and SVWN5) in two Gaussian basis sets (Wachters and Partridge-1 on iron atoms; cc-pVDZ on the rest of atoms) for prediction ...
A Framework to Determine the Probability Density Function for the Output Power of Wind Farms
Liberzon, Daniel
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
Pfeifer, Holger
Adsorption of supramolecular building blocks on graphite: A force field and density functional-mail: axel.gross@uni-ulm.de The adsorption of the oligopyridine isomers 2,4'-BTP and 3,3'- BTP on graphite with an C6R-6-type dispersion correction, and the calculated adsorption energies are compared to the results
Relative stability of nanosized wurtzite and graphitic ZnO from density functional theory
Melnik, Roderick
Relative stability of nanosized wurtzite and graphitic ZnO from density functional theory Bin Wen to determine the relative stability of wurtzite and graphitic phases of ZnO nanostructures. Our results the threshold number, the relative stability of the wurtzite phase is observed. Finally, we discuss
A Density Functional Theory Study of Hydrogen Adsorption in MOF-5 Tim Mueller and Gerbrand Ceder*
Ceder, Gerbrand
. The effect of the framework on the physical structure and electronic structure of the organic linker initio molecular dynamics in the generalized gradient approximation to density functional theory, and calculations indicate that the sites with the strongest interaction with hydrogen are located near the Zn4O
Song, Xueyu
Calculations of free energies in liquid and solid phases: Fundamental measure density, a theoretical description of the free energies and correlation functions of hard-sphere (HS) liquid and solid-Chandler-Andersen perturbation theory, free energies of liquid and solid phases with many interaction potentials can be obtained
Density Functional Study of Polycarbonate. 2. Crystalline Analogs, Cyclic Oligomers dimer and tetramer of bisphenol A polycarbonate (BPA-PC), as well as for the isolated structural units- bonate molecules has led to many studies of this family of polymers. Bisphenol A polycarbonate (BPA
Density Functional Study of Reactions of Phenoxides with Polycarbonate P. Ballone and R. O. Jones*
Density Functional Study of Reactions of Phenoxides with Polycarbonate P. Ballone and R. O. Jones used to study the reactions of chains of bisphenol A polycarbonate (BPA-PC) with sodium phenoxide (Na of the reactions of phenol, LiOPh, and NaOPh with the cyclic tetramer of bisphenol A polycarbonate (BPA
Branching Reactions in Polycarbonate: A Density Functional Study J. Akola and R. O. Jones*
Branching Reactions in Polycarbonate: A Density Functional Study J. Akola and R. O. Jones* Institut on the properties of polymers, and bisphenol A polycarbonate (BPA-PC) is no exception. We describe here the results and rubbers, where the entire system may be viewed as a single cross-linked molecule.2 Polycarbonates (PC
Density Functional Study of Crystalline Analogs of Polycarbonates B. Montanari, P. Ballone, and R of Bisphenol A polycarbonate (BPA-PC) and for the isolated structural unit. The calculations are free of polycarbonate molecules has grown greatly in the past two decades due to a wide range of industrial applications
A Combined Density Functional and Monte Carlo Study of Polycarbonate R. O. Jones and P. Ballone[*
A Combined Density Functional and Monte Carlo Study of Polycarbonate R. O. Jones and P. Ballone and reactivity for organic systems closely related to bisphenol-A-polycarbonate(BPA- PC). The results provide a detailed description of polymers, using bisphenol A polycarbonate (BPA- PC) as an example
A Hybrid Density Functional Theory for Solvation and Solvent-Mediated Interactions
Jin, Zhehui
2012-01-01T23:59:59.000Z
correlation functions of SPC/E water in Fourier space. (a)of cations and anions in SPC/E water obtained from differentis 300K and mass density of SPC/E water is 0.996 g/cm 3 .
Juliano, Steven A.
: Coccinellidae) to Different Densities of Aphis fabae (Hemiptera: Aphididae) ROYA FARHADI,1 HOSSEIN ALLAHYARI,1 on Aphis fabae (Scolpoli) (Hemiptera: Aphididae) by estimating the functional responses of all stages, Aphis fabae, searching efÞciency, han- dling time Black bean aphid, Aphis fabae (Scolpoli) (Hemiptera
Electronvibration coupling in time-dependent density-functional theory: Application to benzene
Bertsch George F.
Electronvibration coupling in time-dependent density-functional theory: Application to benzene G for electronvibration coupling, we apply it to the optical properties of the * transitions in benzene with the electronic excitations. In this work, we have chosen the benzene model for an exploratory study
Szállás, 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); Szász, 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, Eötvös University, Pázmány Péter sétány 1/A, H-1117 Budapest (Hungary); Trinh, X. T.; Son, N. T.; Janzén, E. [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (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 út 8, H-1111 Budapest (Hungary)
2014-09-21T23:59:59.000Z
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.
Relativistic density functional theory modeling of plutonium and americium higher oxide molecules
Titov, Anatoly
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
H. Rudolf Fiebig
2002-10-31T23:59:59.000Z
We study various aspects of extracting spectral information from time correlation functions of lattice QCD by means of Bayesian inference with an entropic prior, the maximum entropy method (MEM). Correlator functions of a heavy-light meson-meson system serve as a repository for lattice data with diverse statistical quality. Attention is given to spectral mass density functions, inferred from the data, and their dependence on the parameters of the MEM. We propose to employ simulated annealing, or cooling, to solve the Bayesian inference problem, and discuss practical issues of the approach.
R. Rodriguez-Guzman; Y. Alhassid; G. F. Bertsch
2007-09-04T23:59:59.000Z
We describe a procedure for mapping a self-consistent mean-field theory (also known as density functional theory) into a shell model Hamiltonian that includes quadrupole-quadrupole and monopole pairing interactions in a truncated space. We test our method in the deformed N=Z sd-shell nuclei Ne-20, Mg-24 and Ar-36, starting from the Hartree-Fock plus BCS approximation of the USD shell model interaction. A similar procedure is then followed using the SLy4 Skyrme energy density functional in the particle-hole channel plus a zero-range density-dependent force in the pairing channel. Using the ground-state solution of this density functional theory at the Hartree-Fock plus BCS level, an effective shell model Hamiltonian is constructed. We use this mapped Hamiltonian to extract quadrupolar and pairing correlation energies beyond the mean field approximation. The rescaling of the mass quadrupole operator in the truncated shell model space is found to be almost independent of the coupling strength used in the pairing channel of the underlying mean-field theory.
Dey, Debarshi
2010-01-01T23:59:59.000Z
2 1.2 Normal Distribution and Simple Linear5 1.3 Skew Normal Distribution andthe Standard Normal Density and Distribution Functions 3.1
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), Linköping University, SE-58183 Linköping (Sweden)] [Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping (Sweden)
2014-05-14T23:59:59.000Z
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 Cu–O 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.
Energy-density-functional calculations including the proton-neutron mixing
Koichi Sato; Jacek Dobaczewski; Takashi Nakatsukasa; Wojciech Satu?a
2013-08-08T23:59:59.000Z
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.
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
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.
Singlet-Triplet Energy Gaps for Diradicals from Fractional-Spin Density-Functional Theory
Ess, Daniel H.; Johnson, E R; Hu, Xiangqian; Yang, W T
2011-01-01T23:59:59.000Z
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.
Quasi-local-density approximation for a van der Waals energy functional
John F. Dobson
2003-11-17T23:59:59.000Z
We discuss a possible form for a theory akin to local density functional theory, but able to produce van der Waals energies in a natural fashion. The usual Local Density Approximation (LDA) for the exchange and correlation energy $E_{xc}$ of an inhomogeneous electronic system can be derived by making a quasilocal approximation for the {\\it interacting} density-density response function $\\chi (\\vec{r},\\vec{r} ^{\\prime},\\omega)$, then using the fluctuation-dissipation theorem and a Feynman coupling-constant integration to generate $E_{xc}$. The first new idea proposed here is to use the same approach except that one makes a quasilocal approximation for the {\\it bare} response $\\chi ^{0}$, rather than for $\\chi $. The interacting response is then obtained by solving a nonlocal screening integral equation in real space. If the nonlocal screening is done at the time-dependent Hartree level, then the resulting energy is an approximation to the full inhomogeneous RPA energy: we show here that the inhomogeneous RPA correlation energy contains a van der Waals term for the case of widely-separated neutral subsystems. The second new idea is to use a particularly simple way of introducing LDA-like local field corrrections into the screening equations, giving a theory which should remain reasonable for all separations of a pair of subsystems, encompassing both the van der Waals limit much as in RPA and the bonding limit much as in LDA theory.
Covariance analysis of finite temperature density functional theory: symmetric nuclear matter
A. Rios; X. Roca-Maza
2014-08-21T23:59:59.000Z
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.
Nuclear energy density functionals: what we can learn about/from their global performance?
Afanasjev, A V; Ray, D; Ring, P
2015-01-01T23:59:59.000Z
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.
Nuclear energy density functionals: what we can learn about/from their global performance?
A. V. Afanasjev; S. E. Agbemava; D. Ray; P. Ring
2015-01-17T23:59:59.000Z
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.
Covariant density functional theory with two-phonon coupling in nuclei
Ring, P.; Litvinova, E.; Tselyaev, V. [Physik Department, Technische Universitat Muenchen, D-85747 Garching (Germany) and State Key Lab Nucl. Phys. and Tech., School of Physics, Peking University, Beijing 100871 (China); GSI Helmholtzzentrum fuer Schwerionenforschung, 64291 Darmstadt (Germany); Nuclear Physics Department, St. Petersburg State University, 198504 St. Petersburg (Russian Federation)
2012-10-20T23:59:59.000Z
A full description of excited states within the framework of density functional theory requires energy dependent self energies. We present a new class of many-body models. It allows a parameter free description of the fragmentation of nuclear states induced by mode coupling of two-quasiparticle and two-phonon configurations. The method is applied for an investigation of low-lying dipole excitations in Sn isotopes with large neutron excess.
Modeling nuclear weak-interaction processes with relativistic energy density functionals
Paar, N; Vale, D; Vretenar, D
2015-01-01T23:59:59.000Z
Relativistic energy density functionals have become a standard framework for nuclear structure studies of ground-state properties and collective excitations over the entire nuclide chart. We review recent developments in modeling nuclear weak-interaction processes: charge-exchange excitations and the role of isoscalar proton-neutron pairing, charged-current neutrino-nucleus reactions relevant for supernova evolution and neutrino detectors, and calculation of beta-decay rates for r-process nucleosynthesis.
Nuclear energy density functionals: What we can learn about/from their global performance?
Afanasjev, A. V.; Agbemava, S. E.; Ray, D. [Department of Physics and Astronomy, Mississippi State University, MS 39762 (United States); Ring, P. [Fakultät für Physik, Technische Universität München, D-85748 Garching (Germany)
2014-10-15T23:59:59.000Z
A short review of recent results on the global performance of covariant energy density functionals is presented. It is focused on an 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.
Application of nuclear density functionals to lepton number violating weak processes
Rodriguez, Tomas R.; Martinez-Pinedo, Gabriel [Technische Universitaet Darmstadt, Magdalenenstr. 12, D-64289, Darmstadt (Germany) and GSI Helmholtzzentrum fuer Schwerionenforschung, Plankstr. 1, D-64291 Darmstadt (Germany)
2012-10-20T23:59:59.000Z
We present an application of energy density functional methods with the Gogny interaction to the calculation of nuclear matrix elements (NME) for neutrinoless double beta decay and double electron capture. Beyond mean field effects have been included by particle number and angular momentum restoration and shape mixing within the generator coordinate method (GCM) framework. We analyze in detail the NME for {sup 116}Cd nucleus which is one of the most promising candidates to detect neutrinoless double beta decay.
Steam Reforming on Transition-metal Carbides from Density-functional Theory
Vojvodic, Aleksandra
2012-05-11T23:59:59.000Z
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.
Generalized second law at linear order for actions that are functions of Lovelock densities
Sudipta Sarkar; Aron C. Wall
2015-05-19T23:59:59.000Z
In this article we consider the second law of black holes (and other causal horizons) in theories where the gravitational action is an arbitrary function of the Lovelock densities. We show that there exists an entropy which increases locally, for linearized perturbations to regular Killing horizons. In addition to a classical increase theorem, we also prove a generalized second law for semiclassical, minimally-coupled matter fields.
T. Duguet; M. Bender; K. Bennaceur; D. Lacroix; T. Lesinski
2009-03-04T23:59:59.000Z
We discuss the origin of pathological behaviors that have been recently identified in particle-number-restoration calculations performed within the nuclear energy density functional framework. A regularization method that removes the problematic terms from the multi-reference energy density functional and which applies (i) to any symmetry restoration- and/or generator-coordinate-method-based configuration mixing calculation and (ii) to energy density functionals depending only on integer powers of the density matrices, was proposed in [D. Lacroix, T. Duguet, M. Bender, arXiv:0809.2041] and implemented for particle-number restoration calculations in [M. Bender, T. Duguet, D. Lacroix, arXiv:0809.2045]. In the present paper, we address the viability of non-integer powers of the density matrices in the nuclear energy density functional. Our discussion builds upon the analysis already carried out in [J. Dobaczewski \\emph{et al.}, Phys. Rev. C \\textbf{76}, 054315 (2007)]. First, we propose to reduce the pathological nature of terms depending on a non-integer power of the density matrices by regularizing the fraction that relates to the integer part of the exponent using the method proposed in [D. Lacroix, T. Duguet, M. Bender, arXiv:0809.2041]. Then, we discuss the spurious features brought about by the remaining fractional power. Finally, we conclude that non-integer powers of the density matrices are not viable and should be avoided in the first place when constructing nuclear energy density functionals that are eventually meant to be used in multi-reference calculations.
Song, Xueyu
density functional theory. The equilibrium interfacial density profiles and interfacial free energies were of density profile. We found that the average interfacial free energy is about 0.78, which is in reasonable of the crystal-melt interface is the interfacial free energy. Experimentally, this quantity can be extracted from
Dean Steve Nelson, MD Associate Dean for Research Wayne Backes, PhD Associate Dean for Fiscal Gregory, PhD Assistant Dean of VA Affairs Paul Rosenfeld, MD Basic Science Department Heads (6) Clinical, MD Director of Basic Sciences Curriculum Michael Levitzky, PhD Assistant Dean at Children's Hospital
Dynamic density functional theory of protein adsorption on polymer-coated nanoparticles
Angioletti-Uberti, Stefano; Dzubiella, Joachim
2014-01-01T23:59:59.000Z
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 th...
Enhanced von Weizsäcker Wang-Govind-Carter kinetic energy density functional for semiconductors
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
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 Weizsäcker 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.
Thermally-assisted-occupation density functional theory with generalized-gradient approximations
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
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.
Arianna Carbone; Arnau Rios; Artur Polls
2014-11-19T23:59:59.000Z
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.
Mao, James X.; Lee, Anita S.; Kitchin, John R.; Nulwala, Hunaid B; Luebke, David R.; Damodaran, Krishnan
2013-04-24T23:59:59.000Z
Density Functional Theory is used to investigate a weakly coordinating room-temperature ionic liquid, 1-ethyl-3-methyl imidazolium tetracyanoborate ([Emim]{sup +}[TCB]{sup -}). Four locally stable conformers of the ion pair were located. Atoms-in-molecules (AIM) and electron density analysis indicated the existence of several hydrogen bonds. Further investigation through the Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations provided insight into the origin of interactions in the [Emim]{sup +}[TCB]{sup -} ion pair. Strength of molecular interactions in the ionic liquid was correlated with frequency shifts of the characteristic vibrations of the ion pair. Harmonic vibrations of the ion pair were also compared with the experimental Raman and Infrared spectra. Vibrational frequencies were assigned by visualizing displacements of atoms around their equilibrium positions and through Potential Energy Distribution (PED) analysis.
Zhang, Ping; Zhao, Xian-Geng
2010-01-01T23:59:59.000Z
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...
Cornaton, Yann; Jensen, Hans Jørgen Aa; Fromager, Emmanuel
2013-01-01T23:59:59.000Z
An alternative separation of short-range exchange and correlation energies is used in the framework of second-order range-separated density-functional perturbation theory. This alternative separation was initially proposed by Toulouse et al. [Theor. Chem. Acc. 114, 305 (2005)] and relies on a long-range interacting wavefunction instead of the non-interacting Kohn-Sham one. When second-order corrections to the density are neglected, the energy expression reduces to a range-separated double-hybrid (RSDH) type of functional, RSDHf, where "f" stands for "full-range integrals" as the regular full-range interaction appears explicitly in the energy expression when expanded in perturbation theory. In contrast to usual RSDH functionals, RSDHf describes the coupling between long- and short-range correlations as an orbital-dependent contribution. Calculations on the first four noble-gas dimers show that this coupling has a significant effect on the potential energy curves in the equilibrium region, improving the accurac...
Fragment Approach to Constrained Density Functional Theory Calculations using Daubechies Wavelets
Ratcliff, Laura E; Mohr, Stephan; Deutsch, Thierry
2015-01-01T23:59:59.000Z
In a recent paper we presented a linear scaling Kohn-Sham density functional theory (DFT) code based on Daubechies wavelets, where a minimal set of localized support functions is optimized in situ and therefore adapted to the chemical properties of the molecular system. Thanks to the systematically controllable accuracy of the underlying basis set, this approach is able to provide an optimal contracted basis for a given system: accuracies for ground state energies and atomic forces are of the same quality as an uncontracted, cubic scaling approach. This basis set offers, by construction, a natural subset where the density matrix of the system can be projected. In this paper we demonstrate the flexibility of this minimal basis formalism in providing a basis set that can be reused as-is, i.e. without reoptimization, for charge-constrained DFT calculations within a fragment approach. Support functions, represented in the underlying wavelet grid, of the template fragments are roto-translated with high numerical p...
Coumarin Dyes for Dye-Sensitized Solar Cells - A Long-Range-Corrected Density Functional Study
Wong, Bryan M; 10.1063/1.3025924
2010-01-01T23:59:59.000Z
The excited-state properties in a series of coumarin solar cell dyes are investigated with a long-range-corrected (LC) functional which asymptotically incorporates Hartree-Fock exchange. Using time-dependent density functional theory (TDDFT), we calculate excitation energies, oscillator strengths, and excited-state dipole moments in each of the dyes as a function of the range-separation paramenter, mu. To investigate the acceptable range of mu and assess the quality of the LC-TDDFT formalism, an extensive comparison is made between LC-BLYP excitation energies and approximate coupled cluster singles and doubles (CC2) calculations. When using a properly-optimized value of mu, we find that the LC technique provides a consistent picture of charge-transfer excitations as a function of molecular size. In contrast, we find that the widely-used B3LYP hybrid functional severely overestimates excited-state dipole moments and underestimates vertical excitations energies, especially for larger dye molecules. The results ...
A study of the density functional methods on the photoabsorption of Bodipy dyes
Unal, Hatice; Mete, Ersen
2013-01-01T23:59:59.000Z
Tunability of the photoabsorption and directional charge injection characteristics of Bodipy-based dye molecules with different carbonyl groups make them promising candidates for photovoltaic applications. In order to study the effect of screening in the Coulomb interaction on the electronic and optical properties of two Bodipy derivatives, we have used linear response time-dependent and exact exchange hybrid density functional approaches. The effect of linear and non-linear solvation models on the electrochemical properties of the dyes has also been discussed.
Interacting boson model from energy density functionals: {gamma}-softness and the related topics
Nomura, K. [Institut fuer Kernphysik, Universitaet zu Koeln, D-50937 Koeln (Germany)
2012-10-20T23:59:59.000Z
A comprehensive way of deriving the Hamiltonian of the interacting boson model (IBM) is described. Based on the fact that the multi-nucleon induced surface deformation in finite nucleus is simulated by effective boson degrees of freedom, the potential energy surface calculated with self-consistent mean-field method employing a given energy density functional (EDF) is mapped onto the IBM analog, and thereby the excitation spectra and transition rates with good symmetry quantum numbers are calculated. Recent applications of the proposed approach are reported: (i) an alternative robust interpretation of the {gamma}-soft nuclei and (ii) shape coexistence in lead isotopes.
Mean-Field Calculation Based on Proton-Neutron Mixed Energy Density Functionals
Koichi Sato; Jacek Dobaczewski; Takashi Nakatsukasa; Wojciech Satu?a
2014-10-10T23:59:59.000Z
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.
Ferromagnetism in GaN: Gd: A density functional theory study
Stevenson, Cynthia; Stevenson, Cynthia
2008-02-04T23:59:59.000Z
First principle calculations of the electronic structure and magnetic interaction of GaN:Gd have been performed within the Generalized Gradient Approximation (GGA) of the density functional theory (DFT) with the on-site Coulomb energy U taken into account (also referred to as GGA+U). The ferromagnetic p-d coupling is found to be over two orders of magnitude larger than the s-d exchange coupling. The experimental colossal magnetic moments and room temperature ferromagnetism in GaN:Gd reported recently are explained by the interaction of Gd 4f spins via p-d coupling involving holes introduced by intrinsic defects such as Ga vacancies.
Schoendorff, George E.; Windus, Theresa L.; De Jong, Wibe A.
2009-12-12T23:59:59.000Z
The coordination of nitrile (acetonitrile, propionitrile, and benzonitrile) and carbonyl (formaldehyde, ethanal, and acetone) ligands to the uranyl dication (UO22+) has been examined using density functional theory (DFT) utilizing relativistic effective core potentials (RECPs). Complexes containing up to six ligands have been modeled for all ligands except formaldehyde, for which no minimum could be found. A comparison of relative binding energies indicates that five coordinate complexes are predominant while a six coordinate complex involving propionitrile ligands might be possible. Additionally, the relative binding energy and the weakening of the uranyl bond is related to the size of the ligand and, in general, nitriles bind more strongly to uranyl than carbonyls.
Tuning Range-Separated Density Functional Theory for Photocatalytic Water Splitting Systems
Bokareva, Olga S; Bokarev, Sergey I; Kühn, Oliver
2015-01-01T23:59:59.000Z
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.
Mark R. Pederson
2014-12-13T23:59:59.000Z
A recent modification of the Perdew-Zunger self-interaction-correction (SIC) to the density-functional formalism (Pederson, Ruzsinszky, Perdew) has provided a framework for explicitly restoring unitary invariance to the expression for the total energy. The formalism depends upon construction of Lowdin orthonormalized Fermi-orbitals (Luken et al) which parametrically depend on variational quasi-classical electronic positions. Derivatives of these quasi-classical electronic positions, required for efficient minimization of the self-interaction corrected energy, are derived and tested here on atoms. Total energies and ionization energies in closed-shell atoms, where correlation is less important, using the PW92 LDA functional are in very good to excellent agreement with experiment and non-relativistic Quantum-Monte-Carlo (QMC) results.
Quasi-particle energy spectra in local reduced density matrix functional theory
Lathiotakis, Nektarios N. [Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, Vass. Constantinou 48, GR-11635 Athens (Greece); Helbig, Nicole [Peter-Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich, D-52425 Jülich (Germany); Rubio, Angel [Nano-Bio Spectroscopy Group and ETSF Scientific Development Centre, Dpto. Física de Materiales, Universidad del País Vasco, CFM CSIC-UPV/EHU-MPC and DIPC, Av. Tolosa 72, E-20018 San Sebastián (Spain); Gidopoulos, Nikitas I. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)
2014-10-28T23:59:59.000Z
Recently, we introduced [N. N. Lathiotakis, N. Helbig, A. Rubio, and N. I. Gidopoulos, Phys. Rev. A 90, 032511 (2014)] local reduced density matrix functional theory (local RDMFT), a theoretical scheme capable of incorporating static correlation effects in Kohn-Sham equations. Here, we apply local RDMFT to molecular systems of relatively large size, as a demonstration of its computational efficiency and its accuracy in predicting single-electron properties from the eigenvalue spectrum of the single-particle Hamiltonian with a local effective potential. We present encouraging results on the photoelectron spectrum of molecular systems and the relative stability of C{sub 20} isotopes. In addition, we propose a modelling of the fractional occupancies as functions of the orbital energies that further improves the efficiency of the method useful in applications to large systems and solids.
Energy Density Functional Study of Nuclear Matrix Elements for Neutrinoless {beta}{beta} Decay
Rodriguez, Tomas R. [GSI Helmholtzzentrum fuer Schwerionenforschung, D-64259 Darmstadt (Germany); Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); CEA, Irfu, SPhN, Centre de Saclay, F-911191 Gif-sur-Yvette (France); Martinez-Pinedo, Gabriel [GSI Helmholtzzentrum fuer Schwerionenforschung, D-64259 Darmstadt (Germany)
2010-12-17T23:59:59.000Z
We present an extensive study of nuclear matrix elements (NME) for the neutrinoless double-beta decay of the nuclei {sup 48}Ca, {sup 76}Ge, {sup 82}Se, {sup 96}Zr, {sup 100}Mo, {sup 116}Cd, {sup 124}Sn, {sup 128}Te, {sup 130}Te, {sup 136}Xe, and {sup 150}Nd based on state-of-the-art energy density functional methods using the Gogny D1S functional. Beyond-mean-field effects are included within the generating coordinate method with particle number and angular momentum projection for both initial and final ground states. We obtain a rather constant value for the NMEs around 4.7 with the exception of {sup 48}Ca and {sup 150}Nd, where smaller values are found. We analyze the role of deformation and pairing in the evaluation of the NME and present detailed results for the decay of {sup 150}Nd.
Mootha, Vamsi K.
Andrea Reilly, MD Milton Pediatric Associates - MGH 10 Hawthorne Place, Suite 110, MA 02114 JonathanCullough, MD Rebecca Niloff, MD Cara O'Reilly, MD Scott Paul, MD Jonathon Brenner, MD John Robinson, MD Heidi-643-8120 Elizabeth Turnock, MD Pediatric Group Practice 55 Fruit Street, YAW 6D, MA 02114 Ronald Benz, MD 617
Nomura, K.; Vretenar, D. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Niksic, T. [Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Otsuka, T. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824-1321 (United States); Shimizu, N. [Department of Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)
2011-07-15T23:59:59.000Z
Microscopic energy density functionals have become a standard tool for nuclear structure calculations, providing an accurate global description of nuclear ground states and collective excitations. For spectroscopic applications, this framework has to be extended to account for collective correlations related to restoration of symmetries broken by the static mean field, and for fluctuations of collective variables. In this paper, we compare two approaches to five-dimensional quadrupole dynamics: the collective Hamiltonian for quadrupole vibrations and rotations and the interacting boson model (IBM). The two models are compared in a study of the evolution of nonaxial shapes in Pt isotopes. Starting from the binding energy surfaces of {sup 192,194,196}Pt, calculated with a microscopic energy density functional, we analyze the resulting low-energy collective spectra obtained from the collective Hamiltonian, and the corresponding IBM Hamiltonian. The calculated excitation spectra and transition probabilities for the ground-state bands and the {gamma}-vibration bands are compared to the corresponding sequences of experimental states.
K. Nomura; T. Niksic; T. Otsuka; N. Shimizu; D. Vretenar
2011-06-14T23:59:59.000Z
Microscopic energy density functionals (EDF) have become a standard tool for nuclear structure calculations, providing an accurate global description of nuclear ground states and collective excitations. For spectroscopic applications this framework has to be extended to account for collective correlations related to restoration of symmetries broken by the static mean field, and for fluctuations of collective variables. In this work we compare two approaches to five-dimensional quadrupole dynamics: the collective Hamiltonian for quadrupole vibrations and rotations, and the Interacting Boson Model. The two models are compared in a study of the evolution of non-axial shapes in Pt isotopes. Starting from the binding energy surfaces of $^{192,194,196}$Pt, calculated with a microscopic energy density functional, we analyze the resulting low-energy collective spectra obtained from the collective Hamiltonian, and the corresponding IBM-2 Hamiltonian. The calculated excitation spectra and transition probabilities for the ground-state bands and the $\\gamma$-vibration bands are compared to the corresponding sequences of experimental states.
J. D. McDonnell; N. Schunck; D. Higdon; J. Sarich; S. M. Wild; W. Nazarewicz
2015-01-15T23:59:59.000Z
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, we apply the Bayesian framework to propagate theoretical statistical uncertainties in predictions of nuclear masses, two-neutron dripline, and fission barriers. Overall, we find that the new mass measurements do not impose a constraint that is strong enough to lead to significant changes in the model parameters. The example discussed in this study sets the stage for quantifying and maximizing the impact of new measurements with respect to current modeling and guiding future experimental efforts, thus enhancing the experiment-theory cycle in the scientific method.
Polycarbonate Simulations with a Density Functional Based Force Field P. Ballone, B. Montanari properties of molecules related to polycarbonate have been used to optimize the parameters describing dynamics simulations of crystalline, amorphous, and liquid polycarbonate systems. Applications include
Chu, Shih-I; Zhou, Zhongyuan
2009-10-27T23:59:59.000Z
We propose a time-dependent density functional theoretical (TDDFT) approach in momentum (\\mathcal{P} ) space for the study of electron transport in molecular devices under arbitrary biases. The basic equation of motion, which is a time...
Pfeifer, Holger
Adsorption of small aromatic molecules on the ,,111... surfaces of noble metals: A density 10 May 2010; published online 10 June 2010 The adsorption of benzene, thiophene, and pyridine on the 111 surface of gold and copper have been studied using density functional theory DFT . Adsorption
Prediction of Iron K-Edge Absorption Spectra Using Time-Dependent Density Functional Theory
George, S.DeBeer; Petrenko, T.; Neese, F.
2009-05-14T23:59:59.000Z
Iron K-edge X-ray absorption pre-edge features have been calculated using a time-dependent density functional approach. The influence of functional, solvation, and relativistic effects on the calculated energies and intensities has been examined by correlation of the calculated parameters to experimental data on a series of 10 iron model complexes, which span a range of high-spin and low-spin ferrous and ferric complexes in O{sub h} to T{sub d} geometries. Both quadrupole and dipole contributions to the spectra have been calculated. We find that good agreement between theory and experiment is obtained by using the BP86 functional with the CP(PPP) basis set on the Fe and TZVP one of the remaining atoms. Inclusion of solvation yields a small improvement in the calculated energies. However, the inclusion of scalar relativistic effects did not yield any improved correlation with experiment. The use of these methods to uniquely assign individual spectral transitions and to examine experimental contributions to backbonding is discussed.
Dynamic density functional theory of protein adsorption on polymer-coated nanoparticles
Stefano Angioletti-Uberti; Matthias Ballauff; Joachim Dzubiella
2014-07-30T23:59:59.000Z
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.
Koppen, Jessica V.; Szcz??niak, Ma?gorzata M., E-mail: bryant@oakland.edu [Department of Chemistry, Oakland University, Rochester, Michigan 48309 (United States); Hapka, Micha?; Modrzejewski, Marcin [Faculty of Chemistry, Warsaw University, Pasteura 1, 02-093 Warszawa (Poland); Cha?asi?ski, Grzegorz [Faculty of Chemistry, Warsaw University, Pasteura 1, 02-093 Warszawa (Poland); Department of Chemistry, Oakland University, Rochester, Michigan 48309 (United States)
2014-06-28T23:59:59.000Z
Donor-acceptor interactions are notoriously difficult and unpredictable for conventional density functional theory (DFT) methodologies. This work presents a reliable computational treatment of gold-ligand interactions of the donor-acceptor type within DFT. These interactions require a proper account of the ionization potential of the electron donor and electron affinity of the electron acceptor. This is accomplished in the Generalized Kohn Sham framework that allows one to relate these properties to the frontier orbitals in DFT via the tuning of range-separated functionals. A donor and an acceptor typically require different tuning schemes. This poses a problem when the binding energies are calculated using the supermolecular method. A two-parameter tuning for the monomer properties ensures that a common functional, optimal for both the donor and the acceptor, is found. A reliable DFT approach for these interactions also takes into account the dispersion contribution. The approach is validated using the water dimer and the (HAuPH{sub 3}){sub 2} aurophilic complex. Binding energies are computed for Au{sub 4} interacting with the following ligands: SCN{sup ?}, benzenethiol, benzenethiolate anion, pyridine, and trimethylphosphine. The results agree for the right reasons with coupled-cluster reference values.
Gunceler, Deniz; Sundararaman, Ravishankar; Schwarz, Kathleen A; Arias, T A
2013-01-01T23:59:59.000Z
Delivering the full benefits of first principles calculations to battery materials demands the development of accurate and computationally-efficient electronic structure methods that incorporate the effects of the electrolyte environment and electrode potential. Realistic electrochemical interfaces containing polar surfaces are beyond the regime of validity of existing continuum solvation theories developed for molecules, due to the presence of significantly stronger electric fields. We present an ab initio theory of the nonlinear dielectric and ionic response of solvent environments within the framework of joint density-functional theory, with precisely the same optimizable parameters as conventional polarizable continuum models. We demonstrate that the resulting nonlinear theory agrees with the standard linear models for organic molecules and metallic surfaces under typical operating conditions. However, we find that the saturation effects in the rotational response of polar solvent molecules, inherent to o...
Jeanmairet, Guillaume; Levesque, Maximilien; Rotenberg, Benjamin; Borgis, Daniel
2014-01-01T23:59:59.000Z
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...
P. W. Zhao; Z. P. Li; J. M. Yao; J. Meng
2010-11-11T23:59:59.000Z
A new parametrization PC-PK1 for the nuclear covariant energy density functional with nonlinear point-coupling interaction is proposed by fitting to observables for 60 selected spherical nuclei, including the binding energies, charge radii and empirical pairing gaps. The success of PC-PK1 is illustrated in its description for infinite nuclear matter and finite nuclei including the ground-state and low-lying excited states. Particularly, PC-PK1 improves the description for isospin dependence of binding energy along either the isotopic or the isotonic chains, which makes it more reliable for application in exotic nuclei. The predictive power of PC-PK1 is also illustrated for the nuclear low-lying excitation states in a five-dimensional collective Hamiltonian in which the parameters are determined by constrained calculations for triaxial shapes.
Qiang Zhao; Jian Min Dong; Jun Ling Song; Wen Hui Long
2014-07-23T23:59:59.000Z
Half-life of proton radioactivity of spherical proton emitters is studied within the scheme of covariant density functional (CDF) theory, and for the first time the potential barrier that prevents the emitted proton is extracted with the similarity renormalization group (SRG) method, in which the spin-orbit potential along with the others that turn out to be non-negligible can be derived automatically. The spectroscopic factor that is significant is also extracted from the CDF calculations. The estimated half-lives are found in good agreement with the experimental values, which not only confirms the validity of the CDF theory in describing the proton-rich nuclei, but also indicates the prediction power of present approach to calculate the half-lives and in turn to extract the structural information of proton emitters.
K. Nomura; R. Rodriguez-Guzman; L. M. Robledo; N. Shimizu
2012-08-23T23:59:59.000Z
We investigate the emergence and evolution of shape coexistence in the neutron-deficient Lead isotopes within the interacting boson model (IBM) plus configuration mixing with microscopic input based on the Gogny energy density functional (EDF). The microscopic potential energy surface obtained from the constrained self-consistent Hartree-Fock-Bogoliubov method employing the Gogny-D1M EDF is mapped onto the coherent-state expectation value of the configuration-mixing IBM Hamiltonian. In this way, the parameters of the IBM Hamiltonian are fixed for each of the three relevant configurations (spherical, prolate and oblate) associated to the mean field minima. Subsequent diagonalization of the Hamiltonian provides the excitation energy of the low-lying states and transition strengths among them. The model predictions for the $0^{+}$ level energies and evolving shape coexistence in the considered Lead chain are consistent both with experiment and with the indications of the Gogny-EDF energy surfaces.
Mussard, Bastien; Ángyán, János G
2015-01-01T23:59:59.000Z
Analytical forces have been derived in the Lagrangian framework for several random phase approximation (RPA) correlated total energy methods based on the range separated hybrid (RSH) approach, which combines a short-range density functional approximation for the short-range exchange-correlation energy with a Hartree-Fock-type long-range exchange and RPA long-range correlation. The RPA correlation energy has been expressed as a ring coupled cluster doubles (rCCD) theory. The resulting analytical gradients have been implemented and tested for geometry optimization of simple molecules and intermolecular charge transfer complexes, where intermolecular interactions are expected to have a non-negligible effect even on geometrical parameters of the monomers.
Yao, J M; Hagino, K; Ring, P; Meng, J
2014-01-01T23:59:59.000Z
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.
Analytic cubic and quartic force fields using density-functional theory
Ringholm, Magnus; Gao, Bin; Thorvaldsen, Andreas J.; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway)] [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); Jonsson, Dan [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway) [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); High Performance Computing Group, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (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); Ekström, 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
We present the first analytic implementation of cubic and quartic force constants at the level of Kohn–Sham 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 exchange–correlation kernels. We use generalized second-order vibrational perturbation theory to calculate the fundamental frequencies of methane, ethane, benzene, and aniline, comparing B3LYP, BLYP, and Hartree–Fock results. The Hartree–Fock 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.
Terminating states as a unique laboratory for testing nuclear energy density functional
M. Zalewski; W. Satula
2007-01-30T23:59:59.000Z
Systematic calculations of favored signature maximum-spin I_max and unfavored signature I_max - 1 terminating states for [f 7/2 ^ n] and [d 3/2 ^ (-1) f 7/2 ^ (n+1)] configurations (n denotes number of valence particles) in A ~ 44 mass region are presented. Following the result of Zdunczuk et al., Phys. Rev. C71 (2005) 024305 the calculations are performed using Skyrme energy density functional with empirical Landau parameters and slightly reduced spin-orbit strength. The aim is to identify and phenomenologically restore rotational symmetry broken by the Skyrme-Hartree-Fock solutions. In particular, it is shown that correlation energy due to symmetry restoration is absolutely crucial in order to reproduce energy splitting E(I_max) - E(I_max -1) in [f 7/2 ^ n] configurations but is relatively less important for [d 3/2 ^ (-1) f 7/2 ^ (n+1)] configurations.
Steam reforming on transition-metal carbides from density-functional theory
Vojvodic, Aleksandra
2009-01-01T23:59:59.000Z
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.
Ad. R. Raduta; F. Gulminelli; M. Oertel
2014-09-15T23:59:59.000Z
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.
Ning Wang; Xizhen Wu; Zhuxia Li; Min Liu; Werner Scheid
2006-09-18T23:59:59.000Z
The Skyrme energy-density functional approach has been extended to study the massive heavy-ion fusion reactions. Based on the potential barrier obtained and the parameterized 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_1Z_2fusion reactions, for example, the $^{238}$U-induced reactions and $^{48}$Ca+$^{208}$Pb the capture excitation functions have been reproduced remarkable well. The influence of structure effects in the reaction partners on the capture cross sections are studied with our parameterized barrier distribution. Through comparing the reactions induced by double-magic nucleus $^{48}$Ca and by $^{32}$S and $^{35}$Cl, the 'threshold-like' behavior in the capture excitation function for $^{48}$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 $^{36}$S, $^{37}$Cl, $^{48}$Ca and $^{50}$Ti bombarding on $^{248}$Cm, $^{247,249}$Bk, $^{250,252,254}$Cf and $^{252,254}$Es, and as well as the reactions lead 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.
Attarian Shandiz, M., E-mail: mohammad.attarianshandiz@mail.mcgill.ca; Gauvin, R. [Department of Materials Engineering, McGill University, Montreal, Quebec H3A 0C5 (Canada)
2014-10-28T23:59:59.000Z
The temperature and pressure dependency of the volume plasmon energy of solids was investigated by density functional theory calculations. The volume change of crystal is the major factor responsible for the variation of valence electron density and plasmon energy in the free electron model. Hence, to introduce the effect of temperature and pressure for the density functional theory calculations of plasmon energy, the temperature and pressure dependency of lattice parameter was used. Also, by combination of the free electron model and the equation of state based on the pseudo-spinodal approach, the temperature and pressure dependency of the plasmon energy was modeled. The suggested model is in good agreement with the results of density functional theory calculations and available experimental data for elements with the free electron behavior.
Alavi, Ali
Coupled cluster benchmarks of water monomers and dimers extracted from density-functional theory functionals in simulations of liquid water, water monomers and dimers were extracted from a PBE simulation liquid water: The importance of monomer deformations Biswajit Santra,1 Angelos Michaelides,1,2,a
A density functional theory model of mechanically activated silyl ester hydrolysis
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 für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany); Center for Nanoscience (CeNS), Geschwister-Scholl-Platz 1, 80539 Munich (Germany); Beyer, Martin K. [Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany) [Institut für Physikalische Chemie, Christian-Albrechts-Universität zu Kiel, Olshausenstraße 40, 24098 Kiel (Germany); Institut für Ionenphysik und Angewandte Physik, Leopold-Franzens-Universität Innsbruck, Technikerstraße 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
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.
Spurious finite-size instabilities in nuclear energy density functionals: spin channel
Pastore, A; Davesne, D; Navarro, J
2015-01-01T23:59:59.000Z
It has been recently shown, that some Skyrme functionals can lead to non-converging results in the calculation of some properties of atomic nuclei. A previous study has pointed out a possible link between these convergence problems and the appearance of finite-size instabilities in symmetric nuclear matter (SNM) around saturation density. We show that the finite-size instabilities not only affect the ground state properties of atomic nuclei, but they can also influence the calculations of vibrational excited states in finite nuclei. We perform systematic fully-self consistent Random Phase Approximation (RPA) calculations in spherical doubly-magic nuclei. We employ several Skyrme functionals and vary the isoscalar and isovector coupling constants of the time-odd term $\\mathbf{s}\\cdot \\Delta \\mathbf{s}$ . We determine critical values of these coupling constants beyond which the RPA calculations do not converge because RPA the stability matrix becomes non-positive.By comparing the RPA calculations of atomic nucl...
Building a Universal Nuclear Energy Density Functional (UNEDF): SciDAC-2 Project
Carlson, Joe; Furnstahl, Dick; Lusk, Rusty; Nazarewicz, Witek; Ng, Esmond; Thompson, Ian; Vary, James
2012-06-30T23:59:59.000Z
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.
Higher-order finite-difference formulation of periodic Orbital-free Density Functional Theory
Ghosh, Swarnava
2014-01-01T23:59:59.000Z
We present a real-space formulation and higher-order finite-difference implementation of periodic Orbital-free Density Functional Theory (OF-DFT). Specifically, utilizing a local reformulation of the electrostatic and kernel terms, we develop a generalized framework suitable for performing OF-DFT simulations with different variants of the electronic kinetic energy. In particular, we develop a self-consistent field (SCF) type fixed-point method for calculations involving linear-response kinetic energy functionals. In doing so, we make the calculation of the electronic ground-state and forces on the nuclei amenable to computations that altogether scale linearly with the number of atoms. We develop a parallel implementation of this formulation using the finite-difference discretization, using which we demonstrate that higher-order finite-differences can achieve relatively large convergence rates with respect to mesh-size in both the energies and forces. Additionally, we establish that the fixed-point iteration c...
Energy Density Functional analysis of shape evolution in N=28 isotones
Z. P. Li; J. M. Yao; D. Vretenar; T. Niksic; H. Chen; J. Meng
2012-09-26T23:59:59.000Z
The structure of low-energy collective states in proton-deficient N=28 isotones is analyzed using structure models based on the relativistic energy density functional DD-PC1. The relativistic Hartree-Bogoliubov model for triaxial nuclei is used to calculate binding energy maps in the $\\beta$-$\\gamma$ plane. The evolution of neutron and proton single-particle levels with quadrupole deformation, and the occurrence of gaps around the Fermi surface, provide a simple microscopic interpretation of the onset of deformation and shape coexistence. Starting from self-consistent constrained energy surfaces calculated with the functional DD-PC1, a collective Hamiltonian for quadrupole vibrations and rotations is employed in the analysis of excitation spectra and transition rates of $^{46}$Ar, $^{44}$S, and $^{42}$Si. The results are compared to available data, and previous studies based either on the mean-field approach or large-scale shell-model calculations. The present study is particularly focused on $^{44}$S, for which data have recently been reported that indicate pronounced shape coexistence.
Complex-energy approach to sum rules within nuclear density functional theory
Nobuo Hinohara; Markus Kortelainen; Witold Nazarewicz; Erik Olsen
2015-01-28T23:59:59.000Z
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, the Thouless theorem for the energy-weighted sum rule, and the dielectric theorem for the inverse energy-weighted sum rule. We demonstrate that calculated sum-rule values agree with those obtained from the matrix formulation of the QRPA. We also discuss the applicability of both the Thouless theorem about the energy-weighted sum rule and the dielectric theorem for the inverse energy-weighted sum rule to nuclear density functional theory in cases when the EDF is not based on a Hamiltonian. The proposed sum-rule technique based on the complex-energy FAM is a tool of choice when optimizing effective interactions or energy functionals. The method is very efficient and well-adaptable to parallel computing. The FAM formulation is especially useful when standard theorems based on commutation relations involving the nuclear Hamiltonian and external field cannot be used.
A study of the observed areal distribution of rainfall as a function of the density of rain gages
Alvarez Bernal, Fernando
1969-01-01T23:59:59.000Z
. W. K. Henry A study was made of reported rainfall as a function of the density oi gages for several geographical areas including Tezas, Colombia, Guyana, Panama, Venezuela, and Ecuador--each having different terrain effects. Consideration..., and Panama areas using mean-monthly data. . . . . . . . . . . . , . . . . . . 40 Comparison of depth-area relations from different gage density for one storm in East Yegua basin Cl?niiydg I l. 'ITRC?'UCTTOK Those "!ho i:ork i!it/ raiuf all iiata know...
Senjean, Bruno; Jensen, Hans Jørgen Aa; Fromager, Emmanuel
2015-01-01T23:59:59.000Z
The computation of excitation energies in range-separated ensemble density-functional theory (DFT) is discussed. The latter approach is appealing as it enables the rigorous formulation of a multi-determinant state-averaged DFT method. In the exact theory, the short-range density functional, that complements the long-range wavefunction-based ensemble energy contribution, should vary with the ensemble weights even when the density is held fixed. This weight dependence ensures that the range-separated ensemble energy varies linearly with the ensemble weights. When the (weight-independent) ground-state short-range exchange-correlation functional is used in this context, curvature appears thus leading to an approximate weight-dependent excitation energy. In order to obtain unambiguous approximate excitation energies, we simply propose to interpolate linearly the ensemble energy between equiensembles. It is shown that such a linear interpolation method (LIM) effectively introduces weight dependence effects. LIM has...
Editorial John Hickner, MD, MSc Editor-in-Chief
Alford, Simon
Health Care, Overland Park, Kan kEVin PEtErSon, MD, MPH University of Minnesota, St. Paul goutHAM rAo, MD
Comparative Density Functional Study of Methanol Decomposition on Cu4 and Co4 Clusters
Mehmood, Faisal; Greeley, Jeffrey P.; Zapol, Peter; Curtiss, Larry A.
2010-11-18T23:59:59.000Z
A density functional theory study of the decomposition of methanol on Cu4 and Co4 clusters is presented. The reaction intermediates and activation barriers have been determined for reaction steps to form H2 and CO. For both clusters, methanol decomposition initiated by C-H and O-H bond breaking was investigated. In the case of a Cu4 cluster, methanol dehydrogenation through hydroxymethyl (CH2OH), hydroxymethylene (CHOH), formyl (CHO), and carbon monoxide (CO) is found to be slightly more favorable. For a Co4 cluster, the dehydrogenation pathway through methoxy (CH3O) and formaldehyde (CH2O) is slightly more favorable. Each of these pathways results in formation of CO and H2. The Co cluster pathway is very favorable thermodynamically and kinetically for dehydrogenation. However, since CO binds strongly, it is likely to poison methanol decomposition to H2 and CO at low temperatures. In contrast, for the Cu cluster, CO poisoning is not likely to be a problem since it does not bind strongly, but the dehydrogenation steps are not energetically favorable. Pathways involving C-O bond cleavage are even less energetically favorable. The results are compared to our previous study of methanol decomposition on Pd4 and Pd8 clusters. Finally, all reaction energy changes and transition state energies, including those for the Pd clusters, are related in a linear, Broensted-Evans-Polanyi plot.
Coclite, Alessandro; De Palma, Pietro; Cutrone, Luigi
2013-01-01T23:59:59.000Z
Flamelet Progress Variable (FPV) combustion models allow the evaluation of all thermo chemical quantities in a reacting flow by computing only the mixture fraction Z and a progress variable C. When using such a method to predict a turbulent combustion in conjunction with a turbulence model, a probability density function (PDF) is required to evaluate statistical averages (e.g., Favre average) of chemical quantities. The choice of the PDF is a compromise between computational costs and accuracy level. The aim of this paper is to investigate the influence of the PDF choice and its modeling aspects in the simulation of non premixed turbulent combustion. Three different models are considered: the standard one, based on the choice of a beta distribution for Z and a Dirac distribution for C; a model employing a beta distribution for both Z and C; a third model obtained using a beta distribution for Z and the statistical most likely distribution (SMLD) for C. The standard model, although widely used, doesn't take in...
Efficient iterative method for solving the Dirac-Kohn-Sham density functional theory
Lin, Lin; Shao, Sihong; E, Weinan
2012-11-06T23:59:59.000Z
We present for the first time an efficient iterative method to directly solve the four-component Dirac-Kohn-Sham (DKS) density functional theory. Due to the existence of the negative energy continuum in the DKS operator, the existing iterative techniques for solving the Kohn-Sham systems cannot be efficiently applied to solve the DKS systems. The key component of our method is a novel filtering step (F) which acts as a preconditioner in the framework of the locally optimal block preconditioned conjugate gradient (LOBPCG) method. The resulting method, dubbed the LOBPCG-F method, is able to compute the desired eigenvalues and eigenvectors in the positive energy band without computing any state in the negative energy band. The LOBPCG-F method introduces mild extra cost compared to the standard LOBPCG method and can be easily implemented. We demonstrate our method in the pseudopotential framework with a planewave basis set which naturally satisfies the kinetic balance prescription. Numerical results for Pt$_{2}$, Au$_{2}$, TlF, and Bi$_{2}$Se$_{3}$ indicate that the LOBPCG-F method is a robust and efficient method for investigating the relativistic effect in systems containing heavy elements.
Development and evaluation of probability density functions for a set of human exposure factors
Maddalena, R.L.; McKone, T.E.; Bodnar, A.; Jacobson, J.
1999-06-01T23:59:59.000Z
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.
Maeta, Takahiro [Graduate School of System Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan); GlobalWafers Japan Co., Ltd., Higashikou, Seirou-machi, Kitakanbara-gun, Niigata 957-0197 (Japan); Sueoka, Koji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja, Okayama 719-1197 (Japan)
2014-08-21T23:59:59.000Z
Ge-based substrates are being developed for applications in advanced nano-electronic devices because of their higher intrinsic carrier mobility than Si. The stability and diffusion mechanism of impurity atoms in Ge are not well known in contrast to those of Si. Systematic studies of the stable sites of 2nd to 6th row element impurity atoms in Ge crystal were undertaken with density functional theory (DFT) and compared with those in Si crystal. It was found that most of the impurity atoms in Ge were stable at substitutional sites, while transition metals in Si were stable at interstitial sites and the other impurity atoms in Si were stable at substitutional sites. Furthermore, DFT calculations were carried out to clarify the mechanism responsible for the diffusion of impurity atoms in Ge crystals. The diffusion mechanism for 3d transition metals in Ge was found to be an interstitial-substitutional diffusion mechanism, while in Si this was an interstitial diffusion mechanism. The diffusion barriers in the proposed diffusion mechanisms in Ge and Si were quantitatively verified by comparing them to the experimental values in the literature.
Microscopic description of fission in Uranium isotopes with the Gogny energy density functional
R. Rodriguez-Guzman; L. M. Robledo
2014-05-25T23:59:59.000Z
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.
Harvesting graphics power for MD simulations
J. A. van Meel; A. Arnold; D. Frenkel; S. F. Portegies Zwart; R. G. Belleman
2007-09-20T23:59:59.000Z
We discuss an implementation of molecular dynamics (MD) simulations on a graphic processing unit (GPU) in the NVIDIA CUDA language. We tested our code on a modern GPU, the NVIDIA GeForce 8800 GTX. Results for two MD algorithms suitable for short-ranged and long-ranged interactions, and a congruential shift random number generator are presented. The performance of the GPU's is compared to their main processor counterpart. We achieve speedups of up to 80, 40 and 150 fold, respectively. With newest generation of GPU's one can run standard MD simulations at 10^7 flops/$.
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
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.
Density functional theory investigation of 3d, 4d, and 5d 13-atom metal clusters
Piotrowski, Mauricio J.; Piquini, Paulo; Da Silva, Juarez L. F. [Departamento de Fisica, Universidade Federal de Santa Maria, Santa Maria 97105-900, RS (Brazil); Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Cx. Postal 369, Sao Carlos 13560-970, SP (Brazil)
2010-04-15T23:59:59.000Z
The knowledge of the atomic structure of clusters composed by few atoms is a basic prerequisite to obtain insights into the mechanisms that determine their chemical and physical properties as a function of diameter, shape, surface termination, as well as to understand the mechanism of bulk formation. Due to the wide use of metal systems in our modern life, the accurate determination of the properties of 3d, 4d, and 5d metal clusters poses a huge problem for nanoscience. In this work, we report a density functional theory study of the atomic structure, binding energies, effective coordination numbers, average bond lengths, and magnetic properties of the 3d, 4d, and 5d metal (30 elements) clusters containing 13 atoms, M{sub 13}. First, a set of lowest-energy local minimum structures (as supported by vibrational analysis) were obtained by combining high-temperature first-principles molecular-dynamics simulation, structure crossover, and the selection of five well-known M{sub 13} structures. Several new lower energy configurations were identified, e.g., Pd{sub 13}, W{sub 13}, Pt{sub 13}, etc., and previous known structures were confirmed by our calculations. Furthermore, the following trends were identified: (i) compact icosahedral-like forms at the beginning of each metal series, more opened structures such as hexagonal bilayerlike and double simple-cubic layers at the middle of each metal series, and structures with an increasing effective coordination number occur for large d states occupation. (ii) For Au{sub 13}, we found that spin-orbit coupling favors the three-dimensional (3D) structures, i.e., a 3D structure is about 0.10 eV lower in energy than the lowest energy known two-dimensional configuration. (iii) The magnetic exchange interactions play an important role for particular systems such as Fe, Cr, and Mn. (iv) The analysis of the binding energy and average bond lengths show a paraboliclike shape as a function of the occupation of the d states and hence, most of the properties can be explained by the chemistry picture of occupation of the bonding and antibonding states.
Bjørnstad, Ottar Nordal
Stability of titanium oxide phases in Kohn-Sham density functional theory A well known problem of stability of titanium oxide phases at room temperature. That is, anatase instead of rutile is predicted as the room temperature phase for titanium oxide. In this work we try to establish the reasons
Sutton, Christopher; Gray, Matthew T.; Brunsfeld, Max; Parrish, Robert M.; Sherrill, C. David; Sears, John S.; Brédas, Jean-Luc, E-mail: jean-luc.bredas@chemistry.gatech.edu, E-mail: thomas.koerzdoerfer@uni-potsdam.de [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)] [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Körzdörfer, Thomas, E-mail: jean-luc.bredas@chemistry.gatech.edu, E-mail: thomas.koerzdoerfer@uni-potsdam.de [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States) [School of Chemistry and Biochemistry and Center for Computational Molecular Science and Technology, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Computational Chemistry, Institute of Chemistry, University of Potsdam, D-14476 Potsdam (Germany)
2014-02-07T23:59:59.000Z
We investigate the torsion potentials in two prototypical ?-conjugated polymers, polyacetylene and polydiacetylene, as a function of chain length using different flavors of density functional theory. Our study provides a quantitative analysis of the delocalization error in standard semilocal and hybrid density functionals and demonstrates how it can influence structural and thermodynamic properties. The delocalization error is quantified by evaluating the many-electron self-interaction error (MESIE) for fractional electron numbers, which allows us to establish a direct connection between the MESIE and the error in the torsion barriers. The use of non-empirically tuned long-range corrected hybrid functionals results in a very significant reduction of the MESIE and leads to an improved description of torsion barrier heights. In addition, we demonstrate how our analysis allows the determination of the effective conjugation length in polyacetylene and polydiacetylene chains.
Lessons Learned Tracy Glauser, M.D.
Lessons Learned Tracy Glauser, M.D. Cincinnati Children's Hospital Medical Center #12;Overview 1. Lessons Learned a. NeuroNEXT Executive Committee b. NINDS clinical trials (NSD-K) study section c. PI
Magnetism in undoped ZnS studied from density functional theory
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
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.
Higher-order adaptive finite-element methods for Kohn–Sham density functional theory
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
We present an efficient computational approach to perform real-space electronic structure calculations using an adaptive higher-order finite-element discretization of Kohn–Sham 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 Gauss–Lobatto quadrature, and a Chebyshev acceleration technique for computing the occupied eigenspace. The proposed approach has been observed to provide a staggering 100–200-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 Kohn–Sham DFT problem. Our studies suggest that staggering computational savings—of the order of 1000-fold—relative 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 Kohn–Sham 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.
Berland, Kristian [Chalmers University of Technology, Sweden] [Chalmers University of Technology, Sweden; Arter, Calvin A [Wake Forest University, Winston-Salem] [Wake Forest University, Winston-Salem; Cooper, Valentino R [ORNL] [ORNL; Lee, Dr. Kyuho [Lawrence Berkeley National Laboratory (LBNL)] [Lawrence Berkeley National Laboratory (LBNL); Lundqvist, Prof. Bengt I. [Chalmers University of Technology, Sweden] [Chalmers University of Technology, Sweden; Schroder, Prof. Elsebeth [Chalmers University of Technology, Sweden] [Chalmers University of Technology, Sweden; Thonhauser, Prof. Timo [Wake Forest University, Winston-Salem] [Wake Forest University, Winston-Salem; Hyldgaard, Per [Chalmers University of Technology, Sweden] [Chalmers University of Technology, Sweden
2014-01-01T23:59:59.000Z
The theoretical description of sparse matter attracts much interest, in particular for those groundstate properties that can be described by density functional theory (DFT). 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, in print] 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 PbTiO3, the adsorption of small molecules within metal-organic frameworks (MOFs), the graphite/diamond phase transition, and the adsorption of an aromaticmolecule 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 Göteborg (Sweden) [Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Göteborg (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 Göteborg (Sweden)] [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Schröder, Elsebeth; Hyldgaard, Per [Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)] [Microtechnology and Nanoscience, MC2, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)
2014-05-14T23:59:59.000Z
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.
Truhlar, Donald G
2009 The performance of the M06-L density functional has been tested for band gaps in seven,13 that is designed for main group thermo- chemistry, transition metal bonding, thermochemical kinet- ics in group-4, group 35, and metal oxide semiconductors. In Sec. II, we describe the test sets
Reformulation of DFT+U as a pseudo-hybrid Hubbard density functional Luis A. Agapito,1, 2
Curtarolo, Stefano
the true energy of the many-body system of the electrons and the approxi- mate energy that we can computeReformulation of DFT+U as a pseudo-hybrid Hubbard density functional Luis A. Agapito,1, 2 Stefano have seen two competing approaches unfold to address these problems: DFT+U and hybrid exact exchange
Malheiro, Carine; Mendiboure, Bruno; Plantier, Frédéric; Miqueu, Christelle [Université Pau et Pays Adour, CNRS, TOTAL - UMR 5150 – LFC-R – Laboratoire des Fluides Complexes et leurs Réservoirs, BP 1155 – PAU, F-64013 (France)] [Université Pau et Pays Adour, CNRS, TOTAL - UMR 5150 – LFC-R – Laboratoire des Fluides Complexes et leurs Réservoirs, BP 1155 – PAU, F-64013 (France); Blas, Felipe J. [Departamento de Física Aplicada, and Centro de Física Teórica y Matemática FIMAT, Universidad de Huelva, 21071 Huelva (Spain)] [Departamento de Física Aplicada, and Centro de Física Teórica y Matemática FIMAT, Universidad de Huelva, 21071 Huelva (Spain)
2014-04-07T23:59:59.000Z
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.
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
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 491 508 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 491 508 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.
The scaling functions of the free energy density and its derivatives for the 3d O(4) model
Engels, Juergen
2011-01-01T23:59:59.000Z
We derive direct representations of the scaling functions of the 3d O(4) model which are relevant for comparisons to other models, in particular QCD. This is done in terms of expansions in the scaling variable z= t/h^{1/Delta}. The expansions around z=0 and the corresponding asymptotic ones for z --> +- infinity overlap such that no interpolation is needed. The expansion coefficients are determined numerically from the data of a previous high statistics simulation of the O(4) model on a three-dimensional lattice of linear extension L=120. From the scaling function of the magnetization we calculate the leading asymptotic coefficients of the scaling function of the free energy density. As a result we obtain the universal amplitude ratio A^+/A^-=1.84(4) for the specific heat. Comparing the scaling function of the energy density to the data we find the non-singular part of the energy density epsilon_{ns}(T) with high precision and at the same time excellent scaling properties.
EMC/FDTD/MD FOR MULTIPHYSICS CHARACTERIZATION OF SEMICONDUCTORS AT THZ FREQUENCIES
Knezevic, Irena
EMC/FDTD/MD FOR MULTIPHYSICS CHARACTERIZATION OF SEMICONDUCTORS AT THZ FREQUENCIES by Keely Willis.1 Ensemble Monte Carlo (EMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.2 Finite difference) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 3 EMC/FDTD for 2D analysis of materials with low carrier density . . . . . . . . . 22 3.1 EMC
Garfunkel, Eric
Hametz, M.D., Clinical Assistant Professor Stanley N. Katz, M.D., Clinical Assistant Professor Steven. Lathrop, M.D., Clinical Associate Professor Lawrence S. Meyers, M.D., Clinical Associate Professor Sandy S
Relativistic energy density functionals: Low-energy collective states of {sup 240}Pu and {sup 166}Er
Li, Z. P. [Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); School of Physical Science and Technology, Southwest University, Chongqing 400715 (China); Niksic, T.; Vretenar, D. [Physics Department, Faculty of Science, University of Zagreb, 10000 Zagreb (Croatia); Ring, P. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Physik-Department der Technischen Universitaet Muenchen, D-85748 Garching (Germany); Meng, J. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China)
2010-06-15T23:59:59.000Z
The empirical relativistic density-dependent, point-coupling energy density functional, adjusted exclusively to experimental binding energies of a large set of deformed nuclei with Aapprox =150-180 and Aapprox =230-250, is tested with spectroscopic data for {sup 166}Er and {sup 240}Pu. Starting from constrained self-consistent triaxial relativistic Hartree-Bogoliubov calculations of binding energy maps as functions of the quadrupole deformation in the beta-gamma plane, excitation spectra and E2 transition probabilities are calculated as solutions of the corresponding microscopic collective Hamiltonian in five dimensions for quadrupole vibrational and rotational degrees of freedom and compared with available data on low-energy collective states.
J. M. Yao; N. Itagaki; J. Meng
2014-09-19T23:59:59.000Z
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. Terasaki; J. Engel
2011-05-19T23:59:59.000Z
Although nuclear energy density functionals are determined primarily by fitting to ground state properties, they are often applied in nuclear astrophysics to excited states, usually through the quasiparticle random phase approximation (QRPA). Here we test the Skyrme functionals SkM* and SLy4 along with the self-consistent QRPA by calculating properties of low-lying vibrational states in a large number of well-deformed even-even rare-earth nuclei. We reproduce trends in energies and transition probabilities associated with gamma-vibrational states, but our results are not perfect and indicate the presences of multi-particle-hole correlations that are not included in the QRPA. The Skyrme functional SkM* performs noticeably better than SLy4. In a few nuclei, changes in the treatment of the pairing energy functional have a significant effect. The QRPA is less successful with "beta-vibrational" states than with the gamma-vibrational states.
Dobaczewski, J; Bender, M; Robledo, L M; Shi, Yue
2015-01-01T23:59:59.000Z
We calculate properties of the ground and excited states of nuclei in the nobelium region for proton and neutron numbers of 92 energy-density-functional (EDF) approaches, based on covariant, Skyrme, and Gogny functionals, each within two different parameter sets. A comparative analysis of the results obtained for odd-even mass staggerings, quasiparticle spectra, and moments of inertia allows us to identify single-particle and shell effects that are characteristic to these different models and to illustrate possible systematic uncertainties related to using the EDF modelling
The structure of mixed {sup 3}He-{sup 4}He droplets doped with OCS: A density functional approach
Leal, Antonio; Mateo, David; Pi, Martí; Barranco, Manuel [Departament ECM, Facultat de Física and IN2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain)] [Departament ECM, Facultat de Física and IN2UB, Universitat de Barcelona, Diagonal 645, 08028 Barcelona (Spain); Navarro, Jesús [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
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.
Potassium permeation through the KcsA channel: a density functional study
Guidoni, Leonardo
; Streptomyces lividans; Ab initio electronic structure calculation; Ionic selectivity; Electronic polarization of the electronic structure for potassium permeation, we have here under- taken a first principles Density-Parrinello Molecular Dynamics [19] and hybrid CPMD/MM calculations [20]. Our investigation is carried out in two steps
Density Functional Theory for Protein Transfer Free Energy Eric A. Mills and Steven S. Plotkin*
Plotkin, Steven S.
-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
Isospin-invariant Skyrme energy-density-functional approach with axial symmetry
J. A. Sheikh; N. Hinohara; J. Dobaczewski; T. Nakatsukasa; W. Nazarewicz; K. Sato
2014-05-20T23:59:59.000Z
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.
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
Gong, Xingao
A density-functional study of small titanium clusters S. H. Wei Department of Physics, Xiangtan-functional theory with a local spin density approximation. We find that the inner-shells (3s3p) of the titanium atom of titanium clusters, Ti7 is found to be a magic cluster, which is in good agreement with the experimental
Sandusky, H W; Granholm, R H; Bohl, D G; Vandersall, K S; Hare, D E; Garcia, F
2006-06-20T23:59:59.000Z
The potential for deflagration-to-detonation transition (DDT) in LX-04 (85/15 HMX/Viton) is being evaluated as a function of loading density, temperature, and confinement. In the high confinement arrangement, a matrix of tests is nearly completed with the LX-04 loaded at {approx} 51, 70, 90, and {approx} 99% of theoretical maximum density (TMD); and temperatures of ambient, 160 C, and 190 C at each loading density. A more limited set of tests with {approx}99 %TMD loadings at medium confinement were conducted at temperatures of ambient and 186 C. LX-04 does not undergo DDT at near TMD loadings in both medium and high confinement, although the latter still results in significant fragmentation. Most porous beds in high confinement undergo DDT, with the minimum run distance to detonation (l) for a 70 %TMD loading at ambient temperature. LX-04 does not transit to detonation for a pour density (51.3 %TMD) loading at 160 C, but does at 190 C with a longer l than at ambient. The limited ambient temperature measurements for l in high confinement are similar to previous data for 91/9 HMX/wax, which has nearly the same %volume of HMX as LX-04.
Tools for incorporating a D-wave contribution in Skyrme energy density functionals
P. Becker; D. Davesne; J. Meyer; A. Pastore; J. Navarro
2014-06-02T23:59:59.000Z
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.
Yan, Xun-Wang [Beijing Computational Science Research Center, Beijing 100084 (China) [Beijing Computational Science Research Center, Beijing 100084 (China); Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China); State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Science, Beijing 100190, China and School of Physics and Electrical Engineering, Anyang Normal University, Henan 455000 (China); Huang, Zhongbing, E-mail: huangzb@hubu.edu.cn [Beijing Computational Science Research Center, Beijing 100084 (China) [Beijing Computational Science Research Center, Beijing 100084 (China); Faculty of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China); Lin, Hai-Qing [Beijing Computational Science Research Center, Beijing 100084 (China)] [Beijing Computational Science Research Center, Beijing 100084 (China)
2013-11-28T23:59:59.000Z
By the first principle calculations based on the van der Waals density functional theory, we study the crystal structures and electronic properties of La-doped phenanthrene. Two stable atomic geometries of La{sub 1}phenanthrene are obtained by relaxation of atomic positions from various initial structures. The structure-I is a metal with two energy bands crossing the Fermi level, while the structure-II displays a semiconducting state with an energy gap of 0.15 eV, which has an energy gain of 0.42 eV per unit cell compared to the structure-I. The most striking feature of La{sub 1}phenanthrene is that La 5d electrons make a significant contribution to the total density of state around the Fermi level, which is distinct from potassium doped phenanthrene and picene. Our findings provide an important foundation for the understanding of superconductivity in La-doped phenanthrene.
Wopperer, P; Reinhard, P -G; Suraud, E
2014-01-01T23:59:59.000Z
Various ways to analyze the dynamical response of clusters and molecules to electromagnetic perturbations exist. Particularly rich information can be obtained from measuring the properties of electrons emitted in the course of the excitation dynamics. Such an analysis of electron signals covers total ionization, Photo-Electron Spectra, Photoelectron Angular Distributions, and ideally combined PES/PAD, with a long history in molecular physics, also increasingly used in cluster physics. Recent progress in the design of new light sources (high intensity and/or frequency, ultra short pulses) opens new possibilities for measurements and thus has renewed the interest on the analysis of dynamical scenarios through these observables, well beyond a simple access to a density of states. This, in turn, has motivated many theoretical investigations of the dynamics of electronic emission for molecules and clusters. A theoretical tool of choice is here Time-Dependent Density Functional Theory (TDDFT) propagated in real tim...
Poster Presentations Marcella Alsan, MD, MPH, PhD
Kay, Mark A.
15 Poster Presentations Marcella Alsan, MD, MPH, PhD The direct and indirect effects of mass vaccination: Evidence from the 1985 Turkish campaign Michele Barry, MD; Stephen Luby, MD; Nancy Federspiel, PhD Global Health Fellows and Scholars Consortium Cynthia M. Castro, PhD; Abby C. King, PhD; Marcia Stefanick
Christian Iliadis; Richard Longland; Art Champagne; Alain Coc; Ryan Fitzgerald
2010-04-23T23:59:59.000Z
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.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
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
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.
Zhang, Yu; Biggs, Jason D.; Healion, Daniel; Govind, Niranjan; Mukamel, Shaul
2012-11-21T23:59:59.000Z
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.
Bankura, Arindam; DiStasio, Robert A; Swartz, Charles W; Klein, Michael L; Wu, Xifan
2015-01-01T23:59:59.000Z
In this work, the solvation and electronic structure of the aqueous chloride ion solution was investigated using Density Functional Theory (DFT) based \\textit{ab initio} molecular dynamics (AIMD). From an analysis of radial distribution functions, coordination numbers, and solvation structures, we found that exact exchange ($E_{\\rm xx}$) and non-local van der Waals (vdW) interactions effectively \\textit{weaken} the interactions between the Cl$^-$ ion and the first solvation shell. With a Cl-O coordination number in excellent agreement with experiment, we found that most configurations generated with vdW-inclusive hybrid DFT exhibit 6-fold coordinated distorted trigonal prism structures, which is indicative of a significantly disordered first solvation shell. By performing a series of band structure calculations on configurations generated from AIMD simulations with varying DFT potentials, we found that the solvated ion orbital energy levels (unlike the band structure of liquid water) strongly depend on the un...
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
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.
Volodymyr P. Sergiievskyi; Guillaume Jeanmairet; Maximilien Levesque; Daniel Borgis
2014-06-11T23:59:59.000Z
Molecular Density Functional Theory (MDFT) offers an efficient implicit- solvent method to estimate molecule solvation free-energies whereas conserving a fully molecular representation of the solvent. Even within a second order ap- proximation for the free-energy functional, the so-called homogeneous reference uid approximation, we show that the hydration free-energies computed for a dataset of 500 organic compounds are of similar quality as those obtained from molecular dynamics free-energy perturbation simulations, with a computer cost reduced by two to three orders of magnitude. This requires to introduce the proper partial volume correction to transform the results from the grand canoni- cal to the isobaric-isotherm ensemble that is pertinent to experiments. We show that this correction can be extended to 3D-RISM calculations, giving a sound theoretical justifcation to empirical partial molar volume corrections that have been proposed recently.
Van der Waals density-functional theory study for bulk solids with BCC, FCC, and diamond structures
Park, Jinwoo; Hong, Suklyun
2015-01-01T23:59:59.000Z
Proper inclusion of van der Waals (vdW) interactions in theoretical simulations based on standard density functional theory (DFT) is crucial to describe the physics and chemistry of systems such as organic and layered materials. Many encouraging approaches have been proposed to combine vdW interactions with standard approximate DFT calculations. Despite many vdW studies, there is no consensus on the reliability of vdW methods. To help further development of vdW methods, we have assessed various vdW functionals through the calculation of structural prop- erties at equilibrium, such as lattice constants, bulk moduli, and cohesive energies, for bulk solids, including alkali, alkali-earth, and transition metals, with BCC, FCC, and diamond structures as the ground state structure. These results provide important information for the vdW-related materials research, which is essential for designing and optimizing materials systems for desired physical and chemical properties.
Phil Attard
2013-11-25T23:59:59.000Z
The probability operator is derived from first principles for an equilibrium quantum system. It is also shown that the superposition states collapse into a mixture of states giving the conventional von Neumann trace form for the quantum average. The mechanism for the collapse is found to be quite general: it results from the conservation law for a conserved, exchangeable variable (such as energy) and the entanglement of the total system wave function that necessarily follows. The relevance of the present results to the einselection mechanism for decoherence, to the quantum measurement problem, and to the classical nature of the macroscopic world are discussed.
Towards time-dependent current-density-functional theory in the non-linear regime
Escartín, J. M.; Vincendon, M.; Romaniello, P.; Dinh, P. M.; Reinhard, P.-G.; Suraud, E.
2015-02-27T23:59:59.000Z
? ? Im [???(r, t)???(r, t)] ? q mc AS(r, t) ?(r, t) , (2b) and are independent of the gauge chosen to represent the electromagnetic potentials. A. The Vignale-Kohn functional in real time Up to second order in spatial derivatives, under the basic... that, while treat- ing the memory instantaneously in time, maintains the dissipating effects of the VK approximation. We have demonstrated the capabilities of the method by apply- ing it to Mg, Ca and Na2 whereby we are modeling a short laser pulse...
Free Energy Calculation in MD Simulation
Nielsen, Steven O.
Free Energy Calculation in MD Simulation #12;Basic Thermodynamics Helmoholtz free energy A = U TS + i Ni dA = wrev (reversible, const N V T) eq (22.9) McQuarrie & Simon Gibbs free energy G = U;Implication of Free Energy A B Keq = [A]/[B] Keq = exp (-G0 /RT) G0 = -RT ln Keq G = G0 + RT ln Q G > 0
Sandusky, H W; Granholm, R H; Bohl, D G; Hare, D E; Vandersall, K S; Garcia, F
2005-06-01T23:59:59.000Z
The potential for deflagration-to-detonation transition (DDT) in LX-04 (85/15 HMX/Viton) is being evaluated as a function of loading density, temperature, and confinement. In the high confinement arrangement, a matrix of tests will be performed with the LX-04 loaded at {approx}50, 70, 90, and {approx}99 %TMD; and temperatures of ambient, 160 C, and 190 C, at each loading density. A more limited set of tests at medium confinement will be conducted. As expected, LX-04 does not undergo DDT at near TMD loadings in both medium and high confinement, although the later still results in significant fragmentation. In high confinement at pour density (50.3 %TMD), LX-04 does not transit to detonation at 160 C, but does at ambient and 190 C with the shortest run distance to detonation (l) at ambient temperature. With a 70% TMD loading at ambient temperature, l was even less. The limited ambient temperature measurements for l in high confinement are similar to previous data for 91/9 HMX/wax, which has nearly the same %volume of HMX as LX-04.
Limbic System Page 1 of 10 Srdjan D. Antic, M.D. Limbic system Emotional Experience
Oliver, Douglas L.
function. NMDA-dependent long-term potentiation is a cellular mechanism responsible for fear conditioning.M. is the most studied patient with Urbach-Wiethe disease. After a battery of tests, which included spiders Srdjan D. Antic, M.D. 3 as well as an appetitive (positive) conditioning. Individuals with larger
Biswajit Santra; Ji?í Klimeš; Alexandre Tkatchenko; Dario Alfè; Ben Slater; Angelos Michaelides; Roberto Car; Matthias Scheffler
2014-08-14T23:59:59.000Z
Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water.
Rodriguez-Guzman, R
2014-01-01T23:59:59.000Z
The most recent parametrization D1M of the Gogny energy density functional is used to describe fission in the isotopes $^{232-280}$ Pu. We resort to the methodology introduced in our previous studies [Phys. Rev. C \\textbf{88}, 054325 (2013) and Phys. Rev. C \\textbf {89}, 054310 (2014)] to compute the fission paths, collective masses and zero point quantum corrections within the Hartree-Fock-Bogoliubov framework. The systematics of the spontaneous fission half-lives t$_{SF}$, masses and charges of the fragments in Plutonium isotopes is analyzed and compared with available experimental data. We also pay attention to isomeric states, the deformation properties of the fragments as well as to the competition between the spontaneous fission and $\\alpha$-decay modes. The impact of pairing correlations on the predicted t$_{SF}$ values is demonstrated with the help of calculations for $^{232-280}$Pu in which the pairing strengths of the Gogny-D1M energy density functional are modified by 5 $\\%$ and 10 $\\%$, respective...
R. Rodriguez-Guzman; L. M. Robledo
2014-05-27T23:59:59.000Z
The most recent parametrization D1M of the Gogny energy density functional is used to describe fission in the isotopes $^{232-280}$ Pu. We resort to the methodology introduced in our previous studies [Phys. Rev. C \\textbf{88}, 054325 (2013) and Phys. Rev. C \\textbf {89}, 054310 (2014)] to compute the fission paths, collective masses and zero point quantum corrections within the Hartree-Fock-Bogoliubov framework. The systematics of the spontaneous fission half-lives t$_{SF}$, masses and charges of the fragments in Plutonium isotopes is analyzed and compared with available experimental data. We also pay attention to isomeric states, the deformation properties of the fragments as well as to the competition between the spontaneous fission and $\\alpha$-decay modes. The impact of pairing correlations on the predicted t$_{SF}$ values is demonstrated with the help of calculations for $^{232-280}$Pu in which the pairing strengths of the Gogny-D1M energy density functional are modified by 5 $\\%$ and 10 $\\%$, respectively. We further validate the use of the D1M parametrization through the discussion of the half-lives in $^{242-262}$Fm. Our calculations corroborate that, though the uncertainties in the absolute values of physical observables are large, the Gogny-D1M Hartree-Fock-Bogoliubov framework still reproduces the trends with mass and/or neutron numbers and therefore represents a reasonable starting point to describe fission in heavy nuclear systems from a microscopic point of view.
Mattsson, Ann Elisabet
2012-01-01T23:59:59.000Z
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.
Simulation of Charged Systems in Heterogeneous Dielectric Media via a True Energy Functional
Vikram Jadhao; Francisco J. Solis; Monica Olvera de la Cruz
2013-09-26T23:59:59.000Z
For charged systems in heterogeneous dielectric media, a key obstacle for molecular dynamics (MD) simulations is the need to solve the Poisson equation in the media. This obstacle can be bypassed using MD methods that treat the local polarization charge density as a dynamic variable, but such approaches require access to a true free energy functional; one that evaluates to the equilibrium electrostatic energy at its minimum. In this letter, we derive the needed functional. As an application, we develop a Car-Parrinello MD method for the simulation of free charges present near a spherical emulsion droplet separating two immiscible liquids with different dielectric constants. Our results show the presence of non-monotonic ionic profiles in the dielectric with lower dielectric constant.
An extended SMLD approach for presumed probability density function in flamelet combustion model
Coclite, Alessandro; De Palma, Pietro; Cutrone, Luigi
2013-01-01T23:59:59.000Z
This paper provides an extension of the standard flamelet progress variable (FPV) approach for turbulent combustion, applying the statistically most likely distribution (SMLD) framework to the joint PDF of the mixture fraction, Z, and the progress variable, C. In this way one does not need to make any assumption about the statistical correlation between Z and C and about the behaviour of the mixture fraction, as required in previous FPV models. In fact, for state-of-the-art models, with the assumption of very-fast-chemistry,Z is widely accepted to behave as a passive scalar characterized by a $\\beta$-distribution function. Instead, the model proposed here, evaluates the most probable joint distribution of Z and C without any assumption on their behaviour and provides an effective tool to verify the adequateness of widely used hypotheses, such as their statistical independence. The model is validated versus three well-known test cases, namely, the Sandia flames. The results are compared with those obtained by ...
Complex-energy approach to sum rules within nuclear density functional theory
Hinohara, Nobuo; Nazarewicz, Witold; Olsen, Erik
2015-01-01T23:59:59.000Z
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...
Yeo, Sang Chul
Ammonia (NH[subscript 3]) nitridation on an Fe surface was studied by combining density functional theory (DFT) and kinetic Monte Carlo (kMC) calculations. A DFT calculation was performed to obtain the energy barriers ...
Javier, Alnald Caintic
2013-08-05T23:59:59.000Z
Computational techniques based on density functional theory (DFT) and experimental methods based on electrochemistry (EC), electrochemical scanning tunneling microscopy (EC-STM), and high-resolution electron energy loss spectroscopy (HREELS) were...
Laird, Brian Bostian
1992-06-01T23:59:59.000Z
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...
Arindam Bankura; Biswajit Santra; Robert A. DiStasio Jr.; Charles W. Swartz; Michael L. Klein; Xifan Wu
2015-03-25T23:59:59.000Z
In this work, the solvation and electronic structure of the aqueous chloride ion solution was investigated using Density Functional Theory (DFT) based \\textit{ab initio} molecular dynamics (AIMD). From an analysis of radial distribution functions, coordination numbers, and solvation structures, we found that exact exchange ($E_{\\rm xx}$) and non-local van der Waals (vdW) interactions effectively \\textit{weaken} the interactions between the Cl$^-$ ion and the first solvation shell. With a Cl-O coordination number in excellent agreement with experiment, we found that most configurations generated with vdW-inclusive hybrid DFT exhibit 6-fold coordinated distorted trigonal prism structures, which is indicative of a significantly disordered first solvation shell. By performing a series of band structure calculations on configurations generated from AIMD simulations with varying DFT potentials, we found that the solvated ion orbital energy levels (unlike the band structure of liquid water) strongly depend on the underlying molecular structures. In addition, these orbital energy levels were also significantly affected by the DFT functional employed for the electronic structure; as the fraction of $E_{\\rm xx}$ was increased, the gap between the highest occupied molecular orbital of Cl$^-$ and the valence band maximum of liquid water steadily increased towards the experimental value.
G. Chechin; D. Ryabov; S. Shcherbinin
2015-02-27T23:59:59.000Z
Some exact interactions between vibrational modes in systems with discrete symmetry can be described by the theory of the bushes of nonlinear normal modes (NNMs) [G.M. Chechin, V.P. Sakhnenko. Physica D 117, 43 (1998)]. Each bush represents a dynamical object conserving the energy of the initial excitation. Existence of bushes of NNMs is ensured by some group-theoretical selection rules. In [G.M. Chechin, et al. Int. J. Non-Linear Mech. 38, 1451 (2003)], existence and stability of the bushes of vibrational modes in the simple octahedral model of mass points interacting via Lennard-Jones potential were investigated. In the present paper, we study these dynamical objects by the density functional theory in SF6 molecule which possesses the same symmetry and structure. We have fully confirmed the results previously obtained in the framework of the group theoretical approach and have found some new properties of the bushes of NNMs.
Hirata, So; Head-Gordon, Martin P.; Szczepanski, Jan; Vala, Martin
2003-06-19T23:59:59.000Z
A uniform, comprehensive theoretical interpretation of spectroscopic data is presented for 53 radical ion species of polycyclic aromatic hydrocarbons (PAHâ€™s) with the aid of (Tammâ€“Dancoff) time-dependent density functional theory (TDDFT). TDDFT is capable of predicting the transition energies to the low-lying excited states of PAH ions with quantitative accuracy (the standard deviation from experimental results being less than 0.3 eV) and their intensity patterns qualitatively correctly. The accuracy is hardly affected by the sizes of PAH ions (azulene through dinaphthocoronene), the types of transitions (Koopmans or satellite transitions), the types of orbi-tals involved (ï°*â†ï°, ï°*â†ï³, or ï³*â†ï° transitions), the types of ions (cations or anions), or other geometrical or electronic perturbations (non-planarity, sp3 carbons, or heterocyclic or non-benzenoid rings)
Lindskog, M., E-mail: martin.lindskog@teorfys.lu.se; Wacker, A. [Mathematical Physics, Lund University, Box 118, 22100 Lund (Sweden); Wolf, J. M.; Liverini, V.; Faist, J. [ETH Institute for Quantum Electronics, ETH-Zürich, 8093 Zürich (Switzerland); Trinite, V.; Maisons, G.; Carras, M. [III-V Lab, 1 Avenue Augustin Fresnel, 91767 Palaiseau (France); Aidam, R.; Ostendorf, R. [Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, 79108 Freiburg (Germany)
2014-09-08T23:59:59.000Z
We study the operation of an 8.5??m quantum cascade laser based on GaInAs/AlInAs lattice matched to InP using three different simulation models based on density matrix (DM) and non-equilibrium Green's function (NEGF) formulations. The latter advanced scheme serves as a validation for the simpler DM schemes and, at the same time, provides additional insight, such as the temperatures of the sub-band carrier distributions. We find that for the particular quantum cascade laser studied here, the behavior is well described by simple quantum mechanical estimates based on Fermi's golden rule. As a consequence, the DM model, which includes second order currents, agrees well with the NEGF results. Both these simulations are in accordance with previously reported data and a second regrown device.
Soderlind, P; Wolfer, W
2007-07-27T23:59:59.000Z
Spin and orbital and electron correlations are known to be important when treating the high-temperature {delta} phase of plutonium within the framework of density-functional theory (DFT). One of the more successful attempts to model {delta}-Pu within this approach has included condensed-matter generalizations of Hund's three rules for atoms, i.e., spin polarization, orbital polarization, and spin-orbit coupling. Here they perform a quantitative analysis of these interactions relative rank for the bonding and electronic structure in {delta}-Pu within the DFT model. The result is somewhat surprising in that spin-orbit coupling and orbital polarization are far more important than spin polarization for a realistic description of {delta}-Pu. They show that these orbital correlations on their own, without any formation of magnetic spin moments, can account for the low atomic density of the {delta} phase with a reasonable equation-of-state. In addition, this unambiguously non-magnetic (NM) treatment produces a one-electron spectra with resonances close to the Fermi level consistent with experimental valence band photoemission spectra.
M. S. Oey; J. S. Parker; V. J. Mikles; X. Zhang
2003-07-10T23:59:59.000Z
We investigate the relationship of the HII region luminosity function (HII LF) to the HII region size distribution and density wave triggering in grand-design spiral galaxies. We suggest that the differential nebular size distribution is described by a power law of slope ~ -4, with flattening at radii below ~ 130 pc. This contrasts with the conventional exponential description, but it is physically and quantitatively consistent with the typical observed value of -2 for the HII LF slope. We have developed an interactive code that computes spatial isochrones for the evolving loci of spiral density waves in disk galaxies. This allows comparison of the nebular spatial distribution with the spatial isochrones for simple rotation curve parameters. Our comparisons for four grand-design galaxies suggest that the corotation radius r_co coincides with the outer ends of the star-forming arms. This value for r_co yields the best spatial correspondence between the HII regions and the isochrones, and also appears to yield a coincidence between the Inner Lindblad Resonance with the radial onset of star formation in the arms. Thus, we suggest that isochrones offer a new, simple, and effective technique for determining r_co, and thus the spiral pattern speed. However, application of the isochrones also demonstrates that evolution of the nebular population is difficult to spatially isolate in these galaxies.
I. A. Shkrob
2006-07-25T23:59:59.000Z
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.
Mehdi Farzanehpour; I. V. Tokatly
2015-06-29T23:59:59.000Z
We use analytic (current) density-potential maps of time-dependent (current) density functional theory (TD(C)DFT) to inverse engineer analytically solvable time-dependent quantum problems. In this approach the driving potential (the control signal) and the corresponding solution of the Schr\\"odinger equation are parametrized analytically in terms of the basic TD(C)DFT observables. We describe the general reconstruction strategy and illustrate it with a number of explicit examples. First we consider the real space one-particle dynamics driven by a time-dependent electromagnetic field and recover, from the general TDDFT reconstruction formulas, the known exact solution for a driven oscillator with a time-dependent frequency. Then we use analytic maps of the lattice TD(C)DFT to control quantum dynamics in a discrete space. As a first example we construct a time-dependent potential which generates prescribed dynamics on a tight-binding chain. Then our method is applied to the dynamics of spin-1/2 driven by a time dependent magnetic field. We design an analytic control pulse that transfers the system from the ground to excited state and vice versa. This pulse generates the spin flip thus operating as a quantum NOT gate.
Morzan, Uriel N.; Ramírez, Francisco F.; Scherlis, Damián A., E-mail: damian@qi.fcen.uba.ar, E-mail: mcgl@qb.ffyb.uba.ar [Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. II, Buenos Aires (C1428EHA) (Argentina); Oviedo, M. Belén; Sánchez, Cristián G. [Departamento de Matemática y Física, Facultad de Ciencias Químicas, INFIQC, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba (Argentina)] [Departamento de Matemática y Física, Facultad de Ciencias Químicas, INFIQC, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba (Argentina); Lebrero, Mariano C. González, E-mail: damian@qi.fcen.uba.ar, E-mail: mcgl@qb.ffyb.uba.ar [Instituto de Química y Fisicoquímica Biológicas, IQUIFIB, CONICET (Argentina)] [Instituto de Química y Fisicoquímica Biológicas, IQUIFIB, CONICET (Argentina)
2014-04-28T23:59:59.000Z
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 matrix—required 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.
Burke, Kieron
Excitations and benchmark ensemble density functional theory for two electrons Aurora Pribram and benchmark ensemble density functional theory for two electrons Aurora Pribram-Jones,1 Zeng-hui Yang,2 John R
Ghadar, Yasaman; Clark, Aurora E.
2012-02-02T23:59:59.000Z
The interaction potentials between immiscible polar and non-polar solvents are a major driving force behind the formation of liquid:liquid interfaces. In this work, the interaction energy of water–pentane dimer has been determined using coupled-cluster theory with single double (triple) excitations [CCSD(T)], 2nd order Möller Plesset perturbation theory (MP2), density fitted local MP2 (DF-LMP2), as well as density functional theory using a wide variety of density functionals and several different basis sets. The M05-2X exchange correlation functionals exhibit excellent agreement with CCSD(T) and DF-LMP2 after taking into account basis set superposition error. The gas phase water–pentane interaction energy is found to be quite sensitive to the specific pentane isomer (2,2- dimethylpropane vs. n-pentane) and relative orientation of the monomeric constituents. Subsequent solution phase cluster calculations of 2,2-dimethylpropane and n-pentane solvated by water indicate a positive free energy of solvation that is in good agreement with available experimental data. Structural parameters are quite sensitive to the density functional employed and reflect differences in the two-body interaction energy calculated by each method. In contrast, cluster calculations of pentane solvation of H2O solute are found to be inadequate for describing the organic solvent, likely due to limitations associated with the functionals employed (B3LYP, BHandH, and M05-2X).
Wilkins, John
Comparison of screened hybrid density functional theory to diffusion Monte Carlo in calculations of total energies of silicon phases and defects Enrique R. Batista,1, * Jochen Heyd,2 Richard G. Hennig,3 for the prediction of defect properties using the Heyd-Scuseria-Ernzerhof HSE screened-exchange hybrid functional
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
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.
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
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.
Johannes Lischner; T. A. Arias
2008-06-27T23:59:59.000Z
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.
Alam, Aftab [Ames Laboratory; Johnson, Duane D. [Ames Laboratory
2014-06-01T23:59:59.000Z
Cerium and its technologically relevant compounds are examples of anomalous mixed valency, originating from two competing oxidation states—itinerant 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.
Net Zero Residential Test Facility Gaithersburg, MD Solar Photovoltaic Panels
Oak Ridge National Laboratory
1 Net Zero Residential Test Facility Gaithersburg, MD Solar Photovoltaic Panels Solar Thermal;NZERTF Gaithersburg, MD 3 Objectives Demonstrate Net-Zero Energy for a home similar in nature: · Demonstrate Net-Zero Energy Usage · Measure All Building Loads (Sensible and Latent) · Operate Dedicated
Yaws, C.L.; Yang, H.C.; Hopper, J.R.; Cawley, W.A. (Lamar Univ., Beaumont, TX (US))
1991-01-01T23:59:59.000Z
Saturated liquid densities for organic chemicals are given as functions of temperature using a modified Rackett equation.
Mehmood, F.; Greeley, J.; Zapol, P.; Curtiss, L. A.
2010-08-12T23:59:59.000Z
A density functional theory study of the decomposition of methanol on Cu{sub 4} and Co{sub 4} clusters is presented. The reaction intermediates and activation barriers have been determined for reaction steps to form H{sub 2} and CO. For both clusters, methanol decomposition initiated by C-H and O-H bond breaking was investigated. In the case of a Cu{sub 4} cluster, methanol dehydrogenation through hydroxymethyl (CH{sub 2}OH), hydroxymethylene (CHOH), formyl (CHO), and carbon monoxide (CO) is found to be slightly more favorable. For a Co{sub 4} cluster, the dehydrogenation pathway through methoxy (CH{sub 3}O) and formaldehyde (CH{sub 2}O) is slightly more favorable. Each of these pathways results in formation of CO and H{sub 2}. The Co cluster pathway is very favorable thermodynamically and kinetically for dehydrogenation. However, since CO binds strongly, it is likely to poison methanol decomposition to H{sub 2} and CO at low temperatures. In contrast, for the Cu cluster, CO poisoning is not likely to be a problem since it does not bind strongly, but the dehydrogenation steps are not energetically favorable. Pathways involving C-O bond cleavage are even less energetically favorable. The results are compared to our previous study of methanol decomposition on Pd{sub 4} and Pd{sub 8} clusters. Finally, all reaction energy changes and transition state energies, including those for the Pd clusters, are related in a linear, Broensted?Evans?Polanyi plot.
Holmes, Sean T.; Dybowski, Cecil [Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716 (United States); Iuliucci, Robbie J. [Department of Chemistry, Washington and Jefferson College, Washington, Pennsylvania 15301 (United States); Mueller, Karl T. [Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802 (United States); Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington 99352 (United States)
2014-10-28T23:59:59.000Z
A quantum-chemical method for modeling solid-state nuclear magnetic resonance chemical-shift tensors by calculations on large symmetry-adapted clusters of molecules is demonstrated. Four hundred sixty five principal components of the {sup 13}C chemical-shielding tensors of 24 organic materials are analyzed. The comparison of calculations on isolated molecules with molecules in clusters demonstrates that intermolecular effects can be successfully modeled using a cluster that represents a local portion of the lattice structure, without the need to use periodic-boundary conditions (PBCs). The accuracy of calculations which model the solid state using a cluster rivals the accuracy of calculations which model the solid state using PBCs, provided the cluster preserves the symmetry properties of the crystalline space group. The size and symmetry conditions that the model cluster must satisfy to obtain significant agreement with experimental chemical-shift values are discussed. The symmetry constraints described in the paper provide a systematic approach for incorporating intermolecular effects into chemical-shielding calculations performed at a level of theory that is more advanced than the generalized gradient approximation. Specifically, NMR parameters are calculated using the hybrid exchange-correlation functional B3PW91, which is not available in periodic codes. Calculations on structures of four molecules refined with density plane waves yield chemical-shielding values that are essentially in agreement with calculations on clusters where only the hydrogen sites are optimized and are used to provide insight into the inherent sensitivity of chemical shielding to lattice structure, including the role of rovibrational effects.
Jackson, Virgil E.; Gutowski, Keith E.; Dixon, David A.
2013-09-12T23:59:59.000Z
The structures, vibrational frequencies and energetics of anhydrous and hydrated complexes of UO2 2+ with the phosphate anions H2PO4 ?, HPO4 2?, and PO4 3? were predicted at the density functional theory (DFT) and MP2 molecular orbital theory levels as isolated gas phase species and in aqueous solution by using self-consistent reaction field (SCRF) calculations with different solvation models. The geometries and vibrational frequencies of the major binding modes for these complexes are compared to experiment where possible and good agreement is found. The uranyl moiety is nonlinear in many of the complexes, and the coordination number (CN) 5 in the equatorial plane is the predominant binding motif. The phosphates are found to bind in both monodentate and bidentate binding modes depending on the charge and the number of water molecules. The SCRF calculations were done with a variety of approaches, and different SCRF approaches were found to be optimal for different reaction types. The acidities of HxPO4 3?x in HxPO4 3?x(H2O)4, x = 0?3 complexes were calculated with different SCRF models and compared to experiment. Phosphate anions can displace water molecules from the first solvation shell at the uranyl exothermically. The addition of water molecules can cause the bonding of H2PO4 ? and HPO4 2? to change from bidentate to monodentate exothermically while maintaining CN 5. The addition of water can generate monodentate structures capable of cross-linking to other uranyl phosphates to form the types of structures found in the solid state. [UO2(HPO4)(H2O)3] is predicted to be a strong base in the gas phase and in aqueous solution. It is predicted to be a much weaker acid than H3PO4 in the gas phase and in solution.
Serial Intraoperative MR Imaging of Brain Shift Arya Nabavi, M.D.1
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
Gherman, Benjamin F.
and the Applicability of Density Functional Theory for Fuel Cell Modeling Nathan E. Schultz, Benjamin F. Gherman Form: August 18, 2006 Electrode poisoning by CO is a major concern in fuel cells. As interest. Introduction Several of the most successful fuel cell applications use a Pt anode as a catalyst
Chu, Shih-I; Zhou, Zhongyuan
2007-01-17T23:59:59.000Z
A spin-dependent localized Hartree-Fock density-functional approach is presented for the efficient and accurate treatment of inner-shell excited states of atomic systems. The approach is applied to the calculation of the total and excitation...
Diebold, Ulrike
-terminated TiO2 rutile (011)-1 Â 1 surface shows an undulated surface topography with exposed two-fold O (O2cThe 2 Â 1 reconstruction of the rutile TiO2(011) surface: A combined density functional theory, X for publication 28 October 2008 Available online 5 November 2008 Keywords: Titanium dioxide Surface reconstruction
Bell, Alexis T.
with H2O2 releases HOOÂ· free radicals and generates V(IV) species, which are capable of generating HOA Density Functional Theory Study of the Mechanism of Free Radical Generation in the System for HOOÂ· generation. It is also found that species containing two pca ligands and an H2O2 molecule do
Aquino, Fredy W.; Govind, Niranjan; Autschbach, Jochen
2011-10-01T23:59:59.000Z
Density functional theory (DFT) calculations of NMR chemical shifts and molecular g-tensors with Gaussian-type orbitals are implemented via second-order energy derivatives within the scalar relativistic zeroth order regular approximation (ZORA) framework. Nonhybrid functionals, standard (global) hybrids, and range-separated (Coulomb-attenuated, long-range corrected) hybrid functionals are tested. Origin invariance of the results is ensured by use of gauge-including atomic orbital (GIAO) basis functions. The new implementation in the NWChem quantum chemistry package is verified by calculations of nuclear shielding constants for the heavy atoms in HX (X=F, Cl, Br, I, At) and H2X (X = O, S, Se, Te, Po), and Te chemical shifts in a number of tellurium compounds. The basis set and functional dependence of g-shifts is investigated for 14 radicals with light and heavy atoms. The problem of accurately predicting F NMR shielding in UF6-nCln, n = 1 to 6, is revisited. The results are sensitive to approximations in the density functionals, indicating a delicate balance of DFT self-interaction vs. correlation. For the uranium halides, the results with the range-separated functionals are mixed.
Sorkin, Anastassia; Iron, Mark A.; Truhlar, Donald G.
2008-02-01T23:59:59.000Z
The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The ground and lower excited states of Fe2, Fe2 -, and FeO+ were studied using a number of density functional theory (DFT) methods. Specific attention was paid to the relative state energies, the internuclear distances (re), and the harmonic vibrational frequencies (öe). A number of factors influencing the calculated values of these properties were examined. These include basis sets, the nature of the density functional chosen, the percentage of Hartree- Fock exchange in the density functional, and constraints on orbital symmetry. A number of different types of generalized gradient approximation (GGA) density functionals (straight GGA, hybrid GGA, meta-GGA, and hybrid meta-GGA) were examined, and it was found that the best results were obtained with hybrid GGA or hybrid meta-GGA functionals that contain nonzero fractions of HF exchange; specifically, the best overall results were obtained with B3LYP, M05, and M06, closely followed by B1LYP. One significant observation was the effect of enforcing symmetry on the orbitals. When a degenerate orbital (ð or ä) is partially occupied in the 4¼ excited state of FeO+, reducing the enforced symmetry (from C6v to C4v to C2v) results in a lower energy since these degenerate orbitals are split in the lower symmetries. The results obtained were compared to higher level ab initio results from the literature and to recent PBE+U plane wave results by Kulik et al. (Phys. Rev. Lett. 2006, 97, 103001). It was found that some of the improvements that were afforded by the semiempirical +U correction can also be accomplished by improving the form of the DFT functional and, in one case, by not enforcing high symmetry on the orbitals.
The Centre for Blood Research Jos Lpez, MD
Strynadka, Natalie
The Centre for Blood Research José López, MD Executive Vice-President of Research Puget Sound Blood for Blood Research Von Willebrand factor (VWF) is the largest protein in the blood and involved in both
Why are MD simulated protein folding times wrong? Dmitry Nerukh
Nerukh, Dmitry
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
Chu, Shih-I; Tong, Xiao-Min
1998-02-01T23:59:59.000Z
to the relativistic regime also has been con- sidered @6,7#. However, with the exception of a recent rela- tivistic local-density-functional calculation @8#, there is no systematic relativistic DFT studies of atomic ground-state properties across the Periodic Table...-interaction energy @1#. A similar problem exists for the relativistic xc energy functionals @6,7#. For a quantitative treatment of photoionization or multipho- ton ionization processes, it is necessary that both the ioniza- tion potential and the excited...
Density functional theory study of first-layer adsorption of ZrO2 and HfO2 on Ge(100)
Kummel, Andrew C.
Density functional theory study of first-layer adsorption of ZrO2 and HfO2 on Ge(100) T.J. Grassman on the Ge(100)-4 Â 2 surface. Surface binding geometries of metal-down (OMGe) and oxygen-down (M OGe) were considered, including both adsorbate and displacement geometries of MOGe. Calculated enthalpies
Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus JJ; Jensen, Lasse
2013-12-10T23:59:59.000Z
A parallel implementation of analytical time-dependent density functional theory gra- dients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G and a molecular host-guest complex (TTF?CBPQT4+). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host-guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experiment for most exchange-correlation functionals. However, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.
Chu, Shih-I
2013-01-01T23:59:59.000Z
-correlation potential which proved accurate in calculations of unperturbed electronic structure of Ar. Calculations is, not including dynamic response of the electron density) differ significantly from those obtained [24]. Electronic structure of atoms and molecules can be encoded in the HHG signal; the latter may
Li, Weixue
in FischerTropsch syn- thesis, which agrees well with experimental findings. The density of states (DOSs14], dehydrogenation [15], hydrogenolysis [16, 17] and FischerTropsch synthesis (FTS) [1822] etc., approaching activity of cobalt, iron and iron carbide in FischerTropsch synthesis (FTS)[2443], relative little
Song, Xueyu
online 18 July 2008 Free energies and correlation functions of liquid and solid hard-sphere HS mixtures theory the free energies of solid and liquid Lennard-Jones LJ mixtures are obtained from correlation, Chandler, and Andersen WCA Refs. 5 and 6 perturbation theory, the free energy is separated into two parts
Silvestrelli, Pier Luigi; Ambrosetti, Alberto [Dipartimento di Fisica e Astronomia, Università di Padova, via Marzolo 8, I–35131 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, Università di Padova, via Marzolo 8, I–35131 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
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.
Fahleson, Tobias; Norman, Patrick, E-mail: panor@ifm.liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Coriani, Sonia, E-mail: coriani@units.it [Dipartimento di Scienze Chimiche e Farmaceutiche, Università degli Studi di Trieste, I-34127 Trieste (Italy); Rizzo, Antonio, E-mail: rizzo@ipcf.cnr.it [CNR - Consiglio Nazionale delle Ricerche, Istituto per i Processi Chimico Fisici (IPCF-CNR), UOS di Pisa, I-56124 Pisa (Italy); Rikken, Geert L. J. A., E-mail: geert.rikken@lncmi.cnrs.fr [Laboratoire National des Champs Magnétiques Intenses, UPR3228, CNRS/INSA/UJF/UPS, Toulouse and Grenoble (France)
2013-11-21T23:59:59.000Z
We report on the results of a systematic ab initio study of the Jones birefringence of noble gases, of furan homologues, and of monosubstituted benzenes, in the gas phase, with the aim of analyzing the behavior and the trends within a list of systems of varying size and complexity, and of identifying candidates for a combined experimental/theoretical study of the effect. We resort here to analytic linear and nonlinear response functions in the framework of time-dependent density functional theory. A correlation is made between the observable (the Jones constant) and the atomic radius for noble gases, or the permanent electric dipole and a structure/chemical reactivity descriptor as the para Hammett constant for substituted benzenes.
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
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.
Einstein M.D. Program 20132014 applicant guide
Emmons, Scott
Einstein M.D. Program 20132014 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop, learning opportunities and experiences that create the unique educational environment at Einstein
Einstein M.D. Program 20112012 applicant guide
Jenny, Andreas
Einstein M.D. Program 20112012 applicant guide O F Y E S H I V A U N I V E R S I T Y Albert Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop, learning opportunities and experiences that create the unique educational environment at Einstein
LSUHSC NO Leadership Program Director, Augusto Ochoa, MD
D: Project 8 Yan Cui, PhD: COBRE Graduate Mentor Internal Advisory Committee Joseph Moerschbaecher, III: Jonna Ellis Promising Junior Investigators Project 2: Jovanny Zabaleta, PhD Project 3: Paulo Rodriguez, PhD Project 4: Timothy Foster, PhD Project 5: John Schieffelin, MD Tulane University Project 6
Diabetes A Growing Epidemic Michael McKee, MD, MPH
Goldman, Steven A.
Diabetes A Growing Epidemic Michael McKee, MD, MPH March 28, 2013 #12;Goals Diabetes Introduction Types of Diabetes Testing Prevention Treatments #12;In Memory of Benno Houver Bernd "Benno" Houver (1973-2013) #12;Diabetes Info 25.8 million people in the USA (8.3%) have diabetes ~25% of people with diabetes do
Kawaguchi, Yoshizo [Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565 (Japan); Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Sasaki, Fumio; Mochizuki, Hiroyuki [Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Ishitsuka, Tomoaki; Tomie, Toshihisa [Research Institute of Instrumentation Frontier, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Ootsuka, Teruhisa [Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Watanabe, Shuji [Graduate School of Science and Engineering, Yamagata University, 1-4-12, Kojirakawa, Yamagata 990-8560 (Japan); Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Shimoi, Yukihiro [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568 (Japan); Yamao, Takeshi; Hotta, Shu [Department of Macromolecular Science and Engineering, Graduate School of Science and Technology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan)
2013-02-28T23:59:59.000Z
We have investigated electronic states in the valence electron bands for the thin films of three thiophene/phenylene co-oligomer (TPCO) compounds, 2,5-bis(4-biphenylyl)thiophene (BP1T), 1,4-bis(5-phenylthiophen-2-yl)benzene (AC5), and 1,4-bis{l_brace}5-[4-(trifluoromethyl)phenyl]thiophen-2-yl{r_brace}benzene (AC5-CF{sub 3}), by using extreme-UV excited photoelectron spectroscopy (EUPS). By comparing both EUPS spectra and secondary electron spectra between AC5 and AC5-CF{sub 3}, we confirm that CF{sub 3} substitution to AC5 deepens valence states by 2 eV, and increases the ionization energy by 3 eV. From the cut-off positions of secondary electron spectra, the work functions of AC5, AC5-CF{sub 3}, and BP1T are evaluated to be 3.8 eV, 4.8 eV, and 4.0 eV, respectively. We calculate molecular orbital (MO) energy levels by the density functional theory and compare results of calculations with those of experiments. Densities of states obtained by broadening MO levels well explain the overall features of experimental EUPS spectra of three TPCOs.
Lao, Ka Un; Herbert, John M., E-mail: herbert@chemistry.ohio-state.edu [Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210 (United States)
2014-01-28T23:59:59.000Z
The performance of second-order symmetry-adapted perturbation theory (SAPT) calculations using Kohn-Sham (KS) orbitals is evaluated against benchmark results for intermolecular interactions. Unlike previous studies of this “SAPT(KS)” methodology, the present study uses non-empirically tuned long-range corrected (LRC) functionals for the monomers. The proper v{sub xc} (r)?0 asymptotic limit is achieved by tuning the range separation parameter in order to satisfy the condition that the highest occupied KS energy level equals minus the molecule's ionization energy, for each monomer unit. Tests for He{sub 2}, Ne{sub 2}, and the S22 and S66 data sets reveal that this condition is important for accurate prediction of the non-dispersion components of the energy, although errors in SAPT(KS) dispersion energies remain unacceptably large. In conjunction with an empirical dispersion potential, however, the SAPT(KS) method affords good results for S22 and S66, and also accurately predicts the whole potential energy curve for the sandwich isomer of the benzene dimer. Tuned LRC functionals represent an attractive alternative to other asymptotic corrections that have been employed in density-functional-based SAPT calculations, and we recommend the use of tuned LRC functionals in both coupled-perturbed SAPT(DFT) calculations and dispersion-corrected SAPT(KS) calculations.
End-to-End Rate-Distortion Optimized MD Mode Selection for Multiple Description Video Coding
Apostolopoulos, John G.
Multiple description (MD) video coding can be used to reduce the detrimental effects caused by transmission over lossy packet networks. A number of approaches have been proposed for MD coding, where each provides a different ...
Chu, Shih-I; Telnov, Dmitry A.
2009-04-03T23:59:59.000Z
We present a time-dependent density-functional-theory approach for the ab initio study of the effect of correlated multielectron responses on the multiphoton ionization (MPI) of diatomic molecules N2, O2, and F2 in intense ...
COMMISSION ON HEALTH SCIENCE, EDUCATION, AND P. Roy Vagelos, M.D.
Lin, Xiaodong
Johnson & Johnson Barbara Bell Coleman Chairperson Amelior Foundation Norman H. Edelman, M.D. Vice Princeton University Steven A. Schroeder, M.D. President and CEO The Robert Wood Johnson Foundation Harold and Dentistry of New Jersey Samuel O. Thier, M.D. President and CEO Partners HealthCare System, Inc. #12
Asbestos-related diseases in automobile mechanics Jacques Ameille, MD1
Paris-Sud XI, UniversitÃ© de
1 Asbestos-related diseases in automobile mechanics Jacques Ameille, MD1 , Nicole Rosenberg, MD2-related diseases in automobile mechanics Corresponding author Jacques Ameille, MD, UnitÃ© de pathologie plaques, automobile mechanics, HRCT inserm-00671970,version1-20Feb2012 Author manuscript, published
Polylithiated (OLi2) functionalized graphane as a potential hydrogen storage material
Hussain, Tanveer; De Sarkar, Abir; Ahuja, Rajeev
2012-01-01T23:59:59.000Z
Hydrogen storage capacity, stability, bonding mechanism and the electronic structure of polylithiated molecules (OLi2) functionalized graphane (CH) has been studied by means of first principle density functional theory (DFT). Molecular dynamics (MD) have confirmed the stability, while Bader charge analysis describe the bonding mechanism of OLi2 with CH. The binding energy of OLi2 on CH sheet has been found to be large enough to ensure its uniform distribution without any clustering. It has been found that each OLi2 unit can adsorb up to six H2 molecules resulting into a storage capacity of 12.90 wt% with adsorption energies within the range of practical H2 storage application.
Cox, Stephen J.; Michaelides, Angelos, E-mail: angelos.michaelides@ucl.ac.uk [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom) [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom); Towler, Michael D. [Department of Earth Sciences, University College London Gower Street, London WC1E 6BT (United Kingdom) [Department of Earth Sciences, University College London Gower Street, London WC1E 6BT (United Kingdom); Theory of Condensed Matter Group, Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Alfè, Dario [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom) [Thomas Young Centre and London Centre for Nanotechnology, 17–19 Gordon Street, London WC1H 0AH (United Kingdom); Department of Earth Sciences, University College London Gower Street, London WC1E 6BT (United Kingdom)
2014-05-07T23:59:59.000Z
High quality reference data from diffusion Monte Carlo calculations are presented for bulk sI methane hydrate, a complex crystal exhibiting both hydrogen-bond and dispersion dominated interactions. The performance of some commonly used exchange-correlation functionals and all-atom point charge force fields is evaluated. Our results show that none of the exchange-correlation functionals tested are sufficient to describe both the energetics and the structure of methane hydrate accurately, while the point charge force fields perform badly in their description of the cohesive energy but fair well for the dissociation energetics. By comparing to ice I{sub h}, we show that a good prediction of the volume and cohesive energies for the hydrate relies primarily on an accurate description of the hydrogen bonded water framework, but that to correctly predict stability of the hydrate with respect to dissociation to ice I{sub h} and methane gas, accuracy in the water-methane interaction is also required. Our results highlight the difficulty that density functional theory faces in describing both the hydrogen bonded water framework and the dispersion bound methane.
Berland, Kristian
2013-01-01T23:59:59.000Z
The adsorption of benzene and C60 on graphene and boron nitride (BN) is studied using density functional theory with the non-local correlation functional vdW-DF. By comparing these systems we can systematically investigate their adsorption nature and differences between the two functional versions vdW-DF1 and vdW-DF2. The bigger size of the C60 molecule makes it bind stronger to the surface than benzene, yet the interface between the molecules and the sheets are similar in nature. The binding separation is more sensitive to the exchange variant used in vdW-DF than to the correlation version. This result is related to the exchange and correlation components of the potential energy curve (PEC). We show that a moderate dipole forms for C60 on graphene, unlike for the other adsorption systems. We find that the corrugation is very sensitive to the variant or version of vdW-DF used, in particular the exchange. Further, we show that this sensitivity arise indirectly through the shift in binding separation caused by ...
Einstein M.D. Program 20142015 APPLICANT GUIDE
Emmons, Scott
Einstein M.D. Program 20142015 APPLICANT GUIDE O F Y E S H I V A U N I V E R S I T Y Albert Einstein College of Medicine #12;2 Welcome Explore how Einstein can give you the skills to develop at Einstein. There are 183 students in the first- year class. 8,193 applicants applied for entrance and 1
Masao Iwamatsu; Yutaka Okabe
2010-06-11T23:59:59.000Z
The square-gradient density-functional model with triple-parabolic free energy, that was used previously to study the homogeneous bubble nucleation [J. Chem. Phys. 129, 104508 (2008)], is used to study the stability of the critical bubble nucleated within the bulk under-saturated stretched fluid. The stability of the bubble is studied by solving the Schr\\"odinger equation for the fluctuation. The negative eigenvalue corresponds to the unstable growing mode of the fluctuation. Our results show that there is only one negative eigenvalue whose eigenfunction represents the fluctuation that corresponds to the isotropically growing or shrinking nucleus. In particular, this negative eigenvalue survives up to the spinodal point. Therefore the critical bubble is not fractal or ramified near the spinodal.
Krishtal, Alisa; Genova, Alessandro; Pavanello, Michele
2015-01-01T23:59:59.000Z
Subsystem Density-Functional Theory (DFT) is an emerging technique for calculating the electronic structure of complex molecular and condensed phase systems. In this topical review, we focus on some recent advances in this field related to the computation of condensed phase systems, their excited states, and the evaluation of many-body interactions between the subsystems. As subsystem DFT is in principle an exact theory, any advance in this field can have a dual role. One is the possible applicability of a resulting method in practical calculations. The other is the possibility of shedding light on some quantum-mechanical phenomenon which is more easily treated by subdividing a supersystem into subsystems. An example of the latter is many-body interactions. In the discussion, we present some recent work from our research group as well as some new results, casting them in the current state-of-the-art in this review as comprehensively as possible.
J. M. Yao; L. S. Song; K. Hagino; P. Ring; J. Meng
2015-01-29T23:59:59.000Z
We report a systematic study of nuclear matrix elements (NMEs) in neutrinoless double-beta decays with a 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. The present systematic studies show that in most of the cases there is a much better agreement with the previous non-relativistic calculation based on the Gogny force than in the case of the nucleus $^{150}$Nd found in Song et al. [Phys. Rev. C 90, 054309 (2014)]. In particular, we find that the total NMEs can be well approximated by the pure axial-vector coupling term with a considerable reduction of the computational effort.
Feng, Min [School of Physics, Nankai University, Tianjin 300071 (China); Shao, Bin [Department of Physics, Tsinghua University, Beijing 100084 (China); Lu, Yuan; Zuo, Xu, E-mail: xzuonku@gmail.com [College of Electronic Information and Optical Engineering, Nankai University, Tianjin 300071 (China)
2014-05-07T23:59:59.000Z
The exchange integrals in magnetoelectric hexagonal ferrite SrCo{sub 2}Ti{sub 2}Fe{sub 8}O{sub 19} have been calculated by using density functional theory. To get 10 inter-sublattice and 3 intra-sublattice exchange integrals, the electronic structures and total energies of 20 spin arrangements have been calculated with General Gradient Approximation (GGA) + U method. The dependence of exchange integrals on U has been studied. The comparison between the exchange integrals in SrFe{sub 12}O{sub 19} and those in SrCo{sub 2}Ti{sub 2}Fe{sub 8}O{sub 19} shows that substitution of Co and Ti decreases the most interactions involving the 12?k sites. The investigation based on our exchange integrals indicates that magnetic interaction between R and S blocks reduces significantly in SrCo{sub 2}Ti{sub 2}Fe{sub 8}O{sub 19}.
Adam P. Hughes; Uwe Thiele; Andrew J. Archer
2015-01-28T23:59:59.000Z
The contribution to the free energy for a film of liquid of thickness $h$ on a solid surface, due to the interactions between the solid-liquid and liquid-gas interfaces is given by the binding potential, $g(h)$. The precise form of $g(h)$ determines whether or not the liquid wets the surface. Note that differentiating $g(h)$ gives the Derjaguin or disjoining pressure. We develop a microscopic density functional theory (DFT) based method for calculating $g(h)$, allowing us to relate the form of $g(h)$ to the nature of the molecular interactions in the system. We present results based on using a simple lattice gas model, to demonstrate the procedure. In order to describe the static and dynamic behaviour of non-uniform liquid films and drops on surfaces, a mesoscopic free energy based on $g(h)$ is often used. We calculate such equilibrium film height profiles and also directly calculate using DFT the corresponding density profiles for liquid drops on surfaces. Comparing quantities such as the contact angle and also the shape of the drops, we find good agreement between the two methods. We also study in detail the effect on $g(h)$ of truncating the range of the dispersion forces, both those between the fluid molecules and those between the fluid and wall. We find that truncating can have a significant effect on $g(h)$ and the associated wetting behaviour of the fluid.
Duguet, T; Ebran, J -P; Lesinski, T; Somà, V
2015-01-01T23:59:59.000Z
This programmatic paper lays down the possibility to reconcile the necessity to resum many-body correlations into the energy kernel with the fact that safe multi-reference energy density functional (EDF) calculations cannot be achieved whenever the Pauli principle is not strictly enforced, as is for example the case when many-body correlations are parametrized under the form of empirical density dependencies. Our proposal is to exploit a newly developed ab initio many-body formalism to guide the construction of safe, explicitly correlated and systematically improvable parametrizations of the {\\it off-diagonal} energy and norm kernels that lie at the heart of the nuclear EDF method. The many-body formalism of interest relies on the concepts of symmetry breaking {\\it and} restoration that have made the fortune of the nuclear EDF method and is, as such, amenable to this guidance. After elaborating on our proposal, we briefly outline the project we plan to execute in the years to come.
T. Duguet; M. Bender; J. -P. Ebran; T. Lesinski; V. Somà
2015-02-12T23:59:59.000Z
This programmatic paper lays down the possibility to reconcile the necessity to resum many-body correlations into the energy kernel with the fact that safe multi-reference energy density functional (EDF) calculations cannot be achieved whenever the Pauli principle is not strictly enforced, as is for example the case when many-body correlations are parametrized under the form of empirical density dependencies. Our proposal is to exploit a newly developed ab initio many-body formalism to guide the construction of safe, explicitly correlated and systematically improvable parametrizations of the {\\it off-diagonal} energy and norm kernels that lie at the heart of the nuclear EDF method. The many-body formalism of interest relies on the concepts of symmetry breaking {\\it and} restoration that have made the fortune of the nuclear EDF method and is, as such, amenable to this guidance. After elaborating on our proposal, we briefly outline the project we plan to execute in the years to come.
Duan, Yuhua; Zhang, Bo; Sorescu, Dan C.; Johnson, Karl; Majzoub, Eric H; Luebke, David R.
2012-07-01T23:59:59.000Z
The structural, electronic, phonon dispersion and thermodynamic properties of MHCO3 (M D Li, Na, K) solids were investigated using density functional theory. The calculated bulk properties for both their ambient and the high-pressure phases are in good agreement with available experimental measurements. Solid phase LiHCO3 has not yet been observed experimentally. We have predicted several possible crystal structures for LiHCO3 using crystallographic database searching and prototype electrostatic ground state modeling. Our total energy and phonon free energy .FPH/ calculations predict that LiHCO3 will be stable under suitable conditions of temperature and partial pressures of CO2 and H2O. Our calculations indicate that the HCO 3 groups in LiHCO3 and NaHCO3 form an infinite chain structure through O#1; #1; #1;H#1; #1; #1;O hydrogen bonds. In contrast, the HCO 3 anions form dimers, .HCO 3 /2, connected through double hydrogen bonds in all phases of KHCO3. Based on density functional perturbation theory, the Born effective charge tensor of each atom type was obtained for all phases of the bicarbonates. Their phonon dispersions with the longitudinal optical–transverse optical splitting were also investigated. Based on lattice phonon dynamics study, the infrared spectra and the thermodynamic properties of these bicarbonates were obtained. Over the temperature range 0–900 K, the FPH and the entropies (S) of MHCO3 (M D Li, Na, K) systems vary as FPH.LiHCO3/ > FPH.NaHCO3/ > FPH.KHCO3/ and S.KHCO3/ > S.NaHCO3/ > S.LiHCO3/, respectively, in agreement with the available experimental data. Analysis of the predicted thermodynamics of the CO2 capture reactions indicates that the carbonate/bicarbonate transition reactions for Na and K could be used for CO2 capture technology, in agreement with experiments.
Rappe, Andrew M.
Hybrid density functional calculations of the band gap of GaxIn1-xN Xifan Wu,1 Eric J. Walter,2 Andrew M. Rappe,3 Roberto Car,1 and Annabella Selloni1 1Chemistry Department, Princeton University Recent theoretical work has provided evidence that hybrid functionals, which include a fraction of exact
Venturi, D. [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States)] [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States); Karniadakis, G.E., E-mail: george_karniadakis@brown.edu [Division of Applied Mathematics, Brown University, Providence, RI 02912 (United States)
2012-08-30T23:59:59.000Z
By using functional integral methods we determine new evolution equations satisfied by the joint response-excitation probability density function (PDF) associated with the stochastic solution to first-order nonlinear partial differential equations (PDEs). The theory is presented for both fully nonlinear and for quasilinear scalar PDEs subject to random boundary conditions, random initial conditions or random forcing terms. Particular applications are discussed for the classical linear and nonlinear advection equations and for the advection-reaction equation. By using a Fourier-Galerkin spectral method we obtain numerical solutions of the proposed response-excitation PDF equations. These numerical solutions are compared against those obtained by using more conventional statistical approaches such as probabilistic collocation and multi-element probabilistic collocation methods. It is found that the response-excitation approach yields accurate predictions of the statistical properties of the system. In addition, it allows to directly ascertain the tails of probabilistic distributions, thus facilitating the assessment of rare events and associated risks. The computational cost of the response-excitation method is order magnitudes smaller than the one of more conventional statistical approaches if the PDE is subject to high-dimensional random boundary or initial conditions. The question of high-dimensionality for evolution equations involving multidimensional joint response-excitation PDFs is also addressed.
Universal Nuclear Energy Density Functional
Carlson, Joseph; Furnstahl, Richard; Horoi, Mihai; Lusk, Rusty; Nazarewicz, Witold; Ng, Esmond; Thompson, Ian; Vary, James
2012-12-01T23:59:59.000Z
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. Until recently such an undertaking was hard to imagine, and even at the present time such an ambitious endeavor would be far beyond what a single researcher or a traditional research group could carry out.
Nehorai, Arye
Brain-Computer Interfaces in Medicine Jerry J. Shih, MD; Dean J. Krusienski, PhD; and Jonathan R. Wolpaw, MD Abstract Brain-computer interfaces (BCIs) acquire brain signals, analyze them, and translate, electrocorticographic, and other brain signals for increasingly complex control of cursors, robotic arms, prostheses
Carmichael, Owen
UC Davis-LLNL Scientific Advisory Committee Timothy Albertson, MD, PhD, Vice Chair, Internal Berglund, MD, PhD, CTSC Program Director Stuart Cohen, MD, Head of Infection Control, UCDMC Jeffrey Elias, PhD, Manager, Grant Coordination **Captain** Hernando Garzon, MD, Emergency Medicine, Kaiser Jeffrey
DOE - Office of Legacy Management -- Johns Hopkins University - MD 02
Office of Legacy Management (LM)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625 1,006 492 742EnergyOn AprilA group currentBradleyTable ofArizonaBuffaloJohns Hopkins University - MD 02 FUSRAP
Boyer, Edmond
physical properties. Because the soil compaction depends on its water content, bulk density and texture was obtained between soil precompression stress, compression index, initial water content, initial bulk density, 1994). Thus, knowing the changes in soil compaction with changes in water content and bulk density
N. Vonta; G. A. Souliotis; M. Veselsky; A. Bonasera
2015-06-16T23:59:59.000Z
The microscopic description of nuclear fission still remains a topic of intense basic research. Un- derstanding nuclear fission, apart from a theoretical point of view, is of practical importance for energy production and the transmutation of nuclear waste. In nuclear astrophysics, fission sets the upper limit to the nucleosynthesis of heavy elements via the r-process. In this work we initiated a systematic study of intermediate energy proton-induced fission using the Constrained Molecu- lar Dynamics (CoMD) code. The CoMD code implements an effective interaction with a nuclear matter compressibility of K=200 (soft EOS) with several forms of the density dependence of the nucleon-nucleon symmetry potential. Moreover, a constraint is imposed in the phase-space occu- pation for each nucleon restoring the Pauli principle at each time step of the collision. A proper choice of the surface parameter of the effective interaction has been made to describe fission. In this work, we present results of fission calculations for proton-induced reactions on : a) 232 Th at 27 and 63 MeV, b) 235 U at 10, 30, 60 and 100 MeV, and c) 238 U at 100 and 660 MeV. The calculated observables include fission-fragment mass distributions, total fission energies, neutron multiplicities and fission times. These observables are compared to available experimental data. We show that the microscopic CoMD code is able to describe the complicated many-body dynamics of the fission process at intermediate and high energy and give a reasonable estimate of the fission time scale. Sensitivity of the results to the density dependence of the nucleon symmetry potential (and, thus, the nuclear symmetry energy) is found. Further improvements of the code are necessary to achieve a satisfactory description of low energy fission in which shell effects play a dominant role.
Chakraborty, N. [Engineering Department, University of Liverpool, Brownlow Hill, Liverpool L69 3GH (United Kingdom); Hawkes, E.R. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Chen, J.H. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551 (United States); Cant, R.S. [Engineering Department, Cambridge University, Trumpington Street, Cambridge CB2 1PZ (United Kingdom)
2008-07-15T23:59:59.000Z
The effects of tangential strain rate and curvature on the surface density function (SDF) and on source terms within the SDF transport equation are studied for lean methane-air and hydrogen-air flames using two-dimensional direct numerical simulations with detailed chemistry. A positive correlation is observed between the SDF and the tangential strain rate, and this is explained in terms of the interaction between the local tangential strain rate and the dilatation rate due to heat release. Curvature is also seen to affect the SDF through the curvature response of both tangential strain rate and dilatation rate on a given flame isosurface. Strain rate and curvature are found to have an appreciable effect on several terms of the SDF transport equation. The SDF straining term in both methane and hydrogen flames is correlated positively with tangential strain rate, as expected, and is also correlated negatively with curvature. For methane flames, the SDF propagation term is found to correlate negatively with flame curvature toward the reactant side of the flame and positively toward the product side. By contrast, for hydrogen flames the SDF propagation term is negatively correlated with curvature throughout the flame brush. The variation of the SDF curvature term with local flame curvature for both methane and hydrogen flames is found to be nonlinear due to the additional stretch induced by the tangential diffusion component of the displacement speed. Physical explanations are provided for all of these effects, and the modeling implications are considered in detail. (author)
Mei, H; Yao, J M; Motoba, T
2015-01-01T23:59:59.000Z
We present a detailed formalism of the microscopic particle-rotor model for hypernuclear low-lying states based on a covariant density functional theory. In this method, the hypernuclear states are constructed by coupling a hyperon to low-lying states of the core nucleus, which are described by the generator coordinate method (GCM) with the particle number and angular momentum projections. We apply this method to study in detail the low-lying spectrum of $^{13}_{~\\Lambda}$C and $^{21}_{~\\Lambda}$Ne hypernuclei. We also briefly discuss the structure of $^{155}_{~~\\Lambda}$Sm as an example of heavy deformed hypernuclei. It is shown that the low-lying excitation spectrum with positive parity states of the hypernuclei, which are dominated by $\\Lambda$ hyperon in $s$-orbital coupled to the core states, are similar to that for the corresponding core states, while the electric quadrupole transition strength, $B(E2)$, from the 2$^+_1$ state to the ground state is reduced according to the mass number of the hypernucle...
Hu, Shenyang Y.; Setyawan, Wahyu; Van Ginhoven, Renee M.; Jiang, Weilin; Henager, Charles H.; Kurtz, Richard J.
2014-02-20T23:59:59.000Z
Density functional theory (DFT) is used to calculate the thermodynamic and kinetic properties of transmutant Mg in 3C-SiC due to high-energy neutron irradiation associated with the fusion nuclear environment. The formation and binding energies of intrinsic defects, Mg-related defects, and clusters in 3C-SiC are systematically calculated. The minimum energy paths and activation energies during point defect migration and small cluster evolution are studied using a generalized solid-state elastic band (G-SSNEB) method with DFT energy calculations. Stable defect structures and possible defect migration mechanisms are identified. The evolution of binding energies during Mg2Si formation demonstrates that the formation of Mg2Si needs to overcome a critical nucleus size and nucleation barrier. It is also found that a compressive stress field exists around the Mg2Si nucleus. These data are important inputs in meso- and macro-scale modeling and experiments to understand and predict the impact of Mg on phase stability, microstructure evolution, and performance of SiC and SiC-based materials during long-term neutron exposures.
Silvestrelli, Pier Luigi
2015-01-01T23:59:59.000Z
The DFT/vdW-WF2s1 method, recently developed to include the van der Waals interactions in the Density Functional Theory and describe adsorption processes on metal surfaces by taking metal-screening effects into account, is applied to the case of the interaction of Xe and graphene with a transition-metal surface, namely Ni(111). In general the adsorption of rare-gas atoms on metal surfaces is important because is prototypical for physisorption processes. Moreover, the interaction of graphene with Ni(111) is of particular interest for practical applications (efficient and large-scale production of high-quality graphene) and, from a theoretical point of view, is particularly challenging, since it can be described by a delicate interplay between chemisorption and physisorption processes. The first-principles simulation of transition metals require particular care also because they can be viewed as intermediate systems between simple metals and insulating crystals. Even in these cases the method performs well as d...
Xue, H. T.; Tang, F. L., E-mail: tfl03@mails.tsinghua.edu.cn [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Department of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Science and Technology on Surface Engineering Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China); Lu, W. J.; Li, X. K.; Zhang, Y. [State Key Laboratory of Advanced Processing and Recycling of Non-ferrous Metals, Department of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050 (China); Feng, Y. D. [Science and Technology on Surface Engineering Laboratory, Lanzhou Institute of Physics, Lanzhou 730000 (China)
2014-08-07T23:59:59.000Z
The phase diagram of the CuInSe{sub 2}-CuGaSe{sub 2} pseudobinary system was determined using a combination of special quasirandom structure approach, ab initio density functional theory calculations, and thermodynamic modelling. It is shown that the CuIn{sub 1?x}Ga{sub x}Se{sub 2} solution phase has a tendency to phase separation at low temperature. The calculated consolute temperature is 485?K. It is found that both the binodal and spinodal curves are significantly asymmetric and on both curves there are a local maximum and a local minimum, which have not been reported in the previous studies. Our phase diagram can well explain the finding that the inhomogeneity of CuIn{sub 0.25}Ga{sub 0.75}Se{sub 2} is higher than that of CuIn{sub 0.75}Ga{sub 0.25}Se{sub 2} at the same temperature, while the previous phase diagrams cannot. Hence, our phase diagram should be more reliable and applicable.
Masao Iwamatsu
2009-04-04T23:59:59.000Z
The generic square-gradient density-functional model with triple-parabolic free energy is used to study the stability of a cavity introduced into the stretched liquid. The various properties of the critical cavity, which is the largest stable cavity within the liquid, are compared with those of the critical bubble of the homogeneous bubble nucleation. It is found that the size of the critical cavity is always smaller than that of the critical bubble, while the work of formation of the former is always higher than the latter in accordance with the conjectures made by Punnathanam and Corti [J. Chem. Phys. {\\bf 119}, 10224 (2003)] deduced from the Lennard-Jones fluids. Therefore their conjectures about the critical cavity size and the work of formation would be more general and valid even for other types of liquid such as metallic liquid or amorphous. However, the scaling relations they found for the critical cavity in the Lennard-Jones fluid are marginally satisfied only near the spinodal.
Minezawa, Noriyuki, E-mail: minezawa@fukui.kyoto-u.ac.jp [Fukui Institute for Fundamental Chemistry, Kyoto University, Sakyo-ku, Kyoto 606-8103 (Japan)
2014-10-28T23:59:59.000Z
Examining photochemical processes in solution requires understanding the solvent effects on the potential energy profiles near conical intersections (CIs). For that purpose, the CI point in solution is determined as the crossing between nonequilibrium free energy surfaces. In this work, the nonequilibrium free energy is described using the combined method of linear-response free energy and collinear spin-flip time-dependent density functional theory. The proposed approach reveals the solvent effects on the CI geometries of stilbene in an acetonitrile solution and those of thymine in water. Polar acetonitrile decreases the energy difference between the twisted minimum and twisted-pyramidalized CI of stilbene. For thymine in water, the hydrogen bond formation stabilizes significantly the CI puckered at the carbonyl carbon atom. The result is consistent with the recent simulation showing that the reaction path via this geometry is open in water. Therefore, the present method is a promising way of identifying the free-energy crossing points that play an essential role in photochemistry of solvated molecules.
Bisetti, Fabrizio [246 Hesse Hall, Mailstop 1740, Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740 (United States); Chen, J.-Y. [Department of Mechanical Engineering, University of California at Berkeley, Berkeley, CA 94720-1740 (United States); Hawkes, Evatt R. [School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, NSW 2052 (Australia); Chen, Jacqueline H. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94551-9051 (United States)
2008-12-15T23:59:59.000Z
Homogeneous charge compression ignition (HCCI) engine technology promises to reduce NO{sub x} and soot emissions while achieving high thermal efficiency. Temperature and mixture stratification are regarded as effective means of controlling the start of combustion and reducing the abrupt pressure rise at high loads. Probability density function methods are currently being pursued as a viable approach to modeling the effects of turbulent mixing and mixture stratification on HCCI ignition. In this paper we present an assessment of the merits of three widely used mixing models in reproducing the moments of reactive scalars during the ignition of a lean hydrogen/air mixture ({phi}=0.1, p=41atm, and T=1070 K) under increasing temperature stratification and subject to decaying turbulence. The results from the solution of the evolution equation for a spatially homogeneous joint PDF of the reactive scalars are compared with available direct numerical simulation (DNS) data [E.R. Hawkes, R. Sankaran, P.P. Pebay, J.H. Chen, Combust. Flame 145 (1-2) (2006) 145-159]. The mixing models are found able to quantitatively reproduce the time history of the heat release rate, first and second moments of temperature, and hydroxyl radical mass fraction from the DNS results. Most importantly, the dependence of the heat release rate on the extent of the initial temperature stratification in the charge is also well captured. (author)
Tawa, G.J.; Martin, R.L.; Pratt, L.R.; Russo, T.V. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States)
1996-02-01T23:59:59.000Z
Electrostatic solvation free energies are calculated using a self consistent reaction field (SCRF) procedure that combines a continuum dielectric model of the solvent with both Hartree-Fock (HF) and density functional theory (DFT) for the solute. Several molecules are studied in aqueous solution. They comprise three groups: nonpolar neutral, polar neutral, and ionic. The calculated values of {Delta}G{sup e1} are sensitive to the atomic radii used to define the solute molecular surface, particularly to the value of the hydrogen radius. However, the values of {Delta}G{sup e1} exhibit reasonable correlation with experiment when a previously determined, physically motivated set of atomic radii were used to define the van der Waals surface of the solute. The standard deviation between theory and experiment is 2.51 kcal/mol for HF and 2.21 kcal/mol for DFT for the 14 molecules examined. The errors with HF or DFT are similar. The relative difference between the calculated values of {Delta}G{sup e1} and experiment is largest for nonpolar neutral molecules, intermediate for polar neutral molecules, and smallest for ions. This is consistent with the expected relative importance of nonelectrostatic contributions to the free energy that are omitted in the model. 92 refs., 4 figs., 6 tabs.
Nakata, Ayako; Tsuneda, Takao; Hirao, Kimihiko [Advanced Science Institute, RIKEN, Wako 351-0198 (Japan); CREST, Japan Science and Technology Agency, Kawaguchi 332-0012 (Japan)
2011-12-14T23:59:59.000Z
A long-range corrected (LC) time-dependent density functional theory (TDDFT) incorporating relativistic effects with spin-orbit couplings is presented. The relativistic effects are based on the two-component zeroth-order regular approximation Hamiltonian. Before calculating the electronic excitations, we calculated the ionization potentials (IPs) of alkaline metal, alkaline-earth metal, group 12 transition metal, and rare gas atoms as the minus orbital (spinor) energies on the basis of Koopmans' theorem. We found that both long-range exchange and spin-orbit coupling effects are required to obtain Koopmans' IPs, i.e., the orbital (spinor) energies, quantitatively in DFT calculations even for first-row transition metals and systems containing large short-range exchange effects. We then calculated the valence excitations of group 12 transition metal atoms and the Rydberg excitations of rare gas atoms using spin-orbit relativistic LC-TDDFT. We found that the long-range exchange and spin-orbit coupling effects significantly contribute to the electronic spectra of even light atoms if the atoms have low-lying excitations between orbital spinors of quite different electron distributions.
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Yamaoka, Hitoshi; Jarrige, Ignace; Schwier, Eike F.; Arita, Masashi; Shimada, Kenya; Tsujii, Naohito; Jiang, Jian; Hayashi, Hirokazu; Iwasawa, Hideaki; Namatame, Hirofumi; et al
2015-03-01T23:59:59.000Z
The electronic structure of Ce?Pd??X? (X = Si, Ge) has been studied using detailed density functional theory (DFT) calculations and high-resolution photoelectron spectroscopy (PES) measurements. The orbital decomposition of the electronic structure by DFT calculations indicates that Ce atoms at the (8c) site surrounded by 16 Pd atoms have a more localized nature and a tendency to be magnetic. Ce atoms in the (4a) site surrounded by 12 Pd and 6 X atoms, on the other, show only a negligible magnetic moment. In the photoemission valence-band spectra we observe a strong f? (Ce??) component with a small fraction of f¹more »(Ce³?) component. The spectral weight of f¹ component near the Fermi level Ce?Pd??Si? is stronger than that for Ce?Pd??Ge? at the 4d-4f resonance, suggesting stronger c-f hybridization in the former. This may hint to the origin of the large electronic specific coefficient of Ce?Pd??Si? compared to Ce?Pd??Ge?.« less
Baer, Marcel D.; Kuo, I-F W.; Tobias, Douglas J.; Mundy, Christopher J.
2014-07-17T23:59:59.000Z
The propensities of the water self ions, H3O+ and OH- , for the air-water interface has implications for interfacial acid-base chemistry. Despite numerous experimental and computational studies, no consensus has been reached on the question of whether or not H3O+ and/or OH- prefer to be at the water surface or in the bulk. Here we report a molecular dynamics simulation study of the bulk vs. interfacial behavior of H3O+ and OH- that employs forces derived from density functional theory with a generalized gradient approximation exchangecorrelation functional (specifically, BLYP) and empirical dispersion corrections. We computed the potential of mean force (PMF) for H3O+ as a function of the position of the ion in a 215-molecule water slab. The PMF is flat, suggesting that H3O+ has equal propensity for the air-water interface and the bulk. We compare the PMF for H3O+ to our previously computed PMF for OH- adsorption, which contains a shallow minimum at the interface, and we explore how differences in solvation of each ion at the interface vs. the bulk are connected with interfacial propensity. We find that the solvation shell of H3O+ is only slightly dependent on its position in the water slab, while OH- partially desolvates as it approaches the interface, and we examine how this difference in solvation behavior is manifested in the electronic structure and chemistry of the two ions. DJT was supported by National Science Foundation grant CHE-0909227. CJM was supported by the U.S. Department of Energy‘s (DOE) Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory (PNNL) is operated for the Department of Energy by Battelle. The potential of mean force required resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DEAC05-00OR22725. The remaining simulations and analysis used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. at at Lawrence Berkeley National Laboratory. MDB is grateful for the support of the Linus Pauling Distinguished Postdoctoral Fellowship Program at PNNL.
G. G. Kozlov
2008-03-13T23:59:59.000Z
We solve exactly the spectral problem for the non-Hermitian operator $H_U f(x)\\equiv f(U-1/x)/x^2$. Despite the absence of orthogonality, the eigen functions of this operator allow one to construct in a simple way the expansion of an arbitrary function in series. Explicit formulas for the expansion coefficients are presented. This problem is shown to be connected with that of calculating the strange attractor's density for the map $x_{n+1}=1/(U-x_n)$. The explicit formula for the strange attractor's density for this map is derived. All results are confirmed by direct computer simulations.
Li, Li; Zhang, Guo; Chen, Lei [Key Laboratory of Chemical Engineering Process and Technology for High-efficiency Conversion, College of Heilongjiang Province, Heilongjiang University, Harbin 150080 (China)] [Key Laboratory of Chemical Engineering Process and Technology for High-efficiency Conversion, College of Heilongjiang Province, Heilongjiang University, Harbin 150080 (China); Bi, Hong-Mei [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China)] [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China); Shi, Ke-Ying, E-mail: shikeying2008@yahoo.cn [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China)] [Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin 150080 (China)
2013-02-15T23:59:59.000Z
Graphical abstract: The Ni(NiO)/semiconducting single-walled carbon nanotubes composite collected from the cathode after electro-deposition shows a high sensitivity to low-concentration NO gas at room temperature (18 °C). Display Omitted Highlights: ? Ni(NiO) nanoparticles were deposited on semiconducting SWCNTs by electro-deposition. ? Ni(NiO)/semiconducting SWCNTs film shows a high sensitivity to NO gas at 18 °C. ?Theoretical calculation reveals electron transfer from SWCNTs to NO via Ni. -- Abstract: Single-walled carbon nanotubes which contains metallic SWCNTs (m-SWCNTs) and semiconducting SWCNTs (s-SWCNTs) have been obtained under electric arc discharge. Their separation can be effectively achieved by the electro-deposition method. The Ni(NiO)/s-SWCNTs composite was found on cathode where Ni was partially oxidized to NiO at ambient condition with Ni(NiO) nanoparticles deposited uniformly on the bundles of SWCNTs. These results were confirmed by Raman spectra, transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–vis–NIR and TG characterizations. Furthermore, investigation of the gas sensing property of Ni(NiO)/s-SWCNTs composite film to NO gas at 18 °C demonstrated the sensitivity was approximately 5% at the concentration of 97 ppb. Moreover, density functional theory (DFT) calculations were performed to explore the sensing mechanism which suggested the adsorption of NO molecules onto the composite through N–Ni interaction as well as the proposition of electron transfer mechanisms from SWCNTs to NO via the Ni medium.
Mutombo, P.; Romanyuk, O., E-mail: romanyuk@fzu.cz [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 16200 Prague (Czech Republic)
2014-05-28T23:59:59.000Z
The atomic structures of non-polar GaN(101{sup ¯}0),?(112{sup ¯}0) and semipolar GaN(202{sup ¯}1),?(202{sup ¯}1{sup ¯}) surfaces were studied using ab initio calculations within density functional theory. The bulk-like truncated (1?×?1) structure with buckled Ga-N or Ga-Ga dimers was found stable on the non-polar GaN(101{sup ¯}0) surface in agreement with previous works. Ga-N heterodimers were found energetically stable on the GaN(112{sup ¯}0)-(1?×?1) surface. The formation of vacancies and substitution site defects was found unfavorable for non-polar GaN surfaces. Semipolar GaN(202{sup ¯}1)-(1?×?1) surface unit cells consist of non-polar (101{sup ¯}0) and semipolar (101{sup ¯}1) nano-facets. The (101{sup ¯}1) nano-facets consist of two-fold coordinated atoms, which form N-N dimers within a (2?×?1) surface unit cell on a GaN(202{sup ¯}1) surface. Dimers are not formed on the GaN(202{sup ¯}1{sup ¯}) surface. The stability of the surfaces with single (101{sup ¯}0) or (101{sup ¯}1) nano-facets was analyzed. A single non-polar (101{sup ¯}0)-(1?×?1) nano-facet was found stable on the GaN(202{sup ¯}1) surface, but unstable on the GaN(202{sup ¯}1{sup ¯}) surface. A single (101{sup ¯}1) nano-facet was found unstable. Semipolar GaN surfaces with (202{sup ¯}1) and (202{sup ¯}1{sup ¯}) polarity can be stabilized with a Ga overlayer at Ga-rich experimental conditions.
Rocca, Jorge J.
Partial Oxidation of Propylene Catalyzed by VO3 Clusters: A Density Functional Theory Study Zhe are carried out to investigate partial oxidation of propylene over neutral VO3 clusters. CdC bond cleavage of propylene with VO3 at room temperature. Formation of hydrogen transfer products H2O + VO2C3H4, CH2d
Duan, Yuhua; Parlinski, K.
2011-01-01T23:59:59.000Z
The structural, electronic, lattice dynamical, optical, thermodynamic, and CO{sub 2} capture properties of monoclinic and triclinic phases of Li{sub 4}SiO{sub 4} are investigated by combining density functional theory with phonon lattice dynamics calculations. We found that these two phases have some similarities in their bulk and thermodynamic properties. The calculated bulk modulus and the cohesive energies of these two phases are close to each other. Although both of them are insulators, the monoclinic phase of Li{sub 4}SiO{sub 4} has a direct band gap of 5.24 eV while the triclinic Li{sub 4}SiO{sub 4} phase has an indirect band gap of 4.98 eV. In both phases of Li{sub 4}SiO{sub 4}, the s orbital of O mainly contributes to the lower-energy second valence band (VB{sub 2}) and the p orbitals contribute to the fist valence band (VB{sub 1}) and the conduction bands (CBs). The s orbital of Si mainly contributes to the lower portions of the VB1 and VB{sub 2}, and Si p orbitals mainly contribute to the higher portions of the VB{sub 1} and VB{sub 2}. The s and p orbitals of Li contribute to both VBs and to CBs, and Li p orbitals have a higher contribution than the Li s orbital. There is possibly a phonon soft mode existing in triclinic {gamma}-Li{sub 4}SiO{sub 4}; in the monoclinic Li{sub 4}SiO{sub 4}, there are three phonon soft modes, which correspond to the one type of Li disordered over a few sites. Their LO-TO splitting indicates that both phases of Li{sub 4}SiO{sub 4} are polar anisotropic materials. The calculated infrared absorption spectra for LO and TO modes are different for these two phases of Li{sub 4}SiO{sub 4}. The calculated relationships of the chemical potential versus temperature and CO{sub 2} pressure for reaction of Li{sub 4}SiO{sub 4} with CO{sub 2} shows that Li{sub 4}SiO{sub 4} could be a good candidate for a high-temperature CO{sub 2} sorbent while used for postcombustion capture technology.
Canonical density matrix perturbation theory
Niklasson, Anders M N; Rubensson, Emanuel H; Rudberg, Elias
2015-01-01T23:59:59.000Z
Density matrix perturbation theory [Niklasson and Challacombe, Phys. Rev. Lett. 92, 193001 (2004)] is generalized to canonical (NVT) free energy ensembles in tight-binding, Hartree-Fock or Kohn-Sham density functional theory. The canonical density matrix perturbation theory can be used to calculate temperature dependent response properties from the coupled perturbed self-consistent field equations as in density functional perturbation theory. The method is well suited to take advantage of sparse matrix algebra to achieve linear scaling complexity in the computational cost as a function of system size for sufficiently large non-metallic materials and metals at high temperatures.
DFT-MD approach to TiO2/liquid interface systems for photocatalysis and dye-sensitised solar cell
Katsumoto, Shingo
DFT-MD approach to TiO2/liquid interface systems for photocatalysis and dye-sensitised solar cell- namics (MD) analysis of TiO2/solution in- terfaces related to photocatalysis and dye- sensitized solar
Valero-Cuevas, Francisco
@chla.usc.edu (323) 3612265 Alan B. Lewis, M.D. Vice Chair, Committee on Clinical Investigations alewis Deirdre Anglin, MD ViceChair, IRB Email: anglin@usc.edu Phone: (323) 2232340 Robert Larsen, MD Vice
2012-01-01T23:59:59.000Z
density profile of the inner 0.5 pc of the Milky Way nuclearold) stars in the central 0.5 pc of the Milky Way nucleara factor of 3 radially out to 0.5 pc from Sgr A* along the
Vehicle Technologies Office Merit Review 2015: Cummins MD & HD Accessory Hybridization CRADA
Broader source: Energy.gov [DOE]
Presentation given by Oak Ridge National Laboratory at 2015 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about Cummins MD &...
Vehicle Technologies Office Merit Review 2014: Cummins MD & HD Accessory Hybridization CRADA
Broader source: Energy.gov [DOE]
Presentation given by Oak Ridge National Laboratory at 2014 DOE Hydrogen and Fuel Cells Program and Vehicle Technologies Office Annual Merit Review and Peer Evaluation Meeting about Cummins MD &...
Andrea E. Reid, M.D., M.P.H. INFORMATION
Goodrich, Lisa V.
to practice State: District of Columbia License No: MD038392 Initial Date: 01/01/2011 Renewal/Expiration Date Providence, RI 02912 9/1980-6/1984 ScB with Honors, Psychology Medical Education: Harvard Medical School 25
Boutaba, Raouf
, Sheikh Iqbal Ahamed, Md. Mostofa Akbar Department of Computer Science and Engineering, Bangladesh.com, sheikh.ahamed@mu.edu, mostofa@cse.buet.ac.bd Abstract. Health monitoring is repeatedly mentioned as one
Catharine Whiteside, MD PhD Vice Provost, Relations with Health Care Institutions
Zandstra, Peter W.
Catharine Whiteside, MD PhD Dean Vice Provost, Relations with Health Care Institutions Office. Professor Andrews received her PhD from the University of Toronto and completed further training
Feng, wanxiang [Chinese Academy of Sciences; Xiao, Di [ORNL; Zhang, Ying [Beijing Normal University; Yao, yugui [Chinese Academy of Sciences
2010-01-01T23:59:59.000Z
We systematically investigate the topological band structures of half-Heusler compounds using first- principles calculations. The modified Becke-Johnson exchange potential together with local-density approxi- mation for the correlation potential MBJLDA has been used here to obtain accurate band inversion strength and band order. Our results show that a large number of half-Heusler compounds are candidates for three- dimensional topological insulators. The difference between band structures obtained using the LDA and MB- JLDA potential is also discussed.
Leroy, Frédéric, E-mail: f.leroy@theo.chemie.tu-darmstadt.de; Böhm, Michael C., E-mail: boehm@theo.chemie.tu-darmstadt.de [Eduard-Zintl-Institut für Anorganische und Physikalische Chemie, Technische Universität Darmstadt, D-64287 Darmstadt (Germany); Schulte, Joachim [Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten (Germany)] [Bruker Biospin GmbH, Silberstreifen, D-76287 Rheinstetten (Germany); Balasubramanian, Ganesh [Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)] [Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)
2014-04-14T23:59:59.000Z
We report reverse nonequilibrium molecular dynamics calculations of the thermal conductivity of isotope substituted (10,10) carbon nanotubes (CNTs) at 300 K. {sup 12}C and {sup 14}C isotopes both at 50% content were arranged either randomly, in bands running parallel to the main axis of the CNTs or in bands perpendicular to this axis. It is found that the systems with randomly distributed isotopes yield significantly reduced thermal conductivity. In contrast, the systems where the isotopes are organized in patterns parallel to the CNTs axis feature no reduction in thermal conductivity when compared with the pure {sup 14}C system. Moreover, a reduction of approximately 30% is observed in the system with the bands of isotopes running perpendicular to the CNT axis. The computation of phonon dispersion curves in the local density approximation and classical densities of vibrational states reveal that the phonon structure of carbon nanotubes is conserved in the isotope substituted systems with the ordered patterns, yielding high thermal conductivities in spite of the mass heterogeneity. In order to complement our conclusions on the {sup 12}C-{sup 14}C mixtures, we computed the thermal conductivity of systems where the {sup 14}C isotope was turned into pseudo-atoms of 20 and 40 atomic mass units.
Vazquez-Mayagoitia, Alvaro [ORNL; Sherrill, David [Georgia Institute of Technology; Apra, Edoardo [ORNL; Sumpter, Bobby G [ORNL
2010-01-01T23:59:59.000Z
A recently proposed double-hybrid functional called XYG3 and a semilocal GGA functional (B97-D) with a semiempirical correction for van der Waals interactions have been applied to study the potential energy curves along the dissociation coordinates of weakly bound pairs of molecules governed by London dispersion and induced dipole forces. Molecules treated in this work were the parallel sandwich, T-shaped, and parallel-displaced benzene dimer, (C6H6)2; hydrogen sulfide and benzene, H2S C6H6; methane and benzene, CH4 C6H6; the methane dimer, (CH4)2; and the pyridine dimer, (C5H5N)2. We compared the potential energy curves of these functionals with previously published benchmarks at the coupled cluster singles, doubles, and perturbative triplets [CCSD(T)] complete-basis-set limit. Both functionals, XYG3 and B97-D, exhibited very good performance, reproducing accurate energies for equilibrium distances and a smooth behavior along the dissociation coordinate. Overall, we found an agreement within a few tenths of one kcal mol-1 with the CCSD(T) results across the potential energy curves.
Strain induced lithium functionalized graphane as a high capacity hydrogen storage material
Hussain, Tanveer; Ahuja, Rajeev
2012-01-01T23:59:59.000Z
Strain effects on the stability, electronic structure, and hydrogen storage capacity of lithium-doped graphane (CHLi) have been investigated by stateof-the art first principle density functional theory (DFT). Molecular dynamics MD) simulations have confirmed the stability of Li on graphane sheet when it is subject to 10% of tensile strain. Under biaxial asymmetric strain, the binding energy of Li of graphane (CH) sheet increases by 52% with respect to its bulk's cohesive energy. With 25% doping concentration of Li on CH sheet,the gravimetric density of hydrogen storage is found to reach up to 12.12wt%. The adsorption energies of H2 are found to be within the range of practical H2 storage applications.
PuReMD-GPU: A reactive molecular dynamics simulation package for GPUs
Kylasa, S.B., E-mail: skylasa@purdue.edu [Department of Elec. and Comp. Eng., Purdue University, West Lafayette, IN 47907 (United States); Aktulga, H.M., E-mail: hmaktulga@lbl.gov [Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, MS 50F-1650, Berkeley, CA 94720 (United States); Grama, A.Y., E-mail: ayg@cs.purdue.edu [Department of Computer Science, Purdue University, West Lafayette, IN 47907 (United States)
2014-09-01T23:59:59.000Z
We present an efficient and highly accurate GP-GPU implementation of our community code, PuReMD, for reactive molecular dynamics simulations using the ReaxFF force field. PuReMD and its incorporation into LAMMPS (Reax/C) is used by a large number of research groups worldwide for simulating diverse systems ranging from biomembranes to explosives (RDX) at atomistic level of detail. The sub-femtosecond time-steps associated with ReaxFF strongly motivate significant improvements to per-timestep simulation time through effective use of GPUs. This paper presents, in detail, the design and implementation of PuReMD-GPU, which enables ReaxFF simulations on GPUs, as well as various performance optimization techniques we developed to obtain high performance on state-of-the-art hardware. Comprehensive experiments on model systems (bulk water and amorphous silica) are presented to quantify the performance improvements achieved by PuReMD-GPU and to verify its accuracy. In particular, our experiments show up to 16× improvement in runtime compared to our highly optimized CPU-only single-core ReaxFF implementation. PuReMD-GPU is a unique production code, and is currently available on request from the authors.
MD/HD Advanced Technology Evaluations | Department of Energy
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your Density Isn't YourTransport(FactDepartment ofLetterEconomy andTermsDepartment1| Department ofEnergyFMCFC
Maximum-likelihood density modification
Terwilliger, Thomas C., E-mail: terwilliger@lanl.gov [Structural Biology Group, Mail Stop M888, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2000-08-01T23:59:59.000Z
A likelihood-based density modification approach is developed that can incorporate expected electron-density information from a wide variety of sources. A likelihood-based approach to density modification is developed that can be applied to a wide variety of cases where some information about the electron density at various points in the unit cell is available. The key to the approach consists of developing likelihood functions that represent the probability that a particular value of electron density is consistent with prior expectations for the electron density at that point in the unit cell. These likelihood functions are then combined with likelihood functions based on experimental observations and with others containing any prior knowledge about structure factors to form a combined likelihood function for each structure factor. A simple and general approach to maximizing the combined likelihood function is developed. It is found that this likelihood-based approach yields greater phase improvement in model and real test cases than either conventional solvent flattening and histogram matching or a recent reciprocal-space solvent-flattening procedure [Terwilliger (1999 ?), Acta Cryst. D55, 1863–1871].
Beste, Ariana [ORNL; Attalla, Moetaz [CSIRO ICT Center, Australia; Jackson, Phil [CSIRO ICT Center, Australia
2012-01-01T23:59:59.000Z
A meta GGA-DFT study of CO{sub 2} activation in aqueous ammonia solutions, with an emphasis on the reaction barrier and molecularity, has been undertaken using the M06-2X functional with an augmented triple-zeta split-valence basis set (6-311++G(d,p)). Up to five base molecules were treated explicitly in order to establish the effects of solvent catalysis in the chemical capture process. Aqueous free energies of solvation were determined for optimized reactant and transition structures using SM8/M06-2X/6-311++G(d,p). The concept of the solvent pre-complex as presented by Dixon and coworkers (Nguyen, M. T.; Matus, M. H.; Jackson, V. E.; Ngan, V. T.; Rustad, J. R.; Dixon, D. A. J. Phys. Chem. A 2008, 112, 10386-10398) was exploited to account for the energetics of disruption of the hydrogen-bonding solvent nano-network prior to the CO{sub 2} activation step. Selected gas- and aqueous-phase thermodynamic quantities have also been derived.
Nagle, John F.
HIV-1 Tat membrane interactions probed using X-ray and neutron scattering, CD spectroscopy and MD translocation, were provided by wide-angle X-ray scattering (WAXS) and neutron scattering. CD spectroscopy for Neutron Research, 100 Bureau Drive, Stop 6102, Gaithersburg, MD 20899, United States d CHESS, Cornell
California Health eQuality Advisory Committee Kenneth W. Kizer, M.D., M.P.H. -Chair
California at Davis, University of
States, Inc. Thomas Williams, Dr.P.H., M.B.A. President and Chief Executive Officer Integrated Healthcare. Scott, M.D., M.P.H., Ex officio Chief Medical Information Officer California Department of Health CareCalifornia Health eQuality Advisory Committee Kenneth W. Kizer, M.D., M.P.H. - Chair Distinguished
Weber, David J.
PRIZE $50,000 grants help further research, bring new discoveries to commercial market BALTIMORE, MD will use the funding to develop technology that will aid in the safer delivery of radiation therapy to continue his research on a safer way to deliver radiation therapy." "This is a fantastic opportunity
HOPKINS, UNIVERSITY OF MD, BALTIMORE FACULTY RESEARCHERS WIN 2014 BIOMARYLAND LIFE PRIZES
Weber, David J.
,000 grants help further research, bring new discoveries to commercial market BALTIMORE, MD (February 19, 2014 for her development of a blood test for the early detection of pancreatic cancer. #12;The LIFE prize the funding to develop technology that will aid in the safer delivery of radiation therapy. Previous winners
Ira Helfand, MD International Physicians for the Prevention of Nuclear War
Robock, Alan
Ira Helfand, MD International Physicians for the Prevention of Nuclear War Physicians for Social Responsibility NUCLEAR FAMINE: A BILLION PEOPLE AT RISK Global Impacts of Limited Nuclear War on Agriculture of studies have shown that a limited, regional nuclear war between India and Pakistan would cause significant
Water adsorption on stepped ZnO surfaces from MD simulation David Raymand a
Goddard III, William A.
Water adsorption on stepped ZnO surfaces from MD simulation David Raymand a , Adri C.T. van Duin b Keywords: Zinc oxide Water Solidgas interfaces Construction and use of effective interatomic interactions force-field for use in molecular dynamics simulations of the ZnO water system. The force
Hot Water DJ: Saving Energy by Pre-mixing Hot Water Md Anindya Prodhan
Whitehouse, Kamin
Hot Water DJ: Saving Energy by Pre-mixing Hot Water Md Anindya Prodhan Department of Computer University of Virginia whitehouse@virginia.edu Abstract After space heating and cooling, water heating consumption. Current water heating systems waste up to 20% of their energy due to poor insulation in pipes
District of Columbia, University of the
in the Anacostia River Watershed (MD). Final Report to the DC Water Resources Research Center Dr. Harriette L hydrocarbons (PAHs), 28 polychlorinated biphenyl congeners (PCBs), 6 Aroclors, 21 pesticides, and five metals (Cd, Cr, Cu, Fe, Pb) plus technical chlordane, percent water and percent lipid. This ABM study
CityBizList US Green Building Council -MD Celebrating Move to
CityBizList US Green Building Council - MD Celebrating Move to Hunt Valley Share Email this Article Baltimore County Executive Jim Smith will join the U.S. Green Building Council Maryland to celebrate Horst, Senior Vice President, U.S. Green Building Council. Horst has served as chair of USGBC's LEED
Vendor Location PHS Assurance# A&G Pharmaceutical, Inc. MD A4404-01
Bandettini, Peter A.
BioScience Labs MD A3467-01 Alpha Genesis, Inc. SC A3645-01 Antibody Research Corporation MO A4489. On the BPA Program website open the current 'BPA Commodity List' and use the 'animal services', 'biological materials' or 'blood/blood products' tabs to search for these vendors. If a vendor is listed, the purchaser
A coupled RISM/MD or MC simulation methodology for solvation free energies
Truong, Thanh N.
A coupled RISM/MD or MC simulation methodology for solvation free energies Holly Freedman, Thanh N methods for determination of solvation free energies. We employ the RISM formulation of solvation free-netted chain equations. We apply this approach to determining free energies of solvation for several small
The Centre for Blood Research Athan Kuliopulos, MD, PhD
Strynadka, Natalie
The Centre for Blood Research Athan Kuliopulos, MD, PhD Director, Hemostasis & Thrombosis coating blood vessel walls rupture and expose collagen, platelets spring into action to form a blood clot, according to the researchers. Compared to other diseases, blood clotting has been very well understood
Advanced age remains an Achilles heel for liver resections. Laurent Sulpice, MD1,3
Paris-Sud XI, Université de
and Karim Boudjema, MD, PhD1,3 1- Service de Chirurgie Hépatobiliaire et Digestive. Centre Hospitalier, Centre Hospitalier Universitaire, Université de Rennes 1, Rennes, France Email : laurent in surgical techniques, perioperative management and postoperative care, LR has become increasingly common
A survey on vehicular cloud computing Md Whaiduzzaman a,n
Melbourne, University of
A survey on vehicular cloud computing Md Whaiduzzaman a,n , Mehdi Sookhak a , Abdullah Gani a , Rajkumar Buyya b a Mobile Cloud Computing Research Lab, Faculty of Computer Science & Information control Intelligent transportation systems Cloud computing Vehicular cloud computing a b s t r a c
Five-Year MD Enrichment Program Application/Plan University of Connecticut School of Medicine
Oliver, Douglas L.
Five-Year MD Enrichment Program Application/Plan University of Connecticut School of Medicine Full_________________________________ Proposed graduation date_________________________ Outline of enrichment plan: (specify date)____________ Please detail on a month-to- month basis your enrichment program (Be specific): Academic Year
Vo, Trinh; Allmen, Paul von; Huang, Chen-Kuo; Ma, James; Bux, Sabah; Fleurial, Jean-Pierre [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)
2014-10-07T23:59:59.000Z
The electronic properties and Seebeck coefficients of Ce{sub 3}Te{sub 4} and La{sub 3}Te{sub 4} are computed using Density Functional Theory with on-site Coulomb interaction correction. We found that the Seebeck coefficients of Ce{sub 3}Te{sub 4} and La{sub 3}Te{sub 4} are almost equal at temperatures larger than the Curie temperature of Ce{sub 3}Te{sub 4}, and in good agreement with the measurements reported by May et al. [Phys. Rev. B 86, 035135 (2012)]. At temperatures below the Curie temperature, the Seebeck coefficient of Ce{sub 3}Te{sub 4} increases due to the ferromagnetic ordering, which leads the f-electron of Ce to contribute to the Seebeck coefficient in the relevant range of electron concentration.
Ulian, Gianfranco; Valdrè, Giovanni, E-mail: giovanni.valdre@unibo.it [Dipartimento di Scienze Biologiche e Geologico-Ambientali, Centro di Ricerca Interdisciplinare di Biomineralogia, Cristallografia e Biomateriali, Università di Bologna “Alma Mater Studiorum” Piazza di Porta San Donato 1, 40126 Bologna (Italy)] [Dipartimento di Scienze Biologiche e Geologico-Ambientali, Centro di Ricerca Interdisciplinare di Biomineralogia, Cristallografia e Biomateriali, Università di Bologna “Alma Mater Studiorum” Piazza di Porta San Donato 1, 40126 Bologna (Italy); Tosoni, Sergio [Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, E-08028 Barcelona (Spain)] [Departament de Química Física and Institut de Química Teòrica i Computacional (IQTCUB), Universitat de Barcelona, C/ Martí i Franquès 1, E-08028 Barcelona (Spain)
2013-11-28T23:59:59.000Z
The quantum chemical characterization of solid state systems is conducted with many different approaches, among which the adoption of periodic boundary conditions to deal with three-dimensional infinite condensed systems. This method, coupled to the Density Functional Theory (DFT), has been proved successful in simulating a huge variety of solids. Only in relatively recent years this ab initio quantum-mechanic approach has been used for the investigation of layer silicate structures and minerals. In the present work, a systematic comparison of different DFT functionals (GGA-PBEsol and hybrid B3LYP) and basis sets (plane waves and all-electron Gaussian-type orbitals) on the geometry, energy, and phonon properties of a model layer silicate, talc [Mg{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}], is presented. Long range dispersion is taken into account by DFT+D method. Results are in agreement with experimental data reported in literature, with minimal deviation given by the GTO/B3LYP-D* method regarding both axial lattice parameters and interaction energy and by PW/PBE-D for the unit-cell volume and angular values. All the considered methods adequately describe the experimental talc infrared spectrum.
SCALING RELATIONS IN DENSITY FUNCTIONAL THEORY AND
Burke, Kieron
are being made to apply DFT to systems of bio- logical interest that would otherwise be unfeasible with traditional wavefunction methods. Although much of present research in DFT development focuses on an extension to the study of models for organometallic catalysts used in the dehydrogenation of alkanes to form alkenes
Density Functional Theory (DFT) Simulated Annealing (SA)
(x,y,z) Z(x,y,z) - $ %) % $% *) uzR )(YL Vycor ," (CaCO3) #12;( %) % $% *) ! "+!" %, $*$ , #12;* (SiO2
Magnetic fields and density functional theory
Jr, F.-Salsbury
2010-01-01T23:59:59.000Z
development of the general theory, Grayce and Harris used an electron gas approach to obtain a local energy
Density functional theory study of acetaldehyde hydrodeoxygenation...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
hydroxyls, which can recombine into a water molecule weakly bound at the Mo site. A terminal oxygen (Ot) defect site thus forms after water desorption. CH3CHO adsorbs at the...
Building a Universal Nuclear Energy Density Functional
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645 3,625govInstrumentstdmadapInactiveVisiting the TWPSuccess Stories Siteandscience, and technologyA ScienceDepartment
Ayala, A.L. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica][Pelotas Univ., RS (Brazil). Inst. de Fisica e Matematica; Ducati, M.B.G. [Rio Grande do Sul Univ., Porto Alegre, RS (Brazil). Inst. de Fisica; Levin, E.M. [Fermi National Accelerator Lab., Batavia, IL (United States)][Nuclear Physics Inst., St. Petersburg (Russian Federation)
1996-10-01T23:59:59.000Z
In this talk we present our detailed study (theory and numbers) on the shadowing corrections to the gluon structure functions for nuclei. Starting from rather controversial information on the nucleon structure function which is originated by the recent HERA data, we develop the Glauber approach for the gluon density in a nucleus based on Mueller formula and estimate the value of the shadowing corrections in this case. Then we calculate the first corrections to the Glauber approach and show that these corrections are big. Based on this practical observation we suggest the new evolution equation which takes into account the shadowing corrections and solve it. We hope to convince you that the new evolution equation gives a good theoretical tool to treat the shadowing corrections for the gluons density in a nucleus and, therefore, it is able to provide the theoretically reliable initial conditions for the time evolution of the nucleus-nucleus cascade. The initial conditions should be fixed both theoretically and phenomenologically before to attack such complicated problems as the mixture of hard and soft processes in nucleus-nucleus interactions at high energy or the theoretically reliable approach to hadron or/and parton cascades for high energy nucleus-nucleus interaction. 35 refs., 24 figs., 1 tab.
Dey, Abhishek; Hocking, Rosalie K.; /Stanford U., Chem. Dept.; Larsen, Peter; Borovik, Andrew S.; /Kansas U.; Hodgson, Keith O.; Hedman, Britt; Solomon, Edward I.; /SLAC,
2006-09-27T23:59:59.000Z
Iron L-edge, iron K-edge, and sulfur K-edge X-ray absorption spectroscopy was performed on a series of compounds [Fe{sup III}H{sub 3}buea(X)]{sup n-} (X = S{sup 2-}, O{sup 2-}, OH{sup -}). The experimentally determined electronic structures were used to correlate to density functional theory calculations. Calculations supported by the data were then used to compare the metal-ligand bonding and to evaluate the effects of H-bonding in Fe{sup III}-O vs Fe{sup III-}S complexes. It was found that the Fe{sup III-}O bond, while less covalent, is stronger than the FeIII-S bond. This dominantly reflects the larger ionic contribution to the Fe{sup III-}O bond. The H-bonding energy (for three H-bonds) was estimated to be -25 kcal/mol for the oxo as compared to -12 kcal/mol for the sulfide ligand. This difference is attributed to the larger charge density on the oxo ligand resulting from the lower covalency of the Fe-O bond. These results were extended to consider an Fe{sup IV-}O complex with the same ligand environment. It was found that hydrogen bonding to Fe{sup IV-}O is less energetically favorable than that to Fe{sup III-}O, which reflects the highly covalent nature of the Fe{sup IV-}O bond.
Boccia, A.; Lanzilotto, V.; Marrani, A. G.; Zanoni, R. [Dipartimento di Chimica, Universita degli Studi di Roma ''La Sapienza'', piazzale Aldo Moro 5, I-00185 Rome (Italy); Stranges, S. [Dipartimento di Chimica, Universita degli Studi di Roma ''La Sapienza'', piazzale Aldo Moro 5, I-00185 Rome (Italy); IOM-CNR, Laboratorio TASC, I-34149 Basovizza, Trieste (Italy); Alagia, M. [IOM-CNR, Laboratorio TASC, I-34149 Basovizza, Trieste (Italy); Fronzoni, G.; Decleva, P. [Dipartimento di Scienze Chimiche, Universita di Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy and IOM-CNR Democritos, Trieste (Italy)
2012-04-07T23:59:59.000Z
We present the results of an experimental and theoretical investigation of monosubstituted ethyl-, vinyl-, and ethynyl-ferrocene (EtFC, VFC, and EFC) free molecules, obtained by means of synchrotron-radiation based C 1s photoabsorption (NEXAFS) and photoemission (C 1s XPS) spectroscopies, and density functional theory (DFT) calculations. Such a combined study is aimed at elucidating the role played by the C-C bond unsaturation degree of the substituent on the electronic structure of the ferrocene derivatives. Such substituents are required for molecular chemical anchoring onto relevant surfaces when ferrocenes are used for molecular electronics hybrid devices. The high resolution C 1s NEXAFS spectra exhibit distinctive features that depend on the degree of unsaturation of the hydrocarbon substituent. The theoretical approach to consider the NEXAFS spectrum made of three parts allowed to disentangle the specific contribution of the substituent group to the experimental spectrum as a function of its unsaturation degree. C 1s IEs were derived from the experimental data analysis based on the DFT calculated IE values for the different carbon atoms of the substituent and cyclopentadienyl (Cp) rings. Distinctive trends of chemical shifts were observed for the substituent carbon atoms and the substituted atom of the Cp ring along the series of ferrocenes. The calculated IE pattern was rationalized in terms of initial and final state effects influencing the IE value, with special regard to the different mechanism of electron conjugation between the Cp ring and the substituent, namely the {sigma}/{pi} hyperconjugation in EtFC and the {pi}-conjugation in VFC and EFC.
Iftner, Christophe; Simon, Aude; Korchagina, Kseniia; Rapacioli, Mathias; Spiegelman, Fernand [Laboratoire de Chimie et Physique Quantiques LCPQ/IRSAMC, Université de Toulouse (UPS) and CNRS, 118 Route de Narbonne, F-31062 Toulouse (France)] [Laboratoire de Chimie et Physique Quantiques LCPQ/IRSAMC, Université de Toulouse (UPS) and CNRS, 118 Route de Narbonne, F-31062 Toulouse (France)
2014-01-21T23:59:59.000Z
We propose in the present paper a SCC-DFTB/FF (Self-Consistent-Charge Density Functional based Tight Binding/Force-Field) scheme adapted to the investigation of molecules trapped in rare gas environments. With respect to usual FF descriptions, the model involves the interaction of quantum electrons in a molecule with rare gas atoms in an anisotropic scheme. It includes polarization and dispersion contributions and can be used for both neutral and charged species. Parameters for this model are determined for hydrocarbon-argon complexes and the model is validated for small hydrocarbons. With the future aim of studying polycyclic aromatic hydrocarbons in Ar matrices, extensive benchmark calculations are performed on (C{sub 6}H{sub 6}){sup +/0}Ar{sub n} clusters against DFT and CCSD(T) calculations for the smaller sizes, and more generally against other experimental and theoretical data. Results on the structures and energetics (isomer ordering and energy separation, cohesion energy per Ar atom) are presented in detail for n = 1–8, 13, 20, 27, and 30, for both neutrals and cations. We confirm that the clustering of Ar atoms leads to a monotonous decrease of the ionization potential of benzene for n ? 20, in line with previous experimental and FF data.
National Nuclear Security Administration (NNSA)
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Yuhua Duan
2012-01-01T23:59:59.000Z
Alkali metal zirconates could be used as solid sorbents for CO{sub 2} capture. The structural, electronic, and phonon properties of Na{sub 2}ZrO{sub 3}, K{sub 2}ZrO{sub 3}, Na{sub 2}CO{sub 3}, and K{sub 2}CO{sub 3} are investigated by combining the density functional theory with lattice phonon dynamics. The thermodynamics of CO{sub 2} absorption/desorption reactions of these two zirconates are analyzed. The calculated results show that their optimized structures are in a good agreement with experimental measurements. The calculated band gaps are 4.339 eV (indirect), 3.641 eV (direct), 3.935 eV (indirect), and 3.697 eV (direct) for Na{sub 2}ZrO{sub 3}, K{sub 2}ZrO{sub 3}, Na{sub 2}CO{sub 3}, and K{sub 2}CO{sub 3}, respectively.The calculated phonon dispersions and phonon density of states for M{sub 2}ZrO{sub 3} and M{sub 2}CO{sub 3} (M = K, Na, Li) revealed that from K to Na to Li, their frequency peaks are shifted to high frequencies due to the molecular weight decreased from K to Li. From the calculated reaction heats and relationships of free energy change versus temperatures and CO{sub 2} pressures of the M{sub 2}ZrO{sub 3} (M = K, Na, Li) reacting with CO{sub 2}, we found that the performance of Na{sub 2}ZrO{sub 3} capturing CO{sub 2} is similar to that of Li{sub 2}ZrO{sub 3} and is better than that of K{sub 2}ZrO{sub 3}. Therefore, Na{sub 2}ZrO{sub 3} and Li{sub 2}ZrO{sub 3} are good candidates of high temperature CO{sub 2} sorbents and could be used for post combustion CO{sub 2} capture technologies.
Maranzana, Andrea, E-mail: andrea.maranzana@unito.it, E-mail: anna.giordana@hotmail.com, E-mail: vincenzo.barone@sns.it, E-mail: mauro.causa@unina.it, E-mail: mipavone@unina.it; Giordana, Anna, E-mail: andrea.maranzana@unito.it, E-mail: anna.giordana@hotmail.com, E-mail: vincenzo.barone@sns.it, E-mail: mauro.causa@unina.it, E-mail: mipavone@unina.it; Indarto, Antonius, E-mail: antonius.indarto@che.itb.ac.id; Tonachini, Glauco, E-mail: glauco.tonachini@unito.it [Dipartimento di Chimica, Università di Torino, Corso Massimo D’Azeglio 48, I-10125 Torino (Italy)] [Dipartimento di Chimica, Università di Torino, Corso Massimo D’Azeglio 48, I-10125 Torino (Italy); Barone, Vincenzo, E-mail: andrea.maranzana@unito.it, E-mail: anna.giordana@hotmail.com, E-mail: vincenzo.barone@sns.it, E-mail: mauro.causa@unina.it, E-mail: mipavone@unina.it [Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa (Italy)] [Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126, Pisa (Italy); Causà, Mauro, E-mail: andrea.maranzana@unito.it, E-mail: anna.giordana@hotmail.com, E-mail: vincenzo.barone@sns.it, E-mail: mauro.causa@unina.it, E-mail: mipavone@unina.it [Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli “Federico II,” Via Cintia, 80126 Napoli (Italy)] [Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università di Napoli “Federico II,” Via Cintia, 80126 Napoli (Italy); Pavone, Michele, E-mail: andrea.maranzana@unito.it, E-mail: anna.giordana@hotmail.com, E-mail: vincenzo.barone@sns.it, E-mail: mauro.causa@unina.it, E-mail: mipavone@unina.it [Dipartimento di Scienze Chimiche, Università di Napoli “Federico II,” Complesso Universitario di Monte Sant’Angelo, Via Cintia, I-80126 Napoli (Italy)] [Dipartimento di Scienze Chimiche, Università di Napoli “Federico II,” Complesso Universitario di Monte Sant’Angelo, Via Cintia, I-80126 Napoli (Italy)
2013-12-28T23:59:59.000Z
Our purpose is to identify a computational level sufficiently dependable and affordable to assess trends in the interaction of a variety of radical or closed shell unsaturated hydro-carbons A adsorbed on soot platelet models B. These systems, of environmental interest, would unavoidably have rather large sizes, thus prompting to explore in this paper the performances of relatively low-level computational methods and compare them with higher-level reference results. To this end, the interaction of three complexes between non-polar species, vinyl radical, ethyne, or ethene (A) with benzene (B) is studied, since these species, involved themselves in growth processes of polycyclic aromatic hydrocarbons (PAHs) and soot particles, are small enough to allow high-level reference calculations of the interaction energy ?E{sub AB}. Counterpoise-corrected interaction energies ?E{sub AB} are used at all stages. (1) Density Functional Theory (DFT) unconstrained optimizations of the A?B complexes are carried out, using the B3LYP-D, ?B97X-D, and M06-2X functionals, with six basis sets: 6-31G(d), 6-311 (2d,p), and 6-311++G(3df,3pd); aug-cc-pVDZ and aug-cc-pVTZ; N07T. (2) Then, unconstrained optimizations by Møller-Plesset second order Perturbation Theory (MP2), with each basis set, allow subsequent single point Coupled Cluster Singles Doubles and perturbative estimate of the Triples energy computations with the same basis sets [CCSD(T)//MP2]. (3) Based on an additivity assumption of (i) the estimated MP2 energy at the complete basis set limit [E{sub MP2/CBS}] and (ii) the higher-order correlation energy effects in passing from MP2 to CCSD(T) at the aug-cc-pVTZ basis set, ?E{sub CC-MP}, a CCSD(T)/CBS estimate is obtained and taken as a computational energy reference. At DFT, variations in ?E{sub AB} with basis set are not large for the title molecules, and the three functionals perform rather satisfactorily even with rather small basis sets [6-31G(d) and N07T], exhibiting deviation from the computational reference of less than 1 kcal mol{sup ?1}. The zero-point vibrational energy corrected estimates ?(E{sub AB}+ZPE), obtained with the three functionals and the 6-31G(d) and N07T basis sets, are compared with experimental D{sub 0} measures, when available. In particular, this comparison is finally extended to the naphthalene and coronene dimers and to three ??? associations of different PAHs (R, made by 10, 16, or 24 C atoms) and P (80 C atoms)
Considering Air Density in Wind Power Production
Zénó Farkas
2011-03-11T23:59:59.000Z
In the wind power production calculations the air density is usually considered as constant in time. Using the CIPM-2007 equation for the density of moist air as a function of air temperature, air pressure and relative humidity, we show that it is worth taking the variation of the air density into account, because higher accuracy can be obtained in the calculation of the power production for little effort.
Considering Air Density in Wind Power Production
Farkas, Zénó
2011-01-01T23:59:59.000Z
In the wind power production calculations the air density is usually considered as constant in time. Using the CIPM-2007 equation for the density of moist air as a function of air temperature, air pressure and relative humidity, we show that it is worth taking the variation of the air density into account, because higher accuracy can be obtained in the calculation of the power production for little effort.
DOE - Office of Legacy Management -- Max Zuckerman and Sons Inc - MD 04
Office of Legacy Management (LM)
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Schachter, L., E-mail: lsch@tandem.nipne.ro; Dobrescu, S. [National Institute for Physics and Nuclear Engineering, Bucharest (Romania)] [National Institute for Physics and Nuclear Engineering, Bucharest (Romania); Stiebing, K. E. [Institut für Kernphysik der J. W. Goethe Universität, Frankfurt/Main (Germany)] [Institut für Kernphysik der J. W. Goethe Universität, Frankfurt/Main (Germany)
2014-02-15T23:59:59.000Z
Double frequency heating (DFH) is a tool to improve the output of highly charged ions particularly from modern electron cyclotron resonance ion source installations with very high RF-frequencies. In order to gain information on the DFH-mechanism and on the role of the lower injected frequency we have carried out a series of dedicated experiments where we have put emphasis on the creation of a discrete resonance surface also for this lower frequency. Our well-established method of inserting an emissive MD (metal-dielectric) liner into the plasma chamber of the source is used in these experiments as a tool of investigation. In this way, the electron temperature and density for both ECR zones is increased in a controlled manner, allowing conclusions on the role of the change of the electron-energy-distribution function with and without DFH.
Tweedie Family Densities: Methods of Evaluation
Smyth, Gordon K.
of Queensland, St Lucia, Q 4072, Australia. 2 University of Southern Queensland, Toowoomba, Q 4350, Australia. Tweedie family densities are characterised by power variance functions of the form V[µ] = µp , where p
Sussman, Joel L.
Theoretical Insight into the Interactions of TMA-Benzene and TMA-Pyrrole with B3LYP Density theoretical investigation of the tetramethylammonium(TMA)-benzene and TMA-pyrrole complexes has been performed density in the 5 6 aromatic system of pyrrole is larger than that in the 6 6 system of benzene
Genome-wide association study of lung function phenotypes in a founder population
Abney, Mark
Genome-wide association study of lung function phenotypes in a founder population Tsung-Chieh Yao, Detroit, Mich, Baltimore, Md, Madison, Wis, and Taoyuan, Taiwan Background: Lung function is a long) associated with lung function. Methods: We performed a genome-wide association study (GWAS) of FEV1, forced
Statistical density modification using local pattern matching
Terwilliger, Thomas C., E-mail: terwilliger@lanl.gov [Mail Stop M888, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2003-10-01T23:59:59.000Z
Statistical density modification can make use of local patterns of density found in protein structures to improve crystallographic phases. A method for improving crystallographic phases is presented that is based on the preferential occurrence of certain local patterns of electron density in macromolecular electron-density maps. The method focuses on the relationship between the value of electron density at a point in the map and the pattern of density surrounding this point. Patterns of density that can be superimposed by rotation about the central point are considered equivalent. Standard templates are created from experimental or model electron-density maps by clustering and averaging local patterns of electron density. The clustering is based on correlation coefficients after rotation to maximize the correlation. Experimental or model maps are also used to create histograms relating the value of electron density at the central point to the correlation coefficient of the density surrounding this point with each member of the set of standard patterns. These histograms are then used to estimate the electron density at each point in a new experimental electron-density map using the pattern of electron density at points surrounding that point and the correlation coefficient of this density to each of the set of standard templates, again after rotation to maximize the correlation. The method is strengthened by excluding any information from the point in question from both the templates and the local pattern of density in the calculation. A function based on the origin of the Patterson function is used to remove information about the electron density at the point in question from nearby electron density. This allows an estimation of the electron density at each point in a map, using only information from other points in the process. The resulting estimates of electron density are shown to have errors that are nearly independent of the errors in the original map using model data and templates calculated at a resolution of 2.6 Å. Owing to this independence of errors, information from the new map can be combined in a simple fashion with information from the original map to create an improved map. An iterative phase-improvement process using this approach and other applications of the image-reconstruction method are described and applied to experimental data at resolutions ranging from 2.4 to 2.8 Å.
Bournel, F.; Carniato, S.; Dufour, G.; Gallet, J.-J.; Ilakovac, V.; Rangan, S.; Rochet, F.; Sirotti, F. [Laboratoire de Chimie Physique Matiere et Rayonnement, Universite Pierre et Marie Curie, 11 rue Pierre et Marie Curie, 75231 Paris Cedex 05 (France); Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, Boite Postale 48, 91192 Gif sur Yvette Cedex (France)
2006-03-15T23:59:59.000Z
The room temperature adsorption of acetonitrile (CH{sub 3}-C{identical_to}N) on Si(111)-7x7 is examined by synchrotron radiation N 1s x-ray photoemission and x-ray absorption spectroscopies. The experimental spectroscopic data point to multiple adsorption geometries. Candidate structures are optimized using density functional theory (DFT), the surface being simulated by silicon clusters encompassing one (adjacent) adatom-rest atom pair. This is followed by the DFT calculation of electron transition energies and cross sections. The comparison of theoretical spectra with experimental ones indicates that the molecule is adsorbed on the surface under two forms, a nondissociated geometry (an sp{sup 2}-hybridized CN) and a dissociated one (leading to a pendent sp-hybridized CN). In the nondissociative mode, the molecule bridges an adatom-rest atom pair. For bridge-type models, the discussion of the core-excited state calculations is focussed on the so-called silicon-molecule mixed-state transitions that strongly depend on the breaking or not of the adatom backbonds and on the attachment of the nitrogen end either to the adatom or to the rest atom. Concerning the dissociated state, the CH bond cleavage leads to a cyanomethyl (Si-CH{sub 2}-CN) plus a silicon monohydride, which accounts for the spectroscopic evidence of a free C{identical_to}N group (we do not find at 300 K any spectroscopic evidence for a C{identical_to}N group datively bonded to a silicon atom via its nitrogen lone pair). Therefore the reaction products of acetonitrile on Si(111)-7x7 are similar to those detected on the Si(001)-2x1 surface at the same temperature, despite the marked differences in the reconstruction of those two surfaces, especially the distance between adjacent silicon broken bonds. In that respect, we discuss how adatom backbond breaking in the course of adsorption may explain why both surface orientations react the same way with acetonitrile.
Carrera, Juan J.; Chu, Shih-I; Tong, Xiao-Min
2005-06-21T23:59:59.000Z
We present an ab initio nonpertubative investigation of the mechanisms responsible for the production of very-high-order harmonic generation (HHG) from Ar atoms and Ar+ ions by means of the self-interaction-free time-dependent density...
Nuclear energy density optimization: Shell structure
M. Kortelainen; J. McDonnell; W. Nazarewicz; E. Olsen; P. -G. Reinhard; J. Sarich; N. Schunck; S. M. Wild; D. Davesne; J. Erler; A. Pastore
2014-04-28T23:59:59.000Z
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. In this work, we propose a new parameterization UNEDF2 of the Skyrme energy density functional. The functional optimization is carried out using the POUNDerS optimization algorithm within the framework of the Skyrme Hartree-Fock-Bogoliubov theory. Compared to the previous parameterization UNEDF1, restrictions on the tensor term of the energy density have been lifted, yielding a very general form of the energy density functional up to second order in derivatives of the one-body density matrix. In order to impose constraints on all the parameters of the functional, selected data on single-particle splittings in spherical doubly-magic nuclei have been included into the experimental dataset. The agreement with both bulk and spectroscopic nuclear properties achieved by the resulting UNEDF2 parameterization is comparable with UNEDF1. While there is a small improvement on single-particle spectra and binding energies of closed shell nuclei, the reproduction of fission barriers and fission isomer excitation energies has degraded. As compared to previous UNEDF parameterizations, the parameter confidence interval for UNEDF2 is narrower. In particular, our results overlap well with those obtained in previous systematic studies of the spin-orbit and tensor terms. UNEDF2 can be viewed as an all-around Skyrme EDF that performs reasonably well for both global nuclear properties and shell structure. However, after adding new data aiming to better constrain the nuclear functional, its quality has improved only marginally. These results suggest that the standard Skyrme energy density has reached its limits and significant changes to the form of the functional are needed.
Paris-Sud XI, UniversitÃ© de
The evaluation within the development and deployment of IMS LD-based didactic materials: The MD2 in the didactic materials creation since it allows developers to check if the features of created material satisfy]. They have been applied to asses IMS LD based didactic material in conjunction with the experience provided
Madhyastha, Harsha V.
FRAppE: Detecting Malicious Facebook Applications Md Sazzadur Rahman, Ting-Kai Huang, Harsha V for the popularity and addictiveness of Facebook. Unfortu- nately, hackers have realized the potential of using apps and campaigns. In this paper, we ask the question: given a Facebook application, can we determine
Alamethicin in lipid bilayers: Combined use of X-ray scattering and MD simulations Jianjun Pan a
Nagle, John F.
Alamethicin in lipid bilayers: Combined use of X-ray scattering and MD simulations Jianjun Pan of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA d Canadian Neutron Beam Centre:1PC with varying amounts of alamethicin (Alm). We combine the use of X-ray diffuse scattering
Lung mast cells are a source of secreted phospholipases A2 Massimo Triggiani, MD, PhD,a
Gelb, Michael
Lung mast cells are a source of secreted phospholipases A2 Massimo Triggiani, MD, PhD,a Giorgio and to examine the expression and release of sPLA2s from primary human lung mast cells (HLMCs). Methods: sPLA2 of asthmatic patients. (J Allergy Clin Immunol 2009;124:558-65.) Key words: Lung mast cells, secreted
Inkpen, Diana
Second Order Co-occurrence PMI for Determining the Semantic Similarity of Words Md. Aminul Islam for calculating the semantic similarity of two target words. Our method, called Second Order Co-occurrence PMI (SOC-PMI), uses Pointwise Mutual Information to sort lists of important neighbor words of the two
Reid, Nancy
Survival in Academy AwardWinning Actors and Actresses Donald A. Redelmeier, MD, and Sheldon M in status from winning an academy award is associated with long-term mortality among actors and actresses. Design: Retrospective cohort analysis. Setting: Academy of Motion Picture Arts and Sciences. Participants
Russell, Lynn
Surface Tensions in NaCl-Water-Air Systems from MD Simulations Ranjit Bahadur, Lynn M. Russell, Ottawa, Ontario K1A 0R6, Canada ReceiVed: July 9, 2007; In Final Form: July 30, 2007 Surface tensions to the surface tension, while the energy-integral and test area methods provide direct estimates. At 1 atm
Chu, Shih-I; Tong, Xiao-Min
2001-06-12T23:59:59.000Z
We present a detailed study of the multiphoton ionization and high-order harmonic generation (HHG) processes of rare-gas atoms (He, Ne, and Ar) in intense pulsed laser fields by means of a self-interaction-free time-dependent density...
Functionalized Graphene Nanoroads for Quantum Well Device. |...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Nanoroads for Quantum Well Device. Functionalized Graphene Nanoroads for Quantum Well Device. Abstract: Using density functional theory, a series of calculations of structural and...
Low density, resorcinol-formaldehyde aerogels
Pekala, R.W.
1988-05-26T23:59:59.000Z
The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer ''clusters''. The covalent crosslinking of these ''clusters'' produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density less than or equal to100 mg/cc; cell size less than or equal to0.1 microns). The aerogels are transparent,dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 A/degree/. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron. 1 fig., 1 tab.
Low density, resorcinol-formaldehyde aerogels
Pekala, R.W.
1989-10-10T23:59:59.000Z
The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer clusters. The covalent crosslinking of these clusters produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density [<=]100 mg/cc; cell size [<=]0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 [angstrom]. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.
Low density, resorcinol-formaldehyde aerogels
Pekala, Richard W. (Pleasant Hill, CA)
1989-01-01T23:59:59.000Z
The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer "clusters". The covalent crosslinking of these "clusters" produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density .ltoreq.100 mg/cc; cell size .ltoreq.0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 .ANG.. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.
Low density, resorcinol-formaldehyde aerogels
Pekala, Richard W. (Pleasant Hill, CA)
1991-01-01T23:59:59.000Z
The polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer "Clusters". The covalent crosslinking of these "clusters" produces gels which when processed under supercritical conditions, produce low density, organic aerogels (density.ltoreq.100 mg/cc; cell size .ltoreq.0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100.circle.. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron.
Coupling MD Simulations and X-ray Absorption Spectroscopy to Study Ions in Solution
Marcos, E. Sanchez; Beret, E. C.; Martinez, J. M.; Pappalardo, R. R. [University of Seville, Dept. of Physical Chemistry (Spain); Ayala, R.; Munoz-Paez, A. [University of Seville, CSIC-ICMSE. Dept. of Inorganic Chemistry (Spain)
2007-11-29T23:59:59.000Z
The structure of ionic solutions is a key-point in understanding physicochemical properties of electrolyte solutions. Among the reduced number of experimental techniques which can supply direct information on the ion environment, X-ray Absorption techniques (XAS) have gained importance during the last decades although they are not free of difficulties associated to the data analysis leading to provide reliable structures. Computer simulations of ions in solution is a theoretical alternative to provide information on the solvation structure. Thus, the use of computational chemistry can increase the understanding of these systems although an accurate description of ionic solvation phenomena represents nowadays a significant challenge to theoretical chemistry. We present: (a) the assignment of features in the XANES spectrum to well defined structural motif in the ion environment, (b) MD-based evaluation of EXAFS parameters used in the fitting procedure to make easier the structural resolution, and (c) the use of the agreement between experimental and simulated XANES spectra to help in the choice of a given intermolecular potential for Computer Simulations. Chemical problems examined are: (a) the identification of the second hydration shell in dilute aqueous solutions of highly-charged cations, such as Cr{sup 3+}, Rh{sup 3+}, Ir{sup 3+}, (b) the invisibility by XAS of certain structures characterized by Computer Simulations but exhibiting high dynamical behavior and (c) the solvation of Br{sup -} in acetonitrile.
Paris-Sud XI, Université de
functional theory of f-band metals : lanthanum, cerium and thorium C1 ) D. Glotzel Institut fur cérium et du thorium à l'aide de la méthode « linear muffin tin orbital » (LMTO) et de l'approximation de centered cubic lanthanum, cerium and thorium have been performed using the linear muffin tin orbital (LMTO
Hulet, E.K.; Wild, J.F.; Lougheed, R.W.; Baisden, P.A.; Dougan, R.J.; Mustafa, M.G.
1980-10-01T23:59:59.000Z
The fragment energies of about 725 coincidence events have now been observed in the spontaneous fission (SF) decay of 105-min /sup 259/Md since its discovery in 1977. The fission of /sup 259/Md is characterized by a symmetric mass distribution, similar to those of /sup 258/Fm and /sup 259/Fm, but with a broad total kinetic energy (anti TKE) distribution which peaks at about 195 MeV, in contrast to those of /sup 258/Fm and /sup 259/Fm, for which the anti TKE is about 240 MeV. This kinetic energy deficit, approx. 40 MeV, has been postulated to be due to the emission of hydrogen-like particles by /sup 259/Md at the scission point in a large fraction of the fissions, leaving the residual fissioning nucleus with 100 protons. The residual nucleus would then be able to divide into two ultrastable tin-like fission fragments, but with less kinetic energy than that observed in the SF of /sup 258/Fm and /sup 259/Fm, because of binding-energy losses and a reduction in the Coulomb repulsion of the major fragments. To test this hypothesis, counter-telescope experiments aimed at detecting and identifying these light particles were performed. In 439 SF events 3 + 3 protons of the appropriate energy were observed, too few to account for the kinetic energy deficit in the fission of /sup 259/Md. There seems to be no explanation for this problem within the framework of current fission theory. These results are discussed along with preliminary measurements of light-particle emission in the SF of /sup 256/Fm. 5 figures.
J. R. Stone
2013-02-11T23:59:59.000Z
The microscopic composition and properties of matter at super-saturation densities have been the subject of intense investigation for decades. The scarcity of experimental and observational data has lead to the necessary reliance on theoretical models. However, there remains great uncertainty in these models, which, of necessity, have to go beyond the over-simple assumption that high density matter consists only of nucleons and leptons. Heavy strange baryons, mesons and quark matter in different forms and phases have to be included to fulfil basic requirements of fundamental laws of physics. In this review the latest developments in construction of the Equation of State (EoS) of high-density matter at zero and finite temperature assuming different composition of the matter are surveyed. Critical comparison of model EoS with available observational data on neutron stars, including gravitational masses, radii and cooling patterns is presented. The effect of changing rotational frequency on the composition of neutron stars during their lifetime is demonstrated. Compatibility of EoS of high-density, low temperature compact objects and low density, high temperature matter created in heavy-ion collisions is discussed.
Density Matrix Topological Insulators
A. Rivas; O. Viyuela; M. A. Martin-Delgado
2013-10-31T23:59:59.000Z
Thermal noise can destroy topological insulators (TI). However we demonstrate how TIs can be made stable in dissipative systems. To that aim, we introduce the notion of band Liouvillian as the dissipative counterpart of band Hamiltonian, and show a method to evaluate the topological order of its steady state. This is based on a generalization of the Chern number valid for general mixed states (referred to as density matrix Chern value), which witnesses topological order in a system coupled to external noise. Additionally, we study its relation with the electrical conductivity at finite temperature, which is not a topological property. Nonetheless, the density matrix Chern value represents the part of the conductivity which is topological due to the presence of quantum mixed edge states at finite temperature. To make our formalism concrete, we apply these concepts to the two-dimensional Haldane model in the presence of thermal dissipation, but our results hold for arbitrary dimensions and density matrices.
Inverse diffusion from knowledge of power densities
Bal, Guillaume; Monard, Francois; Triki, Faouzi
2011-01-01T23:59:59.000Z
This paper concerns the reconstruction of a diffusion coefficient in an elliptic equation from knowledge of several power densities. The power density is the product of the diffusion coefficient with the square of the modulus of the gradient of the elliptic solution. The derivation of such internal functionals comes from perturbing the medium of interest by acoustic (plane) waves, which results in small changes in the diffusion coefficient. After appropriate asymptotic expansions and (Fourier) transformation, this allow us to construct the power density of the equation point-wise inside the domain. Such a setting finds applications in ultrasound modulated electrical impedance tomography and ultrasound modulated optical tomography. We show that the diffusion coefficient can be uniquely and stably reconstructed from knowledge of a sufficient large number of power densities. Explicit expressions for the reconstruction of the diffusion coefficient are also provided. Such results hold for a large class of boundary...
Oakleaf, Megan
2009-01-01T23:59:59.000Z
by The Johns Hopkins University Press, Baltimore, MD 21218. INFORMATION STANDARDS Guiding Questions the information literacy assessments that best fit their needs. #12;Guiding Questions forAssessing Information
Multiple density layered insulator
Alger, Terry W. (Tracy, CA)
1994-01-01T23:59:59.000Z
A multiple density layered insulator for use with a laser is disclosed wh provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation.
Multiple density layered insulator
Alger, T.W.
1994-09-06T23:59:59.000Z
A multiple density layered insulator for use with a laser is disclosed which provides at least two different insulation materials for a laser discharge tube, where the two insulation materials have different thermoconductivities. The multiple layer insulation materials provide for improved thermoconductivity capability for improved laser operation. 4 figs.
Vranjes, J
2015-01-01T23:59:59.000Z
Inhomogeneous plasmas and fluids contain energy stored in inhomogeneity and they naturally tend to relax into lower energy states by developing instabilities or by diffusion. But the actual amount of energy in such inhomogeneities has remained unknown. In the present work the amount of energy stored in a density gradient is calculated for several specific density profiles in a cylindric configuration. This is of practical importance for drift wave instability in various plasmas, and in particular in its application in models dealing with the heating of solar corona because the instability is accompanied with stochastic heating, so the energy contained in inhomogeneity is effectively transformed into heat. It is shown that even for a rather moderate increase of the density at the axis in magnetic structures in the corona by a factor 1.5 or 3, the amount of excess energy per unit volume stored in such a density gradient becomes several orders of magnitude greater than the amount of total energy losses per unit ...
Imboden et al. 1 Genome-wide association study of lung function decline in adults with and1
Boyer, Edmond
,u , Gerard H.9 Koppelman, MD, PhDk , Stefano Guerra, MD, PhD,p,q,v,3 , Florian Kronenberg, MD,w ,10 Mark Kogevinas, MD, p,q,3,4 , Francine Kauffmann, MD,n,o ,13 Debbie L Jarvis, MD,f , Florence Demenais, MD, c
Functional genomics as a window on radiation stress signaling Sally A Amundson*,1
Functional genomics as a window on radiation stress signaling Sally A Amundson*,1 , Michael Bittner 20892, USA; 2 National Human Genome Research Institute, National Institutes of Health, Bethesda, MD before the completion of the human genome draft sequence, a number of techniques for genomic expression
Analysis of the Functional Role of Conserved Residues in the Protein Subunit of Ribonuclease P
Gopalan, Venkat
National Library of Medicine National Institutes of Health Room 8N-805, Building 38A Bethesda, MD 20894Analysis of the Functional Role of Conserved Residues in the Protein Subunit of Ribonuclease P from of Biology, Yale University, New Haven, CT 06520-8103, USA 2 National Center for Biotechnology Information
Department of Materials Science and Engineering University of Maryland, College Park, MD
Rubloff, Gary W.
for engineering practice #12;Topics Covered: I. Electrical and Optical Properties--Organic Photovoltaics A. Introduction: Organic photovoltaics B. Ohm's law C. Energy bands and energy gaps D. Carrier density in metals and semiconductors E. Optical absorption in semiconductors F. Excitons -- Size, Energy, Dynamics G. PN junction H
High Energy Density Capacitors
None
2010-07-01T23:59:59.000Z
BEEST Project: Recapping is developing a capacitor that could rival the energy storage potential and price of today’s best EV batteries. When power is needed, the capacitor rapidly releases its stored energy, similar to lightning being discharged from a cloud. Capacitors are an ideal substitute for batteries if their energy storage capacity can be improved. Recapping is addressing storage capacity by experimenting with the material that separates the positive and negative electrodes of its capacitors. These separators could significantly improve the energy density of electrochemical devices.
atheroprotective high-density lipoprotein: Topics by E-print...
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the mean-field energy functional. By studying the latter we derive global properties of high-density ground state configurations in bounded domains and in infinite space. Our main...
Evolution of particle density in high-energy pp collisions
I. Bautista; C. Pajares; J. Dias de Deus
2012-03-09T23:59:59.000Z
We study the evolution of the particle density, dn/d\\eta at fixed \\eta with the beam rapidity Y in the framework of string percolation model. Our main results are: (i) The width of the "plateau" increases proportionally to Y, (ii) limiting fragmentation is violated, and (iii) the particle density, reduces to a step function.
Observation of the density minimum in deeply supercooled confined water
Chen, Sow-Hsin
of SANS data allows us to determine the absolute value of the density of D2O as a function of temperature remarkable physical properties of liquid water (1), the density maximum is probably the most well known is considered to be the most accurate model for reproducing experimental data when used with a simple spherical
Optimally focused cold atom systems obtained using density-density correlations
Putra, Andika; Campbell, Daniel L.; Price, Ryan M.; Spielman, I. B. [Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology, College Park, Maryland 20742 (United States)] [Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology, College Park, Maryland 20742 (United States); De, Subhadeep [Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology, College Park, Maryland 20742 (United States) [Joint Quantum Institute, University of Maryland and National Institute of Standards and Technology, College Park, Maryland 20742 (United States); CSIR-National Physical Laboratory, New Delhi 110012 (India)
2014-01-15T23:59:59.000Z
Resonant absorption imaging is a common technique for detecting the two-dimensional column density of ultracold atom systems. In many cases, the system's thickness along the imaging direction greatly exceeds the imaging system's depth of field, making the identification of the optimally focused configuration difficult. Here we describe a systematic technique for bringing Bose-Einstein condensates (BEC) and other cold-atom systems into an optimal focus even when the ratio of the thickness to the depth of field is large: a factor of 8 in this demonstration with a BEC. This technique relies on defocus-induced artifacts in the Fourier-transformed density-density correlation function (the power spectral density, PSD). The spatial frequency at which these artifacts first appear in the PSD is maximized on focus; the focusing process therefore both identifies and maximizes the range of spatial frequencies over which the PSD is uncontaminated by finite-thickness effects.
Fiber felts as low density structural materials
Milewski, J.V.; Newfield, S.E.
1981-01-01T23:59:59.000Z
Short fiber felts structures can be made which provide improvements in properties over foams. In applications where resistance to compression set or stress relaxation are important, bonded fiber felts excel due to the flexing of individual fibers within their elastic limit. Felts of stainless steel and polyester fibers were prepared by deposition from liquid slurries. Compressive properties were determined as a function of felt parent material, extent of bonding, felt density, and length-to-diameter (L/D) ratio of starting fibers.
Low density microcellular foams
LeMay, James D. (Castro Valley, CA)
1991-01-01T23:59:59.000Z
Disclosed is a process of producing microcellular foam which comprises the steps of: (a) selecting a multifunctional epoxy oligomer resin; (b) mixing said epoxy resin with a non-reactive diluent to form a resin-diluent mixture; (c) forming a diluent containing cross-linked epoxy gel from said resin-diluent mixture; (d) replacing said diluent with a solvent therefore; (e) replacing said solvent with liquid carbon dioxide; and (f) vaporizing off said liquid carbon dioxide under supercritical conditions, whereby a foam having a density in the range of 35-150 mg/cc and cell diameters less than about 1 .mu.m is produced. Also disclosed are the foams produced by the process.
Low density microcellular foams
LeMay, James D. (Castro Valley, CA)
1992-01-01T23:59:59.000Z
Disclosed is a process of producing microcellular from which comprises the steps of: (a) selecting a multifunctional epoxy oligomer resin; (b) mixing said epoxy resin with a non-reactive diluent to form a resin-diluent mixture; (c) forming a diluent containing cross-linked epoxy gel from said resin-diluent mixture; (d) replacing said diluent with a solvent therefore; (e) replacing said solvent with liquid carbon dioxide; and (f) vaporizing off said liquid carbon dioxide under supercritical conditions, whereby a foam having a density in the range of 35-150 mg/cc and cell diameters less than about 1 .mu.m is produced. Also disclosed are the foams produced by the process.
Oberacker, V E
2015-01-01T23:59:59.000Z
In this manuscript we provide an outline of the numerical methods used in implementing the density constrained time-dependent Hartree-Fock (DC-TDHF) method and provide a few examples of its application to nuclear fusion. In this approach, dynamic microscopic calculations are carried out on a three-dimensional lattice and there are no adjustable parameters, the only input is the Skyrme effective NN interaction. After a review of the DC-TDHF theory and the numerical methods, we present results for heavy-ion potentials $V(R)$, coordinate-dependent mass parameters $M(R)$, and precompound excitation energies $E^{*}(R)$ for a variety of heavy-ion reactions. Using fusion barrier penetrabilities, we calculate total fusion cross sections $\\sigma(E_\\mathrm{c.m.})$ for reactions between both stable and neutron-rich nuclei. We also determine capture cross sections for hot fusion reactions leading to the formation of superheavy elements.
Low density microcellular foams
LeMay, J.D.
1991-11-19T23:59:59.000Z
Disclosed is a process of producing microcellular foam which comprises the steps of: (a) selecting a multifunctional epoxy oligomer resin; (b) mixing said epoxy resin with a non-reactive diluent to form a resin-diluent mixture; (c) forming a diluent containing cross-linked epoxy gel from said resin-diluent mixture; (d) replacing said diluent with a solvent therefore; (e) replacing said solvent with liquid carbon dioxide; and (f) vaporizing off said liquid carbon dioxide under supercritical conditions, whereby a foam having a density in the range of 35-150 mg/cc and cell diameters less than about 1 [mu]m is produced. Also disclosed are the foams produced by the process. 8 figures.
Nuclear Energy Density Optimization
M. Kortelainen; T. Lesinski; J. Moré; W. Nazarewicz; J. Sarich; N. Schunck; M. V. Stoitsov; S. Wild
2010-05-27T23:59:59.000Z
We carry out state-of-the-art optimization of a nuclear energy density of Skyrme type in the framework of the Hartree-Fock-Bogoliubov (HFB) theory. The particle-hole and particle-particle channels are optimized simultaneously, and the experimental data set includes both spherical and deformed nuclei. The new model-based, derivative-free optimization algorithm used in this work has been found to be significantly better than standard optimization methods in terms of reliability, speed, accuracy, and precision. The resulting parameter set UNEDFpre results in good agreement with experimental masses, radii, and deformations and seems to be free of finite-size instabilities. An estimate of the reliability of the obtained parameterization is given, based on standard statistical methods. We discuss new physics insights offered by the advanced covariance analysis.
Low density microcellular foams
Aubert, James H. (Albuquerque, NM); Clough, Roger L. (Albuquerque, NM); Curro, John G. (Placitas, NM); Quintana, Carlos A. (Albuquerque, NM); Russick, Edward M. (Albuquerque, NM); Shaw, Montgomery T. (Mansfield Center, CT)
1987-01-01T23:59:59.000Z
Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the resultant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Means for subjecting such a solvent to one-dimensional cooling are also provided. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 .mu.m and a volume such that the foams have a length greater than 1 cm are provided.
Low density microcellular foams
Aubert, J.H.; Clough, R.L.; Curro, J.G.; Quintana, C.A.; Russick, E.M.; Shaw, M.T.
1985-10-02T23:59:59.000Z
Low density, microporous polymer foams are provided by a process which comprises forming a solution of polymer and a suitable solvent followed by rapid cooling of the solution to form a phase-separated system and freeze the phase-separated system. The phase-separated system comprises a polymer phase and a solvent phase, each of which is substantially continuous within the other. The morphology of the polymer phase prior to and subsequent to freezing determine the morphology of the resultant foam. Both isotropic and anisotropic foams can be produced. If isotropic foams are produced, the polymer and solvent are tailored such that the solution spontaneously phase-separates prior to the point at which any component freezes. The morphology of the resultant polymer phase determines the morphology of the reusltant foam and the morphology of the polymer phase is retained by cooling the system at a rate sufficient to freeze one or both components of the system before a change in morphology can occur. Anisotropic foams are produced by forming a solution of polymer and solvent that will not phase separate prior to freezing of one or both components of the solution. In such a process, the solvent typically freezes before phase separation occurs. The morphology of the resultant frozen two-phase system determines the morphology of the resultant foam. The process involves subjecting the solution to essentially one-dimensional cooling. Foams having a density of less than 0.1 g/cc and a uniform cell size of less than 10 ..mu..m and a volume such that the foams have a length greater than 1 cm are provided.
Fuel-Borne Catalyst Assisted DPF regeneration on a Renault truck MD9 Engine
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your Density Isn't YourTransport inEnergy0.pdfTechnologies ProgramOutfitted with SCR | Department of Energy
DOE Zero Energy Ready Home Case Study 2013: Nexus EnergyHomes, Frederick, MD
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DOE Zero Energy Ready Home Case Study, Nexus EnergyHomes, Frederick, MD,
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
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VA-MD-DC Hydrogen Education for Decision Makers | Department of Energy
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your DensityEnergy U.S.-China Electric Vehicle and03/02 TUE 08:59CapabilityVulnerabilities |2 1
Evaluation of Powertrain Options and Component Sizing for MD and HD
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels DataDepartment of Energy Your Density Isn't Your Destiny:RevisedAdvisoryStandardGeneration |10 DOEGoalsEvaluation11 DOEEmissions from
Density-dependent acoustic properties of PBX 9502
Brown, Geoffrey W [Los Alamos National Laboratory; Thompson, Darla G [Los Alamos National Laboratory; Deluca, Racci [Los Alamos National Laboratory; Hartline, Ernest L [Los Alamos National Laboratory; Hagelberg, Stephanie I [Los Alamos National Laboratory
2009-07-31T23:59:59.000Z
We have measured the longitudinal and shear acoustic velocities of PBX 9502 as a function of density for die-pressed samples over the range 1.795 g/cc to 1.888 g/cc. The density dependence of the velocities is linear. Thermal cycling of PBX 9502 is known to induce irreversible volume growth. We have measured this volume growth dependence on density for a subset of the pressed parts and find that the most growth occurs for the samples with lowest initial density. The acoustic velocity changes due to the volume growth are significant and reflect damage in the samples.
Collapsibility of Lung Volume by Paired Inspiratory and Expiratory CT
Collapsibility of Lung Volume by Paired Inspiratory and Expiratory CT Scans: Correlations with Lung Function and Mean Lung Density Tsuneo Yamashiro, MD, Shin Matsuoka, MD, PhD, Brian J. Bartholmai, MD, Rau: To evaluate the relationship between measurements of lung volume (LV) on inspiratory/expiratory computed
The density of states approach for the simulation of finite density quantum field theories
K. Langfeld; B. Lucini; A. Rago; R. Pellegrini; L. Bongiovanni
2015-03-02T23:59:59.000Z
Finite density quantum field theories have evaded first principle Monte-Carlo simulations due to the notorious sign-problem. The partition function of such theories appears as the Fourier transform of the generalised density-of-states, which is the probability distribution of the imaginary part of the action. With the advent of Wang-Landau type simulation techniques and recent advances, the density-of-states can be calculated over many hundreds of orders of magnitude. Current research addresses the question whether the achieved precision is high enough to reliably extract the finite density partition function, which is exponentially suppressed with the volume. In my talk, I review the state-of-play for the high precision calculations of the density-of-states as well as the recent progress for obtaining reliable results from highly oscillating integrals. I will review recent progress for the $Z_3$ quantum field theory for which results can be obtained from the simulation of the dual theory, which appears to free of a sign problem.
The Column Density Distribution of the Lyman-Alpha Forest: A Measure of Small Scale Power
Lam Hui; Nickolay Y. Gnedin; Yu Zhang
1997-02-19T23:59:59.000Z
Absorption lines in the Lyman-alpha forest can be thought of as peaks in neutral hydrogen density along lines of sight. The column density distribution (the number density of absorption lines as a function of column density) is then a statistic of density peaks, which contains information about the underlying power spectrum. In particular, we show that the slope of the distribution provides a measure of power on scales smaller than those probed by studies of present-day large scale structure.
Thermal Density Functional Theory in Context Aurora Pribram-Jones,
Burke, Kieron
.3. Consequences 4 III.2.4. Extension to degenerate ground states 4 III.3. Kohn-Sham scheme 5 III.3.1. Exchange [1], and the various methods for modeling it are di- verse [2Â4]. The field includes enormous with useful accuracy. It is important to understand, from the outset, that the logic and methodology of KS
Magnetic and antimagnetic rotation in covariant density functional theory
Zhao, P. W.; Liang, H. Z.; Peng, J.; Ring, P.; Zhang, S. Q.; Meng, J. [State Key Lab Nucl. Phys. and Tech., School of Physics, Peking University, Beijing 100871 (China); Department of Physics, Beijing Normal University, Beijing 100875 (China); State Key Lab Nucl. Phys. and Tech., School of Physics, Peking University, Beijing 100871 (China) and Physik Department, Technische Universitat Muenchen, D-85747 Garching (Germany); State Key Lab Nucl. Phys. and Tech., School of Physics, Peking University, Beijing 100871 (China); State Key Lab Nucl. Phys. and Tech., School of Physics, Peking University, Beijing 100871 (China) and Department of Physics, University of Stellenbosch, Stellenbosch (South Africa)
2012-10-20T23:59:59.000Z
Progress on microscopic and self-consistent description of the magnetic rotation and antimagnetic rotation phenomena in tilted axis cranking relativistic mean-field theory based on a point-coupling interaction are briefly reviewed. In particular, the microscopic pictures of the shears mechanism in {sup 60}Ni and the two shears-like mechanism in {sup 105}Cd are discussed.
Spectroscopic properties of nuclear Skyrme energy density functionals
D. Tarpanov; J. Dobaczewski; J. Toivanen; B. G. Carlsson
2014-11-27T23:59:59.000Z
We address the question of how to improve the agreement between theoretical nuclear single-particle energies (SPEs) and experiment. Empirically, in doubly magic nuclei, the SPEs can be deduced from spectroscopic properties of odd nuclei that have one more, or one less neutron or proton. Theoretically, bare SPEs, before being confronted with experiment, must be corrected for the effects of the particle-vibration-coupling (PVC). In the present work, we determine the PVC corrections in a fully self-consistent way. Then, we adjust the SPEs, with PVC corrections included, to empirical data. In this way, the agreement with experiment, on average, improves; nevertheless, large discrepancies still remain. We conclude that the main source of disagreement is still in the underlying mean fields, and not in including or neglecting the PVC corrections.
A Simulation Study of Functional Density-Based Inverse Regression
Boyer, Edmond
,version1-22Dec2011 Author manuscript, published in "Revista Investigacion Operacional 32, 2 (2011) 146
Yield Strength as a Function of Dislocation Density
Collins, Gary S.
-displacement graphs as well as obvious excursions and yield points ·These perfect indents give a guideline for what a micro-hardness indenter, which uses a square pyramidal indenter tip. 10 m Procedures and Methods Before/23/2, using known elastic modulus to find tip radius. E* is the elastic modulus, R is the indenter tip radius
Element orbitals for Kohn-Sham density functional theory
Lin, Lin
2013-01-01T23:59:59.000Z
ranging from 128 atoms to 4394 atoms. ing C and H as sparseranging from 128 atoms to 4394 atoms. The length of thefor 128 atoms to 98.8 a.u. for 4394 atoms. The number of
Density functional study of hydrogen adsorption on beryllium (0001)
Allouche, A. [Physique des Interactions Ioniques et Moleculaires, CNRS and Universite de Provence, Campus Scientifique de Saint Jerome, service 242, 13397 Marseille Cedex 20 (France)
2008-08-15T23:59:59.000Z
Beryllium, tungsten, and carbon are planned as wall materials for the future international tokamak. Although beryllium is not situated in a region submitted to the most dramatic plasma-wall interaction, its reactivity toward hydrogen atom impinging is of fundamental importance. This paper is devoted to theoretical study of hydrogen adsorption on the beryllium (0001) surface based on the first-principles discrete Fourier transform method. Comparison is proposed to former theoretical works and to thermal-desorption spectroscopy.
Mass Spectrometry and Density Functional Theory Characterizations of DNA Modifications
Williams, Renee Therese
2012-01-01T23:59:59.000Z
Containing 1,2-GpG, 1,2-ApG, and 1,3-GpXpG CisplatinODNs) containing a 1,2-GpG, 1,2-ApG, or 1,3-GpXpG cisplatinODNs containing a 1,2-GpG, 1,2-ApG or 1,3-GpXpG intrastrand
Measurement of Proton Structure and Parton Density Functions from HERA
Raicevic, Natasa [University of Montenegro, Faculty of Science, Dzordza Vasingtona BB, 20000 Podgorica (Montenegro)
2010-01-21T23:59:59.000Z
A preliminary result is reported of the charged current and neutral current inclusive cross sections from e{sup +}p and e{sup -}p scattering obtained from a combination of published measurements from H1 and ZEUS. Taking into account the systematic error correlations in a coherent approach, a reduction of experimental uncertainties for combined results is achieved compared to the separate results of the H1 and ZEUS experiments. The combined results are used as input for a next-to-leading order (NLO) QCD parton distribution determination.
United abominations: Density functional studies of heavy metal chemistry
Schoendorff, George
2012-04-02T23:59:59.000Z
Carbonyl and nitrile addition to uranyl (UO{sup 2}{sup 2+}) are studied. The competition between nitrile and water ligands in the formation of uranyl complexes is investigated. The possibility of hypercoordinated uranyl with acetone ligands is examined. Uranyl is studied with diactone alcohol ligands as a means to explain the apparent hypercoordinated uranyl. A discussion of the formation of mesityl oxide ligands is also included. A joint theory/experimental study of reactions of zwitterionic boratoiridium(I) complexes with oxazoline-based scorpionate ligands is reported. A computational study was done of the catalytic hydroamination/cyclization of aminoalkenes with zirconium-based catalysts. Techniques are surveyed for programming for graphical processing units (GPUs) using Fortran.
van der Waals Density Functional for Atoms and Surfaces
Langreth, David C.
and G¨oteborg University, S412 96 G¨oteborg, Sweden (2) Department of Physics and Astronomy, Rutgers of its nonlocal nature, the van der Waals interaction is not correctly described by the local or semi in a uniform electron gas the van der Waals interaction is described through the limiting behavior [4, 8, 7
A Combined Density Functional Theory and Monte Carlo Study of...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
to the first order nature. Despite many experimental efforts to enhance the isothermal entropy change in manganites, the maximum obtained value merely reaches a modest value in...
Sandia Energy - Statistical Mechanics with Density Functional Theory
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del Sol Home Distribution GridDocumentsInstitute ofSitingStaff Home DETLStandards
Comments on: Statistical Mechanics with Density Functional Theory Accuracy
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AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE
The Materials Project: Combining Density Functional Theory Calculations
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOE Office of ScienceandMesa del SolStrengthening a solidSynthesis of 2Dand WaterThe Future isThe IronThe
Paris-Sud XI, Université de
Function in Chronic Heart Failure Short Title: RV dysfunction and prognosis in CHF Soulef Guendouz, MD1 Journal 2012;76(1):127-36" #12;2 ABSTRACT Aims: Chronic heart failure (CHF) has a poor prognosis. Our aims or emergent transplantation or emergent ventricular assist-device implantation or acute heart failure. RV-2D
Density matrix of black hole radiation
Lasma Alberte; Ram Brustein; Andrei Khmelnitsky; A. J. M. Medved
2015-02-09T23:59:59.000Z
Hawking's model of black hole evaporation is not unitary and leads to a mixed density matrix for the emitted radiation, while the Page model describes a unitary evaporation process in which the density matrix evolves from an almost thermal state to a pure state. We compare a recently proposed model of semiclassical black hole evaporation to the two established models. In particular, we study the density matrix of the outgoing radiation and determine how the magnitude of the off-diagonal corrections differs for the three frameworks. For Hawking's model, we find power-law corrections to the two-point functions that induce exponentially suppressed corrections to the off-diagonal elements of the full density matrix. This verifies that the Hawking result is correct to all orders in perturbation theory and also allows one to express the full density matrix in terms of the single-particle density matrix. We then consider the semiclassical theory for which the corrections, being non-perturbative from an effective field-theory perspective, are much less suppressed and grow monotonically in time. In this case, the R\\'enyi entropy for the outgoing radiation is shown to grow linearly at early times; but this growth slows down and the entropy eventually starts to decrease at the Page time. In addition to comparing models, we emphasize the distinction between the state of the radiation emitted from a black hole, which is highly quantum, and that of the radiation emitted from a typical classical black body at the same temperature.
Yener, Aylin
Rev 0310 Directions to the River's Edge Catering & Conference Center, Naval Air Station Patuxent. Physical address is 46870 Tate Road Bldg 2815, Patuxent River, MD. 20670. REC&C (301) 342-6210. From River For mapping GPS program reference, Lexington Park, MD is the town just outside the base gates
Generation of Gaussian Density Fields
Hugo Martel
2005-07-15T23:59:59.000Z
This document describes analytical and numerical techniques for the generation of Gaussian density fields, which represent cosmological density perturbations. The mathematical techniques involved in the generation of density harmonics in k-space, the filtering of the density fields, and the normalization of the power spectrum to the measured temperature fluctuations of the Cosmic Microwave Background, are presented in details. These techniques are well-known amongst experts, but the current literature lacks a formal description. I hope that this technical report will prove useful to new researchers moving into this field, sparing them the task of reinventing the wheel.
Minimization of Fractional Power Densities
Minimization of Fractional Power Densities. Robert Hardt, Rice University. Abstract: A k dimensional rectifiable current is given by an oriented k dimensional
Sanahuja, Blai
Advances in modeling gradual solar energetic particle events q D. Lario * Applied Physics Laboratory, Johns Hopkins University, 11100 Johns Hopkins Road, Laurel, MD 20723, USA Received 19 October 2002; accepted 8 July 2005 Abstract Solar energetic particles pose one of the most serious hazards
Quantum Mechanics as a Classical Theory XVI: Positive-Definite Densities
L. S. F. Olavo
1997-04-02T23:59:59.000Z
In this paper we will turn our attention to the problem of obtaining phase-space probability density functions. We will show that it is possible to obtain functions which assume only positive values over all its domain of definition.
Detecting Density Variations and Nanovoids
Miller, Michael K [ORNL; Longstreth-Spoor, L. [Washington University, St. Louis; Kelton, K. F. [Washington University, St. Louis
2011-01-01T23:59:59.000Z
A combination of simulated and experimental data has been used to investigate the size range of nanovoids that can be detected in atom probe tomography data. Simulated atom probe tomography data have revealed that nanovoids as small as 1 nm in diameter can be detected in atom probe tomography data with the use of iso-density surfaces. Iso-density surfaces may be used to quantify the size, morphology and number density of nanovoids and other variations in density in atom probe tomography data. Experimental data from an aluminum-yttrium-iron metallic glass ribbon have revealed the effectiveness of this approach. Combining iso-density surfaces with atom maps also permits the segregation of solute to the nanovoids to be investigated. Field ion microscopy and thin section atom maps have also been used to detect pores and larger voids.
Generalized Holographic Quantum Criticality at Finite Density
B. Goutéraux; E. Kiritsis
2013-01-23T23:59:59.000Z
We show that the near-extremal solutions of Einstein-Maxwell-Dilaton theories, studied in ArXiv:1005.4690, provide IR quantum critical geometries, by embedding classes of them in higher-dimensional AdS and Lifshitz solutions. This explains the scaling of their thermodynamic functions and their IR transport coefficients, the nature of their spectra, the Gubser bound, and regulates their singularities. We propose that these are the most general quantum critical IR asymptotics at finite density of EMD theories.
Nuclear Energy Density Optimization: UNEDF2
M. Kortelainen; J. McDonnell; W. Nazarewicz; E. Olsen; P. -G. Reinhard; J. Sarich; N. Schunck; S. M. Wild; D. Davesne; J. Erler; A. Pastore
2014-10-30T23:59:59.000Z
The parameters of the UNEDF2 nuclear energy density functional (EDF) model were obtained in an optimization to experimental data consisting of nuclear binding energies, proton radii, odd-even mass staggering data, fission-isomer excitation energies, and single particle energies. In addition to parameter optimization, sensitivity analysis was done to obtain parameter uncertainties and correlations. The resulting UNEDF2 is an all-around EDF. However, the sensitivity analysis also demonstrated that the limits of current Skyrme-like EDFs have been reached and that novel approaches are called for.
Modelling charge transfer reactions with the frozen density embedding formalism
Pavanello, Michele [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Neugebauer, Johannes [Institute for Physical and Theoretical Chemistry, Technische Universitaet Braunschweig, Hans-Sommer-Strasse 10, 38106 Braunschweig (Germany)
2011-12-21T23:59:59.000Z
The frozen density embedding (FDE) subsystem formulation of density-functional theory is a useful tool for studying charge transfer reactions. In this work charge-localized, diabatic states are generated directly with FDE and used to calculate electronic couplings of hole transfer reactions in two {pi}-stacked nucleobase dimers of B-DNA: 5{sup '}-GG-3{sup '} and 5{sup '}-GT-3{sup '}. The calculations rely on two assumptions: the two-state model, and a small differential overlap between donor and acceptor subsystem densities. The resulting electronic couplings agree well with benchmark values for those exchange-correlation functionals that contain a high percentage of exact exchange. Instead, when semilocal GGA functionals are used the electronic couplings are grossly overestimated.
Delp, Scott
, Stanford, CA, 3Diagnostic Radiology Center, Veterans Affairs Palo Alto Health Care System, Palo Alto, CA(212) 584-4662. 1089-7860,p;2003,07,04,287,296,ftx,en;smr00305x. Cine Phase-Contrast Magnetic Resonance
Low density metal hydride foams
Maienschein, Jon L. (Oakland, CA); Barry, Patrick E. (Pleasant Hill, CA)
1991-01-01T23:59:59.000Z
Disclosed is a low density foam having a porosity of from 0 to 98% and a density less than about 0.67 gm/cc, prepared by heating a mixture of powered lithium hydride and beryllium hydride in an inert atmosphere at a temperature ranging from about 455 to about 490 K for a period of time sufficient to cause foaming of said mixture, and cooling the foam thus produced. Also disclosed is the process of making the foam.
T. Thomas; P. Katgert
2005-10-10T23:59:59.000Z
We study the morphology-radius (MR-) and morphology-density (MD-) relations for a sample of about 850 galaxies (with M = -22), the S0 galaxies and the early spirals have different Sigma1-distributions. The reason for this is that Sigma1 is much less correlated with R than is Sigma10, and thus has much less cross-talk from the (MR-) relation. On average, the 'normal' ellipticals populate environments with higher projected density than do the S0 galaxies while the early spirals populate even less dense environments. The segregation of the brightest ellipticals and the late spirals is driven mostly by global factors, while the segregation between 'normal' ellipticals, S0 galaxies and early spirals is driven primarily by local factors.
SUPPRESSION OF DIELECTRONIC RECOMBINATION DUE TO FINITE DENSITY EFFECTS
Nikolic, D.; Gorczyca, T. W.; Korista, K. T. [Western Michigan University, Kalamazoo, MI (United States); Ferland, G. J. [University of Kentucky, Lexington, KY (United States); Badnell, N. R. [University of Strathclyde, Glasgow (United Kingdom)
2013-05-01T23:59:59.000Z
We have developed a general model for determining density-dependent effective dielectronic recombination (DR) rate coefficients in order to explore finite-density effects on the ionization balance of plasmas. Our model consists of multiplying by a suppression factor those highly-accurate total zero-density DR rate coefficients which have been produced from state-of-the-art theoretical calculations and which have been benchmarked by experiment. The suppression factor is based upon earlier detailed collision-radiative calculations which were made for a wide range of ions at various densities and temperatures, but used a simplified treatment of DR. A general suppression formula is then developed as a function of isoelectronic sequence, charge, density, and temperature. These density-dependent effective DR rate coefficients are then used in the plasma simulation code Cloudy to compute ionization balance curves for both collisionally ionized and photoionized plasmas at very low (n{sub e} = 1 cm{sup -3}) and finite (n{sub e} = 10{sup 10} cm{sup -3}) densities. We find that the denser case is significantly more ionized due to suppression of DR, warranting further studies of density effects on DR by detailed collisional-radiative calculations which utilize state-of-the-art partial DR rate coefficients. This is expected to impact the predictions of the ionization balance in denser cosmic gases such as those found in nova and supernova shells, accretion disks, and the broad emission line regions in active galactic nuclei.
Symmetry energy systematics and its high density behavior
Lie-Wen Chen
2015-06-30T23:59:59.000Z
We explore the systematics of the density dependence of nuclear matter symmetry energy in the ambit of microscopic calculations with various energy density functionals, and find that the symmetry energy from subsaturation density to supra-saturation density can be well determined by three characteristic parameters of the symmetry energy at saturation density $\\rho_0 $, i.e., the magnitude $E_{\\text{sym}}({\\rho_0 })$, the density slope $L$ and the density curvature $K_{\\text{sym}}$. This finding opens a new window to constrain the supra-saturation density behavior of the symmetry energy from its (sub-)saturation density behavior. In particular, we obtain $L=46.7 \\pm 12.8$ MeV and $K_{\\text{sym}}=-166.9 \\pm 168.3$ MeV as well as $E_{\\text{sym}}({2\\rho _{0}}) \\approx 40.2 \\pm 12.8$ MeV and $L({2\\rho _{0}}) \\approx 8.9 \\pm 108.7$ MeV based on the present knowledge of $E_{\\text{sym}}({\\rho_{0}}) = 32.5 \\pm 0.5$ MeV, $E_{\\text{sym}}({\\rho_c}) = 26.65 \\pm 0.2$ MeV and $L({\\rho_c}) = 46.0 \\pm 4.5$ MeV at $\\rho_{\\rm{c}}= 0.11$ fm$^{-3}$ extracted from nuclear mass and the neutron skin thickness of Sn isotopes. Our results indicate that the symmetry energy cannot be stiffer than a linear density dependence.In addition, we also discuss the quark matter symmetry energy since the deconfined quarks could be the right degree of freedom in dense matter at high baryon densities.
Transverse momentum dependent quark densities from Lattice QCD
Bernhard Musch,Philipp Hagler,John Negele,Andreas Schafer
2011-02-01T23:59:59.000Z
We study transverse momentum dependent parton distribution functions (TMDs) with non-local operators in lattice QCD, using MILC/LHPC lattices. Results obtained with a simpli?ed operator geometry show visible dipole de- formations of spin-dependent quark momentum densities. We discuss the basic concepts of the method, including renormalization of the gauge link, and an ex- tension to a more elaborate operator geometry that would allow us to analyze process-dependent TMDs such as the Sivers-function.
Intercrystalline density on nanocrystalline nickel
Haasz, T.R.; Aust, K.T. [Univ. of Toronto, Ontario (Canada). Dept. of Metallurgy and Materials Science] [Univ. of Toronto, Ontario (Canada). Dept. of Metallurgy and Materials Science; Palumbo, G. [Ontario Hydro Research Div., Toronto, Ontario (Canada)] [Ontario Hydro Research Div., Toronto, Ontario (Canada); El-Sherik, A.M.; Erb, U. [Queen`s Univ., Kingston, Ontario (Canada). Dept. of Materials and Metallurgical Engineering] [Queen`s Univ., Kingston, Ontario (Canada). Dept. of Materials and Metallurgical Engineering
1995-02-01T23:59:59.000Z
Most methods currently available for the synthesis of nanostructured materials result in considerable residual porosity. Studies concerned with the novel structures and properties of these materials are thus compromised by the intrinsically high levels of porosity. As recently shown by Kristic et al., porosity can have a significant effect on fundamental materials properties such as Young`s modulus. One of the most promising techniques for the production of fully dense nanocrystalline materials is electrodeposition. In the present work, the residual porosity and density of nanostructured nickel produced by the electrodeposition method is assessed and discussed in light of the intrinsic intercrystalline density of nickel.
Evaluation of Tweedie exponential dispersion model densities by Fourier inversion
Smyth, Gordon K.
and Computing University of Southern Queensland Toowoomba Queensland 4350 Australia Gordon K. Smyth Bioinformatics Division Walter and Eliza Hall Institute of Medical Research Melbourne, Vic 3050, Australia August with power variance functions V (µ) = µp for p (0, 1). These distri- butions do not generally have density
Computing spectral densities in finite temperature field theory
Jeon, S. (Physics Department FM-15, University of Washington, Seattle, Washington 98195 (United States))
1993-05-15T23:59:59.000Z
Convenient Cutkosky-like diagrammatic rules for computing the spectral densities of arbitrary two-point correlation functions in finite temperature field theory are derived. The approach is based on an explicit analytic continuation of imaginary-time Feynman diagrams. The application of this method to the perturbative evaluation of transport coefficients is briefly discussed.
Direct Experimental Determination of Spectral Densities of Molecular Complexes
Leonardo A. Pachon; Paul Brumer
2014-10-15T23:59:59.000Z
Determining the spectral density of a molecular system immersed in a proteomic scaffold and in contact to a solvent is a fundamental challenge in the coarse-grained description of, e.g., electron and energy transfer dynamics. Once the spectral density is characterized, all the time scales are captured and no artificial separation between fast and slow processes need be invoked. Based on the fluorescence Stokes shift function, we utilize a simple and robust strategy to extract the spectral density of a number of molecular complexes from available experimental data. Specifically, we show that experimental data for dye molecules in several solvents, amino acid proteins in water, and some photochemical systems (e.g., rhodopsin and green fluorescence proteins), are well described by a three-parameter family of sub-Ohmic spectral densities that are characterized by a fast initial Gaussian-like decay followed by a slow algebraic-like decay rate at long times.
Direct experimental determination of spectral densities of molecular complexes
Pachón, Leonardo A. [Grupo de Física Atómica y Molecular, Instituto de Física, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No. 52-21, Medellín (Colombia); Chemical Physics Theory Group, Department of Chemistry and Center for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 (Canada); Brumer, Paul [Chemical Physics Theory Group, Department of Chemistry and Center for Quantum Information and Quantum Control, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)
2014-11-07T23:59:59.000Z
Determining the spectral density of a molecular system immersed in a proteomic scaffold and in contact to a solvent is a fundamental challenge in the coarse-grained description of, e.g., electron and energy transfer dynamics. Once the spectral density is characterized, all the time scales are captured and no artificial separation between fast and slow processes need to be invoked. Based on the fluorescence Stokes shift function, we utilize a simple and robust strategy to extract the spectral density of a number of molecular complexes from available experimental data. Specifically, we show that experimental data for dye molecules in several solvents, amino acid proteins in water, and some photochemical systems (e.g., rhodopsin and green fluorescence proteins), are well described by a three-parameter family of sub-Ohmic spectral densities that are characterized by a fast initial Gaussian-like decay followed by a slow algebraic-like decay rate at long times.
Observation of the Density Minimum in Deeply Supercooled Confined Water
Dazhi Liu; Yang Zhang; Chia-Cheng Chen; Chung-Yuan Mou; Peter H Poole; Sow-Hsin Chen
2007-04-17T23:59:59.000Z
Small angle neutron scattering (SANS) is used to measure the density of heavy water contained in 1-D cylindrical pores of mesoporous silica material MCM-41-S-15, with pores of diameter of 15+-1 A. In these pores the homogenous nucleation process of bulk water at 235 K does not occur and the liquid can be supercooled down to at least 160 K. The analysis of SANS data allows us to determine the absolute value of the density of D2O as a function of temperature. We observe a density minimum at 210+-5 K with a value of 1.041+-0.003 g/cm3. We show that the results are consistent with the predictions of molecular dynamics simulations of supercooled bulk water. This is the first experimental report of the existence of the density minimum in supercooled water.
Direct Experimental Determination of Spectral Densities of Molecular Complexes
Pachon, Leonardo A
2014-01-01T23:59:59.000Z
Determining the spectral density of a molecular system immersed in a proteomic scaffold and in contact to a solvent is a fundamental challenge in the coarse-grained description of, e.g., electron and energy transfer dynamics. Once the spectral density is characterized, all the time scales are captured and no artificial separation between fast and slow processes need be invoked. Based on the fluorescence Stokes shift function, we utilize a simple and robust strategy to extract the spectral density of a number of molecular complexes from available experimental data. Specifically, we show that experimental data for dye molecules in several solvents, amino acid proteins in water, and some photochemical systems (e.g., rhodopsin and green fluorescence proteins), are well described by a three-parameter family of sub-Ohmic spectral densities that are characterized by a fast initial Gaussian-like decay followed by a slow algebraic-like decay rate at long times.
Statistical density modification using local pattern matching
Terwilliger, Thomas C.
2007-01-23T23:59:59.000Z
A computer implemented method modifies an experimental electron density map. A set of selected known experimental and model electron density maps is provided and standard templates of electron density are created from the selected experimental and model electron density maps by clustering and averaging values of electron density in a spherical region about each point in a grid that defines each selected known experimental and model electron density maps. Histograms are also created from the selected experimental and model electron density maps that relate the value of electron density at the center of each of the spherical regions to a correlation coefficient of a density surrounding each corresponding grid point in each one of the standard templates. The standard templates and the histograms are applied to grid points on the experimental electron density map to form new estimates of electron density at each grid point in the experimental electron density map.
M. Aslam Chaudhry
1999-01-01T23:59:59.000Z
Two representations of the extended gamma functions ? 2,0 0,2 [(b,x)] are proved. These representations are exploited to find a transformation relation between two Fox’s H-functions. These results are used to solve Fox’s H-function in terms of Meijer’s G-function for certain values of the parameters. A closed form representation of the kernel of the Bessel type integral transform is also proved. 1.
Training Session: Frederick, MD
Broader source: Energy.gov [DOE]
This 3.5-hour training provides builders with a comprehensive review of zero net-energy-ready home construction including the business case, detailed specifications, and opportunities to be...
citation: Natio Hyattsville, MD
Illinois at Chicago, University of
Reform 75 Monitoring Health Care Reform: SelfReports of Health Insurance Premium Assistance & Program SESSION 1 SUMMARY 71 KAREN CYBULSKI, ANNE CIEMNECKI, AND KAREN BOGEN SESSION 2: Monitoring Health Care Survey 101 MARC W. ZODET, STEVEN C. HILL, AND SAMUEL H. ZUVEKAS The RWJF Health Care Public
Nishikawa, Takeshi, E-mail: nishikawa.takeshi@okayama-u.ac.jp [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan)
2014-07-15T23:59:59.000Z
Most conventional atomic models in a plasma do not treat the effect of the plasma on the free-electron state density. Using a nearest neighbor approximation, the state densities in hydrogenic plasmas for both bound and free electrons were evaluated and the effect of the plasma on the atomic model (especially for the state density of the free electron) was studied. The model evaluates the electron-state densities using the potential distribution formed by the superposition of the Coulomb potentials of two ions. The potential from one ion perturbs the electronic state density on the other. Using this new model, one can evaluate the free-state density without making any ad-hoc assumptions. The resulting contours of the average ionization degree, given as a function of the plasma temperature and density, are shifted slightly to lower temperatures because of the effect of the increasing free-state density.
The center of lateral iso-density contours for inclined cosmic air showers
Montanus, J M C
2015-01-01T23:59:59.000Z
The lateral density of a cosmic air shower with a non-zero zenith angle is azimuthally asymmetric. The azimuthal asymmetry consist of a stretching of the iso-density contours to ellipses and to a shift of the center of the elliptic contours with respect to the core of the shower. The aim of the paper is to investigate the shift of the center of the elliptic iso-density contours for different zenith angles . On the basis of a model a qualitative equation is derived for the iso-density contours of inclined showers including the shift. to obtain a quantitative equation MC densities are investigated. The shift can be incorporated in an analytic expression of the azimuthal asymmetry of the lateral density as a function of the polar coordinates and parameterized by the zenith angle. Its predictions for asymmetric lateral densities are compared with densities obtained with MC simulations.