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Note: This page contains sample records for the topic "density functional theory" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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1

Density Functional Theory Approach to Nuclear Fission  

E-Print Network (OSTI)

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

N. Schunck

2012-12-13T23:59:59.000Z

2

Thermal Density Functional Theory in Context  

E-Print Network (OSTI)

This chapter introduces thermal density functional theory, starting from the ground-state theory and assuming a background in quantum mechanics and statistical mechanics. We review the foundations of density functional theory (DFT) by illustrating some of its key reformulations. The basics of DFT for thermal ensembles are explained in this context, as are tools useful for analysis and development of approximations. We close by discussing some key ideas relating thermal DFT and the ground state. This review emphasizes thermal DFT's strengths as a consistent and general framework.

Pribram-Jones, Aurora; Gross, E K U; Burke, Kieron

2013-01-01T23:59:59.000Z

3

Nuclear fission in covariant density functional theory  

E-Print Network (OSTI)

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.

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

2013-09-12T23:59:59.000Z

4

Symmetry energy in nuclear density functional theory  

E-Print Network (OSTI)

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

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

2013-07-22T23:59:59.000Z

5

Symmetry energy in nuclear density functional theory  

E-Print Network (OSTI)

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

Nazarewicz, W; Satula, W; Vretenar, D

2013-01-01T23:59:59.000Z

6

Some challenges for Nuclear Density Functional Theory  

E-Print Network (OSTI)

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

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

2006-06-20T23:59:59.000Z

7

The Materials Project: Combining Density Functional Theory Calculation...  

NLE Websites -- All DOE Office Websites (Extended Search)

The Materials Project The Materials Project: Combining Density Functional Theory Calculations with Supercomputing Centers for New Materials Discovery May 2, 2013 jain2 Anubhav Jain...

8

First-Principles Density Functional Theory Study of Grain Boundary ...  

Science Conference Proceedings (OSTI)

Presentation Title, First-Principles Density Functional Theory Study of Grain ... It was found that both the vacancy formation energy and diffusion activation†...

9

Constrained Density-Functional Theory--Configuration Interaction  

E-Print Network (OSTI)

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

Kaduk, Benjamin James

2012-01-01T23:59:59.000Z

10

Dynamical density functional theory for dense atomic liquids  

E-Print Network (OSTI)

Starting from Newton's equations of motion, we derive a dynamical density functional theory (DDFT) applicable to atomic liquids. The theory has the feature that it requires as input the Helmholtz free energy functional from equilibrium density functional theory. This means that, given a reliable equilibrium free energy functional, the correct equilibrium fluid density profile is guaranteed. We show that when the isothermal compressibility is small, the DDFT generates the correct value for the speed of sound in a dense liquid. We also interpret the theory as a dynamical equation for a coarse grained fluid density and show that the theory can be used (making further approximations) to derive the standard mode coupling theory that is used to describe the glass transition. The present theory should provide a useful starting point for describing the dynamics of inhomogeneous atomic fluids.

A. J. Archer

2006-04-25T23:59:59.000Z

11

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

Science Conference Proceedings (OSTI)

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

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

2011-09-15T23:59:59.000Z

12

Density Functional Theory with Dissipation: Transport through Single Molecules  

SciTech Connect

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

Kieron Burke

2012-04-30T23:59:59.000Z

13

Exact-exchange density functional theory for neutron drops  

Science Conference Proceedings (OSTI)

We compute the ground-state properties of finite systems of neutrons in an external harmonic trap, interacting via the Minnesota potential, using the ''exact-exchange'' form of orbital-dependent density functional theory. We compare our results with Hartree-Fock calculations and find very close agreement. Within the context of the interaction studied, we conclude that this simple orbital-dependent functional brings conventional nuclear density functional theory to the level of Hartree-Fock in an ab initio fashion. Our work is a first step toward higher order ab initio nuclear functionals based on realistic nucleon-nucleon interactions.

Drut, Joaquin E. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545-0001 (United States); Department of Physics, Ohio State University, Columbus, Ohio 43210-1117 (United States); Platter, Lucas [Fundamental Physics, Chalmers University of Technology, SE-41296 Goeteborg (Sweden); Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195 (United States); Department of Physics, Ohio State University, Columbus, Ohio 43210-1117 (United States)

2011-07-15T23:59:59.000Z

14

The benchmark of gutzwiller density functional theory in hydrogen systems  

SciTech Connect

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

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

2012-02-23T23:59:59.000Z

15

Correlation Testing in Nuclear Density Functional Theory  

E-Print Network (OSTI)

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

M. G. Bertolli

2012-08-07T23:59:59.000Z

16

Density functional theory and optimal transportation with Coulomb cost  

E-Print Network (OSTI)

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

Codina Cotar; Gero Friesecke; Claudia KlŁppelberg

2011-04-04T23:59:59.000Z

17

Improved association in a classical density functional theory for water  

E-Print Network (OSTI)

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

Eric J. Krebs; Jeff B. Schulte; David Roundy

2013-09-07T23:59:59.000Z

18

Hybrid Dynamic Density Functional Theory for Polymer Melts and Blends  

E-Print Network (OSTI)

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

Takashi Honda; Toshihiro Kawakatsu

2006-09-05T23:59:59.000Z

19

Nuclear Density Functional Theory and the Equation of State  

E-Print Network (OSTI)

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

Yeunhwan Lim

2011-04-06T23:59:59.000Z

20

Nuclear Density Functional Theory and the Equation of State  

E-Print Network (OSTI)

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

Lim, Yeunhwan

2011-01-01T23:59:59.000Z

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


21

Nonlinear eigenvalue problems in Density Functional Theory calculations  

SciTech Connect

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

Fattebert, J

2009-08-28T23:59:59.000Z

22

Curvature and Frontier Orbital Energies in Density Functional Theory  

SciTech Connect

Perdew et al. [Phys. Rev. Lett 49, 1691 (1982)] discovered and proved two different properties that exact Kohn-Sham density functional theory (DFT) must obey: (i) The exact total energy versus particle number must be a series of linear segments between integer electron points; (ii) Across an integer number of electrons, the exchange-correlation potential may ``jumpíí by a constant, known as the derivative discontinuity (DD). Here, we show analytically that in both the original and the generalized Kohn-Sham formulation of DFT, the two are in fact two sides of the same coin. Absence of a derivative discontinuity necessitates deviation from piecewise linearity, and the latter can be used to correct for the former, thereby restoring the physical meaning of the orbital energies. Using selected small molecules, we show that this results in a simple correction scheme for any underlying functional, including semi-local and hybrid functionals as well as Hartree-Fock theory, suggesting a practical correction for the infamous gap problem of density functional theory. Moreover, we show that optimally-tuned range-separated hybrid functionals can inherently minimize both DD and curvature, thus requiring no correction, and show that this can be used as a sound theoretical basis for novel tuning strategies.

Stein, Tamar; Autschbach, Jochen; Govind, Niranjan; Kronik, Leeor; Baer, Roi

2012-12-20T23:59:59.000Z

23

Fragment-based Time-dependent Density-functional Theory  

E-Print Network (OSTI)

Using the Runge-Gross theorem that establishes the foundation of Time-dependent Density Functional Theory (TDDFT) we prove that for a given electronic Hamiltonian, choice of initial state, and choice of fragmentation, there is a unique single-particle potential (dubbed time-dependent partition potential) which, when added to each of the pre-selected fragment potentials, forces the fragment densities to evolve in such a way that their sum equals the exact molecular density at all times. This uniqueness theorem suggests new ways of computing time-dependent properties of electronic systems via fragment-TDDFT calculations. We derive a formally exact relationship between the partition potential and the total density, and illustrate our approach on a simple model system for binary fragmentation in a laser field.

Mosquera, Martin A; Wasserman, Adam

2013-01-01T23:59:59.000Z

24

Density Functional Theory for the Photoionization Dynamics of Uracil  

E-Print Network (OSTI)

Photoionization dynamics of the RNA base Uracil is studied in the framework of Density Functional Theory (DFT). The photoionization calculations take advantage of a newly developed parallel version of a multicentric approach to the calculation of the electronic continuum spectrum which uses a set of B-spline radial basis functions and a Kohn-Sham density functional hamiltonian. Both valence and core ionizations are considered. Scattering resonances in selected single-particle ionization channels are classified by the symmetry of the resonant state and the peak energy position in the photoelectron kinetic energy scale; the present results highlight once more the site specificity of core ionization processes. We further suggest that the resonant structures previously characterized in low-energy electron collision experiments are partly shifted below threshold by the photoionization processes. A critical evaluation of the theoretical results providing a guide for future experimental work on similar biosystems.

Toffoli, D; Gianturco, F A; Lucchese, R R

2007-01-01T23:59:59.000Z

25

A Density Functional Theory Study of Formaldehyde Adsorption on Ceria  

Science Conference Proceedings (OSTI)

Molecular adsorption of formaldehyde on the stoichiometric CeO2(111) and CeO2(110) surfaces was studied using periodic density functional theory. Two adsorption modes (strong chemisorbed and weak physisorbed) were identified on both surfaces. This is consistent with recent experimental observations. On the (111) surface, formaldehyde strongly chemisorbs with an adsorption energy of 0.86 eV to form a dioxymethylene-like structure, in which a surface O lifts from the surface to bind with the C of formaldehyde. A weak physisorbed state with adsorption energy of 0.28 eV was found with the O of formaldehyde interacting with a surface Ce. On the (110) surface, dioxymethyelene formation was also observed, with an adsorption energy of 1.31 eV. The weakly adsorbed state of formaldehyde on the (110) surface was energetically comparable to the weak adsorption state on the (111) surface, but adsorption occurred through a formaldehyde C and surface O interaction. Analysis of the local density of states and charge density differences after adsorption shows that strong covalent bonding occurs between the C of formaldehyde and surface O when dioxymethylene forms. Calculated vibrational frequencies also confirm dioxymethylene formation. Our results also show that as the coverage increases, the adsorption of formaldehyde on the (111) surface becomes weak, but is nearly unaffected on the (110) surface. This work was supported by a Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL). The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory, which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Computing time was made under a Computational Grand Challenge ďComputational CatalysisĒ. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC).

Mei, Donghai; Deskins, N. Aaron; Dupuis, Michel

2007-11-01T23:59:59.000Z

26

Optimized local basis set for Kohn-Sham density functional theory  

Science Conference Proceedings (OSTI)

We develop a technique for generating a set of optimized local basis functions to solve models in the Kohn-Sham density functional theory for both insulating and metallic systems. The optimized local basis functions are obtained by solving a minimization ... Keywords: Discontinuous Galerkin, Electronic structure, GMRES, Kohn-Sham density functional theory, Molecular dynamics, Optimized local basis set, Preconditioning, Pulay force, Trace minimization

Lin Lin; Jianfeng Lu; Lexing Ying; Weinan E

2012-05-01T23:59:59.000Z

27

Density Functional Theory Study of Copper Oxide as Low-cost ...  

Science Conference Proceedings (OSTI)

Density Functional Theory Study of Copper Oxide as Low-cost Photovoltaic Material ∑ Dye-sensitized Solar Cells with Anodized Aluminum Alloy-based Counter-†...

28

Density Functional Theory Calculations of Mass Transport in UO2  

SciTech Connect

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

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

2012-06-26T23:59:59.000Z

29

Fast plane wave density functional theory molecular dynamics calculations on multi-GPU machines  

Science Conference Proceedings (OSTI)

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 ... Keywords: Density functional theory, Electronic structure, First-principles, GPU, Molecular dynamics, Plane wave pseudopotential

Weile Jia, Jiyun Fu, Zongyan Cao, Long Wang, Xuebin Chi, Weiguo Gao, Lin-Wang Wang

2013-10-01T23:59:59.000Z

30

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

E-Print Network (OSTI)

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

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

2012-12-27T23:59:59.000Z

31

Subspace accelerated inexact Newton method for large scale wave functions calculations in Density Functional Theory  

SciTech Connect

We describe an iterative algorithm to solve electronic structure problems in Density Functional Theory. The approach is presented as a Subspace Accelerated Inexact Newton (SAIN) solver for the non-linear Kohn-Sham equations. It is related to a class of iterative algorithms known as RMM-DIIS in the electronic structure community. The method is illustrated with examples of real applications using a finite difference discretization and multigrid preconditioning.

Fattebert, J

2008-07-29T23:59:59.000Z

32

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

E-Print Network (OSTI)

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

Cheng, Chiao-Lun

2008-01-01T23:59:59.000Z

33

Density functional theory study of the conductivity of the biphenalenyl radical dimer  

E-Print Network (OSTI)

We present ab initio molecular calculations at different levels of density functional theory (DFT) for the spiro-biphenalenyl neurtral radical in its singlet and triplet states. We performed calculations on the dimer to ...

Lu, Aiyan

2007-01-01T23:59:59.000Z

34

The Materials genome : rapid materials screening for renewable energy using high-throughput density functional theory  

E-Print Network (OSTI)

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, ...

Jain, Anubhav, Ph.D. Massachusetts Institute of Technology

2011-01-01T23:59:59.000Z

35

Fission of actinides and superheavy nuclei: covariant density functional theory perspective  

E-Print Network (OSTI)

The current status of the application of covariant density functional theory to the description of fission barriers in actinides and superheavy nuclei is reviewed. The achievements and open problems are discussed.

A. V. Afanasjev

2013-03-05T23:59:59.000Z

36

Empirical Proton-Neutron Interactions and Nuclear Density Functional Theory: Global, Regional and Local Comparisons  

E-Print Network (OSTI)

Calculations of nuclear masses, using nuclear density functional theory, are presented for even-even nuclei spanning the nuclear chart. The resulting binding energy differences can be interpreted in terms of valence proton-neutron interactions. These are compared globally, regionally, and locally with empirical values. Overall, excellent agreement is obtained. Discrepancies highlight neglected degrees of freedom and can point to improved density functionals.

Stoitsov, M; Casten, R F; Nazarewicz, W; Satula, W

2006-01-01T23:59:59.000Z

37

Empirical Proton-Neutron Interactions and Nuclear Density Functional Theory: Global, Regional, and Local Comparisons  

Science Conference Proceedings (OSTI)

Calculations of nuclear masses, using nuclear density functional theory, are presented for even-even nuclei spanning the nuclear chart. The resulting binding energy differences can be interpreted in terms of valence proton-neutron interactions. These are compared globally, regionally, and locally with empirical values. Overall, excellent agreement is obtained. Discrepancies highlight neglected degrees of freedom and can point to improved density functionals.

Stoitsov, Mario [ORNL; Cakirli, R. B. [Yale University; Casten, R. F. [Yale University; Nazarewicz, Witold [ORNL; Satula, W. [Warsaw University

2007-01-01T23:59:59.000Z

38

Empirical Proton-Neutron Interactions and Nuclear Density Functional Theory: Global, Regional and Local Comparisons  

E-Print Network (OSTI)

Calculations of nuclear masses, using nuclear density functional theory, are presented for even-even nuclei spanning the nuclear chart. The resulting binding energy differences can be interpreted in terms of valence proton-neutron interactions. These are compared globally, regionally, and locally with empirical values. Overall, excellent agreement is obtained. Discrepancies highlight neglected degrees of freedom and can point to improved density functionals.

M. Stoitsov; R. B. Cakirli; R. F. Casten; W. Nazarewicz; W. Satula

2006-11-14T23:59:59.000Z

39

Covariant Density Functional Theory--highlights on recent progress and applications  

SciTech Connect

The density functional theory with a few number of parameters allows a very successful phenomenological description of ground state properties of nuclei all over the nuclear chart. The recent progress on the application of the covariant density functional theory (CDFT) for nuclear structure and astrophysics as well as its extensions by the group in Beijing is summarized. In particular, its application to magnetic moments is discussed in details.

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); Li, J.; Zhao, P. W.; Liang, H. Z. [State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Yao, J. M. [School of Physical Science and Technology, Southwest University, Chongqing 400715 (China)

2011-05-06T23:59:59.000Z

40

Density Functional Theory in Surface Chemistry and Catalysis  

SciTech Connect

Recent advances in the understanding of reactivity trends for chemistry at transition metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. Current status of the field is discussed with an emphasis on the role of coupling between theory and experiment and future challenges.

Norskov, Jens

2011-05-19T23:59:59.000Z

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


41

Magnetic and antimagnetic rotation in covariant density functional theory  

Science Conference Proceedings (OSTI)

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.

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

42

Effective 3-Body Interaction for Mean-Field and Density-Functional Theory  

Science Conference Proceedings (OSTI)

Density functionals for nuclei usually include an effective 3-body interaction that depends on a fractional power of the density. Using insights from the many-body theory of the low-density two-component Fermi gas, we consider a new, nonlocal, form for the energy functional that is consistent with the Fock-space representation of interaction operators. In particular, there is a unique spatially nonlocal generalization of the contact form of the interaction that preserves the {rho}{sup 7/3} density dependence required by the many-body theory. We calculate the ground-state energies for particles in a harmonic trap by using the nonlocal induced 3-body interaction and compare them to numerically accurate Green's function Monte Carlo calculations. Using no free parameters, we find that a nonlocality in the space domain provides a better description of the weak-coupling regime than the local-density approximation.

Gezerlis, Alexandros [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Bertsch, G. F. [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States); Institute for Nuclear Theory, University of Washington, Seattle, Washington 98195-1560 (United States)

2010-11-19T23:59:59.000Z

43

Fission barriers in actinides in covariant density functional theory: the role of triaxiality  

E-Print Network (OSTI)

Relativistic mean field theory allowing for triaxial deformations is applied for a systematic study of fission barriers in the actinide region. Different pairing schemes are studied in details and it is shown that covariant density functional theory is able to describe fission barriers on a level of accuracy comparable with non-relativistic calculations, even with the best phenomenological macroscopic+microscopic approaches. Triaxiality in the region of the first saddle plays a crucial role in achieving that.

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

2010-10-09T23:59:59.000Z

44

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

Science Conference Proceedings (OSTI)

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

Vojvodic, Aleksandra

2012-05-11T23:59:59.000Z

45

Communication: Density functional theory overcomes the failure of predicting intermolecular interaction energies  

Science Conference Proceedings (OSTI)

Density-functional theory (DFT) revolutionized the ability of computational quantum mechanics to describe properties of matter and is by far the most often used method. However, all the standard variants of DFT fail to predict intermolecular interaction energies. In recent years, a number of ways to go around this problem has been proposed. We show that some of these approaches can reproduce interaction energies with median errors of only about 5% in the complete range of intermolecular configurations. Such errors are comparable to typical uncertainties of wave-function-based methods in practical applications. Thus, these DFT methods are expected to find broad applications in modelling of condensed phases and of biomolecules.

Podeszwa, Rafal [Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice (Poland); Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Szalewicz, Krzysztof [Institute of Chemistry, University of Silesia, Szkolna 9, 40-006 Katowice (Poland)

2012-04-28T23:59:59.000Z

46

Stress Isotherms of Porous Thin Materials: Theoretical Predictitions From a Nonlocal Density Functional Theory  

SciTech Connect

Recent beam bending (BB) experiments of microporous t31rns with very small pores have shown that the fluid confined in these pores exhibits monotonic compressive stresses as the relative pressure is varied from vacuum to saturation (relative vapor pressure, p/p. = 1). The variation of the stress near saturation is found to be linear in hz(p) and given by the saturated liquid density to within 20%. Capillary condensed fluids are traditionally described by the Laplace-Kelvin (LK) theory. LK theory correctly predicts the slope of the stress near saturation to be pl, but also predicts that the stress should be zero at saturation and tensile between saturation aud the capillary transition pressure. Hence LK theory does not capture the monotonic compressive stress observed in BB experiments. This report describes the results of density functional theory calculations for a simple fluid continued to a slit pore network. We show how the presence of even a small amount of polydispersity in pore size leads to both a monotonic compressive stress as well as the observed LK slope.

Frink, L.J.D.; van Swol, F.

1998-11-11T23:59:59.000Z

47

A density functional theory and time-dependent density functional theory investigation on the anchor comparison of triarylamine-based dyes  

SciTech Connect

To understand the effects of the anchor part in organic dyes on the energy conversion efficiency of dye-sensitized solar cells (DSCs), two different anchor groups used in metal-free triphenylamine (TPA)-based organic dyes for DSCs have been theoretically compared. Density functional theory (DFT) and time-dependent DFT (TDDFT) study of geometry properties, excitations, and electronic structures of triarylamine-based dyes (TC1 and TPAR1) before and after binding to titanium has been performed under the level of TD-PBE1PBE/6-311G(d,p)//B3LYP/6-311G(d,p). The result shows that cyanoacrylic acid anchor favors better photoelectrochemical properties of DSCs than that of rhodanine-3-acetic acid anchor via providing more shift of TiO{sub 2} conduction band toward the vacuum energy levels (larger open circuit potentials) and more favorable conjugation with titanium. This study is expected to shed light on the design of metal-free organic dyes for DSCs.

Peng Bo; Yang Siqi; Li Lanlan; Cheng Fangyi; Chen Jun [Institute of New Energy Material Chemistry and Key Laboratory of Energy-Material Chemistry, Chemistry College, Nankai University, Tianjin 300071 (China)

2010-01-21T23:59:59.000Z

48

Ferromagnetism in GaN: Gd: A density functional theory study  

SciTech Connect

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.

Stevenson, Cynthia; Stevenson, Cynthia

2008-02-04T23:59:59.000Z

49

Construction of the free energy landscape by the density functional theory  

E-Print Network (OSTI)

On the basis of the density functional theory, we give a clear definition of the free energy landscape. To show the usefulness of the definition, we construct the free energy landscape for rearrangement of atoms in an FCC crystal of hard spheres. In this description, the cooperatively rearranging region (CRR) is clealy related to the hard spheres involved in the saddle between two adjacent basins. A new concept of the simultaneously rearranging region (SRR) emerges naturally as spheres defined by the difference between two adjacent basins. We show that the SRR and the CRR can be determined explicitly from the free energy landscape. 1 1

Takashi Yoshidome; Akira Yoshimori; Takashi Odagaki

2005-01-01T23:59:59.000Z

50

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

SciTech Connect

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

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

2011-05-01T23:59:59.000Z

51

Troubleshooting time-dependent density-functional theory for photochemical applications: Oxirane  

Science Conference Proceedings (OSTI)

The development of analytic-gradient methodology for excited states within conventional time-dependent density-functional theory (TDDFT) would seem to offer a relatively inexpensive alternative to better established quantum-chemical approaches for the modeling of photochemical reactions. However, even though TDDFT is formally exact, practical calculations involve the use of approximate functional, in particular the TDDFT adiabatic approximation, the use of which in photochemical applications must be further validated. Here, we investigate the prototypical case of the symmetric CC ring opening of oxirane. We demonstrate by direct comparison with the results of high-quality quantum Monte Carlo calculations that, far from being an approximation on TDDFT, the Tamm-Dancoff approximation is a practical necessity for avoiding triplet instabilities and singlet near instabilities, thus helping maintain energetically reasonable excited-state potential energy surfaces during bond breaking. Other difficulties one would encounter in modeling oxirane photodynamics are pointed out.

Cordova, Felipe; Doriol, L. Joubert; Ipatov, Andrei; Casida, Mark E.; Filippi, Claudia; Vela, Alberto [Laboratoire de Chimie Theorique, Departement de Chimie Molecularie (DCM, UMR CNRS/UJF 5250), Institut de Chimie Moleculaire de Grenoble (ICMG, FR2607), Universite Joseph Fourier - Grenoble I, 301 rue de la Chimie, BP 53, F-38041 Grenoble Cedex 9 (France); Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, Niels Bohrweg 2, Leiden NL-2333 CA Netherlands (Netherlands); Departamento de Quimica, Cinvestav, Avenida Instituto Politecnico Nacional 2508, A.P. 14-740, Mexico D.F. 07000 (Mexico)

2007-10-28T23:59:59.000Z

52

Equilibrium gas-liquid-solid contact angle from density-functional theory  

E-Print Network (OSTI)

We investigate the equilibrium of a fluid in contact with a solid boundary through a density-functional theory. Depending on the conditions, the fluid can be in one phase, gas or liquid, or two phases, while the wall induces an external field acting on the fluid particles. We first examine the case of a liquid film in contact with the wall. We construct bifurcation diagrams for the film thickness as a function of the chemical potential. At a specific value of the chemical potential, two equally stable films, a thin one and a thick one, can coexist. As saturation is approached, the thickness of the thick film tends to infinity. This allows the construction of a liquid-gas interface that forms a well defined contact angle with the wall.

Pereira, Antonio

2010-01-01T23:59:59.000Z

53

Accuracy of Density Functional Theory in Prediction of Carbon Dioxide Adsorbent Materials  

E-Print Network (OSTI)

We have performed a thorough computational study to assess the accuracy of density functional theory (DFT) methods in describing the interactions of CO2 with model alkali-earth-metal (AEM, Ca and Li) decorated carbon structures, namely anthracene (C14H10) molecules. We find that gas-adsorption energy and equilibrium structure results obtained with both standard (i.e. LDA and GGA) and hybrid (i.e. PBE0 and B3LYP) exchange-correlation functionals of DFT differ significantly from results obtained with second-order Moller-Plesset perturbation theory (MP2), an accurate computational quantum chemistry method. The major disagreements found can be mostly rationalized in terms of electron correlation errors that lead to inaccurate charge transfers and electrostatic Coulomb interactions between the molecules. Interestingly, we show that when the concentration of AEM atoms in anthracene is tuned to resemble as closely as possible to the electronic structure of AEM-decorated graphene, hybrid exchange-correlation DFT and ...

Cazorla, Claudio

2012-01-01T23:59:59.000Z

54

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

E-Print Network (OSTI)

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

Vojvodic, Aleksandra

2009-01-01T23:59:59.000Z

55

Combinatorial density functional theory-based screening of surface alloys for the oxygen reduction reaction.  

DOE Green Energy (OSTI)

A density functional theory (DFT) -based, combinatorial search for improved oxygen reduction reaction (ORR) catalysts is presented. A descriptor-based approach to estimate the ORR activity of binary surface alloys, wherein alloying occurs only in the surface layer, is described, and rigorous, potential-dependent computational tests of the stability of these alloys in aqueous, acidic environments are presented. These activity and stability criteria are applied to a database of DFT calculations on nearly 750 binary transition metal surface alloys; of these, many are predicted to be active for the ORR but, with few exceptions, they are found to be thermodynamically unstable in the acidic environments typical of low-temperature fuel cells. The results suggest that, absent other thermodynamic or kinetic mechanisms to stabilize the alloys, surface alloys are unlikely to serve as useful ORR catalysts over extended periods of operation.

Greeley, J.; Norskov, J.; Center for Nanoscale Materials; Technical Univ. of Denmark

2009-03-26T23:59:59.000Z

56

Density-functional theory study of gramicidin A ion channel geometry and electronic properties  

E-Print Network (OSTI)

Understanding the mechanisms underlying ion channel function from the atomic-scale requires accurate ab initio modelling as well as careful experiments. Here, we present a density functional theory (DFT) study of the ion channel gramicidin A, whose inner pore conducts only monovalent cations and whose conductance has been shown to depend on the side chains of the amino acids in the channel. We investigate the ground-state geometry and electronic properties of the channel in vacuum, focusing on their dependence on the side chains of the amino acids. We find that the side chains affect the ground state geometry, while the electrostatic potential of the pore is independent of the side chains. This study is also in preparation for a full, linear scaling DFT study of gramicidin A in a lipid bilayer with surrounding water. We demonstrate that linear scaling DFT methods can accurately model the system with reasonable computational cost. Linear scaling DFT allows ab initio calculations with 10,000 to 100,000 atoms an...

Todorovi?, Milica; Gillan, M J; Miyazaki, Tsuyoshi

2013-01-01T23:59:59.000Z

57

Carbon dioxide adsorption and activation on Ceria (110): A density functional theory study  

E-Print Network (OSTI)

Ceria (CeO2) is a promising catalyst for the reduction of carbon dioxide (CO2) to liquid fuels and commodity chemicals, in part because of its high oxygen storage capacity, yet the fundamentals of CO2 adsorption and initial activation on CeO2 surfaces remain largely unknown. We use density functional theory, corrected for onsite Coulombic interactions (DFT+U), to explore various adsorption sites and configurations for CO2 on stoichiometric and reduced CeO2 (110). Our model of reduced CeO2 (110) contains oxygen vacancies at the topmost atomic layer and undergoes surface reconstruction upon introduction of these vacancies. We find that CO2 adsorption on reduced CeO2 (110) is thermodynamically favored over the corresponding adsorption on stoichiometric CeO2 (110). The most stable adsorption configuration consists of CO2 adsorbed parallel to the reduced CeO2 (110) surface, with the molecule situated near the site of the oxygen vacancy. Structural changes in the CO2 molecule are also observed upon adsorption, so t...

Cheng, Zhuo; Lo, Cynthia S

2012-01-01T23:59:59.000Z

58

Study of Hydrogen Bonding in Small Water Clusters with Density Functional Theory Calculations  

DOE Green Energy (OSTI)

The unique characteristics of hydrogen bonding have left our understanding of liquid water far from complete in terms of its structure and properties. In order to better describe the hydrogen bond in water, we seek to understand the electronic states which show sensitivity to hydrogen bonding. We investigate the structure of unoccupied valence states by performing X-ray Absorption calculations on water clusters using Density Functional Theory. For each water cluster, studying how valence electronic structure is perturbed by changes in the local hydrogen bonding environment facilitates our description of the hydrogen bond. Also in this framework, we move toward a depiction of local structures in liquid water by comparison to experimental X-ray absorption spectra. We find consistent localization along internal bonds in the electronic structures of pre- and post-edge states for single-donor species. In addition, we propose a molecular orbital bonding-antibonding picture to explain this directional localization from dimer calculations, and show that the pre- and post-edge spectral regions have a resulting relationship.

Wendlandt, Johanna; /Wisconsin U., Madison /SLAC, SSRL

2005-12-15T23:59:59.000Z

59

Adaptive local basis set for Kohn-Sham density functional theory in a discontinuous Galerkin framework I: Total energy calculation  

E-Print Network (OSTI)

Kohn-Sham density functional theory is one of the most widely used electronic structure theories. Uniform discretization of the Kohn-Sham Hamiltonian generally results in a large number of basis functions per atom in order to resolve the rapid oscillations of the Kohn-Sham orbitals around the nuclei. Previous attempts to reduce the number of basis functions per atom include the usage of atomic orbitals and similar objects, but the atomic orbitals generally require fine tuning in order to reach the chemical accuracy. We present a novel discretization scheme that adaptively and systematically builds the rapid oscillations of the Kohn-Sham orbitals around the nuclei as well as environmental effects into the basis functions. The resulting basis functions are localized in the real space, and are discontinuous in the global domain. The continuous Kohn-Sham orbitals and the electron density are evaluated from the discontinuous basis functions using the discontinuous Galerkin (DG) framework. Our method is implemented...

Lin, Lin; Ying, Lexing; E, Weinan

2011-01-01T23:59:59.000Z

60

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

Science Conference Proceedings (OSTI)

Background: The reactions with the neutron-rich 48Ca beam and actinide targets resulted in the detection of new superheavy (SH) nuclides with Z=104 118. The unambiguous identification of the new isotopes, however, still poses a problem because their -decay chains terminate by spontaneous fission (SF) before reaching the known region of the nuclear chart. The understanding of the competition between -decay and SF channels in SH nuclei is, therefore, of crucial importance for our ability to map the SH region and to assess its extent. Purpose: We perform self-consistent calculations of the competing decay modes of even-even SH isotopes with 108 Z 126 and 148 N 188. Methods: We use the state-of-the-art computational framework based on self-consistent symmetry-unrestricted nuclear density functional theory capable of describing the competition between nuclear attraction and electrostatic repulsion. We apply the SkM* Skyrme energy density functional. The collective mass tensor of the fissioning superfluid nucleus is computed by means of the cranking approximation to the adiabatic time-dependent Hartree-Fock-Bogoliubov (HFB) approach. This paper constitutes a systematic self-consistent study of spontaneous fission in the SH region, carried out at a full HFB level, that simultaneously takes into account both triaxiality and reflection asymmetry. Results: Breaking axial symmetry and parity turns out to be crucial for a realistic estimate of collective action; it results in lowering SF lifetimes by more than 7 orders of magnitude in some cases. We predict two competing SF modes: reflection symmetric modes and reflection asymmetric modes. Conclusions: The shortest-lived SH isotopes decay by SF; they are expected to lie in a narrow corridor formed by 280Hs, 284Fl, and 118284Uuo that separates the regions of SH nuclei synthesized in cold-fusion and hot-fusion reactions. The region of long-lived SH nuclei is expected to be centered on 294Ds with a total half-life of 1.5 days. Our survey provides a solid benchmark for the future improvements of self-consistent SF calculations in the region of SH nuclei.

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

2013-01-01T23:59:59.000Z

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61

Recent advances in the use of density functional theory to design efficient solar energy-based renewable systems  

Science Conference Proceedings (OSTI)

This article reviews the use of Density Functional Theory (DFT) to study the electronic and optical properties of solar-active materials and dyes used in solar energy conversion applications (dye-sensitized solar cells and water splitting). We first give a brief overview of the DFT its development

Ramy Nashed; Yehea Ismail; Nageh K. Allam

2013-01-01T23:59:59.000Z

62

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

DOE Green Energy (OSTI)

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

Liu, P.; Choi, Y.M.

2011-05-16T23:59:59.000Z

63

Density Functional Theory Study of Methanol Decomposition on the CeO2(110) Surface  

Science Conference Proceedings (OSTI)

Methanol decomposition on the stoichiometric CeO2(110) surface has been investigated using density functional theory slab calculations. Three possible initial steps to decompose methanol by breaking one of three bonds (O?H, C?O and C?H) of methanol were examined. The relative order of thermodynamic stability for the three possible bond scission steps is: C?H > O?H > C?O. We further isolated transition state and determined activation energy for each bond-breaking mode using the nudged elastic method. The activation barrier for the most favorable dissociation mode, the O?H bond scission, is 0.3 eV on the (110) surface. An even lower activation barrier ( C?O > C?H. Our results are consistent with the previous experimental observation that methoxy is the dominant surface species after a stoichiometric CeO2 surface was exposed to methanol. The experimentally observed methanol chemistry was determined by the kinetics of initial dissociation steps rather than the thermodynamic stability of product states. Surface coverage of methanol was found to affect the relative stability between molecular and dissociative adsorption modes. Dissociative adsorption modes are preferred thermodynamically for methanol coverage up to 0.5 ML but only molecular adsorption was stable at full monolayer coverage. This work was supported by a Laboratory Directed Research and Development (LDRD) project of the Pacific Northwest National Laboratory (PNNL). The computations were performed using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), which is a U.S. Department of Energy national scientific user facility located at PNNL in Richland, Washington. Computing time was made under a Computational Grand Challenge ďComputational CatalysisĒ. Part of the computing time was also granted by the National Energy Research Scientific Computing Center (NERSC).

Mei, Donghai; Deskins, N. Aaron; Dupuis, Michel; Ge, Qingfeng

2008-03-20T23:59:59.000Z

64

Perspective: Advances and challenges in treating van der Waals dispersion forces in density functional theory  

E-Print Network (OSTI)

of the previous noble gas and group III atom. Fur- thermore, the dispersion energy, Edisp, is scaled according range dispersion interaction with the underlying exchange or XC functionals. A. Gas phase clustersPerspective: Advances and challenges in treating van der Waals dispersion forces in density

Alavi, Ali

65

Prediction of [superscript 57] Fe Mossbauer Parameters by Density Functional Theory: A Benchmark Study  

E-Print Network (OSTI)

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 ...

Bochevarov, Arteum D.

66

Oxygen Reduction Reaction on Dispersed and Core-Shell Metal Alloy Catalysts: Density Functional Theory Studies  

E-Print Network (OSTI)

Pt-based alloy surfaces are used to catalyze the electrochemical oxygen reduction reaction (ORR), where molecular oxygen is converted into water on fuel cell electrodes. In this work, we address challenges due to the cost of high Pt loadings in the cathode electrocatalyst, as well as those arising from catalyst durability. We aim to develop an increased understanding of the factors that determine ORR activity together with stability against surface segregation and dissolution of Pt-based alloys. We firstly focus on the problem of determining surface atomic distribution resulting from surface segregation phenomena. We use first-principles density functional theory (DFT) calculations on PtCo and Pt3Co overall compositions, as well as adsorption of water and atomic oxygen on PtCo(111) and Pt-skin structures. The bonding between water and surfaces of PtCo and Pt-skin monolayers are investigated in terms of orbital population. Also, on both surfaces, the surface reconstruction effect due to high oxygen coverage and water co-adsorption is investigated. Although the PtCo structures show good activity, a large dissolution of Co atoms tends to occur in acid medium. To tackle this problem, we examine core-shell structures which showed improved stability and activity compared to Pt(111), in particular, one consisting of a surface Pt-skin monolayer over an IrCo or Ir3Co core, with or without a Pd interlayer between the Pt surface and the Ir-Co core. DFT analysis of surface segregation, surface stability against dissolution, surface Pourbaix diagrams, and reaction mechanisms provide useful predictions on catalyst durability, onset potential for water oxidation, surface atomic distribution, coverage of oxygenated species, and activity. The roles of the Pd interlayer in the core-shell structures that influence higher ORR activity are clarified. Furthermore, the stability and activity enhancement of new shell-anchor-core structures of Pt/Fe-C/core, Pt/Co-C/core and Pt/Ni-C/core are demonstrated with core materials of Ir, Pd3Co, Ir3Co, IrCo and IrNi. Based on the analysis, Pt/Fe-C/Ir, Pt/Co-C/Ir, Pt/Ni-C/Ir, Pt/Co-C/Pd3Co, Pt/Fe-C/Pd3Co, Pt/Co- C/Ir3Co, Pt/Fe-C/Ir3Co, Pt/Co-C/IrCo, Pt/Co-C/IrNi, and Pt/Fe-C/IrNi structures show promise in terms of both improved durability and relatively high ORR activity.

Hirunsit, Pussana

2010-08-01T23:59:59.000Z

67

Density Functional Theory Study of Surface Carbonate Formation on BaO(001)  

Science Conference Proceedings (OSTI)

Periodic density functional theory calculations have been used to study the formation and stability of surface carbonate on BaO(001) upon CO2 exposures. CO2 adsorbs at Lewis basic Os site forming anionic surface carbonate ( ) species until one monolayer coverage (1ML). Certain amount of electrons has been transferred from the surface to CO2 after CO2 adsorption. The adsorption energy of CO2 decreases with the increasing coverage as a combinative result of the less electrons accepted by each adsorbed CO2 and the lateral repulsive interactions. At ?CO2 0.75 ML, dramatic surface reconstruction had been found for the parallel pattern of surface carbonates that initially arranged on BaO(001). Due to strong lateral repulsion between the surface carbonates, the surface reconstruction actually pulls the surface Ba atom out of the surface plane, suggesting a possible onset of phase transition from surface carbonate overlayer to crystalline bulk-like barium carbonate. Surface free energy calculations have been performed to study the stability of surface carbonate at different temperature and pressure conditions. Our calculations indicate that surface carbonates decompose at 850 K at low coverage. For the fully covered carbonate overlayer, surface carbonate will become unstable at about 600 K. This is in good agreement with previous experimental observations. Finally, the effect of surface hydroxyl on the stability of surface carbonate is investigated. At low hydroxyl coverage, the neighboring hydroxyl stabilizes surface carbonate. On the fully hydroxylated BaO surface, the chelating bicarbonate instead of surface carbonate is formed upon CO2 adsorption. This work, performed in the Institute for Interfacial Catalysis at Pacific Northwest National Laboratory (PNNL), was partially supported by a PNNL Laboratory Directed Research and Development (LDRD) project. Computing time was granted by the National Energy Research Scientific Computing Center (NERSC) under project No. m752, and also by the scientific user project (st30469) using the Molecular Science Computing Facility in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL). The EMSL is a U.S. DOE national scientific user facility located at PNNL, and supported by the DOEís Office of Biological and Environmental Research.

Mei, Donghai

2010-02-04T23:59:59.000Z

68

Restoration of the Derivative Discontinuity in Kohn-Sham Density Functional Theory: An Efficient Scheme for Energy Gap Correction  

E-Print Network (OSTI)

From the perspective of perturbation theory, we propose a systematic procedure for the evaluation of the derivative discontinuity (DD) of the exchange-correlation energy functional in Kohn-Sham density functional theory (KS-DFT), wherein the exact DD can in principle be obtained by summing up all the perturbation corrections to infinite order. Truncation of the perturbation series at low order yields an efficient scheme for obtaining the approximate DD. While the zeroth-order theory yields a vanishing DD, the first-order correction to the DD can be expressed as an explicit universal functional of the ground-state density and the KS lowest unoccupied molecular orbital density, allowing the direct evaluation of the DD in the standard KS method without extra computational cost. The fundamental gap can be predicted by adding the estimated DD to the KS gap. This scheme is shown to be accurate in the prediction of the fundamental gaps for a wide variety of atoms and molecules.

Jeng-Da Chai; Po-Ta Chen

2012-11-03T23:59:59.000Z

69

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

E-Print Network (OSTI)

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

Ong, Shyue Ping

70

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

Science Conference Proceedings (OSTI)

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

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

2012-11-21T23:59:59.000Z

71

Accuracy of density functional theory in predicting formation energies of ternary oxides from binary oxides and its implication on phase stability  

E-Print Network (OSTI)

The evaluation of reaction energies between solids using density functional theory (DFT) is of practical importance in many technological fields and paramount in the study of the phase stability of known and predicted ...

Hautier, Geoffroy

72

Supplemental Material for Angular Momentum Dependent Orbital Free Density Functional Theory  

E-Print Network (OSTI)

for Energy and the Environment, Princeton University, Princeton, New Jersey 08544, USA 2 Material Science region [Fig. 1(c)], (r) = R R(rR) + I(r), (1) where R(rR) is the electron density inside the MT sphere centered on site R, I(r) is the interstitial electron density which is 0 inside the spheres and rR = r - R

Florian, Libisch

73

Density Functional Theory Simulations Predict New Materials for Magnesium-Ion Batteries (Fact Sheet), NREL Highlights, Science  

SciTech Connect

Multivalence is identified in the light element, B, through structure morphology. Boron sheets exhibit highly versatile valence, and the layered boron materials may hold the promise of a high-energy-density magnesium-ion battery. Practically, boron is superior to previously known multivalence materials, especially transition metal compounds, which are heavy, expensive, and often not benign. Based on density functional theory simulations, researchers at the National Renewable Energy Laboratory (NREL) have predicted a series of stable magnesium borides, MgB{sub x}, with a broad range of stoichiometries, 2 < x < 16, by removing magnesium atoms from MgB{sub 2}. The layered boron structures are preserved through an in-plane topological transformation between the hexagonal lattice domains and the triangular domains. The process can be reversibly switched as the charge transfer changes with Mg insertion/extraction. The mechanism of such a charge-driven transformation originates from the versatile valence state of boron in its planar form. The discovery of these new physical phenomena suggests the design of a high-capacity magnesium-boron battery with theoretical energy density 876 mAh/g and 1550 Wh/L.

2011-10-01T23:59:59.000Z

74

Helium under high pressure: A comparative study of all-electron and pseudopotential methods within density functional theory  

E-Print Network (OSTI)

We have calculated the ground state electronic structure of He under pressure from 0 to 1500 GPa using both all-electron full-potential and pseudopotential methods based on the density functional theory (DFT). We find that throughout this pressure range, pseudopotentials yield essentially the same energy-volume curve for all of bcc, fcc, and hcp configurations as does the full-potential method, a strong indication that pseudopotential approximation works well for He both as the common element in some giant planets and as detrimental impurities in fusion reactor materials. The hcp lattice is always the most stable structure and bcc the least stable one. Since the energy preference of hcp over fcc and bcc is within 0.01 eV below 100 GPa and about 0.1 eV at 1500 GPa, on the same order of the error bar in local or semi-local density approximations in DFT, phase transitions can only be discussed with more precise description of electron correlation in Quantum Monte Carlo or DFT-based GW methods.

Xiao, W; Geng, W T

2012-01-01T23:59:59.000Z

75

Quantifying the importance of orbital over spin correlations in delta-Pu within density-functional theory  

SciTech Connect

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.

Soderlind, P; Wolfer, W

2007-07-27T23:59:59.000Z

76

New density functional theory approaches for enabling prediction of chemical and physical properties of plutonium and other actinides.  

SciTech Connect

Density Functional Theory (DFT) based Equation of State (EOS) construction is a prominent part of Sandia's capabilities to support engineering sciences. This capability is based on amending experimental data with information gained from computational investigations, in parts of the phase space where experimental data is hard, dangerous, or expensive to obtain. A prominent materials area where such computational investigations are hard to perform today because of limited accuracy is actinide and lanthanide materials. The Science of Extreme Environment Lab Directed Research and Development project described in this Report has had the aim to cure this accuracy problem. We have focused on the two major factors which would allow for accurate computational investigations of actinide and lanthanide materials: (1) The fully relativistic treatment needed for materials containing heavy atoms, and (2) the needed improved performance of DFT exchange-correlation functionals. We have implemented a fully relativistic treatment based on the Dirac Equation into the LANL code RSPt and we have shown that such a treatment is imperative when calculating properties of materials containing actinides and/or lanthanides. The present standard treatment that only includes some of the relativistic terms is not accurate enough and can even give misleading results. Compared to calculations previously considered state of the art, the Dirac treatment gives a substantial change in equilibrium volume predictions for materials with large spin-orbit coupling. For actinide and lanthanide materials, a Dirac treatment is thus a fundamental requirement in any computational investigation, including those for DFT-based EOS construction. For a full capability, a DFT functional capable of describing strongly correlated systems such as actinide materials need to be developed. Using the previously successful subsystem functional scheme developed by Mattsson et.al., we have created such a functional. In this functional the Harmonic Oscillator Gas is providing the necessary reference system for the strong correlation and localization occurring in actinides. Preliminary testing shows that the new Hao-Armiento-Mattsson (HAM) functional gives a trend towards improved results for the crystalline copper oxide test system we have chosen. This test system exhibits the same exchange-correlation physics as the actinide systems do, but without the relativistic effects, giving access to a pure testing ground for functionals. During the work important insights have been gained. An example is that currently available functionals, contrary to common belief, make large errors in so called hybridization regions where electrons from different ions interact and form new states. Together with the new understanding of functional issues, the Dirac implementation into the RSPt code will permit us to gain more fundamental understanding, both quantitatively and qualitatively, of materials of importance for Sandia and the rest of the Nuclear Weapons complex.

Mattsson, Ann Elisabet

2012-01-01T23:59:59.000Z

77

The 2 1 reconstruction of the rutile TiO2(011) surface: A combined density functional theory, X-ray diffraction, and scanning  

E-Print Network (OSTI)

t An extensive search for possible structural models of the (2 √? 1)-reconstructed rutile TiO2(011) surface was carried out by means of density functional theory (DFT) calculations. A number of models were iden- tified that have much lower surface energies than the previously-proposed `titanyl' and `microfaceting' models

Diebold, Ulrike

78

"Kohn-Shamification" of the classical density-functional theory of inhomogeneous polar molecular liquids with application to liquid hydrogen chloride  

E-Print Network (OSTI)

The Gordian knot of density-functional theories for classical molecular liquids remains finding an accurate free-energy functional in terms of the densities of the atomic sites of the molecules. Following Kohn and Sham, we show how to solve this problem by considering noninteracting molecules in a set of effective potentials. This shift in perspective leads to an accurate and computationally tractable description in terms of simple three-dimensional functions. We also treat both the linear- and saturation- dielectric responses of polar systems, presenting liquid hydrogen chloride as a case study.

Johannes Lischner; T. A. Arias

2008-06-27T23:59:59.000Z

79

Correcting Density Functional Theory for Accurate Predictions of Compound Enthalpies of Formation: Fitted Elemental-Phase Reference Energies  

Science Conference Proceedings (OSTI)

Despite the great success that theoretical approaches based on density functional theory have in describing properties of solid compounds, accurate predictions of the enthalpies of formation ({Delta}H{sub f}) of insulating and semiconducting solids still remain a challenge. This is mainly due to incomplete error cancellation when computing the total energy differences between the compound total energy and the total energies of its elemental constituents. In this paper we present an approach based on GGA + U calculations, including the spin-orbit coupling, which involves fitted elemental-phase reference energies (FERE) and which significantly improves the error cancellation resulting in accurate values for the compound enthalpies of formation. We use an extensive set of 252 binary compounds with measured {Delta}H{sub f} values (pnictides, chalcogenides, and halides) to obtain FERE energies and show that after the fitting, the 252 enthalpies of formation are reproduced with the mean absolute error MAE = 0.054 eV/atom instead of MAE {approx} 0.250 eV/atom resulting from pure GGA calculations. When applied to a set of 55 ternary compounds that were not part of the fitting set the FERE method reproduces their enthalpies of formation with MAE = 0.048 eV/atom. Furthermore, we find that contributions to the total energy differences coming from the spin-orbit coupling can be, to a good approximation, separated into purely atomic contributions which do not affect {Delta}H{sub f}. The FERE method, hence, represents a simple and general approach, as it is computationally equivalent to the cost of pure GGA calculations and applies to virtually all insulating and semiconducting compounds, for predicting compound {Delta}H{sub f} values with chemical accuracy. We also show that by providing accurate {Delta}H{sub f} the FERE approach can be applied for accurate predictions of the compound thermodynamic stability or for predictions of Li-ion battery voltages.

Stevanovic, V.; Lany, S.; Zhang, X.; Zunger, A.

2012-03-15T23:59:59.000Z

80

A density functional theory study of the oxidation of methanol to formaldehyde over vanadia supported on silica, titania, and zirconia  

DOE Green Energy (OSTI)

Density functional theory was used to investigate the mechanism and kinetics of methanol oxidation to formaldehyde over vanadia supported on silica, titania, and zirconia. The catalytically active site was modeled as an isolated VO{sub 4} unit attached to the support. The calculated geometry and vibrational frequencies of the active site are in good agreement with experimental measurements both for model compounds and oxide-supported vanadia. Methanol adsorption is found to occur preferentially with the rupture of a V-O-M bond (M = Si, Ti, Zr) and with preferential attachment of a methoxy group to V. The vibrational frequencies of the methoxy group are in good agreement with those observed experimentally as are the calculated isobars. The formation of formaldehyde is assumed to occur via the transfer of an H atom of a methoxy group to the O atom of the V=O group. The activation energy for this process is found to be in the range of 199-214 kJ/mol and apparent activation energies for the overall oxidation of methanol to formaldehyde are predicted to lie in the range of 112-123 kJ/mol, which is significantly higher than that found experimentally. Moreover, the predicted turnover frequency (TOF) for methanol oxidation is found to be essentially independent of support composition, whereas experiments show that the TOF is 10{sup 3} greater for titania- and zirconia-supported vanadia than for silica-supported vanadia. Based on these findings, it is proposed that the formation of formaldehyde from methoxy groups may require pairs of adjacent VO{sub 4} groups or V{sub 2}O{sub 7} dimer structures.

Khaliullin, Rustam Z.; Bell, Alexis T.

2002-09-05T23:59:59.000Z

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81

On the Accuracy of van der Waals Inclusive Density-Functional Theory Exchange-Correlation Functionals for Ice at Ambient and High Pressures  

E-Print Network (OSTI)

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 proper...

Santra, Biswajit; Tkatchenko, Alexandre; AlfŤ, Dario; Slater, Ben; Michaelides, Angelos; Car, Roberto; Scheffler, Matthias

2013-01-01T23:59:59.000Z

82

On the Accuracy of van der Waals Inclusive Density-Functional Theory Exchange-Correlation Functionals for Ice at Ambient and High Pressures  

E-Print Network (OSTI)

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.

Biswajit Santra; Ji?Ū Klimeö; Alexandre Tkatchenko; Dario AlfŤ; Ben Slater; Angelos Michaelides; Roberto Car; Matthias Scheffler

2013-07-12T23:59:59.000Z

83

Sedimentation of a two-dimensional colloidal mixture exhibiting liquid-liquid and gas-liquid phase separation: a dynamical density functional theory study  

E-Print Network (OSTI)

We present dynamical density functional theory results for the time evolution of the density distribution of a sedimenting model two-dimensional binary mixture of colloids. The interplay between the bulk phase behaviour of the mixture, its interfacial properties at the confining walls, and the gravitational field gives rise to a rich variety of equilibrium and non-equilibrium morphologies. In the fluid state, the system exhibits both liquid-liquid and gas-liquid phase separation. As the system sediments, the phase separation significantly affects the dynamics and we explore situations where the final state is a coexistence of up to three different phases. Solving the dynamical equations in two-dimensions, we find that in certain situations the final density profiles of the two species have a symmetry that is different from that of the external potentials, which is perhaps surprising, given the statistical mechanics origin of the theory. The paper concludes with a discussion on this.

Alexandr Malijevsky; Andrew J. Archer

2013-09-17T23:59:59.000Z

84

Accurate dipole polarizabilities for water clusters n=2-12 at the coupled-cluster level of theory and benchmarking of various density functionals.  

Science Conference Proceedings (OSTI)

The static dipole polarizabilities of water clusters (2 {le} N {le} 12) are determined at the coupled-cluster level of theory (CCSD). For the dipole polarizability of the water monomer it was determined that the role of the basis set is more important than that of electron correlation and that the basis set augmentation converges with two sets of diffuse functions. The CCSD results are used to benchmark a variety of density functionals while the performance of several families of basis sets (Dunning, Pople, and Sadlej) in producing accurate values for the polarizabilities was also examined. The Sadlej family of basis sets was found to produce accurate results when compared to the ones obtained with the much larger Dunning basis sets. It was furthermore determined that the PBE0 density functional with the aug-cc-pVDZ basis set produces overall remarkably accurate polarizabilities at a moderate computational cost.

Hammond, J.; Govind, N.; Kowalski, K.; Autschbach, J.; Xantheas, S.; PNNL; Univ. of Buffalo

2009-12-07T23:59:59.000Z

85

Density-dependent covariant energy density functionals  

Science Conference Proceedings (OSTI)

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.

Lalazissis, G. A. [Physics Department, Aristotle University of Thessaloniki, GR-54124 (Greece)

2012-10-20T23:59:59.000Z

86

Linear-response and real-time time-dependent density functional theory studies of core-level near-edge x-ray absorption  

Science Conference Proceedings (OSTI)

We discuss our implementation and application of time-dependent density functional theory (TDDFT) to core-level near-edge absorption spectroscopy, using both linear-response (LR) and real-time (RT) approaches. We briefly describe our restricted window TDDFT (REWTDDFT) approach for core excitations which has also been reported by others groups. This is followed by a detailed discussion of real-time TDDFT techniques tailored to core excitations, including obtaining spectral information through delta-function excitation, post-processing time-dependent signals, and resonant excitation through quasi-monochromatic excitation. We present results for the oxygen K-edge of water and carbon dioxide; the carbon K-edge of carbon dioxide; the ruthenium L3-edge for the hexaamminerutheium(III) ion, including scalar relativistic corrections via the zeroth order regular approximation (ZORA); and the carbon and fluorine K-edges for a series of fluorobenzenes. In all cases, the calculated spectra are found to be in good agreement with experiment, requiring only a uniform shift on the order of a few percent. Real-time TDDFT visualization of excited state charge densities are used to visually examine the nature of each excitation, which gives insight into the effects of atoms bound to the absorbing center.

Lopata, Kenneth A.; Van Kuiken, Benjamin E.; Khalil, Munira; Govind, Niranjan

2012-09-03T23:59:59.000Z

87

Density functional theory studies on theelectronic, structural, phonon dynamicaland thermo-stability properties of bicarbonates MHCO3, M D Li, Na, K  

Science Conference Proceedings (OSTI)

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 opticalĖtransverse 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 0Ė900 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.

Duan, Yuhua; Zhang, Bo; Sorescu, Dan C.; Johnson, Karl; Majzoub, Eric H; Luebke, David R.

2012-07-01T23:59:59.000Z

88

Building a Universal Nuclear Energy Density Functional  

NLE Websites -- All DOE Office Websites (Extended Search)

Building a Universal Nuclear Energy Density Functional Building a Universal Nuclear Energy Density Functional VaryMatrix.png Collaboration with mathematicians and computational...

89

Density Functional Theory and Molecular Dynamics Studies on Energetics and Kinetics for Electro-Active Polymers: PVDF and P(VDF-TrFE)  

E-Print Network (OSTI)

We use first principles methods to study static and dynamical mechanical properties of the ferroelectric polymer Poly(vinylidene fluoride) (PVDF) and its copolymer with trifluoro ethylene (TrFE). We use density functional theory [within the generalized gradient approximation (DFT-GGA)] to calculate structures and energetics for various crystalline phases for PVDF and P(VDF-TrFE). We find that the lowest energy phase for PVDF is a non-polar crystal with a combination of trans (T) and gauche (G) bonds; in the case of the copolymer the role of the extra (bulkier) F atoms is to stabilize T bonds. This leads to the higher crystallinity and piezoelectricity observed experimentally. Using the MSXX first principles-based force field (FF) with molecular dynamics (MD), we find that the energy barrier necessary to nucleate a kink (gauche pairs separated by trans bonds) in an all-T crystal is much lower (14.9 kcal/mol) in P(VDF-TrFE) copolymer than in PVDF (24.8 kcal/mol). This correlates with the observation that the polar phase of the copolymer exhibits a solid-solid a transition to a non-polar phase under heating while PVDF directly melts. We also studied the mobility of an interface between a polar and non-polar phases under uniaxial stress; we find a lower threshold stress and a higher mobility in the copolymer as compared with PVDF. Finally, considering plastic deformation under applied shear, we find that the chains for P(VDF-TrFE) have a very low resistance to sliding, particularly along the chain direction. The atomistic characterization of these "unit mechanisms" provides essential input to mesoscopic or macroscopic models of electro-active polymers.

H. B. Su; Alejandro Strachan; William A. Goddard III

2004-08-09T23:59:59.000Z

90

Density functional theory study of the structural, electronic, lattice dynamical, and thermodynamic properties of Li4SiO4 and its capability for CO2 capture  

SciTech Connect

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.

Duan, Yuhua; Parlinski, K.

2011-01-01T23:59:59.000Z

91

Nuclear Energy Density Functionals Constrained by Low-Energy QCD  

E-Print Network (OSTI)

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

Vretenar, Dario

2008-01-01T23:59:59.000Z

92

Nuclear Energy Density Functionals Constrained by Low-Energy QCD  

E-Print Network (OSTI)

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

Dario Vretenar

2008-02-06T23:59:59.000Z

93

Density Functional Theory Study of CO Adsorption on Cu(I)-ZSM-5 Xiaobo Zheng,* Yihua Zhang, and Alexis T. Bell*  

E-Print Network (OSTI)

lithiumionsolvationby HMPA: Vandyshev, V.N.;Korolev,V.P.;Krest0v.G. A. Thermochim.Acta 1990,169,57.Goralski, P National Supercomputer Facility, a resource of the Center for Theory and Simulations in Science

Bell, Alexis T.

94

Development of Novel Density Functionals for Thermochemical Kinetics  

E-Print Network (OSTI)

A new density functional theory (DFT) exchange-correlation functional for the exploration of reaction mechanisms is proposed. This new functional, denoted BMK (Boese-Martin for Kinetics), has an accuracy in the 2 kcal/mol range for transition state barriers but, unlike previous attempts at such a functional, this improved accuracy does not come at the expense of equilibrium properties. This makes it a general-purpose functional whose domain of applicability has been extended to transition states, rather than a specialized functional for kinetics. The improvement in BMK rests on the inclusion of the kinetic energy density together with a large value of the exact exchange mixing coefficient. For this functional, the kinetic energy density appears to correct `back' the excess exact exchange mixing for ground-state properties, possibly simulating variable exchange.

Boese, A D; Martin, Jan M. L.

2004-01-01T23:59:59.000Z

95

Instabilities in the Nuclear Energy Density Functional  

E-Print Network (OSTI)

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

M. Kortelainen; T. Lesinski

2010-02-05T23:59:59.000Z

96

Velocity Probability Density Functions for Oceanic Floats  

Science Conference Proceedings (OSTI)

Probability density functions (PDFs) of daily velocities from subsurface floats deployed in the North Atlantic and equatorial Atlantic Oceans are examined. In general, the PDFs are approximately Gaussian for small velocities, but with significant ...

Annalisa Bracco; J. H. LaCasce; Antonello Provenzale

2000-03-01T23:59:59.000Z

97

Velocity Probability Density Functions from Altimetry  

Science Conference Proceedings (OSTI)

Probability density functions (pdfs) are employed to evaluate the distribution of velocities in the global ocean. This study computes pdfs of ocean surface velocity using altimetric data from the TOPEX/Poseidon satellite. Results show that the ...

Sarah T. Gille; Stefan G. Llewellyn Smith

2000-01-01T23:59:59.000Z

98

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

SciTech Connect

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

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

2009-01-01T23:59:59.000Z

99

Energy Density Functional for Nuclei and Neutron Stars  

Science Conference Proceedings (OSTI)

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

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

2013-01-01T23:59:59.000Z

100

Neutron skin uncertainties of Skyrme energy density functionals  

E-Print Network (OSTI)

Background: Neutron-skin thickness is an excellent indicator of isovector properties of atomic nuclei. As such, it correlates strongly with observables in finite nuclei that depend on neutron-to-proton imbalance and the nuclear symmetry energy that characterizes the equation of state of neutron-rich matter. A rich worldwide experimental program involving studies with rare isotopes, parity violating electron scattering, and astronomical observations is devoted to pinning down the isovector sector of nuclear models. Purpose: We assess the theoretical systematic and statistical uncertainties of neutron-skin thickness and relate them to the equation of state of nuclear matter, and in particular to nuclear symmetry energy parameters. Methods: We use the nuclear superfluid Density Functional Theory with several Skyrme energy density functionals and density dependent pairing. To evaluate statistical errors and their budget, we employ the statistical covariance technique. Results: We find that the errors on neutron skin increase with neutron excess. Statistical errors due to uncertain coupling constants of the density functional are found to be larger than systematic errors, the latter not exceeding 0.06 fm in most neutron-rich nuclei across the nuclear landscape. The single major source of uncertainty is the poorly determined slope L of the symmetry energy that parametrizes its density dependence. Conclusions: To provide essential constraints on the symmetry energy of the nuclear energy density functional, next-generation measurements of neutron skins are required to deliver precision better than 0.06 fm.

M. Kortelainen; J. Erler; W. Nazarewicz; N. Birge; Y. Gao; E. Olsen

2013-07-16T23:59:59.000Z

Note: This page contains sample records for the topic "density functional theory" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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101

Validation of Density Functional Theory for Materials  

Science Conference Proceedings (OSTI)

... One of the the crucial aspects in high-throughput computational screening of metal-organic frameworks (MOFs) for carbon capture and other ...

2013-07-18T23:59:59.000Z

102

Functional compression : theory and application  

E-Print Network (OSTI)

We consider the problem of functional compression. The objective is to separately compress possibly correlated discrete sources such that an arbitrary deterministic function of those sources can be computed given the ...

Doshi, Vishal D. (Vishal Devendra)

2008-01-01T23:59:59.000Z

103

Building A Universal Nuclear Energy Density Functional (UNEDF)  

Science Conference Proceedings (OSTI)

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

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

104

Green's functions for theories with massless particles (in theory)  

E-Print Network (OSTI)

Using the method of perturbative renormalization developed by Epstein and Glaser (ibid., vol.XIX, no.3, p.211 (1973)) it is shown that Green's functions exist for theories with massless particles such as QED, and lambda : phi /sup 2n/ theories. Growth properties are given in momentum space. In the case of QED, it is also shown that one can perform the physical mass renormalization. (6 refs).

Blanchard, P

1975-01-01T23:59:59.000Z

105

Determining Relative f and d Orbital Contributions to M?Cl Covalency in MCl62Ė (M = Ti, Zr, Hf, U) and UOCl5 Using Cl K-Edge X-ray Absorption Spectroscopy and Time-Dependent Density Functional Theory  

SciTech Connect

Chlorine K-edge X-ray absorption spectroscopy (XAS) and ground-state and time-dependent hybrid density functional theory (DFT) were used to probe electronic structure for O{sub h}-MCl{sub 6}{sup 2-}(M = Ti, Zr, Hf, U) and C{sub 4v}-UOCl{sub 5}{sup -}, and to determine the relative contributions of valence 3d, 4d, 5d, 6d, and 5f orbitals in M-Cl bonding. Spectral interpretations were guided by time-dependent DFT calculated transition energies and oscillator strengths, which agree well with the experimental XAS spectra. The data provide new spectroscopic evidence for the involvement of both 5f and 6d orbitals in actinide-ligand bonding in UCl{sub 6}{sup 2-}. For the MCl{sub 6}{sup 2-}, where transitions into d orbitals of t{sub 2g} symmetry are spectroscopically resolved for all four complexes, the experimentally determined Cl 3p character per M-Cl bond increases from 8.3(4)% (TiCl{sub 6}{sup 2-}) to 10.3(5)% (ZrCl{sub 6}{sup 2-}), 12(1)% (HfCl{sub 6}{sup 2-}), and 26 18(1)% (UCl{sub 6}{sup 2-}). Chlorine K-edge XAS spectra of UOCl{sub 5}{sup -} provide additional insights into the transition assignments by 27 lowering the symmetry to C{sub 4v}, where five pre-edge transitions into both 5f and 6d orbitals are observed. For UCl{sub 6}{sup 2-}, the XAS data 28 suggest that orbital mixing associated with the U 5f orbitals is considerably lower than that of the U 6d orbitals. For both UCl{sub 6}{sup 2-}29 and UOCl{sub 5}{sup -}, the ground-state DFT calculations predict a larger 5f contribution to bonding than is determined experimentally. 30 These findings are discussed in the context of conventional theories of covalent bonding for d- and f-block metal complexes.

Minasian, Stefan G.; Keith, Jason M.; Batista, Enrique R.; Boland, Kevin S.; Clark, David L.; Conradson, Steven D.; Kozimor, Stosh A.; Martin, Richard L.; Schwarz, Daniel E.; Shuh, David K.; Wagner, Gregory L.; Wilkerson, Marianne P.; Wolfsberg, Laura E.; Yang, Ping

2012-03-09T23:59:59.000Z

106

Nonextensive theory of dark matter and gas density profiles  

E-Print Network (OSTI)

Pronounced core-halo patterns of dark matter and gas density profiles, observed in relaxed galaxies and clusters, were hitherto fitted by empirical power-laws. On the other hand, similar features are well known from astrophysical plasma environments, subject to long-range interactions, modeled in the context of nonextensive entropy generalization. We link nonextensive statistics to the problem of density distributions in large-scale structures and provide fundamentally derived density profiles, representing accurately the characteristics of both, dark matter and hot plasma distributions, as observed or generated in simulations. The bifurcation of the density distribution into a kinetic dark matter and thermodynamic gas branch turns out as natural consequence of the theory and is controlled by a single parameter kappa, measuring physically the degree of coupling within the system. Consequently, it is proposed to favor nonextensive distributions, derived from the fundamental physical context of entropy generali...

Leubner, M P

2005-01-01T23:59:59.000Z

107

A first-principles density functional theory study of the electronic structural and thermodynamic properties of M2ZrO3 and M2CO3 (M=Na, K) and their capabilities for CO2 capture  

SciTech Connect

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.

Yuhua Duan

2012-01-01T23:59:59.000Z

108

SURFACE SYMMETRY ENERGY OF NUCLEAR ENERGY DENSITY FUNCTIONALS  

Science Conference Proceedings (OSTI)

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

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

2010-12-20T23:59:59.000Z

109

Nonextensive theory of dark matter and gas density profiles  

E-Print Network (OSTI)

Pronounced core-halo patterns of dark matter and gas density profiles, observed in relaxed galaxies and clusters, were hitherto fitted by empirical power-laws. On the other hand, similar features are well known from astrophysical plasma environments, subject to long-range interactions, modeled in the context of nonextensive entropy generalization. We link nonextensive statistics to the problem of density distributions in large-scale structures and provide fundamentally derived density profiles, representing accurately the characteristics of both, dark matter and hot plasma distributions, as observed or generated in simulations. The bifurcation of the density distribution into a kinetic dark matter and thermodynamic gas branch turns out as natural consequence of the theory and is controlled by a single parameter kappa, measuring physically the degree of coupling within the system. Consequently, it is proposed to favor nonextensive distributions, derived from the fundamental physical context of entropy generalization and accounting for nonlocality and long-range interactions in gravitationally coupled systems, when modeling observed density profiles of astrophysical structures.

M. P. Leubner

2006-02-27T23:59:59.000Z

110

The nuclear energy density functional formalism  

E-Print Network (OSTI)

The present document focuses on the theoretical foundations of the nuclear energy density functional (EDF) method. As such, it does not aim at reviewing the status of the field, at covering all possible ramifications of the approach or at presenting recent achievements and applications. The objective is to provide a modern account of the nuclear EDF formalism that is at variance with traditional presentations that rely, at one point or another, on a {\\it Hamiltonian-based} picture. The latter is not general enough to encompass what the nuclear EDF method represents as of today. Specifically, the traditional Hamiltonian-based picture does not allow one to grasp the difficulties associated with the fact that currently available parametrizations of the energy kernel $E[g',g]$ at play in the method do not derive from a genuine Hamilton operator, would the latter be effective. The method is formulated from the outset through the most general multi-reference, i.e. beyond mean-field, implementation such that the single-reference, i.e. "mean-field", derives as a particular case. As such, a key point of the presentation provided here is to demonstrate that the multi-reference EDF method can indeed be formulated in a {\\it mathematically} meaningful fashion even if $E[g',g]$ does {\\it not} derive from a genuine Hamilton operator. In particular, the restoration of symmetries can be entirely formulated without making {\\it any} reference to a projected state, i.e. within a genuine EDF framework. However, and as is illustrated in the present document, a mathematically meaningful formulation does not guarantee that the formalism is sound from a {\\it physical} standpoint. The price at which the latter can be enforced as well in the future is eventually alluded to.

T. Duguet

2013-09-02T23:59:59.000Z

111

Ab initio and density functional studies of hydrocarbon adsorption in zeolites.  

SciTech Connect

The adsorption energies of methane and ethane in zeolites are investigated with ab initio molecular orbital theory and density functional theory. In this work we have used zeolite cluster models containing two, three, and five tetrahedral (Si, Al) atoms and have found equilibrium structures for complexes of methane, ethane, and propane with an acid site. If a large enough cluster is used and correlation effects are included via perturbation theory, the calculated adsorption energy for ethane is about 5 kcal/mol compared with the experimental value of 7.5 kcal/mol. The B3LYP density functional method gives a much smaller binding of {approximately}1 kcal/mol for ethane. The reason for the failure of density fictional theory is unclear.

Curtiss, L. A.

1998-08-21T23:59:59.000Z

112

Free energies, vacancy concentrations and density distribution anisotropies in hard--sphere crystals: A combined density functional and simulation study  

E-Print Network (OSTI)

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.

M. Oettel; S. Goerig; A. Haertel; H. Loewen; M. Radu; T. Schilling

2010-09-03T23:59:59.000Z

113

Density Functional Studies of Methanol Decomposition on Subnanometer Pd Clusters  

DOE Green Energy (OSTI)

A density functional theory study of the decomposition of methanol on subnanometer palladium clusters (primarily Pd4) is presented. Methanol dehydrogenation through C-H bond breaking to form hydroxymethyl (CH2OH) as the initial step, followed by steps involving formation of hydroxymethylene (CHOH), formyl (CHO), and carbon monoxide (CO), is found to be the most favorable reaction pathway. A competing dehydrogenation pathway with O-H bond breaking as the first step, followed by formation of methoxy (CH3O) and formaldehyde (CH2O), is slightly less favorable. In contrast, pathways involving C-O bond cleavage are much less energetically favorable, and no feasible pathways involving C-O bond formation to yield dimethyl ether (CH3OCH3) are found. Comparisons of the results are made with methanol decomposition products adsorbed on more extended Pd surfaces; all reaction intermediates are found to bind slightly more strongly to the clusters than to the surfaces.

Mehmood, Faisal; Greeley, Jeffrey P.; Curtiss, Larry A.

2009-12-31T23:59:59.000Z

114

Nuclear Parton Densities and Structure Functions  

E-Print Network (OSTI)

We calculate nuclear parton distribution functions (PDFs), using the constituent quark model. We find the bounded valon distributions in a nuclear to be related to free valon distributions in a nucleon. By using improved bounded valon distributions for a nuclear with atomic number $A$ and the partonic structure functions inside the valon, we can calculate the nuclear structure function in $x$ space. The results for nuclear structure-function ratio $F_2^A/F_2^D$ at some values of $A$ are in good agreement with the experimental data.

S. Atashbar Tehrani; Ali N. Khorramian; A. Mirjalili

2004-10-27T23:59:59.000Z

115

Microscopically-based energy density functionals for nuclei using the density matrix expansion: Implementation and pre-optimization  

E-Print Network (OSTI)

In a recent series of papers, Gebremariam, Bogner, and Duguet derived a microscopically based nuclear energy density functional by applying the Density Matrix Expansion (DME) to the Hartree-Fock energy obtained from chiral effective field theory (EFT) two- and three-nucleon interactions. Due to the structure of the chiral interactions, each coupling in the DME functional is given as the sum of a coupling constant arising from zero-range contact interactions and a coupling function of the density arising from the finite-range pion exchanges. Since the contact contributions have essentially the same structure as those entering empirical Skyrme functionals, a microscopically guided Skyrme phenomenology has been suggested in which the contact terms in the DME functional are released for optimization to finite-density observables to capture short-range correlation energy contributions from beyond Hartree-Fock. The present paper is the first attempt to assess the ability of the newly suggested DME functional, which has a much richer set of density dependencies than traditional Skyrme functionals, to generate sensible and stable results for nuclear applications. The results of the first proof-of-principle calculations are given, and numerous practical issues related to the implementation of the new functional in existing Skyrme codes are discussed. Using a restricted singular value decomposition (SVD) optimization procedure, it is found that the new DME functional gives numerically stable results and exhibits a small but systematic reduction of our test $\\chi^2$ function compared to standard Skyrme functionals, thus justifying its suitability for future global optimizations and large-scale calculations.

M. Stoitsov; M. Kortelainen; S. K. Bogner; T. Duguet; R. J. Furnstahl; B. Gebremariam; N. Schunck

2010-09-17T23:59:59.000Z

116

Level densities of nickel isotopes: microscopic theory versus experiment  

E-Print Network (OSTI)

We apply a spin-projection method to calculate microscopically the level densities of a family of nickel isotopes $^{59-64}$Ni using the shell model Monte Carlo approach in the complete $pfg_{9/2}$ shell. Accurate ground-state energies of the odd-mass nickel isotopes, required for the determination of excitation energies, are determined using the Green's function method recently introduced to circumvent the odd particle-number sign problem. Our results are in excellent agreement with recent measurements based on proton evaporation spectra and with level counting data at low excitation energies. We also compare our results with neutron resonance data, assuming equilibration of parity and a spin-cutoff model for the spin distribution at the neutron binding energy, and find good agreement with the exception of $^{63}$Ni.

M. Bonett-Matiz; Abhishek Mukherjee; Y. Alhassid

2013-05-01T23:59:59.000Z

117

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

E-Print Network (OSTI)

Calculations of free energies in liquid and solid phases: Fundamental measure density, 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

Song, Xueyu

118

The Probability Density Function of Ocean Surface Slopes and Its Effects on Radar Backscatter  

Science Conference Proceedings (OSTI)

Based on Longuet-Higginsís theory of the probability distribution of wave amplitude and wave period and on some observations, a new probability density function (PDF) of ocean surface slopes is derived. It is where ?x and ?y are the slope ...

Y. Liu; X-H. Yan; W. T. Liu; P. A. Hwang

1997-05-01T23:59:59.000Z

119

Theory and Computation | Center for Functional Nanomaterials  

NLE Websites -- All DOE Office Websites (Extended Search)

Theory and Computation theory and computation Flexible computational infrastructure, software tools and theoretical consultation are provided to support modeling and understanding...

120

Density-gradient theory: a macroscopic approach to quantum confinement and tunneling in semiconductor devices  

Science Conference Proceedings (OSTI)

Density-gradient theory provides a macroscopic approach to modeling quantum transport that is particularly well adapted to semiconductor device analysis and engineering. After some introductory observations, the basis of the theory in macroscopic and ... Keywords: Continuum, Density-gradient, Electron transport, Quantum confinement, Quantum tunneling, Semiconductor device simulation, Thermodynamics

M. G. Ancona

2011-06-01T23:59:59.000Z

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


121

Variational Two-electron Reduced Density Matrix Theory for Many ...  

E-Print Network (OSTI)

Sep 16, 2005 ... Abstract: The energy and properties of a many-electron atom or ... of a two- electron reduced density matrix (2-RDM) that is constrained to†...

122

Relativistic Nuclear Energy Density Functionals: adjusting parameters to binding energies  

E-Print Network (OSTI)

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

T. Niksic; D. Vretenar; P. Ring

2008-09-08T23:59:59.000Z

123

Subsystem functionals and the missing ingredient of confinement physics in density functionals  

E-Print Network (OSTI)

The subsystem functional scheme is a promising approach recently proposed for constructing exchange-correlation density functionals. In this scheme, the physics in each part of real materials is described by mapping to a ...

Hao, Feng

124

Density functional theory (DFT) and ab initio molecular orbital calculations have been employed to determine the structures and energies of the isomers of the OH-toluene adduct, the methyl hydroxycyclohexadienyl radical, and their corresponding transitio  

NLE Websites -- All DOE Office Websites (Extended Search)

Laboratory Investigation of Organic Aerosol Formation from Aromatic Hydrocarbons (DOE Award No. DE-FG02-02ER63098) Prepared by Luisa T. Molina, Renyi Zhang and Mario J. Molina Our work for this DOE funded project includes: (1) measurements of the kinetics and mechanism of the gas-phase oxidation reactions of the aromatic hydrocarbons initiated by OH; (2) measurements of aerosol formation from the aromatic hydrocarbons; and (3) theoretical studies to elucidate the OH-toluene reaction mechanism using quantum-chemical and rate theories. (1) Measurements of Gas-Phase Kinetics and Mechanism Work has been accomplished to develop laboratory instrumentation to conduct kinetic and mechanistic measurements of the aromatic hydrocarbon reactions initiated by OH, using

125

DENSITY-FUNCTIONAL STUDY OF Zr-BASED ACTINIDE ALLOYS: 2. U-Pu-Zr SYSTEM  

Science Conference Proceedings (OSTI)

Density-functional theory, previously used to describe phase equilibria in the U-Zr alloys [1], is applied to study ground state properties of the bcc U-Pu-Zr solid solutions. Calculated heats of formation of the Pu-U and Pu-Zr alloys are in a good agreement with CALPHAD assessments. We found that account for spin-orbit coupling is important for successful description of Pu-containing alloys.

Landa, A; Soderlind, P; Turchi, P; Vitos, L; Ruban, A

2009-02-09T23:59:59.000Z

126

Probability density function method for variable-density pressure-gradient-driven turbulence and mixing  

SciTech Connect

Probability density function (PDF) methods are extended to variable-density pressure-gradient-driven turbulence. We apply the new method to compute the joint PDF of density and velocity in a non-premixed binary mixture of different-density molecularly mixing fluids under gravity. The full time-evolution of the joint PDF is captured in the highly non-equilibrium flow: starting from a quiescent state, transitioning to fully developed turbulence and finally dissipated by molecular diffusion. High-Atwood-number effects (as distinguished from the Boussinesq case) are accounted for: both hydrodynamic turbulence and material mixing are treated at arbitrary density ratios, with the specific volume, mass flux and all their correlations in closed form. An extension of the generalized Langevin model, originally developed for the Lagrangian fluid particle velocity in constant-density shear-driven turbulence, is constructed for variable-density pressure-gradient-driven flows. The persistent small-scale anisotropy, a fundamentally 'non-Kolmogorovian' feature of flows under external acceleration forces, is captured by a tensorial diffusion term based on the external body force. The material mixing model for the fluid density, an active scalar, is developed based on the beta distribution. The beta-PDF is shown to be capable of capturing the mixing asymmetry and that it can accurately represent the density through transition, in fully developed turbulence and in the decay process. The joint model for hydrodynamics and active material mixing yields a time-accurate evolution of the turbulent kinetic energy and Reynolds stress anisotropy without resorting to gradient diffusion hypotheses, and represents the mixing state by the density PDF itself, eliminating the need for dubious mixing measures. Direct numerical simulations of the homogeneous Rayleigh-Taylor instability are used for model validation.

Bakosi, Jozsef [Los Alamos National Laboratory; Ristorcelli, Raymond J [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

127

Weak Bonds from a Semilocal Density Functional with the Right Ingredients  

E-Print Network (OSTI)

Computationally-efficient semilocal approximations of density functional theory at the level of the local spin density approximation (LSDA) or generalized gradient approximation (GGA) poorly describe weak interactions. We show improved descriptions for weak bonds (without loss of accuracy for strong ones) from a newly-developed semilocal meta-GGA (MGGA), by applying it to: 1) the binding energy curve of graphene adsorbed on a Ni (111) surface, where both chemi- and physisorption minima are present; 2) stacking of DNA/RNA nucleobases. We argue that this improvement comes from using the right MGGA dimensionless ingredient to recognize all degrees of orbital overlap.

Sun, Jianwei; Fang, Yuan; Haunschild, Robin; Hao, Pan; Ruzsinszky, Adrienn; Csonka, Gabor I; Scuseria, Gustavo E; Perdew, John P

2013-01-01T23:59:59.000Z

128

Parabolic Whittaker Functions and Topological Field Theories I  

E-Print Network (OSTI)

First, we define a generalization of the standard quantum Toda chain inspired by a construction of quantum cohomology of partial flags spaces GL(\\ell+1)/P, P a parabolic subgroup. Common eigenfunctions of the parabolic quantum Toda chains are generalized Whittaker functions given by matrix elements of infinite-dimensional representations of gl(\\ell+1). For maximal parabolic subgroups (i.e. for P such that GL(\\ell+1)/P=\\mathbb{P}^{\\ell}) we construct two different representations of the corresponding parabolic Whittaker functions as correlation functions in topological quantum field theories on a two-dimensional disk. In one case the parabolic Whittaker function is given by a correlation function in a type A equivariant topological sigma model with the target space \\mathbb{P}^{\\ell}. In the other case the same Whittaker function appears as a correlation function in a type B equivariant topological Landau-Ginzburg model related with the type A model by mirror symmetry. This note is a continuation of our project of establishing a relation between two-dimensional topological field theories (and more generally topological string theories) and Archimedean (\\infty-adic) geometry. From this perspective the existence of two, mirror dual, topological field theory representations of the parabolic Whittaker functions provide a quantum field theory realization of the local Archimedean Langlands duality for Whittaker functions. The established relation between the Archimedean Langlands duality and mirror symmetry in two-dimensional topological quantum field theories should be considered as a main result of this note.

Anton Gerasimov; Dimitri Lebedev; Sergey Oblezin

2010-02-12T23:59:59.000Z

129

108- Density Functional Theory Study of Oxygen Vacancy Migration ...  

Science Conference Proceedings (OSTI)

125- Influence of Gas Flow Rate Ratio on the Structural Properties of a-SiC:H Prepared by ... 145- The Synergy of XRD and XRF in a Shale and Slate Analysis.

130

Density Functional Theory Based Calculations of Site Occupancy in ...  

Science Conference Proceedings (OSTI)

A comparison is made between the site occupancy behavior based on two .... First Principles Modeling of Shape Memory Alloy Magnetic Refrigeration Materials ... Forming-Crush Simulation Optimization Using Internal State Variable Model.

131

Density Functional Theory Simulations Predict New Materials for...  

NLE Websites -- All DOE Office Websites (Extended Search)

of these new physical phenomena suggests the design of a high- capacity magnesium-boron battery. NREL is a national laboratory of the U.S. Department of Energy, Office of Energy...

132

RICE UNIVERSITY Linear Scaling Density Functional Theory with  

E-Print Network (OSTI)

Scho¨nle1 , Dirk Kamin2 , Volker Westphal1 , Silvio O. Rizzoli2 , and Stefan W. Hell *; 1 1 Department laser (Fiber Drive, Blue Sky, Re- search, Milpitas, CA, USA) at a wavelength of 635 nm and it was turned by a re- search grant from the German Ministry for Education and Research (BMBF): Nanolive. MAL

Scuseria, Gustavo E.

133

Test Functions Space in Noncommutative Quantum Field Theory  

E-Print Network (OSTI)

It is proven that the $\\star$-product of field operators implies that the space of test functions in the Wightman approach to noncommutative quantum field theory is one of the Gel'fand-Shilov spaces $S^{\\beta}$ with $\\beta test functions smears the noncommutative Wightman functions, which are in this case generalized distributions, sometimes called hyperfunctions. The existence and determination of the class of the test function spaces in NC QFT is important for any rigorous treatment in the Wightman approach.

M. Chaichian; M. Mnatsakanova; A. Tureanu; Yu. Vernov

2007-06-12T23:59:59.000Z

134

Probability density function transformation using seeded localized averaging  

SciTech Connect

Seeded Localized Averaging (SLA) is a spectrum acquisition method that averages pulse-heights in dynamic windows. SLA sharpens peaks in the acquired spectra. This work investigates the transformation of the original probability density function (PDF) in the process of applying SLA procedure. We derive an analytical expression for the resulting probability density function after an application of SLA. In addition, we prove the following properties: 1) for symmetric distributions, SLA preserves both the mean and symmetry. 2) for uni-modal symmetric distributions, SLA reduces variance, sharpening the distributions peak. Our results are the first to prove these properties, reinforcing past experimental observations. Specifically, our results imply that in the typical case of a spectral peak with Gaussian PDF the full width at half maximum (FWHM) of the transformed peak becomes narrower even with averaging of only two pulse-heights. While the Gaussian shape is no longer preserved, our results include an analytical expression for the resulting distribution. Examples of the transformation of other PDFs are presented. (authors)

Dimitrov, N. B. [Operations Research Dept., Naval Postgraduate School, Monterey, CA 93943 (United States); Jordanov, V. T. [Yantel, LLC, Santa Fe, NM 87508 (United States)

2011-07-01T23:59:59.000Z

135

Complete density perturbations in the Jordan-Fierz-Brans-Dicke theory  

E-Print Network (OSTI)

In the context of scalar-tensor theories we study the evolution of the density contrast for Jordan-Fierz-Brans-Dicke theories in a Friedmann-Lemaitre-Robertson-Walker Universe. Calculations are performed in the Einstein Frame with the cosmological background described as Lambda-Cold Dark Matter (Lambda-CDM) and supplemented by a Jordan-Fierz-Brans-Dicke field. By using a completely general procedure valid for all scalar-tensor theories, we obtain the exact fourth-order differential equation for the density contrast evolution in modes of arbitrary size. In the case of sub-Hubble modes, the expression reduces to a simpler but still fourth-order equation that is then compared with the standard (quasistatic) approximation. Differences with respect to the evolution as predicted by the standard Concordance Lambda-CDM model are observed depending on the value of the coupling.

J. A. R. Cembranos; A. de la Cruz Dombriz; L. Olano Garcia

2013-07-01T23:59:59.000Z

136

Spectral functions for composite fields and viscosity in hot scalar field theory  

E-Print Network (OSTI)

We derive a spectral representation for the two-point Green function for arbitrary composite field operators in Thermo Field Dynamics (TFD). A simple way for calculating the spectral density within TFD is pointed out and compared with known results from the imaginary time formalism. The method is applied to hot $\\phi^4$ theory. We give a compact derivation of the one-loop contribution to the shear viscosity and show that it is dominated by low-momentum plasmons.

Enke Wang; Xiaofei Zhang; Ulrich Heinz

1995-09-19T23:59:59.000Z

137

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

Science Conference Proceedings (OSTI)

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

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

2010-02-01T23:59:59.000Z

138

Reconstruction of Neutral Hydrogen Density Profiles in HANBIT Magnetic Mirror Device Using Bayesian Probability Theory  

SciTech Connect

Hydrogen is the main constitute of plasmas in HANBIT magnetic mirror device, therefore, measurement of the emission from excited levels of hydrogen atoms is an important diagnostic tool. From the emissivity of H{sub {alpha}} radiation one can derive quantities such as the neutral hydrogen density and the source rate. An unbiased and consistent probability theory based approach within the framework of Bayesian inference is applied to the reconstruction of H{sub {alpha}} emissivity profiles and hydrogen neutral density profiles in HANBIT magnetic mirror device.

Yoon, J.-S.; Seo, D.-C.; Na, H.-K.; Yoon, S.-W. [Korea Basic Science Institute (Korea, Republic of)

2005-01-15T23:59:59.000Z

139

A van der Waals density functional mapping of attraction in DNA dimers  

E-Print Network (OSTI)

The dispersion interaction between a pair of parallel DNA double-helix structures is investigated by means of the van der Waals density functional (vdW-DF) method. Each double-helix structure consists of an infinite repetition of one B-DNA coil with 10 base pairs. This parameter-free density functional theory (DFT) study illustrates the initial step in a proposed vdW-DF computational strategy for large biomolecular problems. The strategy is to first perform a survey of interaction geometries, based on the evaluation of the van der Waals (vdW) attraction, and then limit the evaluation of the remaining DFT parts (specifically the expensive study of the kinetic-energy repulsion) to the thus identified interesting geometries. Possibilities for accelerating this second step is detailed in a separate study. For the B-DNA dimer, the variation in van der Waals attraction is explored at relatively short distances (although beyond the region of density overlap) for a 360 degrees rotation. This study highlights the role...

Londero, Elisa; Schroder, Elsebeth

2013-01-01T23:59:59.000Z

140

Decision Support with Belief Functions Theory for Seabed Characterization  

E-Print Network (OSTI)

The seabed characterization from sonar images is a very hard task because of the produced data and the unknown environment, even for an human expert. In this work we propose an original approach in order to combine binary classifiers arising from different kinds of strategies such as one-versus-one or one-versus-rest, usually used in the SVM-classification. The decision functions coming from these binary classifiers are interpreted in terms of belief functions in order to combine these functions with one of the numerous operators of the belief functions theory. Moreover, this interpretation of the decision function allows us to propose a process of decisions by taking into account the rejected observations too far removed from the learning data, and the imprecise decisions given in unions of classes. This new approach is illustrated and evaluated with a SVM in order to classify the different kinds of sediment on image sonar.

Martin, Arnaud

2008-01-01T23:59:59.000Z

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


141

Multiloop World-Line Green Functions from String Theory  

E-Print Network (OSTI)

We show how the multiloop bosonic Green function of closed string theory reduces to the world-line Green function as defined by Schmidt and Schubert in the limit where the string world-sheet degenerates into a $\\Phi^3$ particle diagram. To obtain this correspondence we have to make an appropriate choice of the local coordinates defined on the degenerate string world sheet. We also present a set of simple rules that specify, in the explicit setting of the Schottky parametrization, which is the corner of moduli space corresponding to a given multiloop $\\Phi^3$ diagram.

Kaj Roland; Haru-Tada Sato

1996-04-24T23:59:59.000Z

142

An Improved Method for Estimating the Wind Power Density Distribution Function  

Science Conference Proceedings (OSTI)

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

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

2010-07-01T23:59:59.000Z

143

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

Science Conference Proceedings (OSTI)

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

Mark L. Morrissey; J. Scott Greene

2012-07-01T23:59:59.000Z

144

Lattice Calculation of Thermal Properties of Low-Density Neutron Matter with Pionless NN Effective Field Theory  

E-Print Network (OSTI)

Thermal properties of low-density neutron matter are investigated by determinantal quantum Monte Carlo lattice calculations on 3+1 dimensional cubic lattices. Nuclear effective field theory (EFT) is applied using the pionless single- and two-parameter neutron-neutron interactions, determined from the $^1S_0$ scattering length and effective range. The determination of the interactions and the calculations of neutron matter are carried out consistently by applying EFT power counting rules. The thermodynamic limit is taken by the method of finite-size scaling, and the continuum limit is examined in the vanishing lattice filling limit. The $^1S_0$ pairing gap at $T \\approx 0$ is computed directly from the off-diagonal long-range order of the spin pair-pair correlation function, and is found to be approximately 30% smaller than BCS calculations with the conventional nucleon-nucleon potentials. The critical temperature $T_c$ of the normal-to-superfluid phase transition and the pairing temperature scale $T^\\ast$ are determined, and the temperature-density phase diagram is constructed. The physics of low-density neutron matter is clearly identified as being a BCS-Bose-Einstein condensation crossover.

T. Abe; R. Seki

2007-08-19T23:59:59.000Z

145

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

E-Print Network (OSTI)

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

T. Duguet; J. Sadoudi

2010-10-19T23:59:59.000Z

146

A functional density-based nonparametric approach for statistical calibration  

Science Conference Proceedings (OSTI)

In this paper a new nonparametric functional method is introduced for predicting a scalar random variable Y from a functional random variable X. The resulting prediction has the form of a weighted average of the training data set, where ...

Noslen HernŠndez; Rolando J. Biscay; Nathalie Villa-Vialaneix; Isneri Talavera

2010-11-01T23:59:59.000Z

147

Green s functions in full-potential multiple-scattering theory  

Science Conference Proceedings (OSTI)

One-electron Green s functions play a central role in multiple-scattering theory (MST) based electronic- structure methods. Robust methods exist for calculating the Green s function for crystal potentials that are spherically symmetric about atomic centers. When applied to potentials of general shape, these same techniques result in pathologies in the small-r behavior of the electronic charge density because a portion of the Green s function can become singular at the origin for that case. We propose an algebraic method that eliminates the singular behavior by making use of the equivalence of two terms that involve poles in the inverse of the sine matrix. Our accurate calculations illustrate the limitations of previous methods for treating this problem that rely on extrapolating the solutions near the origin.

Rusanu, Aurelian [ORNL; Stocks, George Malcolm [ORNL; Wang, Yang [Pittsburgh Supercomputing Center; Faulkner, John Sam [Florida Atlantic University

2011-01-01T23:59:59.000Z

148

DENSITY  

Science Conference Proceedings (OSTI)

... Table 2: Principal mineral phases found in the granite rock. Mineral phase. ... Table 4. Average density of 12 granite rocks by Archimedes and CT. ...

2007-01-08T23:59:59.000Z

149

Applications of Skyrme energy-density functional to fusion reactions spanning the fusion barriers  

E-Print Network (OSTI)

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.

Min Liu; Ning Wang; Zhuxia Li; Xizhen Wu; Enguang Zhao

2005-09-26T23:59:59.000Z

150

United abominations: Density functional studies of heavy metal chemistry  

Science Conference Proceedings (OSTI)

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.

Schoendorff, George

2012-04-02T23:59:59.000Z

151

Gravitational Clustering in Redshift Space: Non-Gaussian Tail of the Cosmological Density Distribution Function  

E-Print Network (OSTI)

We study the non-Gaussian tail of the probability distribution function of density in cosmological N-Body simulations for a variety of initial conditions. We compare the behaviour of the non-Gaussian tail in the real space with that in the redshift space. The form of the PDF in redshift space is of great significance as galaxy surveys probe this and not the real space analogue predicted using theoretical models. We model the non-Gaussian tail using the halo model. In the weakly non-linear regime the moments of counts in cells in the redshift space approach the values expected from perturbation theory for moments in real space. We show that redshift space distortions in the non-linear regime dominate over signatures of initial conditions or the cosmological background. We illustrate this using Skewness and higher moments of counts in cells, as well as using the form of the non-Gaussian tail of the distribution function. We find that at scales smaller than the scale of non-linearity the differences in Skewness, etc. for different models are very small compared to the corresponding differences in real space. We show that bias also leads to smaller values of higher moments, but the redshift space distortions are typically the dominant effect.

J. S. Bagla; Suryadeep Ray

2006-04-28T23:59:59.000Z

152

Quasiparticle spectra from a nonempirical optimally tuned range-separated hybrid density functional  

SciTech Connect

We present a method for obtaining quasiparticle excitation energies from a DFT-based calculation, but with accuracy that is comparable to that of many-body perturbation theory within the GW approximation. The approach uses a range-separated hybrid density functional, with asymptotically exact and short-range fractional Fock exchange. The functional contains two parameters - the range separation and the short-range Fock fraction. Both are determined non-empirically, per system, based on satisfaction of exact physical constraints for the ionization potential and many-electron self-interaction, respectively. The accuracy of the method is demonstrated on the important benchmark molecule, 3,4,9,10-perylene-tetracarboxylic-dianydride (PTCDA), where it is shown to be the only non-empirical DFT-based method comparable to GW calculations. For any finite system, we envision that the approach could be useful directly as an inexpensive alternative to GW that offers good accuracy for both frontier and non-frontier quasiparticle excitation energies, opening the door to the studyof presently out of reach large-scale systems.

Refaely-Abramson, Sivan; Sharifzadeh, Sahar; Govind, Niranjan; Autschbach, Jochen; Neaton, Jeffrey B.; Baer, Roi; Kronik, Leeor

2012-11-28T23:59:59.000Z

153

Antisymmetrized Green's function approach to $(e,e')$ reactions with a realistic nuclear density  

E-Print Network (OSTI)

A completely antisymmetrized Green's function approach to the inclusive quasielastic $(e,e')$ scattering, including a realistic one-body density, is presented. The single particle Green's function is expanded in terms of the eigenfunctions of the nonhermitian optical potential. This allows one to treat final state interactions consistently in the inclusive and in the exclusive reactions. Nuclear correlations are included in the one-body density. Numerical results for the response functions of $^{16}$O and $^{40}$Ca are presented and discussed.

F. Capuzzi; C. Giusti; F. D. Pacati; D. N. Kadrev

2004-10-26T23:59:59.000Z

154

Towards a Microscopic Reaction Description Based on Energy Density Functionals  

SciTech Connect

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

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

2011-09-26T23:59:59.000Z

155

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

E-Print Network (OSTI)

Nuclear Physics A 770 (2006) 1­31 Relativistic nuclear energy density functional constrained by low 10 February 2006 Available online 3 March 2006 Abstract A relativistic nuclear energy density of Sn and Pb nuclei are studied as test cases for the isospin dependence of the underlying interactions

Weise, Wolfram

156

Shape control of conditional output probability density functions for linear stochastic systems with random parameters  

Science Conference Proceedings (OSTI)

This paper presents a controller design for shaping conditional output probability density functions (pdf) for non-Gaussian dynamic stochastic systems whose coefficients are random and represented by their known pdfs. The moment-generating ...

Aiping Wang; Yongji Wang; Hong Wang

2011-03-01T23:59:59.000Z

157

Small-Scale and Mesoscale Variability in Cloudy Boundary Layers: Joint Probability Density Functions  

Science Conference Proceedings (OSTI)

The joint probability density function (PDF) of vertical velocity and conserved scalars is important for at least two reasons. First, the shape of the joint PDF determines the buoyancy flux in partly cloudy layers. Second, the PDF provides a ...

Vincent E. Larson; Jean-Christophe Golaz; William R. Cotton

2002-12-01T23:59:59.000Z

158

Using Probability Density Functions to Derive Consistent Closure Relationships among Higher-Order Moments  

Science Conference Proceedings (OSTI)

Parameterizations of turbulence often predict several lower-order moments and make closure assumptions for higher-order moments. In principle, the low- and high-order moments share the same probability density function (PDF). One closure ...

Vincent E. Larson; Jean-Christophe Golaz

2005-04-01T23:59:59.000Z

159

Non-Gaussian Velocity Probability Density Functions: An Altimetric Perspective of the Mediterranean Sea  

Science Conference Proceedings (OSTI)

Velocity probability density functions (PDFs) are a key tool to study complex flows and are of great importance to model particle dispersion. The PDFs of geostrophic velocities derived from sea level anomalies maps for the Mediterranean Sea have ...

Jordi Isern-Fontanet; Emilio GarcŪa-Ladona; Jordi Font; Antonio GarcŪa-Olivares

2006-11-01T23:59:59.000Z

160

Colle-Salvetti-type local density functional for the exchange-correlation energy in two dimensions  

Science Conference Proceedings (OSTI)

We derive an approximate local density functional for the exchange-correlation energy to be used in density-functional calculations of two-dimensional systems. In the derivation we employ the Colle-Salvetti wave function within the scheme of Salvetti and Montagnani [Phys. Rev. A 63, 052109 (2001)] to satisfy the sum rule for the exchange-correlation hole. We apply the functional to the two-dimensional homogeneous electron gas as well as to a set of quantum dots and find a very good agreement with exact reference data.

Sakiroglu, S. [Nanoscience Center, Department of Physics, University of Jyvaeskylae, P. O. Box 35, FI-40014 Jyvaeskylae (Finland); Physics Department, Faculty of Arts and Sciences, Dokuz Eyluel University, 35160 Izmir (Turkey); Raesaenen, E. [Nanoscience Center, Department of Physics, University of Jyvaeskylae, P. O. Box 35, FI-40014 Jyvaeskylae (Finland)

2010-07-15T23:59:59.000Z

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


161

A note on the (anti-)BRST invariant Lagrangian densities for the free abelian 2-form gauge theory  

E-Print Network (OSTI)

We show that the previously known off-shell nilpotent (s_{(a)b}^2 = 0) and absolutely anticommuting (s_b s_{ab} + s_{ab} s_b = 0) Becchi-Rouet-Stora-Tyutin (BRST) transformations (s_b) and anti-BRST transformations (s_{ab}) are the symmetry transformations of the appropriate Lagrangian densities of a four (3 + 1)-dimensional (4D) free Abelian 2-form gauge theory which do not explicitly incorporate a very specific constrained field condition through a Lagrange multiplier 4D vector field. The above condition, which is the analogue of the Curci-Ferrari restriction of the non-Abelian 1-form gauge theory, emerges from the Euler-Lagrange equations of motion of our present theory and ensures the absolute anticommutativity of the transformations s_{(a)b}. Thus, the coupled Lagrangian densities, proposed in our present investigation, are aesthetically more appealing and more economical.

Saurabh Gupta; R. P. Malik

2008-05-08T23:59:59.000Z

162

N-density representability and the optimal transport limit of the Hohenberg-Kohn functional  

E-Print Network (OSTI)

We derive and analyze a hierarchy of approximations to the strongly correlated limit of the Hohenberg-Kohn functional. These "density representability approximations" are obtained by first noting that in the strongly correlated limit, N-representability of the pair density reduces to the requirement that the pair density must come from a symmetric N-point density. One then relaxes this requirement to the existence of a representing symmetric k-point density with k < N. The approximate energy can be computed by simulating a fictitious k-electron system. We investigate the approximations by deriving analytically exact results for a 2-site model problem, and by incorporating them into a self-consistent Kohn-Sham calculation for small atoms. We find that the low order representability conditions already capture the main part of the correlations.

Friesecke, Gero; Pass, Brendan; Cotar, Codina; KlŁppelberg, Claudia

2013-01-01T23:59:59.000Z

163

An exchange functional that tests the robustness of the plasmon description of the van der Waals density functional  

E-Print Network (OSTI)

Is the plasmon description within the non-local correlation of the van der Waals density functional by Dion and coworkers (vdW-DF1) robust enough to describe all exchange-correlation components? To address this question, we design an exchange functional, termed LV-PW86r based on this plasmon description as well as recent analysis on exchange in the large $s$-regime. In the regime with reduced gradients $s=|\

Kristian Berland; Per Hyldgaard

2013-09-06T23:59:59.000Z

164

Nuclear energy density functional from chiral two- and three-nucleon interactions  

E-Print Network (OSTI)

An improved density-matrix expansion is used to calculate the nuclear energy density functional from chiral two- and three-nucleon interactions. The two-body interaction comprises long-range one- and two-pion exchange contributions and a set of contact terms contributing up to fourth power in momenta. In addition we employ the leading order chiral three-nucleon interaction with its parameters $c_E, c_D$ and $c_{1,3,4}$ fixed in calculations of nuclear few-body systems. With this input the nuclear energy density functional is derived to first order in the two- and three-nucleon interaction. We find that the strength functions $F_\

J. W. Holt; N. Kaiser; W. Weise

2011-07-29T23:59:59.000Z

165

Nonlocal theory of electromagnetic wave decay into two electromagnetic waves in a rippled density plasma channel  

SciTech Connect

Parametric decay of a large amplitude electromagnetic wave into two electromagnetic modes in a rippled density plasma channel is investigated. The channel is taken to possess step density profile besides a density ripple of axial wave vector. The density ripple accounts for the momentum mismatch between the interacting waves and facilitates nonlinear coupling. For a given pump wave frequency, the requisite ripple wave number varies only a little w.r.t. the frequency of the low frequency decay wave. The radial localization of electromagnetic wave reduces the growth rate of the parametric instability. The growth rate decreases with the frequency of low frequency electromagnetic wave.

Sati, Priti; Tripathi, V. K. [Indian Institute of Technology, Hauz Khas, Delhi 110054 (India)

2012-12-15T23:59:59.000Z

166

Energy density functional analysis of shape coexistence in {sup 44}S  

SciTech Connect

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.

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

167

Green function identities in Euclidean quantum field theory  

E-Print Network (OSTI)

Given a generic Lagrangian system of even and odd fields, we show that any infinitesimal transformation of its classical Lagrangian yields the identities which Euclidean Green functions of quantum fields satisfy.

G. Sardanashvily

2006-04-01T23:59:59.000Z

168

Some nonrenormalizable theories are well-behaved  

E-Print Network (OSTI)

Some nonrenormalizable theories are less singular than all renormalizable theories. One can use lattice simulations to extract physical information from these nice nonrenormalizable theories. This paper discusses four nonrenormalizable theories that have finite euclidian and minkowskian Green's functions. Two of them have finite energy densities and describe scalar bosons of finite mass. The space of nonsingular nonrenormalizable theories is vast.

Kevin Cahill

2013-03-17T23:59:59.000Z

169

The ESO Slice Project (ESP) galaxy redshift survey: II. The luminosity function and mean galaxy density  

E-Print Network (OSTI)

(Abridged) The ESO Slice Project (ESP) is a galaxy redshift survey we have completed as an ESO Key-Project over ~23 square degrees, in a region near the South Galactic Pole. The survey is nearly complete to the limiting magnitude b_J=19.4 and consists of 3342 galaxies with reliable redshift determination. The ESP survey is intermediate between shallow, wide angle samples and very deep, one-dimensional pencil beams: spanning a volume of ~ 5 x 10^4 Mpc^3 at the sensitivity peak (z ~ 0.1), it provides an accurate determination of the "local" luminosity function and the mean galaxy density. We find that, although a Schechter function is an acceptable representation of the luminosity function over the entire range of magnitudes (M -17. The amplitude and the alpha and M^* parameters of our luminosity function are in good agreement with those of the AUTOFIB redshift survey (Ellis et al. 1996). Viceversa, our amplitude is significantly higher, by a factor ~ 1.6 at M ~ M^*, than that found for both the Stromlo-APM (Loveday et al. 1992) and the Las Campanas (Lin et al. 1996) redshift surveys. Also the faint end slope of our luminosity function is significantly steeper than that found in these two surveys. Large over- and under- densities are clearly seen in our data. In particular, we find evidence for a "local" underdensity (for D < 140 Mpc) and a significant overdensity at z ~ 0.1. When these radial density variations are taken into account, our derived luminosity function reproduces very well the observed counts for b_J < 19.4, including the steeper than Euclidean slope for b_J < 17.

E. Zucca; G. Zamorani; G. Vettolani; A. Cappi; R. Merighi; M. Mignoli; G. M. Stirpe; H. MacGillivray; C. Collins; C. Balkowski; V. Cayatte; S. Maurogordato; D. Proust; G. Chincarini; L. Guzzo; D. Maccagni; R. Scaramella; A. Blanchard; M. Ramella

1997-05-13T23:59:59.000Z

170

A new approach in signal processing for sodium boiling noise detection by probability density function estimates  

Science Conference Proceedings (OSTI)

The probability density function (pdf) method of noise signal processing has been investigated for its capability and quality in detecting sodium boiling noise. In an attempt to identify proper features of the pdf for sodium boiling noise detection, the segmented areas under the pdf curves have been found sensitive to sodium boiling noise. New approaches have been followed in selecting the feature threshold and achieving the targeted probabilities for false and missed sodium boiling noise detection.

Reddy, C.P.; Singh, O.P.; Vyjayanthi, R.K.; Prabhakar, R.

1988-03-01T23:59:59.000Z

171

Probability Density Functions to Represent Magnetic Fields at the Solar Surface  

E-Print Network (OSTI)

Numerical simulations of magneto-convection and analysis of solar magnetogram data provide empirical probability density functions (PDFs) for the line-of-sight component of the magnetic field. In this paper, we theoretically explore effects of several types of PDFs on polarized Zeeman line formation. We also propose composite PDFs to account for randomness in both field strength and orientation. Such PDFs can possibly mimic random fields at the solar surface.

Sampoorna, M

2009-01-01T23:59:59.000Z

172

The Gamma Transitions, Level Densities and Gamma Strength Function of Isotopes Yb-172 and Sm-153  

E-Print Network (OSTI)

This report is presented the level densities and gamma strength function which is extracted from primary gamma transitions of (n,2g) measurement on the Dalat Nuclear Research Reactor (DNRR). The comparisons with others results and model calculations, there are outside the scope of uncertainty. These research results are showed that having of complement research for deformed nucleus in order to evaluate nuclear structure models.

Vuong Huu Tan; Pham Dinh Khang; Nguyen Xuan Hai; Ho Huu Thang; Dao Manh Trinh; Nguyen An Son

2013-08-22T23:59:59.000Z

173

Application of nuclear density functionals to lepton number violating weak processes  

Science Conference Proceedings (OSTI)

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.

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

174

Particle production in field theories coupled to strong external sources. II: Generating functions  

E-Print Network (OSTI)

We discuss a method for computing the generating function for the multiplicity distribution in field theories with strong time dependent external sources. At leading order, the computation of the generating function reduces to finding a pair of solutions of the classical equations of motion, with non-standard temporal boundary conditions.

Francois Gelis; Raju Venugopalan

2006-05-23T23:59:59.000Z

175

Smoothness of the Gap Function in the BCS-Bogoliubov Theory of Superconductivity  

E-Print Network (OSTI)

We deal with the gap equation in the BCS-Bogoliubov theory of superconductivity, where the gap function is a function of the temperature $T$ only. We show that the squared gap function is of class $C^2$ on the closed interval $[\\,0,\\,T_c\\,]$. Here, $T_c$ stands for the transition temperature. Furthermore, we show that the gap function is monotonically decreasing on $[0,\\,T_c]$ and obtain the behavior of the gap function at $T=T_c$. We mathematically point out some more properties of the gap function.

Shuji Watanabe

2010-06-07T23:59:59.000Z

176

The Luminosity Function and Mean Galaxy Density from the ESP galaxy Redshift Survey  

E-Print Network (OSTI)

We summarise the main results obtained over the last two years by the ESO Slice Project (ESP) redshift survey, concerning the luminosity function and mean density of galaxies, and their implications for the galaxy number counts at bright magnitudes. The bj-band luminosity function is characterised by a steep faint-end, which raises above a "global" Schechter fit for M_bj > -17 + 5log(h) and is well described by a power-law with slope ~ -1.6. This steepening is mostly produced by galaxies with emission lines, with a clear trend for galaxies with larger [OII] equivalent widths to show a steeper faint end (and a fainter M*). The normalization of the luminosity function is about a factor of 1.6 higher that that from the Stromlo-APM survey. We find that, in fact, the mean density can be seen to increase out to ~140/h Mpc. If we take this into account when computing the expected cumulative number counts from the observed luminosity function, we are able to reproduce the observed steep counts at bright (bj<17) magnitudes very accurately.

E. Zucca; G. Zamorani; P. Vettolani

1998-10-06T23:59:59.000Z

177

A study of the density functional methods on the photoabsorption of Bodipy dyes  

E-Print Network (OSTI)

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.

Unal, Hatice; Mete, Ersen

2013-01-01T23:59:59.000Z

178

Theory of pixel lensing towards M31 I the density contribution and mass of MACHOs  

E-Print Network (OSTI)

POINT-AGAPE is an Anglo-French collaboration which is employing the IsaacNewton Telescope (INT) to conduct a pixel-lensing survey towards M31. In thispaper we investigate what we can learn from pixel-lensing observables about theMACHO mass and fractional contribution in M31 and the Galaxy for the case ofspherically-symmetric near-isothermal haloes. We employ detailed pixel-lensingsimulations which include many of the factors which affect the observables. Fora maximum MACHO halo we predict an event rate in V of up to 100 per season forM31 and 40 per season for the Galaxy. However, the Einstein radius crossingtime is generally not measurable and the observed full-width half-maximumduration provides only a weak tracer of lens mass. Nonetheless, we find thatthe near-far asymmetry in the spatial distribution of M31 MACHOs providessignificant information on their mass and density contribution. We present alikelihood estimator for measuring the fractional contribution and mass of bothM31 and Galaxy MACHOs which perm...

Kerins, E J; Evans, N W; Hewett, P C; Lastennet, E; Le Du, Y; Melchior, A L; Smartt, S J; Valls-Gabaud, D

2000-01-01T23:59:59.000Z

179

Energy density functional study of nuclear matrix elements for neutrinoless $??$ decay  

E-Print Network (OSTI)

We present an extensive study of nuclear matrix elements (NME) for the neutrinoless double beta decay of the nuclei $^{48}$Ca, $^{76}$Ge, $^{82}$Se, $^{96}$Zr, $^{100}$Mo, $^{116}$Cd, $^{124}$Sn, $^{128}$Te, $^{130}$Te, $^{136}$Xe, and $^{150}$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 NME's around 4.7 with the exception of $^{48}$Ca and $^{150}$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 $^{150}$Nd.

TomŠs R. RodrŪguez; G. Martinez-Pinedo

2010-08-31T23:59:59.000Z

180

Electronic structure calculations with the Tran-Blaha modified Becke-Johnson Density Functional  

Science Conference Proceedings (OSTI)

We report a series of calculations testing the predictions of the Tran-Blaha functional for the electronic structure and magnetic properties of condensed systems. We find a general improvement in the properties of semiconducting and insulating systems, relative to calculations with standard generalized gradient approximations, although this is not always by the same mechanism as other approaches such as the quasiparticle GW method. In ZnO the valence bands are narrowed and the band gap is increased to a value in much better agreement with experiment. The Zn d states do not move to higher binding energy as they do in local-density approximation+U calculations. The functional is effective for systems with hydride anions, where correcting self-interaction errors in the 1s state is important. Similarly, it correctly opens semiconducting gaps in the alkaline-earth hexaborides. It correctly stabilizes an antiferromagnetic insulating ground state for the undoped cuprate parent CaCuO{sub 2}, but seriously degrades the agreement with experiment for ferromagnetic Gd relative to the standard local-spin-density approximation and generalized gradient approximations. This is due to positioning of the minority-spin 4f states at too low an energy. Conversely, the position of the La 4f conduction bands of La{sub 2}O{sub 3} is in reasonable accord with experiment as it is with standard functionals. The functional narrows the Fe d bands of the parent compound LaFeAsO of the iron high-temperature superconductors while maintaining the high Fe spectral weight near the Fermi energy.

Singh, David J [ORNL

2010-01-01T23:59:59.000Z

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


181

Excited states and electron transfer in solution : models based on density functional theory  

E-Print Network (OSTI)

Our understanding of organic materials for solar energy conversion stands to benefit greatly from accurate, computationally tractable electronic structure methods for excited states. Here we apply two approaches based on ...

Kowalczyk, Timothy Daniel

2012-01-01T23:59:59.000Z

182

Optical Properties of Cd1-xZnxSe from Density Functional Theory  

Science Conference Proceedings (OSTI)

For the purpose of exchange-correlation energy (Exc) determination in ... by Combining Thermoelectric Materials and Dye-Sensitized Solar Cell in Series.

183

Electrochemical Windows of Room-Temperature Ionic Liquids from Molecular Dynamics and Density Functional Theory Calculations  

E-Print Network (OSTI)

We investigated the cathodic and anodic limits of six room-temperature ionic liquids (ILs) formed from a combination of two common cations, 1-butyl-3-methylimidazolium (BMIM) and N,N-propylmethylpyrrolidinium (P13), and ...

Ong, Shyue Ping

184

Structure, magnetism, and adhesion at Cr/Fe interfaces from density functional theory  

E-Print Network (OSTI)

of industry due to its high melting point and wear resistance. For example, steel gun barrels are sub- jected has been aimed primarily at ceramic coatings/ liners (see, e.g. [4] and references therein). Ceramic­silicide ceramic/ iron interfaces (e.g., ZrC [7], TiC [8­10], and MoSi2 [11] on Fe substrates). While ceramics

Carter, Emily A.

185

van der Waals Corrected Density Functional Theory Calculations on Zeolitic Imidazolate Frameworks  

E-Print Network (OSTI)

separation of methane and carbon dioxide. J. Mater. Chem. ,Synthesis, structure, and carbon dioxide capture propertiesstructure, and carbon dioxide cap- ture properties of

Ray, Keith G.

2013-01-01T23:59:59.000Z

186

van der Waals Corrected Density Functional Theory Calculations on Zeolitic Imidazolate Frameworks  

E-Print Network (OSTI)

binding site and gas molecule, dispersion or a combinationsimple dispersion bound systems, such as noble gas dimersgas uptake differently due to the competition between surface area and strong dispersion

Ray, Keith G.

2013-01-01T23:59:59.000Z

187

Adsorption of binary hydrocarbon mixtures in carbon slit pores: A density functional theory study  

SciTech Connect

Adsorption of binary hydrocarbons mixtures involving methane in carbon slit pores is theoretically studied here from the viewpoints of separation and of the effect of impurities on methane storage. It is seen that even small amounts of ethane, propane, or butane can significantly reduce the methane capacity of carbons. Optimal pore sizes and pressures, depending on impurity concentration, are noted in the present work, suggesting that careful adsorbent and process design can lead to enhanced separation. These results are consistent with earlier literature studies for the infinite dilution limit. For methane storage applications a carbon micropore width of 11.4 {angstrom} (based on distance between centers of carbon atoms on opposing walls) is found to be the most suitable from the point of view of lower impurity uptake during high-pressure adsorption and greater impurity retention during low-pressure delivery. The results also theoretically confirm unusual recently reported observations of enhanced methane adsorption in the presence of a small amount of heavier hydrocarbon impurity.

Bhatia, S.K. [Univ. of Queensland, Brisbane, Queensland (Australia). Dept. of Chemical Engineering

1998-10-13T23:59:59.000Z

188

Density Functional Theory Calculations on Hydrated Dimethylarsinic Acid and Iron Oxide Clusters.  

E-Print Network (OSTI)

??Dimethylarsinic Acid (DMA) or (CH3)2AsO2H is an important organoarsenical compound detected in arsenic speciation studies of environmental samples and synthesized during pyrolysis of oil shale.Ö (more)

Adamescu, Adrian

2012-01-01T23:59:59.000Z

189

Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory  

E-Print Network (OSTI)

in comparison with gas-phase water, ice close to the meltingcrystalline ice at two different temperatures, and gas-phaseof gas-phase water, liquid water and crystalline ice using

Nordlund, Dennis

2008-01-01T23:59:59.000Z

190

First-principles Study Using Hybrid-density Functional Theory for the ...  

Science Conference Proceedings (OSTI)

Alloy compositions for active optical transitions and the formation energy are compared ... Advanced Materials and Processes for Solid Oxide Fuel Cells.

191

Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory  

E-Print Network (OSTI)

Radiation Laboratory (SSRL). The UHV surface scienceSciences. The work at the SSRL BL 5.1 and ALS BL 11.0.2 wasto thank the staff at SSRL and ALS for all their assistance.

Nordlund, Dennis

2008-01-01T23:59:59.000Z

192

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

E-Print Network (OSTI)

Lifetimes of super-heavy (SH) nuclei are primarily governed by alpha decay and spontaneous fission (SF). Here we study the competing decay modes of even-even SH isotopes with 108 cold fusion" and "hot fusion" reactions. The region of long-lived SH nuclei is expected to be centered on $^{294}$Ds with a total half-life of ?1.5 days.

A. Staszczak; A. Baran; W. Nazarewicz

2012-08-06T23:59:59.000Z

193

Electronic structure effects in liquid water studied by photoelectron spectroscopy and density functional theory  

DOE Green Energy (OSTI)

We present valence photoelectron emission spectra of liquid water in comparison with gas-phase water, ice close to the melting point, low temperature amorphous and crystalline ice. All aggregation states have major electronic structure changes relative to the free molecule, with rehybridization and development of bonding and anti-bonding states accompanying the hydrogen bond formation. Sensitivity to the local structural order, most prominent in the shape and splitting of the occupied 3a{sub 1} orbital, is understood from the electronic structure averaging over various geometrical structures, and reflects the local nature of the orbital interaction.

Nordlund, Dennis; Odelius, Michael; Bluhm, Hendrik; Ogasawara, Hirohito; Pettersson, Lars G.M.; Nilsson, Anders

2008-04-29T23:59:59.000Z

194

First-principles Study Using Hybrid-density Functional Theory for the ...  

Science Conference Proceedings (OSTI)

A21: First-Principles Molecular Dynamics Simulation of Chemical ... A3: Investigation on Co-combustion Kinetics of Anthracite Coal and Biomass Char by ... Lithium Redox Process for Thermochemical Water-Splitting as Energy Conversion.

195

Probability Density Functions of Liquid Water Path and Total Water Content of Marine Boundary Layer Clouds: Implications for Cloud Parameterization  

Science Conference Proceedings (OSTI)

Mathematical forms of probability density functions (PDFs) of liquid water path (LWP) and total water content for marine boundary layer clouds are investigated using the homogeneity, skewness, and kurtosis of PDFs of LWP obtained from observations ...

Hideaki Kawai; Jo„o Teixeira

2012-03-01T23:59:59.000Z

196

Small-Scale and Mesoscale Variability of Scalars in Cloudy Boundary Layers: One-Dimensional Probability Density Functions  

Science Conference Proceedings (OSTI)

A key to parameterization of subgrid-scale processes is the probability density function (PDF) of conserved scalars. If the appropriate PDF is known, then grid box average cloud fraction, liquid water content, temperature, and autoconversion can ...

Vincent E. Larson; Robert Wood; Paul R. Field; Jean-Christophe Golaz; Thomas H. Vonder Haar; William R. Cotton

2001-07-01T23:59:59.000Z

197

Fast Calculations of Electrostatic Solvation Free Energy from Reconstructed Solvent Density Using Proximal Radial Distribution Functions  

SciTech Connect

Although detailed atomic models may be applied for a full description of solvation, simpler phenomenologicalmodels are particularly useful to interpret the results for scanning many large, complex systems, where a full atomic model is too computationally expensive to use. Among the most costly are solvation free-energy evaluations by simulation. Here we develop a fast way to calculate electrostatic solvation free energy while retaining much of the accuracy of explicit solvent free-energy simulation. The basis of our method is to treat the solvent not as a structureless dielectric continuum but as a structured medium by making use of universal proximal radial distribution functions. Using a deca-alanine peptide as a test case, we compare the use of our theory with free-energy simulations and traditional continuum estimates of the electrostatic solvation free energy.

Lin, Bin; Wong, Ka-Yiu; Hu, Char Y.; Kokubo, Hironori; Pettitt, Bernard M.

2011-07-07T23:59:59.000Z

198

Gradient formula for the beta-function of 2d quantum field theory  

E-Print Network (OSTI)

We give a non-perturbative proof of a gradient formula for beta functions of two-dimensional quantum field theories. The gradient formula has the form \\partial_{i}c = - (g_{ij}+\\Delta g_{ij} +b_{ij})\\beta^{j} where \\beta^{j} are the beta functions, c and g_{ij} are the Zamolodchikov c-function and metric, b_{ij} is an antisymmetric tensor introduced by H. Osborn and \\Delta g_{ij} is a certain metric correction. The formula is derived under the assumption of stress-energy conservation and certain conditions on the infrared behaviour the most significant of which is the condition that the large distance limit of the field theory does not exhibit spontaneously broken global conformal symmetry. Being specialized to non-linear sigma models this formula implies a one-to-one correspondence between renormalization group fixed points and critical points of c.

Friedan, Daniel

2009-01-01T23:59:59.000Z

199

The structure of Green functions in quantum field theory with a general state  

E-Print Network (OSTI)

In quantum field theory, the Green function is usually calculated as the expectation value of the time-ordered product of fields over the vacuum. In some cases, especially in degenerate systems, expectation values over general states are required. The corresponding Green functions are essentially more complex than in the vacuum, because they cannot be written in terms of standard Feynman diagrams. Here, a method is proposed to determine the structure of these Green functions and to derive nonperturbative equations for them. The main idea is to transform the cumulants describing correlations into interaction terms.

Christian Brouder

2007-10-30T23:59:59.000Z

200

Study of Possible Ultraviolet Zero of the Beta Function in Gauge Theories with Many Fermions  

E-Print Network (OSTI)

We study the possibility of an ultraviolet (UV) zero in the $n$-loop beta function of U(1) and non-Abelian gauge theories with $N_f$ fermions for large $N_f$. The effect of scheme transformations on the coefficients of different powers of $N_f$ in the $n$-loop term in the beta function is calculated. A general scheme-independent criterion is given for determining whether or not the $n$-loop beta function has a UV zero for large $N_f$. We compare the results with exact integral representations of the leading terms in the beta functions for the respective Abelian and non-Abelian theories in the limit $N_f \\to \\infty$ limit with $N_f \\alpha$ finite. As part of this study, new analytic and numerical results are presented for certain coefficients, denoted $b_{n,n-1}$, that control the large-$N_f$ behavior at $n$-loop order in the beta function. We also investigate various test functions incorporating a power-law and essential UV zero in the beta function and determine their manifestations in series expansions in powers of coupling and in powers of $1/N_f$.

Robert Shrock

2013-11-20T23:59:59.000Z

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


201

Precise evaluation of thermal response functions by optimized density matrix renormalization group schemes  

E-Print Network (OSTI)

This paper provides a study and discussion of earlier as well as novel more efficient schemes for the precise evaluation of finite-temperature response functions of strongly correlated quantum systems in the framework of the time-dependent density matrix renormalization group (tDMRG). The computational costs and bond dimensions as functions of time and temperature are examined for the example of the spin-1/2 XXZ Heisenberg chain in the critical XY phase and the gapped N\\'eel phase. The matrix product state purifications occurring in the algorithms are in one-to-one relation with corresponding matrix product operators. This notational simplification elucidates implications of quasi-locality on the computational costs. Based on the observation that there is considerable freedom in designing efficient tDMRG schemes for the calculation of dynamical correlators at finite temperatures, a new class of optimizable schemes, as recently suggested in arXiv:1212.3570, is explained and analyzed numerically. A specific novel near-optimal scheme that requires no additional optimization reaches maximum times that are typically increased by a factor of two, when compared against earlier approaches. These increased reachable times make many more physical applications accessible. For each of the described tDMRG schemes, one can devise a corresponding transfer matrix renormalization group (TMRG) variant.

Thomas Barthel

2013-01-10T23:59:59.000Z

202

The Gluon Green's function in N=4 supersymmetric Yang-Mills theory.  

E-Print Network (OSTI)

energy limit of scattering amplitudes in the N = 4 supersymmetric YangĖ Mills theory is studied by solving the corresponding BFKL equation in the nextĖ toĖleading approximation. The gluon Greenís function is analysed using a newly proposed method suitable... (~ka) ??(~kb) f ( ~ka, ~kb,Y ? ln s s0 ) , (1) where s0 = |~ka||~kb| is the Regge scale. The energy dependence is determined by the universal processĖindependent gluon Greenís function f . The impact factors, ?,??, depend on the process under study...

Andersen, Jeppe R; Sabio Vera, Agustin

203

An application of Green-function methods to gravitational radiation theory  

E-Print Network (OSTI)

Previous work in the literature has studied gravitational radiation in black-hole collisions at the speed of light. In particular, it had been proved that the perturbative field equations may all be reduced to equations in only two independent variables, by virtue of a conformal symmetry at each order in perturbation theory. The Green function for the perturbative field equations is here analyzed by studying the corresponding second-order hyperbolic operator with variable coefficients, instead of using the reduction method from the retarded flat-space Green function in four dimensions. After reduction to canonical form of this hyperbolic operator, the integral representation of the solution in terms of the Riemann function is obtained. The Riemann function solves a characteristic initial-value problem for which analytic formulae leading to the numerical solution are derived.

Giampiero Esposito

2005-04-27T23:59:59.000Z

204

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

Science Conference Proceedings (OSTI)

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

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

1999-06-01T23:59:59.000Z

205

Efficiency of caviton formation as a function of plasma density gradient  

SciTech Connect

The effect of a zeroth-order density gradient on the development of cavitons has been investigated experimentally and numerically. The cavitons were produced via excitation of electron plasma waves (EPW) with a modest ({ital E}{sup 2}/4{pi}{ital nT}{sub {ital e}}{much lt}1) resonant radio-frequency pump. The location of the resonance, on an inverse-parabolic density profile, was varied, with all other parameters being held constant. The depth of the caviton, and the strength of its associated trapped electric fields, are found to depend strongly on the density gradient scale length at the critical layer, with a maximum occurring when this length is infinite, at the flat top of the density profile. The results are accounted for by the dependence on the density gradient of the EPW convection rate and wave-breaking time. The study helps illuminate recent large-scale ionospheric density modification experiments.

Bauer, B.S.; Wong, A.Y.; Scurry, L.; Decyk, V.K. (Department of Physics, University of California, Los Angeles, Los Angeles, California 90024 (USA))

1990-08-01T23:59:59.000Z

206

Free-energy functionals of the electrostatic potential for Poisson-Boltzmann theory  

E-Print Network (OSTI)

In simulating charged systems, it is often useful to treat some ionic components of the system at the mean-field level and solve the Poisson-Boltzmann (PB) equation to get their respective density profiles. The numerically intensive task of solving the PB equation at each step of the simulation can be bypassed using variational methods that treat the electrostatic potential as a dynamic variable. But such approaches require the access to a true free-energy functional; a functional that not only provides the correct solution of the PB equation upon extremization, it also evaluates to the true free energy of the system at its minimum. Moreover, the numerical efficiency of such procedures is further enhanced if the free-energy functional is local and is expressed in terms of the electrostatic potential. Existing PB functionals of the electrostatic potential, while possessing the local structure, are not free-energy functionals. We present a variational formulation with a local free-energy functional of the potential. In addition, we also construct a nonlocal free-energy functional of the electrostatic potential. These functionals are suited for employment in simulation schemes based on the ideas of dynamical optimization.

Vikram Jadhao; Francisco J. Solis; Monica Olvera de la Cruz

2013-09-26T23:59:59.000Z

207

Connected Green function approach to ground state symmetry breaking in $?^4_{1+1}$-theory  

E-Print Network (OSTI)

Using the cluster expansions for n-point Green functions we derive a closed set of dynamical equations of motion for connected equal-time Green functions by neglecting all connected functions higher than $4^{th}$ order for the $\\lambda \\Phi^4$-theory in $1+1$ dimensions. We apply the equations to the investigation of spontaneous ground state symmetry breaking, i.e. to the evaluation of the effective potential at temperature $T=0$. Within our momentum space discretization we obtain a second order phase transition (in agreement with the Simon-Griffith theorem) and a critical coupling of $\\lambda_{crit}/4m^2=2.446$ as compared to a first order phase transition and $\\lambda_{crit}/4m^2=2.568$ from the Gaussian effective potential approach.

J. M. Haeuser; W. Cassing; A. Peter; M. H. Thoma

1994-08-23T23:59:59.000Z

208

Method of sampling certain probability densities without inversion of their distribution functions  

SciTech Connect

A Monte Carlo device is described which bypasses the inversion x = p/sup -1/(r) involved in directly sampling the distribution P(x) of a stochastic variable x with given density p(x). The method is practical for all linear and a broad class of quadratic densities. (auth)

Everett, C.J.; Cashwell, E.D.; Turner, G.D.

1973-09-01T23:59:59.000Z

209

Beyond the Gas Phase: Towards Modeling Bulk Ionic Liquids with a Comparison of Density Functional Tight Binding (DFTB) to Density Functional Theory (DFT).  

E-Print Network (OSTI)

??Coal-fired power plants are a leading contributor to the increase in CO2 released into the atmosphere. Alkanolamines are considered a potential solvent to capture thisÖ (more)

Danser, Mandelle Ann

2010-01-01T23:59:59.000Z

210

Scaling theory of the Peierls charge density wave in metal nanowires D. F. Urban,1 C. A. Stafford,2 and Hermann Grabert1  

E-Print Network (OSTI)

Scaling theory of the Peierls charge density wave in metal nanowires D. F. Urban,1 C. A. Stafford,2 URBAN, STAFFORD, AND GRABERT PHYSICAL REVIEW B 75, 205428 2007 205428-2 #12;Ekin = L q 0 m q,R0 R0 bq0=8kF -1 . URBAN, STAFFORD, AND GRABERT PHYSICAL REVIEW B 75, 205428 2007 205428-4 #12;scaling

Stafford, Charles

211

Non-delta-function electronic spectral densities in individual quantum dots  

Science Conference Proceedings (OSTI)

Using a simplified model approach we estimate the optical line shape of the transition lines observable in photoluminescence experiments on quantum dots. We use the theory based on the interaction of electrons with the longitudinal optical phonons only. ... Keywords: 73.21.La, 73.63.Kv, 78.67.Hc, Electron-phonon coupling, Luminescence, Quantum dots

Karel KrŠl

2008-03-01T23:59:59.000Z

212

Sub-L* Galaxies at Redshifts z~4, 3, and 2: Their UV Luminosity Function and Luminosity Density  

E-Print Network (OSTI)

We use very deep (R_lim=27) UGRI imaging to study the evolution of the faint end of the UV-selected galaxy luminosity function from z~4 to z~2. We find that the luminosity function evolves with time and that this evolution is differential with luminosity: the number of sub-L* galaxies increases from z~4 to z~3 by at least a factor of 2.3, while the bright end of the LF remains unchanged. Potential systematic biases restrict our ability to draw strong conclusions at lower redshifts, z~2, but we can say that the number density of sub-L* galaxies at z~2.2 is at least as high as it is at z~3. Turning to the UV luminosity density of the Universe, we find that the luminosity density starts dropping with increasing redshift already beginning at z=3 (earlier than recently thought - Steidel et al. 1999) and that this drop is dominated by the same sub-L* galaxies that dominate the evolution of the LF. This differential evolution of the luminosity function suggests that differentially comparing key diagnostics of dust, stellar populations, etc. as a function of z and L should let us isolate the key mechanisms that drive galaxy evolution at high redshift.

Marcin Sawicki; David Thompson

2005-09-15T23:59:59.000Z

213

Simulation Of Wave Function And Probability Density Of Modified Poschl Teller Potential Derived Using Supersymmetric Quantum Mechanics  

Science Conference Proceedings (OSTI)

SUSY quantum mechanics can be applied to solve Schrodinger equation for high dimensional system that can be reduced into one dimensional system and represented in lowering and raising operators. Lowering and raising operators can be obtained using relationship between original Hamiltonian equation and the (super) potential equation. In this paper SUSY quantum mechanics is used as a method to obtain the wave function and the energy level of the Modified Poschl Teller potential. The graph of wave function equation and probability density is simulated by using Delphi 7.0 programming language. Finally, the expectation value of quantum mechanics operator could be calculated analytically using integral form or probability density graph resulted by the programming.

Angraini, Lily Maysari [STKIP Hamzanwadi Selong East Lombok, NTB, PostGraduate student at Physics Department UNS, Jl. Ir. Sutami 36 A, Surakarta (Indonesia); Suparmi,; Variani, Viska Inda [Physics Department UNS, Jl. Ir. Sutami 36 A, Surakarta (Indonesia)

2010-12-23T23:59:59.000Z

214

Optimization of density functional tight-binding and classical reactive molecular dynamics for high-throughput simulations of carbon materials  

Science Conference Proceedings (OSTI)

Carbon materials and nanostructures (fullerenes, nanotubes) are promising building blocks of nanotechnology. Potential applications include optical and electronic devices, sensors, and nano-scale machines. The multiscale character of processes related ... Keywords: ACM proceedings, BLAS, Cray XT5, LAPACK, advanced materials, density-functional tight binding, high-throughput, linear algebra, material science, molecular dynamics, multiscale-modeling, quantum chemistry, scientific libraries, scientific-computing

Jacek Jakowski; Bilel Hadri; Steven J. Stuart; Predrag Krstic; Stephan Irle; Dulma Nugawela; Sophya Garashchuk

2012-07-01T23:59:59.000Z

215

Functioning, Item Response TheoryImplicit Theories and Beta Change in Longitudinal Evaluations of Training Effectiveness: An Investigation Using Item Response Theory  

E-Print Network (OSTI)

Golembiewski, Billingsly, and Yeager (1976) conceptualized three distinct types of change that might result from development interventions, called alpha, beta, and gamma change. Recent research has found that beta and gamma change do occur as hypothesized, but the phenomena are somewhat infrequent and the precise conditions under which they occur have not been established. This study used confirmatory factor analysis and item response theory to identify gamma and beta change on a multidimensional, multisource managerial performance appraisal instrument and to examine relations among the change types, training program content, and raters' implicit theories of performance. Results suggested that coverage in training was a necessary but not sufficient condition for beta and gamma change to occur. Further, although gamma change was detected only in the trainee group, beta change was detected in self-ratings from trainees and in ratings collected from their superiors. Because trainees ' superiors were involved in post-training follow-up, this finding was interpreted as a possible diffusion of treatments effect (Campbell & Stanley, 1963). Contrary to expectations, there were no interpretable relations between raters' implicit theories of performance and either of the change types. Perhaps relatedly, more implicit theory change was detected among individuals providing observer ratings than in the trainees

S. Bartholomew Craig; Robert J. Harvey (chair; Kevin D. Carlson; John Donovan; Roseanne J. Foti; Neil M. A. Hauenstein; S. Bartholomew Craig

2002-01-01T23:59:59.000Z

216

Quantum theory of stimulated Cerenkov radiation of transverse electromagnetic waves by a low-density electron beam in a medium  

Science Conference Proceedings (OSTI)

The quantum theory of stimulated Cerenkov radiation of transverse electromagnetic waves by an electron beam in an anisotropic medium is presented. Relativistic quantum nonlinear equations of the Cerenkov beam instability are obtained. In the linear approximation, the quantum dispersion equation is derived and the instability growth increments are determined. The nonlinear problem of the saturation of the quantum Cerenkov beam instability is solved. (cerenkov radiation)

Kuzelev, Mikhail V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2010-01-31T23:59:59.000Z

217

Assignment of near-edge x-ray absorption fine structure spectra of metalloporphyrins by means of time-dependent density-functional calculations  

Science Conference Proceedings (OSTI)

The C 1s and N 1s near-edge x-ray absorption fine structure (NEXAFS) spectra of three prototype tetraphenyl porphyrin (TPP) molecules are discussed in the framework of a combined experimental and theoretical study. We employ time-dependent density-functional theory (TDDFT) to compute the NEXAFS spectra of the open- and closed-shell metalloporphyrins CoTPP and ZnTPP as well as the free-base 2HTPP in realistic nonplanar conformations. Using Becke's well-known half-and-half hybrid functional, the computed core excitation spectra are mostly in good agreement with the experimental data in the low-energy region below the appropriate ionization threshold. To make these calculations feasible, we apply a new, simple scheme based on TDDFT using a modified single-particle input spectrum. This scheme is very easy to implement in standard codes and allows one to compute core excitation spectra at a similar cost as ordinary UV/vis spectra even for larger molecules. We employ these calculations for a detailed assignment of the NEXAFS spectra including subtle shifts in certain peaks of the N 1s spectra, which depend on the central coordination of the TPP ligand. We furthermore assign the observed NEXAFS resonances to the individual molecular subunits of the investigated TPP molecules.

Schmidt, Norman; Fink, Rainer [Department Chemie und Pharmazie, Lehrstuhl fuer Physikalische Chemie II and ICMM, Universitaet Erlangen-Nuernberg, Egerlandstrasse 3, 91058 Erlangen (Germany); Hieringer, Wolfgang [Department Chemie und Pharmazie, Lehrstuhl fuer Theoretische Chemie, Universitaet Erlangen-Nuernberg, Egerlandstrasse 3, 91058 Erlangen (Germany)

2010-08-07T23:59:59.000Z

218

QCD at nonzero density and canonical partition functions with Wilson fermions  

SciTech Connect

We present a reduction method for Wilson-Dirac fermions with nonzero chemical potential which generates a dimensionally reduced fermion matrix. The size of the reduced fermion matrix is independent of the temporal lattice extent and the dependence on the chemical potential is factored out. As a consequence the reduced matrix allows a simple evaluation of the Wilson fermion determinant for any value of the chemical potential and hence the exact projection to the canonical partition functions.

Alexandru, Andrei [Physics Department, George Washington University Washington, D.C. 20052 (United States); Wenger, Urs [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, Sidlerstrasse 5, CH-3012 Bern (Switzerland)

2011-02-01T23:59:59.000Z

219

Density Dependence of the Mass Function of Globular Star Clusters in the Sombrero Galaxy and its Dynamical Implications  

E-Print Network (OSTI)

We have constructed the mass function of globular star clusters in the Sombrero galaxy in bins of different internal half-mass density rho_h and projected galactocentric distance R. This is based on the published measurements of the magnitudes and effective radii of the clusters by Spitler et al. (2006) in BVR images taken with the ACS on HST. We find that the peak of the mass function M_p increases with rho_h by a factor of about 4 but remains nearly constant with R. Our results are almost identical to those presented recently by McLaughlin & Fall (2007) for globular clusters in the Milky Way. The mass functions in both galaxies agree with a simple, approximate model in which the clusters form with a Schechter initial mass function and evolve subsequently by stellar escape driven by internal two-body relaxation. These findings therefore undermine recent claims that the present peak of the mass function of globular clusters must have been built into the initial conditions.

Rupali Chandar; S. Michael Fall; Dean E. McLaughlin

2007-09-10T23:59:59.000Z

220

DEFLAGRATION-TO-DETONATION TRANSITION IN LX-04 AS A FUNCTION OF LOADING DENSITY, TEMPERATURE, AND CONFINEMENT  

DOE Green Energy (OSTI)

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.

Sandusky, H W; Granholm, R H; Bohl, D G; Hare, D E; Vandersall, K S; Garcia, F

2005-06-01T23:59:59.000Z

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


221

Traffic scheduling mechanism based on graph theory for Power Saving mode of IEEE 802.11 distributed coordinator function  

Science Conference Proceedings (OSTI)

In IEEE 802.11 Power Saving (PS) mode specified for Independent Basic Service Set (IBSS), mobile stations announce their pending data packets within Announcement Traffic Indication Message (ATIM) window immediately after the reception ... Keywords: IEEE 80211, MAC protocol, ad hoc networks, distributed coordinator, energy efficiency, graph theory, medium access control, power saving, power-efficient, time synchronisation function, traffic scheduling

M. H. Ye; C. T. Lau; A. B. Premkumar

2009-03-01T23:59:59.000Z

222

An extended SMLD approach for presumed probability density function in flamelet combustion model  

E-Print Network (OSTI)

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 ...

Coclite, Alessandro; De Palma, Pietro; Cutrone, Luigi

2013-01-01T23:59:59.000Z

223

Study of Scheme Transformations to Remove Higher-Loop Terms in the $?$ Function of a Gauge Theory  

E-Print Network (OSTI)

Since three-loop and higher-loop terms in the $\\beta$ function of a gauge theory are scheme-dependent, one can, at least for sufficiently small coupling, carry out a scheme transformation that removes these terms. A basic question concerns the extent to which this can be done at an infrared fixed point of an asymptotically free gauge theory. This is important for quantitative analyses of the scheme dependence of such a fixed point. Here we study a scheme transformation $S_{R,m}$ with $m \\ge 2$ that is constructed so as to remove the terms in the beta function at loop order $\\ell=3$ to $\\ell=m+1$, inclusive. Starting from an arbitrary initial scheme, we present general expressions for the coefficients of terms of loop order $\\ell$ in the beta function in the transformed scheme from $\\ell=m+2$ up to $\\ell=8$. Extending a previous study of $S_{R,2}$, we investigate the range of applicability of the $S_{R,3}$ scheme transformation in an asymptotically free SU($N_c$) gauge theory with an infrared zero in $\\beta$ depending on the number, $N_f$, of fermions in the theory. We show that this $S_{R,3}$ scheme transformation can only be applied self-consistently in a restricted range of $N_f$ with a correspondingly small value of infrared fixed-point coupling. We also study the effect of higher-loop terms on the beta function of a U(1) gauge theory.

Robert Shrock

2013-05-28T23:59:59.000Z

224

A First Principles Density-Functional Calculation of the Electronic and Vibrational Structure of the Key Melanin Monomers  

E-Print Network (OSTI)

We report first principles density functional calculations for hydroquinone (HQ), indolequinone (IQ) and semiquinone (SQ). These molecules are believed to be the basic building blocks of the eumelanins, a class of bio-macromolecules with important biological functions (including photoprotection) and with potential for certain bioengineering applications. We have used the DeltaSCF (difference of self consistent fields) method to study the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), Delta_HL. We show that Delta_HL is similar in IQ and SQ but approximately twice as large in HQ. This may have important implications for our understanding of the observed broad band optical absorption of the eumelanins. The possibility of using this difference in Delta_HL to molecularly engineer the electronic properties of eumelanins is discussed. We calculate the infrared and Raman spectra of the three redox forms from first principles. Each of the molecules have significantly different infrared and Raman signatures, and so these spectra could be used in situ to non-destructively identify the monomeric content of macromolecules. It is hoped that this may be a helpful analytical tool in determining the structure of eumelanin macromolecules and hence in helping to determine the structure-property-function relationships that control the behaviour of the eumelanins.

B. J. Powell; T. Baruah; N. Bernstein; K. Brake; Ross H. McKenzie; P. Meredith; M. R. Pederson

2004-01-23T23:59:59.000Z

225

The tensor part of the Skyrme energy density functional. III. Time-odd terms at high spin  

E-Print Network (OSTI)

This article extends previous studies on the effect of tensor terms in the Skyrme energy density functional by breaking of time-reversal invariance. We have systematically probed the impact of tensor terms on properties of superdeformed rotational bands calculated within the cranked Hartree-Fock-Bogoliubov approach for different parameterizations covering a wide range of values for the isoscalar and isovector tensor coupling constants. We analyze in detail the contribution of the tensor terms to the energies and dynamical moments of inertia and study their impact on quasi-particle spectra. Special attention is devoted to the time-odd tensor terms, the effect of variations of their coupling constants and finite-size instabilities.

V. Hellemans; P. -H. Heenen; M. Bender

2011-12-15T23:59:59.000Z

226

Density functional theory study of CHx ,,x=13... adsorption on clean and CO precovered Rh,,111... surfaces  

E-Print Network (OSTI)

to its high selectivity and activity for methane partial oxidation or steam reforming to synthesis gas American Institute of Physics. DOI: 10.1063/1.2751155 I. INTRODUCTION Methane dissociation and activation

Li, Weixue

227

Application of Density Functional Theory to the Study of the Reaction of NO with Char-Bound Nitrogen during Combustion  

E-Print Network (OSTI)

-Bound Nitrogen during Combustion Alejandro Montoya,, Thanh N. Truong,*,§ and Adel F. Sarofim Department. The calculations were carried out to simulate combustion conditions resulting in the absence and presence and in stratospheric ozone depletion. One of the anthropogenic sources of N2O is the combustion of coal, particularly

Truong, Thanh N.

228

Oxygen Overlayers on Pd(111) Studied by Density Functional Theory Mira Todorova, Karsten Reuter, and Matthias Scheffler*  

E-Print Network (OSTI)

of the wavefunction in the interstitial is Ewf max = 20 Ryd and for the potential E pot max = 196 Ryd. For the (2 √? 2

229

Density-functional theory study of the initial oxygen incorporation in Pd(111) Mira Todorova, Karsten Reuter, and Matthias Scheffler  

E-Print Network (OSTI)

) and Potential (pot), Cut-off for the Spherical Harmonics Representation, and the Muffin-Tin Radii Ewf 16 Ry Epot

230

A Density Functional Theory of a Nickel-based Anode Catalyst for Application in a Direct Propane Fuel Cell .  

E-Print Network (OSTI)

??The maximum theoretical energy efficiency of fuel cells is much larger than those of the steam-power-turbine cycles that are currently used for generating electrical power.Ö (more)

Vafaeyan, Shadi

2012-01-01T23:59:59.000Z

231

Warped Conformal Field Theory  

E-Print Network (OSTI)

We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the 2d conformal group, but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near horizon geometry of any extremal black hole are identical to those of a 2d field theory with chiral scaling. We consider two examples: black holes in warped AdS_3 in topologically massive gravity, and in string theory. In both cases, the density of states in the 2d field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.

Detournay, Stephane; Hofman, Diego M

2012-01-01T23:59:59.000Z

232

Warped Conformal Field Theory  

E-Print Network (OSTI)

We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the 2d conformal group, but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near horizon geometry of any extremal black hole are identical to those of a 2d field theory with chiral scaling. We consider two examples: black holes in warped AdS_3 in topologically massive gravity, and in string theory. In both cases, the density of states in the 2d field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.

Stephane Detournay; Thomas Hartman; Diego M. Hofman

2012-10-01T23:59:59.000Z

233

Comparative Study of Selected Wave Function and Density Functional Methods for Noncovalent Interaction Energy Calculations Using the Extended S22 Data Set  

Science Conference Proceedings (OSTI)

In this paper, an extension of the S22 data set of Jurecka et al. (Jure?ka, P.; äponer, J.; ?ernż, J.; Hobza, P. Phys. Chem. Chem. Phys. 2006, 8, 1985.), the data set of benchmark CCSD(T)/CBS interaction energies of twenty-two noncovalent complexes in equilibrium geometries, is presented. The S22 data set has been extended by including the stretched (one shortened and three elongated) complex geometries of the S22 data set along the main noncovalent interaction coordinate. The goal of this work is to assess the accuracy of the popular wave function methods (MP2-, MP3- and, CCSD-based) and density functional methods (with and without empirical correction for the dispersion energy) for noncovalent complexes based on a statistical evaluation not only in equilibrium, but also in nonequilibrium geometries. The results obtained in this work provide information on whether an accurate and balanced description of the different interaction types and complex geometry distortions can be expected from the tested methods. This information has an important implication in the calculation of large molecular complexes, where the number of distant interacting molecular fragments, often in far from equilibrium geometries, increases rapidly with the system size. The best performing WFT methods were found to be the SCS-CCSD (spin-component scaled CCSD, according to Takatani, T.; Hohenstein, E. G.; Sherrill, C. D. J. Chem. Phys. 2008, 128, 124111), MP2C (dispersion-corrected MP2, according to Hesselmann, A. J. Chem. Phys. 2008, 128, 144112), and MP2.5 (scaled MP3, according to Pito?Šk, M.; NeogrŠdy, P.; ?ernż, J.; Grimme, S.; Hobza, P. ChemPhysChem 2009, 10, 282.). Since none of the DFT methods fulfilled the required statistical criteria proposed in this work, they cannot be generally recommended for large-scale calculations. The DFT methods still have the potential to deliver accurate results for large molecules, but most likely on the basis of an error cancellation.

Grafova, Lucie; Pitonak, Michal; Rezac, Jan; Hobza, Pavel

2010-08-10T23:59:59.000Z

234

Quantum field theory in the presence of a medium: Green's function expansions  

SciTech Connect

Starting from a Lagrangian and using functional-integration techniques, series expansions of Green's function of a real scalar field and electromagnetic field, in the presence of a medium, are obtained. The parameter of expansion in these series is the susceptibility function of the medium. Relativistic and nonrelativistic Langevin-type equations are derived. Series expansions for Lifshitz energy in finite temperature and for an arbitrary matter distribution are derived. Covariant formulations for both scalar and electromagnetic fields are introduced. Two illustrative examples are given.

Kheirandish, Fardin [Department of Physics, Islamic Azad University, Shahreza-Branch, Shahreza (Iran, Islamic Republic of); Salimi, Shahriar [Department of Physics, University of Kurdistan, Sanandaj (Iran, Islamic Republic of)

2011-12-15T23:59:59.000Z

235

E Matrix' for the Loewdin alpha function, expanded in a Taylor series: an analytic treatment of molecular charge density near the origin  

Science Conference Proceedings (OSTI)

A displaced STO can be expanded in spherical harmonics with the coefficient function or Loewdin or functions characterized by a C matrix. These or functions themselves may be expanded in a Taylor series that is characterized by its own E Matrix. This expansion is necessary for the representation of the or function by a power series and for its evaluation about the origin. As an application, the power series for the molecular charge density in the vicinity of the center of a model diatomic molecule. The analytic approach is general and yields excellent results.

Jones, H.W.; Bussery, B.; Weatherford, C.A.

1987-01-01T23:59:59.000Z

236

Of energy and the economy : theory and evidence for their functional relationship  

E-Print Network (OSTI)

This paper offers a set of explicit functional relationships that link energy and the economy. Despite the reliance on energy permeating the whole economy, no such complete relationships had been presented before. How ...

Chang, Vincent H. (Vincent Hua-Cheng)

2007-01-01T23:59:59.000Z

237

The Intrusion Depth of Density Currents Flowing into Stratified Water Bodies  

Science Conference Proceedings (OSTI)

Theory and laboratory experiments are presented describing the depth at which a density current intrudes into a linearly stratified water column, as a function of the entrainment ratio E, the buoyancy flux in the dense current B, and the ...

Mathew Wells; Parthiban Nadarajah

2009-08-01T23:59:59.000Z

238

Coulomb gauge Green functions and Gribov copies in SU(2) lattice gauge theory  

E-Print Network (OSTI)

We reconsider the lattice measurement of Green functions in Coulomb gauge, both in 2+1 and 3+1 dimensions, using an improved gauge fixing scheme. The influence of Gribov copies is examined and we find clear indications that Green functions are more strongly affected than previously assumed, in particular for low momenta. Qualitatively, our improved lattice results in the infra-red compare more favourably with recent continuum calculations in the Hamiltonian approach.

M. Quandt; G. Burgio; S. Chimchinda; H. Reinhardt

2007-10-02T23:59:59.000Z

239

The least type of an entire function of order {rho} element of (0,1) having positive zeros with prescribed averaged densities  

Science Conference Proceedings (OSTI)

The problem of the least type of entire functions of order {rho} element of (0,1) all of whose zeros lie on the same ray and have the prescribed upper and lower mean {rho}-densities is solved. A complete investigation of the value of the extremal type is carried out, including a description of its asymptotic behaviour. Bibliography: 14 titles.

Braichev, Georgii G [Moscow State Pedagogical University, Moscow (Russian Federation)

2012-07-31T23:59:59.000Z

240

The theory of social functions: challenges for computational social science and multi-agent learning  

Science Conference Proceedings (OSTI)

A basic claim of this paper is that the foundational theoretical problem of the social sciences - the possibility of unconscious, unplanned forms of cooperation and intelligence among intentional agents (the very hard issue of the 'invisible hand', of ... Keywords: Agents, Cognitive architecture, Emergence, Intention, Learning, Social functions, Social simulation

Cristiano Castelfranchi

2001-04-01T23:59:59.000Z

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


241

Theory and simulation of quantum photovoltaic devices based on the non-equilibrium Green's function formalism  

Science Conference Proceedings (OSTI)

This article reviews the application of the non-equilibrium Green's function formalism to the simulation of novel photovoltaic devices utilizing quantum confinement effects in low dimensional absorber structures. It covers well-known aspects of the fundamental ... Keywords: NEGF, Photovoltaics, Quantum dot, Quantum well

U. Aeberhard

2011-12-01T23:59:59.000Z

242

Solitons, Tau-functions and Hamiltonian Reduction for Non-Abelian Conformal Affine Toda Theories  

E-Print Network (OSTI)

We consider the Hamiltonian reduction of the two-loop Wess-Zumino-Novikov-Witten model (WZNW) based on an untwisted affine Kac-Moody algebra $\\cgh$. The resulting reduced models, called {\\em Generalized Non-Abelian Conformal Affine Toda (G-CAT)}, are conformally invariant and a wide class of them possesses soliton solutions; these models constitute non-abelian generalizations of the Conformal Affine Toda models. Their general solution is constructed by the Leznov-Saveliev method. Moreover, the dressing transformations leading to the solutions in the orbit of the vacuum are considered in detail, as well as the $\\tau$-functions, which are defined for any integrable highest weight representation of $\\cgh$, irrespectively of its particular realization. When the conformal symmetry is spontaneously broken, the G-CAT model becomes a generalized Affine Toda model, whose soliton solutions are constructed. Their masses are obtained exploring the spontaneous breakdown of the conformal symmetry, and their relation to the fundamental particle masses is discussed.

L. A. Ferreira; J. L. Miramontes; J. Sanchez Guillen

1994-12-15T23:59:59.000Z

243

Probabilistic Quantitative Precipitation Forecasts Based on Reforecast Analogs: Theory and Application  

Science Conference Proceedings (OSTI)

A general theory is proposed for the statistical correction of weather forecasts based on observed analogs. An estimate is sought for the probability density function (pdf) of the observed state, given todayís numerical forecast. Assume that an ...

Thomas M. Hamill; Jeffrey S. Whitaker

2006-11-01T23:59:59.000Z

244

A short remark on negative energy densities and quantum inequalities  

E-Print Network (OSTI)

In quantum field theory it is generally known that the energy density may be negative at a given point in spacetime. A number of papers have shown that there is a restriction on this energy density which is called a quantum inequality (QI). A QI is the lower bound to the "weighted average" of the energy density at a given point integrated over a time dependent sampling function. In this paper we give an example of a sampling function for which there is no QI.

Solomon, Dan

2009-01-01T23:59:59.000Z

245

A short remark on negative energy densities and quantum inequalities  

E-Print Network (OSTI)

In quantum field theory it is generally known that the energy density may be negative at a given point in spacetime. A number of papers have shown that there is a restriction on this energy density which is called a quantum inequality (QI). A QI is the lower bound to the "weighted average" of the energy density at a given point integrated over a time dependent sampling function. In this paper we give an example of a sampling function for which there is no QI.

Dan Solomon

2009-01-05T23:59:59.000Z

246

ROHF Theory Made Simple  

E-Print Network (OSTI)

Restricted open-shell Hartree-Fock (ROHF) theory is formulated as a projected self-consistent unrestricted HF (UHF) model by mathematically constraining spin density eigenvalues. The resulting constrained UHF (CUHF) wave function is identical to that obtained from Roothaan's effective Fock operator. Our $\\alpha$ and $\\beta$ CUHF Fock operators are parameter-free and have canonical orbitals and orbital energies that are physically meaningful as in UHF, except for eliminating spin contamination. The present approach removes ambiguities in ROHF orbital energies and the non-uniqueness of methods that build upon them. We present benchmarks to demonstrate CUHF physical correctness and good agreement with experimental results.

Tsuchimochi, Takashi

2010-01-01T23:59:59.000Z

247

Numerical simulation of clarifier-thickener units treating ideal suspensions with a flux density function having two inflection points  

Science Conference Proceedings (OSTI)

We consider a nonconvex conservation law modelling the settling of particles in ideal clarifier-thickener units. The flux function of this conservation law has an explicit spatial dependence that is discontinuous. Previous works by two of the authors, ... Keywords: Clarifier-thickener, Conservation law, Continuous sedimentation, Discontinuous flux, Finite difference method, Numerical simulation

R. BŁRger; F. Concha; K. H. Karlsen; A. NarvŠEz

2006-08-01T23:59:59.000Z

248

Probability Densities in Strong Turbulence  

E-Print Network (OSTI)

According to modern developments in turbulence theory, the "dissipation" scales (u.v. cut-offs) $\\eta$ form a random field related to velocity increments $\\delta_{\\eta}u$. In this work we, using Mellin's transform combined with the Gaussain large -scale boundary condition, calculate probability densities (PDFs) of velocity increments $P(\\delta_{r}u,r)$ and the PDF of the dissipation scales $Q(\\eta, Re)$, where $Re$ is the large-scale Reynolds number. The resulting expressions strongly deviate from the Log-normal PDF $P_{L}(\\delta_{r}u,r)$ often quoted in the literature. It is shown that the probability density of the small-scale velocity fluctuations includes information about the large (integral) scale dynamics which is responsible for deviation of $P(\\delta_{r}u,r)$ from $P_{L}(\\delta_{r}u,r)$. A framework for evaluation of the PDFs of various turbulence characteristics involving spatial derivatives is developed. The exact relation, free of spurious Logarithms recently discussed in Frisch et al (J. Fluid Mech. {\\bf 542}, 97 (2005)), for the multifractal probability density of velocity increments, not based on the steepest descent evaluation of the integrals is obtained and the calculated function $D(h)$ is close to experimental data. A novel derivation (Polyakov, 2005), of a well-known result of the multi-fractal theory [Frisch, "Turbulence. {\\it Legacy of A.N.Kolmogorov}", Cambridge University Press, 1995)), based on the concepts described in this paper, is also presented.

Victor Yakhot

2005-12-12T23:59:59.000Z

249

Kinetics of the sulfur oxidation on palladium: A combined in situ x-ray photoelectron spectroscopy and density-functional study  

Science Conference Proceedings (OSTI)

We studied the reaction kinetics of sulfur oxidation on the Pd(100) surface by in situ high resolution x-ray photoelectron spectroscopy and ab initio density functional calculations. Isothermal oxidation experiments were performed between 400 and 500 K for small amounts ({approx}0.02 ML) of preadsorbed sulfur, with oxygen in large excess. The main stable reaction intermediate found on the surface is SO{sub 4}, with SO{sub 2} and SO{sub 3} being only present in minor amounts. Density-functional calculations depict a reaction energy profile, which explains the sequential formation of SO{sub 2}, SO{sub 3}, and eventually SO{sub 4}, also highlighting that the in-plane formation of SO from S and O adatoms is the rate limiting step. From the experiments we determined the activation energy of the rate limiting step to be 85 {+-} 6 kJ mol{sup -1} by Arrhenius analysis, matching the calculated endothermicity of the SO formation.

Gotterbarm, Karin; Hoefert, Oliver; Lorenz, Michael P. A.; Streber, Regine; Papp, Christian [Lehrstuhl fuer Physikalische Chemie II, Universitaet Erlangen-Nuernberg, Egerlandstr. 3, 91058 Erlangen (Germany); Luckas, Nicola; Vines, Francesc [Lehrstuhl fuer Theoretische Chemie, Universitaet Erlangen-Nuernberg, Egerlandstr. 3, 91058 Erlangen (Germany); Steinrueck, Hans-Peter [Lehrstuhl fuer Physikalische Chemie II, Universitaet Erlangen-Nuernberg, Egerlandstr. 3, 91058 Erlangen (Germany); Erlangen Catalysis Resource Center (ECRC), Universitaet Erlangen-Nuernberg, Egerlandstr. 3, 91058 Erlangen (Germany); Interdisciplinary Center for Interface Controlled Processes, Egerlandstr. 3, 91058 Erlangen (Germany); Goerling, Andreas [Lehrstuhl fuer Theoretische Chemie, Universitaet Erlangen-Nuernberg, Egerlandstr. 3, 91058 Erlangen (Germany); Interdisciplinary Center for Interface Controlled Processes, Egerlandstr. 3, 91058 Erlangen (Germany)

2012-03-07T23:59:59.000Z

250

SIZES, HALF-MASS DENSITIES, AND MASS FUNCTIONS OF STAR CLUSTERS IN THE MERGER REMNANT NGC 1316: CLUES TO THE FATE OF SECOND-GENERATION GLOBULAR CLUSTERS  

SciTech Connect

We study mass functions of globular clusters derived from Hubble Space Telescope/Advanced Camera for Surveys images of the early-type merger remnant galaxy NGC 1316, which hosts a significant population of metal-rich globular clusters of intermediate age ({approx}3 Gyr). For the old, metal-poor ({sup b}lue{sup )} clusters, the peak mass of the mass function M{sub p} increases with internal half-mass density {rho}{sub h} as M{sub p}{proportional_to}{rho}{sub h}{sup 0.44}, whereas it stays approximately constant with galactocentric distance R{sub gal}. The mass functions of these clusters are consistent with a simple scenario in which they formed with a Schechter initial mass function and evolved subsequently by internal two-body relaxation. For the intermediate-age population of metal-rich ({sup r}ed{sup )} clusters, the faint end of the previously reported power-law luminosity function of the clusters with R{sub gal} > 9 kpc is due to many of those clusters having radii larger than the theoretical maximum value imposed by the tidal field of NGC 1316 at their R{sub gal}. This renders disruption by two-body relaxation ineffective. Only a few such diffuse clusters are found in the inner regions of NGC 1316. Completeness tests indicate that this is a physical effect. Using comparisons with star clusters in other galaxies and cluster disruption calculations using published models, we hypothesize that most red clusters in the low-{rho}{sub h} tail of the initial distribution have already been destroyed in the inner regions of NGC 1316 by tidal shocking, and that several remaining low-{rho}{sub h} clusters will evolve dynamically to become similar to 'faint fuzzies' that exist in several lenticular galaxies. Finally, we discuss the nature of diffuse red clusters in early-type galaxies.

Goudfrooij, Paul, E-mail: goudfroo@stsci.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2012-05-10T23:59:59.000Z

251

Stability of critical bubble in stretched fluid of square-gradient density-functional model with triple-parabolic free energy  

E-Print Network (OSTI)

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.

Masao Iwamatsu; Yutaka Okabe

2010-06-11T23:59:59.000Z

252

Modelling charge transfer reactions with the frozen density embedding formalism  

SciTech Connect

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.

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

253

Critical cavity in the stretched fluid studied using square-gradient density-functional model with triple-parabolic free energy  

E-Print Network (OSTI)

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.

Masao Iwamatsu

2009-04-04T23:59:59.000Z

254

The effect of Niobium on the defect chemistry and corrosion kinetics of tetragonal ZrO? : a density functional theory study  

E-Print Network (OSTI)

Abstract Advanced Zirconium based alloys used in the nuclear industry today, such as ZIRLOTM , M5 contain up to wt 1.2% Niobium [8]. Experimental effort to determine the effect of Nb on corrosion behaviour of these alloys ...

Otgonbaatar, Uuganbayar

2013-01-01T23:59:59.000Z

255

UNDERSTANDING THE LOCAL ATOMIC LEVEL EFFECTS OF DOPANTS IN COMPLEX METAL HYDRIDES USING SYNCHROTRON XRAY ABSORPTION SPECTROSCOPY AND DENSITY FUNCTIONAL THEORY  

SciTech Connect

This work resulted in five peer-reviewed journal publications (appended), as well as one doctoral dissertation and two masters theses.

Dobbins, Tabbetha

2013-02-15T23:59:59.000Z

256

Scaling Theory and Numerical Simulations of Aerogel Sintering  

E-Print Network (OSTI)

A simple scaling theory for the sintering of fractal aerogels is presented. The densification at small scales is described by an increase of the lower cut-off length a accompanied by a decrease of the upper cut-off length ?, in order to conserve the total mass of the system. Scaling laws are derived which predict how a, ? and the specific pore surface area ? should depend on the density ?. Following the general ideas of the theory, numerical simulations of sintering are proposed starting from computer simulations of aerogel structure based on a diffusion-limited cluster-cluster aggregation gelling process. The numerical results for a, ? and ? as a function of ? are discussed according to the initial aerogel density. The scaling theory is only fully recovered in the limit of very low density where the original values of a and ? are well separated. These numerical results are compared with experiments on partially densified aerogels.

Rťmi Jullien; Nathalie Olivi-tran; Anwar Hasmy; Thierry Woignier; Daniel Bourret; Robert Sempťrť

2008-01-01T23:59:59.000Z

257

A computer simulated phantom study of tomotherapy dose optimization based on probability density functions (PDF) and potential errors caused by low reproducibility of PDF  

SciTech Connect

Lung tumor motion trajectories measured by four-dimensional CT or dynamic MRI can be converted to a probability density function (PDF), which describes the probability of the tumor at a certain position, for PDF based treatment planning. Using this method in simulated sequential tomotherapy, we study the dose reduction of normal tissues and more important, the effect of PDF reproducibility on the accuracy of dosimetry. For these purposes, realistic PDFs were obtained from two dynamic MRI scans of a healthy volunteer within a 2 week interval. The first PDF was accumulated from a 300 s scan and the second PDF was calculated from variable scan times from 5 s (one breathing cycle) to 300 s. Optimized beam fluences based on the second PDF were delivered to the hypothetical gross target volume (GTV) of a lung phantom that moved following the first PDF. The reproducibility between two PDFs varied from low (78%) to high (94.8%) when the second scan time increased from 5 s to 300 s. When a highly reproducible PDF was used in optimization, the dose coverage of GTV was maintained; phantom lung receiving 10%-20% prescription dose was reduced by 40%-50% and the mean phantom lung dose was reduced by 9.6%. However, optimization based on PDF with low reproducibility resulted in a 50% underdosed GTV. The dosimetric error increased nearly exponentially as the PDF error increased. Therefore, although the dose of the tumor surrounding tissue can be theoretically reduced by PDF based treatment planning, the reliability and applicability of this method highly depend on if a reproducible PDF exists and is measurable. By correlating the dosimetric error and PDF error together, a useful guideline for PDF data acquisition and patient qualification for PDF based planning can be derived.

Sheng, Ke; Cai Jing; Brookeman, James; Molloy, Janelle; Christopher, John; Read, Paul [Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908 (United States); Department of Radiology, University of Virginia, Charlottesville, Virginia 22908 (United States); Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908 and Department of Radiation Oncology, Mayo Clinic, Rochester, Minnesota 55905 (United States); Department of Radiology, University of Virginia, Charlottesville, Virginia 22908 (United States); Department of Radiation Oncology, University of Virginia, Charlottesville, Virginia 22908 (United States)

2006-09-15T23:59:59.000Z

258

CO Oxidation on supported single Pt atoms - Experimental and Ab Initio density functional studies of CO interaction with Pt atom on theta-alumina(010) surface  

Science Conference Proceedings (OSTI)

Although there are only a few known examples of supported single atoms, they are unique because they bridge the gap between homogenous and heterogeneous catalysis. The metal center is single supported atoms can be isoelectronic with their homogenous catalyst counterpart and may allow mechanistic pathways normally seen in homogenous catalysts. Here, we report CO oxidation activity of mono-disperse single Pt atoms supported on an inert substrate, -alumina (Al2O3), in the presence of stoichiometric oxygen. Since CO oxidation on single Pt atoms cannot occur via a conventional Langmuir-Hinshelwood scheme (L-H scheme) which requires at least one Pt-Pt bond, we have carried out a first principles density functional theoretical study of a proposed pathway which is a variation on the conventional L-H scheme and is inspired by organometallic chemistry of platinum. We find that a single supported Pt atom prefers to bond to O2 over CO. The CO then bonds with the oxygenated Pt atom and forms a carbonate which dissociates to liberate CO2, leaving an oxygen atom on Pt. A subsequent reaction with another CO molecule regenerates the single atom catalyst. An in-situ diffuse reflectance infrared study of CO adsorption on the catalyst s supported single atoms has been carried out to infer information on CO absorption modes and compare the observed spectra with calculated ones for intermediates in the proposed CO oxidation pathway. Our results clearly show that supported Pt single atoms are catalytically active and that this catalytic activity can occur without involving the substrate. Characterization by electron microscopy and X-ray absorption studies of the mono-disperse Pt/ -Al2O3, synthesized by solution methods, are also presented.

Narula, Chaitanya Kumar [ORNL; Debusk, Melanie Moses [ORNL; Yoon, Mina [ORNL; Allard Jr, Lawrence Frederick [ORNL; Mullins, David R [ORNL; Wu, Zili [ORNL; Yang, Xiaofan [ORNL; Veith, Gabriel M [ORNL; Stocks, George Malcolm [ORNL

2013-01-01T23:59:59.000Z

259

Single-Nucleon Densities  

NLE Websites -- All DOE Office Websites (Extended Search)

Densities Densities This web page presents single-nucleon densities calculated for a variety of nuclei in the range A=2-10 with some preliminary results for A=11,12. These are from variational Monte Carlo calculations (VMC) using the Argonne v18 two-nucleon and Urbana X three-nucleon potentials (AV18+UX). (Urbana X is intermediate between the Urbana IX and Illinois-7 models; it has the form of UIX supplemented with a two-pion S-wave piece, while the strengths of its terms are taken from the IL7 model. It does NOT have the three-pion-ring term of IL7.) These VMC wave functions are the starting trial functions for a number of recent Green's function Monte Carlo (GFMC) calculations: Brida, et al., Phys. Rev. C 84, 024319 (2011); McCutchan, et al., Phys. Rev. C 86, 024315 (2012);

260

Rigorous luminosity function determination in presence of a background: theory and application to two intermediate redshift clusters  

E-Print Network (OSTI)

In this paper we present a rigorous derivation of the luminosity function (LF) in presence of a background. Our approach is free from the logical contradictions of assigning negative values to positively defined quantities and avoid the use of incorrect estimates for the 68 % confidence interval (error bar). It accounts for Poisson fluctuations ignored in previous approaches and does not requires binning of the data. The method is extensible to more complex situations, does not require the existence of an environment--independent LF, and clarifies issues common to field LF derivations. We apply the method to two clusters of galaxies at intermediate redshift (z~0.3) with among the deepest and widest K_s observations ever taken. Finally, we point out short-comings of flip--flopping magnitudes.

S. Andreon; G. Punzi; A. Grado

2005-03-31T23:59:59.000Z

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261

Algorithmic information theory  

E-Print Network (OSTI)

We introduce algorithmic information theory, also known as the theory of Kolmogorov complexity. We explain the main concepts of this quantitative approach to defining `information'. We discuss the extent to which Kolmogorov's and Shannon's information theory have a common purpose, and where they are fundamentally different. We indicate how recent developments within the theory allow one to formally distinguish between `structural' (meaningful) and `random' information as measured by the Kolmogorov structure function, which leads to a mathematical formalization of Occam's razor in inductive inference. We end by discussing some of the philosophical implications of the theory.

Grunwald, Peter D

2008-01-01T23:59:59.000Z

262

Density-based Energy Decomposition Analysis for Intermolecular Interactions with Variationally Determined Intermediate State Energies  

DOE Green Energy (OSTI)

The first purely density-based energy decomposition analysis (EDA) for intermolecular binding is developed within the density functional theory. The most important feature of this scheme is to variationally determine the frozen density energy, based on a constrained search formalism and implemented with the Wu-Yang algorithm [Q. Wu and W. Yang, J. Chem. Phys. 118, 2498 (2003) ]. This variational process dispenses with the Heitler-London antisymmetrization of wave functions used in most previous methods and calculates the electrostatic and Pauli repulsion energies together without any distortion of the frozen density, an important fact that enables a clean separation of these two terms from the relaxation (i.e., polarization and charge transfer) terms. The new EDA also employs the constrained density functional theory approach [Q. Wu and T. Van Voorhis, Phys. Rev. A 72, 24502 (2005)] to separate out charge transfer effects. Because the charge transfer energy is based on the density flow in real space, it has a small basis set dependence. Applications of this decomposition to hydrogen bonding in the water dimer and the formamide dimer show that the frozen density energy dominates the binding in these systems, consistent with the noncovalent nature of the interactions. A more detailed examination reveals how the interplay of electrostatics and the Pauli repulsion determines the distance and angular dependence of these hydrogen bonds.

Wu, Q.; Ayers, P.W.; Zhang, Y.

2009-10-28T23:59:59.000Z

263

A lattice gauge theory model for graphene  

E-Print Network (OSTI)

In this Ph.D. thesis a model for graphene in presence of quantized electromagnetic interactions is introduced. The zero and low temperature properties of the model are studied using rigorous renormalization group methods and lattice Ward identities. In particular, it is shown that, at all orders in renormalized perturbation theory, the Schwinger functions and the response functions decay with interaction dependent anomalous exponents. Regarding the 2-point Schwinger function, the wave function renormalization diverges in the infrared limit, while the effective Fermi velocity flows to the speed of light. Concerning the response functions, those associated to a Kekul\\'e distortion of the honeycomb lattice and to a charge density wave instability are enhanced by the electromagnetic electron-electron interactions (their scaling in real space is depressed), while the lowest order correction to the scaling exponent of the density-density response function is vanishing. Then, the model in presence of a fixed Kekul\\'e distortion is studied, and it is shown that the interaction strongly renormalizes the effective amplitude of the lattice distortion. Finally, the effect of the electronic repulsion on the Peierls-Kekul\\'e instability is discussed by deriving a non-BCS gap equation, from which we find evidence that strong electromagnetic interactions facilitate the spontaneous distortion of the lattice and the opening of a gap. This thesis is based on joint work with A. Giuliani and V. Mastropietro.

Marcello Porta

2011-05-06T23:59:59.000Z

264

Classical Phase Space Density for the Relativistic Hydrogen Atom  

E-Print Network (OSTI)

Quantum mechanics is considered to arise from an underlying classical structure (``hidden variable theory'', ``sub-quantum mechanics''), where quantum fluctuations follow from a physical noise mechanism. The stability of the hydrogen ground state can then arise from a balance between Lorentz damping and energy absorption from the noise. Since the damping is weak, the ground state phase space density should predominantly be a function of the conserved quantities, energy and angular momentum. A candidate for this phase space density is constructed for ground state of the relativistic hydrogen problem of a spinless particle. The first excited states and their spherical harmonics are also considered in this framework. The analytic expression of the ground state energy can be reproduced, provided averages of certain products are replaced by products of averages. This analysis puts forward that quantum mechanics may arise from an underlying classical level as a slow variable theory, where each new quantum operator relates to a new, well separated time interval.

Th. M. Nieuwenhuizen

2005-11-15T23:59:59.000Z

265

Analytic progress in open string field theory  

E-Print Network (OSTI)

Open string field theory provides an action functional for open string fields, and it is thus a manifestly off-shell formulation of open string theory. The solutions to the equation of motion of open string field theory ...

Kiermaier, Michael Stefan

2009-01-01T23:59:59.000Z

266

Definition: Density Log | Open Energy Information  

Open Energy Info (EERE)

Density Log Density Log Jump to: navigation, search Dictionary.png Density Log Density logging is a well logging tool that can provide a continuous record of a formation's bulk density along the length of a borehole. In geology, bulk density is a function of the density of the minerals forming a rock (i.e. matrix) and the fluid enclosed in the pore spaces.[1] View on Wikipedia Wikipedia Definition Density logging is a well logging tool that can provide a continuous record of a formation's bulk density along the length of a borehole. In geology, bulk density is a function of the density of the minerals forming a rock and the fluid enclosed in the pore spaces. This is one of three well logging tools that are commonly used to calculate porosity, the other two being sonic logging and neutron porosity logging

267

Density estimation for data with rounding errors  

Science Conference Proceedings (OSTI)

Rounding of data is common in practice. The problem of estimating the underlying density function based on data with rounding errors is addressed. A parametric maximum likelihood estimator and a nonparametric bootstrap kernel density estimator are proposed. ... Keywords: Bootstrapping, Deconvolution density estimation, Fast Fourier transformation, Kernel density estimation, Measurement error

B. Wang, W. Wertelecki

2013-09-01T23:59:59.000Z

268

Diffusion, Uptake and Release of Hydrogen in p-type Gallium Nitride: Theory and Experiment  

DOE Green Energy (OSTI)

The diffusion, uptake, and release of H in p-type GaN are modeled employing state energies from density-function theory and compared with measurements of deuterium uptake and release using nuclear-reaction analysis. Good semiquantitative agreement is found when account is taken of a surface permeation barrier.

MYERS JR.,SAMUEL M.; WRIGHT,ALAN F.; PETERSEN,GARY A.; WAMPLER,WILLIAM R.; SEAGER,CARLETON H.; CRAWFORD,MARY H.; HAN,JUNG

2000-06-27T23:59:59.000Z

269

Dynamic van der Waals Theory of Two-Phase Fluids in Heat Flow Akira Onuki  

E-Print Network (OSTI)

Dynamic van der Waals Theory of Two-Phase Fluids in Heat Flow Akira Onuki Department of Physics as a functional of the order parameter and the energy density. Let us consider one-component fluids, where-component fluids the effect is drastically altered due to latent heat generation or absorption at the interface [12

270

Investigation of the Effect of Functional Group Substitutions on the Gas-Phase Electron Affinities and Ionization Energies of Room-Temperature Ionic Liquids Ions using Density Functional Theory  

E-Print Network (OSTI)

The cathodic and anodic stabilities of room-temperature ionic liquids (ILs) are important factors in their applications in electrochemical devices. In this work, we investigated the electron affinities of cations and ...

Ong, Shyue Ping

271

Statics and dynamics of inhomogeneous liquids via the internal-energy functional  

E-Print Network (OSTI)

We give a variational formulation of classical statistical mechanics where the one-body density and the local entropy distribution constitute the trial fields. Using Levy's constrained search method it is shown that the grand potential is a functional of both distributions, that it is minimal in equilibrium, and that the minimizing fields are those at equilibrium. The functional splits into a sum of entropic, external energetic and internal energetic contributions. Several common approximate Helmholtz free energy density functionals, such as the Rosenfeld fundamental measure theory for hard sphere mixtures, are transformed to internal energy functionals. The variational derivatives of the internal energy functional are used to generalize dynamical density functional theory to include the dynamics of the microscopic entropy distribution, as is relevant for studying heat transport and thermal diffusion.

Matthias Schmidt

2011-10-20T23:59:59.000Z

272

Green's functions and hydrodynamics for isotopic binary diffusion  

E-Print Network (OSTI)

We study classical binary fluid mixtures in which densities vary on very short time (ps) and length (nm) scales, such that hydrodynamics does not apply. In a pure fluid with a localized heat pulse the breakdown of hydrodynamics was overcome using Green's functions which connect the initial densities to those at later times. Numerically it appeared that for long times the results from the Green's functions would approach hydrodynamics. In this paper we extend the Green's functions theory to binary mixtures. For the case of isothermal isobaric mutual diffusion in isotopic binary mixtures and ideal binary mixtures, which is easier to handle than heat conduction yet still non-trivial, we show analytically that in the Green's function approach one recovers hydrodynamic behaviour at long time scales provided the system reaches local equilibrium at long times. This is a first step toward giving the Green's function theory a firmer basis because it can for this case be considered as an extension of hydrodynamics.

R. van Zon; E. G. D. Cohen

2005-08-10T23:59:59.000Z

273

Equivalence of QCD in the epsilon-regime and chiral Random Matrix Theory with or without chemical potential  

E-Print Network (OSTI)

We prove that QCD in the epsilon-regime of chiral Perturbation Theory is equivalent to chiral Random Matrix Theory for zero and both non-zero real and imaginary chemical potential mu. To this aim we prove a theorem that relates integrals over fermionic and bosonic variables to super-Hermitian or super-Unitary groups also called superbosonization. Our findings extend previous results for the equivalence of the partition functions, spectral densities and the quenched two-point densities. We can show that all k-point density correlation functions agree in both theories for an arbitrary number of quark flavors, for either mu=0 or mu=/=0 taking real or imaginary values. This implies the equivalence for all individual k-th eigenvalue distributions which are particularly useful to determine low energy constants from Lattice QCD with chiral fermions.

Francesco Basile; Gernot Akemann

2007-10-01T23:59:59.000Z

274

One-Particle Spectral Function and Local Density of States in a Phenomenological Mixed-Phase Model for High-Temperature Superconductors  

SciTech Connect

The dynamical properties of a recently introduced phenomenological model for high-temperature superconductors are investigated. In the clean limit, it was observed that none of the homogeneous or striped states that are induced by the model at low temperatures can reproduce the recent angle-resolved photoemission results for La{sub 2-x}Sr{sub x}CuO{sub 4} [Yoshida et al., Phys. Rev. Lett. 91, 027001 (2003)], which show a signal with two branches in the underdoped regime. On the other hand, upon including quenched disorder in the model and breaking the homogeneous state into 'patches' that are locally either superconducting or antiferromagnetic, the two-branch spectra can be reproduced. In this picture, the nodal regions are caused by d-wave superconducting clusters. Studying the density of states (DOS), a pseudogap is observed, caused by the mixture of the gapped antiferromagnetic state and a d-wave superconductor. The local DOS can be interpreted using a mixed-phase picture, similar to what is observed in tunneling experiments. It is concluded that a simple phenomenological model for cuprates can capture several of the one-particle features observed in the underdoped regime of these materials.

Mayr, Matthias [Max-Planck-Institut fur Feskorperforschung, Stuttgart, Germany; Alvarez, Gonzalo [ORNL; Moreo, Adriana [ORNL; Dagotto, Elbio R [ORNL

2006-01-01T23:59:59.000Z

275

Electroweak Theory  

Science Conference Proceedings (OSTI)

The electroweak theory unifies two basic forces of nature: the weak force and electromagnetism. This 2007 book is a concise introduction to the structure of the electroweak theory and its applications. It describes the structure and properties of field ...

E. A. Paschos

2010-06-01T23:59:59.000Z

276

Renormalized weak plasma turbulence theory  

SciTech Connect

A renormalized Vlasov turbulence theory, derived by neglecting a mode coupling term in the Direct Interaction Approximation, is discussed. The theory reduces correctly to weak turbulence theory; it predicts both diffusion and polarization effects of the turbulent medium on test particles, as well as the inverse effects of the test particles on the medium. A heuristic, physical algorithm is presented for constructing the equations. The theory of the renormalized dielectric function is reviewed.

Krommes, J.A.; Kleva, R.G.

1979-02-01T23:59:59.000Z

277

Controlling the Electronic Properties of Nanodiamonds Via Surface Chemical Functionalization: A DFT Study  

E-Print Network (OSTI)

The electronic properties of chemically functionalized nanodiamonds are studied using density functional theory calculations. HOMO-LUMO gap and relative stabilities are calculated for different surface functionalization schemes and diamond nanocrystal morphologies. The effects of chemical decoration on the size and nature of the HOMO-LUMO gap of the various systems considered are discussed in detail. We conclude that surface chemical functionalization has the potential to become an accessible route for controlling the electronic properties of nanodiamonds.

Brown, Noam

2013-01-01T23:59:59.000Z

278

Functionalized Graphene Nanoroads for Quantum Well Device  

Science Conference Proceedings (OSTI)

Using density functional theory, a series of calculations of structural and electronic properties of Si-substituted graphene were conducted. Through substituting C atoms by Si atoms on graphene in the present study, we found that the band gap of graphene can be continuously tuned with differently substitutional concentration. To utilize such substitution-induced band gap changes, we proposed a special design to fabricate graphene-based quantum well device.

Zhou, Yungang; Yang, Ping; Wang, Zhiguo; Xiao, Hai Yan; Zu, Xiaotao T.; Sun, Xin; Khaleel, Mohammad A.; Gao, Fei

2011-03-02T23:59:59.000Z

279

Bivariate density estimation using BV regularisation  

Science Conference Proceedings (OSTI)

The problem of bivariate density estimation is studied with the aim of finding the density function with the smallest number of local extreme values which is adequate with the given data. Adequacy is defined via Kuiper metrics. The concept of the taut-string ... Keywords: Density estimation, Modality, Regularisation

Andreas Obereder; Otmar Scherzer; Arne Kovac

2007-08-01T23:59:59.000Z

280

The resonance absorption probability function for neutron and multiplicative integral  

E-Print Network (OSTI)

The analytical approximations for the moderating neutrons flux density like Fermi spectra, widely used in reactor physics, involve the probability function for moderating neutron to avoid the resonant absorption obtained using some restrictive assumptions regarding the acceptable resonances width. By means of multiplicative integral (Volterra integral) theory for a commutative algebra an analytical expression for the probability function is obtained rigorously without any restrictive assumptions.

Rusov, V D; Kosenko, S I; Chernegenko, S A

2012-01-01T23:59:59.000Z

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


281

The resonance absorption probability function for neutron and multiplicative integral  

E-Print Network (OSTI)

The analytical approximations for the moderating neutrons flux density like Fermi spectra, widely used in reactor physics, involve the probability function for moderating neutron to avoid the resonant absorption obtained using some restrictive assumptions regarding the acceptable resonances width. By means of multiplicative integral (Volterra integral) theory for a commutative algebra an analytical expression for the probability function is obtained rigorously without any restrictive assumptions.

V. D. Rusov; V. A. Tarasov; S. I. Kosenko; S. A. Chernegenko

2012-08-05T23:59:59.000Z

282

High Island Densities and Long Range Repulsive Interactions: Fe on Epitaxial Graphene  

SciTech Connect

The understanding of metal nucleation on graphene is essential for promising future applications, especially of magnetic metals which can be used in spintronics or computer storage media. A common method to study the grown morphology is to measure the nucleated island density n as a function of growth parameters. Surprisingly, the growth of Fe on graphene is found to be unusual because it does not follow classical nucleation: n is unexpectedtly high, it increases continuously with the deposited amount ? and shows no temperature dependence. These unusual results indicate the presence of long range repulsive interactions. Kinetic Monte Carlo simulations and density functional theory calculations support this conclusion. In addition to answering an outstanding question in epitaxial growth, i.e., to find systems where long range interactions are present, the high density of magnetic islands, tunable with ?, is of interest for nanomagnetism applications.

Binz, Steven M.; Hupalo, Myron; Liu, Xiaojie; Wang, Cai-Zhuang; Lu, Wen-Cai; Thiel, Kai-Ming; Conrad, E.H.; Tringides, Michael C.

2012-07-13T23:59:59.000Z

283

Rosenfeld functional for non-additive hard spheres  

E-Print Network (OSTI)

The fundamental measure density functional theory for hard spheres is generalized to binary mixtures of arbitrary positive and moderate negative non-additivity between unlike components. In bulk the theory predicts fluid-fluid phase separation into phases with different chemical compositions. The location of the accompanying critical point agrees well with previous results from simulations over a broad range of non-additivities and both for symmetric and highly asymmetric size ratios. Results for partial pair correlation functions show good agreement with simulation data.

Matthias Schmidt

2004-07-01T23:59:59.000Z

284

Invariants from classical field theory  

Science Conference Proceedings (OSTI)

We introduce a method that generates invariant functions from perturbative classical field theories depending on external parameters. By applying our methods to several field theories such as Abelian BF, Chern-Simons, and two-dimensional Yang-Mills theory, we obtain, respectively, the linking number for embedded submanifolds in compact varieties, the Gauss' and the second Milnor's invariant for links in S{sup 3}, and invariants under area-preserving diffeomorphisms for configurations of immersed planar curves.

Diaz, Rafael [Grupo de Fisica-Matematica, Universidad Experimental Politecnica de las Fuerzas Armadas, Caracas 1010 (Venezuela); Leal, Lorenzo [Centro de Fisica Teorica y Computacional, Universidad Central de Venezuela, Caracas 1041-A (Venezuela)

2008-06-15T23:59:59.000Z

285

Theory and experiment testing flux-line cutting physics  

Science Conference Proceedings (OSTI)

We discuss predictions of five proposed theories for the critical state of type-II superconductors accounting for both flux cutting and flux transport (depinning). The theories predict different behaviours for the ratio E{sub y}/E{sub z} of the transverse and parallel components of the in-plane electric field produced just above the critical current of a type-II superconducting slab as a function of the angle of an in-plane applied magnetic field. We present experimental results measured using an epitaxially grown YBCO thin film favouring one of the five theories, i.e. the extended elliptic critical-state model. We conclude that when the current density J is neither parallel nor perpendicular to the local magnetic flux density B, both flux cutting and flux transport occur simultaneously when J exceeds the critical current density J{sub c}, indicating an intimate relationship between flux cutting and depinning. We also conclude that the dynamical properties of the superconductor when J exceeds J{sub c} depend in detail upon two nonlinear effective resistivities for flux cutting ({rho}{sub c}) and flux flow ({rho}{sub f}) and their ratio r = {rho}{sub c}/{rho}{sub f}.

Clem, John R.; Weigand, Marcus; Durrell, J. H.; Campbell, A. M.

2011-03-29T23:59:59.000Z

286

Weak-coupling analysis of the single-site large-N gauge theory coupled to adjoint fermions  

E-Print Network (OSTI)

We consider the leading-order expression at weak-coupling for a single-site large-N gauge theory coupled to adjoint fermions. We study the case of overlap and wilson fermions. We extend the theory to real values of the number of fermion flavors and restrict ourselves to asymptotically free theories. Using a four-dimensional density function for the distribution of the eigenvalues of the link variables, we show that it is possible to recover the infinite-volume continuum limit for a certain range of fermion flavors if we use fermions with a bare mass of zero. Our use of the four-dimensional density function is supported by a direct analysis of the lattice action.

Robert Lohmayer; Rajamani Narayanan

2013-05-06T23:59:59.000Z

287

Quantum Field Theory and Representation Theory  

E-Print Network (OSTI)

Quantum Field Theory and Representation Theory Peter Woit woit@math.columbia.edu Department of Mathematics Columbia University Quantum Field Theory and Representation Theory ­ p.1 #12;Outline of the talk · Quantum Mechanics and Representation Theory: Some History Quantum Field Theory and Representation Theory

Woit, Peter

288

Propagation of radiation in fluctuating multiscale plasmas. I. Kinetic theory  

SciTech Connect

A theory for propagation of radiation in a large scale plasma with small scale fluctuations is developed using a kinetic description in terms of the probability distribution function of the radiation in space, time, and wavevector space. Large scale effects associated with spatial variations in the plasma density and refractive index of the plasma wave modes and small scale effects such as scattering of radiation by density clumps in fluctuating plasma, spontaneous emission, damping, and mode conversion are included in a multiscale kinetic description of the radiation. Expressions for the Stokes parameters in terms of the probability distribution function of the radiation are used to enable radiation properties such as intensity and polarization to be calculated.

Tyshetskiy, Yu.; Pal Singh, Kunwar; Thirunavukarasu, A.; Robinson, P. A.; Cairns, Iver H. [School of Physics, University of Sydney, NSW 2006 (Australia)

2012-11-15T23:59:59.000Z

289

Wall-Fluid and Liquid-Gas Interfaces of Model Colloid-Polymer Mixtures by Simulation and Theory  

E-Print Network (OSTI)

We perform a study of the interfacial properties of a model suspension of hard sphere colloids with diameter $\\sigma_c$ and non-adsorbing ideal polymer coils with diameter $\\sigma_p$. For the mixture in contact with a planar hard wall, we obtain from simulations the wall-fluid interfacial free energy, $\\gamma_{wf}$, for size ratios $q=\\sigma_p/\\sigma_c=0.6$ and 1, using thermodynamic integration, and study the (excess) adsorption of colloids, $\\Gamma_c$, and of polymers, $\\Gamma_p$, at the hard wall. The interfacial tension of the free liquid-gas interface, $\\gamma_{lg}$, is obtained following three different routes in simulations: i) from studying the system size dependence of the interfacial width according to the predictions of capillary wave theory, ii) from the probability distribution of the colloid density at coexistence in the grand canonical ensemble, and iii) for statepoints where the colloidal liquid wets the wall completely, from Young's equation relating $\\gamma_{lg}$ to the difference of wall-liquid and wall-gas interfacial tensions, $\\gamma_{wl}-\\gamma_{wg}$. In addition, we calculate $\\gamma_{wf}, \\Gamma_c$, and $\\Gamma_p$ using density functional theory and a scaled particle theory based on free volume theory. Good agreement is found between the simulation results and those from density functional theory, while the results from scaled particle theory quantitatively deviate but reproduce some essential features. Simulation results for $\\gamma_{lg}$ obtained from the three different routes are all in good agreement. Density functional theory predicts $\\gamma_{lg}$ with good accuracy for high polymer reservoir packing fractions, but yields deviations from the simulation results close to the critical point.

Andrea Fortini; Marjolein Dijkstra; Matthias Schmidt; Paul P. F. Wessels

2005-01-07T23:59:59.000Z

290

Scattering Length Density Calculator  

Science Conference Proceedings (OSTI)

... For energy dependent cross sections please go to ... The neutron scattering length density is defined ... To calculate scattering length densities enter a ...

291

The smooth cut-off Hierarchical Reference Theory of fluids  

E-Print Network (OSTI)

We provide a comprehensive presentation of the Hierarchical Reference Theory (HRT) in the smooth cut-off formulation. A simple and self-consistent derivation of the hierarchy of differential equations is supplemented by a comparison with the known sharp cut-off HRT. Then, the theory is applied to a hard core Yukawa fluid (HCYF): a closure, based on a mean spherical approximation ansatz, is studied in detail and its intriguing relationship to the self consistent Ornstein-Zernike approximation is discussed. The asymptotic properties, close to the critical point are investigated and compared to the renormalization group results both above and below the critical temperature. The HRT free energy is always a convex function of the density, leading to flat isotherms in the two-phase region with a finite compressibility at coexistence. This makes HRT the sole liquid-state theory able to obtain directly fluid-fluid phase equilibrium without resorting to the Maxwell construction. The way the mean field free energy is modified due to the inclusion of density fluctuations suggests how to identify the spinodal curve. Thermodynamic properties and correlation functions of the HCYF are investigated for three values of the inverse Yukawa range: z=1.8, z=4 and z=7 where Monte Carlo simulations are available. The stability of the liquid-vapor critical point with respect to freezing is also studied.

Alberto Parola; Davide Pini; Luciano Reatto

2009-01-14T23:59:59.000Z

292

A Theory of Equatorial Deep Jets  

Science Conference Proceedings (OSTI)

A simple linear theory of the circulation in a meridionally bounded equatorial ocean driven by density mixing localized near the eastern boundary is used to model the subthermocline circulation of the equatorial oceans. The mixing is modeled by a ...

Joseph Pedlosky

2002-12-01T23:59:59.000Z

293

In Theory  

NLE Websites -- All DOE Office Websites (Extended Search)

5, 1998 5, 1998 Number 11 For every fundamental particle, the theory of supersymmetry proposes a supersymmetric partner, a "sparticle" in SUSY jargon. The electron, e, for example, has a SUSY spartner, the selectron ~ e. Would every Fermilab theorist have a SUSY "stheorist"? Probably not, but theorists worldwide will be watching Tevatron Run II for the first experimental evidence for SUSY. In Theory f INSIDE 2 Supersymmetry 7 Supersymmetry Workshop 8 MiniBooNE 10 Fishing 12 Paperless Papers 14 CDF Party The Fermilab Stheory Group ~ The Fermilab Theory Group by Meher Antia Without resorting to tricky mathematics or exotic physics, anyone can see that much of the stuff the world is made of has mass. Things can be touched and felt; they have some bulk, unlike, say, light which is intangible and

294

PP Theory  

NLE Websites -- All DOE Office Websites (Extended Search)

Present Theory of Present Theory of Fundamental Particles and Forces An Article Written Originally for Midlevel Teachers Back Before World War II, it was known that the nucleus was composed of closely packed protons and neutrons, but little was known about the "strong force" that kept them together. From 1950 to 1970, accelerators were built which were designed to probe nuclei with higher speed and more energetic, charged particles such as electrons and protons. The result was that hundreds of new particles were discovered and their properties defined. In 1963, a theory was proposed that a major group of these particles, called hadrons, could be thought of as made from a few, more fundamental particles, called quarks. Protons and neutrons are members of the hadron

295

The Use of the Weibull Three-Parameter Model for Estimating Mean Wind Power Densities  

Science Conference Proceedings (OSTI)

The Weibull three-parameter model is discussed for estimation of mean wind power densities. This probability density function is a generalization of a number of more conventional density functions. Using wind speed observations, it is shown that ...

L. Van Der Auwera; F. De Meyer; L. M. Malet

1980-07-01T23:59:59.000Z

296

Static spherically symmetric perfect fluid solutions in $f(R)$ theories of gravity  

E-Print Network (OSTI)

Static spherically symmetric perfect fluid solutions are studied in metric $f(R)$ theories of gravity. We show that pressure and density do not uniquely determine $f(R)$ ie. given a matter distribution and an equation state, one cannot determine the functional form of $f(R)$. However, we also show that matching the outside Schwarzschild-de Sitter-metric to the metric inside the mass distribution leads to additional constraints that severely limit the allowed fluid configurations.

T. Multamaki; I. Vilja

2006-12-29T23:59:59.000Z

297

Single site model of large N gauge theories coupled to adjoint fermions  

E-Print Network (OSTI)

We consider a single site large N gauge theory coupled to adjoint fermions at weak coupling. We study the distribution of the eigenvalues of the link variables using a four-dimensional density function. We show that it is possible to recover the infinite-volume continuum limit for a certain range of fermion flavors if we use fermions with a bare mass of zero.

Robert Lohmayer; Rajamani Narayanan

2013-11-12T23:59:59.000Z

298

Materials Theory, Modeling and Simulation | ORNL  

NLE Websites -- All DOE Office Websites (Extended Search)

Functional Materials for Energy Chemistry and Physics at Interfaces Materials Synthesis from Atoms to Systems Materials Characterization Materials Theory and Simulation Quantum...

299

Gauge transformations in lattice chiral theories  

E-Print Network (OSTI)

We show that gauge-transformation properties of correlation functions in chiral gauge theories on the finite lattice are determined in a general way.

Werner Kerler

2004-12-21T23:59:59.000Z

300

Optimization Online - Nonsmooth Optimization for Production Theory  

E-Print Network (OSTI)

Dec 27, 2007 ... Abstract: Production theory needs generalizations so that it can incorporate broader class of production functions. A generalized Hotelling's†...

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


301

Energy trapping from Hagedorn densities of states  

E-Print Network (OSTI)

In this note, we construct simple stochastic toy models for holographic gauge theories in which distributions of energy on a collection of sites evolve by a master equation with some specified transition rates. We build in only energy conservation, locality, and the standard thermodynamic requirement that all states with a given energy are equally likely in equilibrium. In these models, we investigate the qualitative behavior of the dynamics of the energy distributions for different choices of the density of states for the individual sites. For typical field theory densities of states (\\log(\\rho(E)) ~ E^{\\alphaenergy spread out relatively quickly. For large N gauge theories with gravitational duals, the density of states for a finite volume of field theory degrees of freedom typically includes a Hagedorn regime (\\log(\\rho(E)) ~ E). We find that this gives rise to a trapping of energy in subsets of degrees of freedom for parametrically long time scales before the energy leaks away. We speculate that this Hagedorn trapping may be part of a holographic explanation for long-lived gravitational bound states (black holes) in gravitational theories.

Connor Behan; Klaus Larjo; Nima Lashkari; Brian Swingle; Mark Van Raamsdonk

2013-04-26T23:59:59.000Z

302

Considering Air Density in Wind Power Production  

E-Print Network (OSTI)

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.

Zťnů Farkas

2011-03-11T23:59:59.000Z

303

Is There a Nonrecursive Decidable Equational Theory?  

Science Conference Proceedings (OSTI)

The Church-Turing Thesis (CTT) is often paraphrased as ``every computable function is computable by means of a Turing machine.'' The author has constructed a family of equational theories that are not Turing-decidable, that is, given one of the theories, ... Keywords: Church-Turing Thesis, Turing decidability, effective procedure, pseudorecursive theory, quotidian procedure

Benjamin Wells

2002-05-01T23:59:59.000Z

304

Symmetry-adapted distributed approximating functionals: Theory and application to the ro-vibrational states of H{sub 3}{sup +}  

SciTech Connect

Symmetry-adapted Distributed Approximating Functionals (SADAFs) are derived and used to obtain a coordinate representation for the {und A}diabatically Adjusting {und P}rincipal Axis {und H}yperspherical (APH) coordinates kinetic energy operator. The resulting expressions are tested by computing (J=0) ro-vibrational states for the well-studied H{sub 3}{sup +} molecular ion system, by iterative diagonalization of the Hamiltonian matrix using the Arnoldi procedure. The SADAF representation and APH coordinate system are found to be computationally robust and accurate. {copyright} {ital 1999 American Institute of Physics.}

Iyengar, S.S. [Department of Chemistry, University of Houston, Houston, Texas 77204-5641 (United States); Parker, G.A. [Department of Physics, University of Oklahoma, Norman, Oklahoma (United States); Kouri, D.J. [Department of Chemistry and Department of Physics, University of Houston, Houston, Texas 77204-5641 (United States); Hoffman, D.K. [Department of Chemistry and Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States)

1999-06-01T23:59:59.000Z

305

Estimate of dielectric density using spectroscopic ellipsometry  

Science Conference Proceedings (OSTI)

The optical dielectric functions for hafnium oxide and hafnium silicate films were extracted from spectroscopic ellipsometry measurements and the density then calculated using a previously proposed method. The values obtained were then compared to those ... Keywords: Density, Gadolinium oxide, Hafnium silicate, Medium energy ion scattering, Spectroscopic ellipsometry, X-ray reflectometry

W. Davey; O. Buiu; M. Werner; I. Z. Mitrovic; S. Hall; P. Chalker

2009-07-01T23:59:59.000Z

306

SU(2) Yang-Mills Theory in Savvidy Background at Finite Temperature and Chemical Potential  

E-Print Network (OSTI)

The one-loop effective energy density of a pure SU(2) Yang-Mills theory in the Savvidy background, at finite temperature and chemical potential is examined with emphasis on the unstable modes. After identifying the stable and unstable modes, the stable modes are treated in the quadratic approximation. For the unstable modes, the full expansion including the cubic and the quartic terms in the fluctuations is used. The functional integrals for the unstable modes are evaluated and added to the results for the stable modes. The resulting energy density is found to be {\\it{real}}, coinciding with the real part of the energy density in the quadratic approximation of earlier study. There is now {\\it{no imaginary part.}} Numerical results are presented for the variation of the energy density with temperature for various choices of the chemical potential.

R. Parthasarathy; Alok Kumar

2006-09-13T23:59:59.000Z

307

6th ANL/MSU/JINA/INT FRIB Theory Workshop  

NLE Websites -- All DOE Office Websites (Extended Search)

Home Participants Program & Talks Location Access Lodging Transportation Restaurants Forms 6th ANL/MSU/JINA/INT FRIB Theory Workshop Computational Forefront in Nuclear Theory: Preparing for FRIB Argonne National Laboratory, March 23 - 26, 2010 This workshop will concentrate on advances in theoretical methods for computing properties of nuclei and reactions relevant to the experimental program at FRIB. Although we expect a significant number of talks on methods that require the largest available and planned computers, there will also be talks on new methods that do not require such large machines. Topics quantum Monte Carlo -- no-core shell model -- coupled-cluster method -- unitary correlated-operator method -- shell model -- continuum shell model -- Gamow shell model -- energy density functionals -- cranking -- heavy-ion

308

Quantum field theory without divergences  

E-Print Network (OSTI)

It is shown that loop divergences emerging in the Green functions in quantum field theory originate from correspondence of the Green functions to {\\em unmeasurable} (and hence unphysical) quantities. This is because no physical quantity can be measured in a point, but in a region, the size of which is constrained by the resolution of measuring equipment. The incorporation of the resolution into the definition of quantum fields $\\phi(x)\\to\\phi^{(A)}(x)$ and appropriate change of Feynman rules results in finite values of the Green functions. The Euclidean $\\phi^4$-field theory is taken as an example.

Altaisky, M V

2010-01-01T23:59:59.000Z

309

Quantum field theory without divergences  

E-Print Network (OSTI)

It is shown that loop divergences emerging in the Green functions in quantum field theory originate from correspondence of the Green functions to {\\em unmeasurable} (and hence unphysical) quantities. This is because no physical quantity can be measured in a point, but in a region, the size of which is constrained by the resolution of measuring equipment. The incorporation of the resolution into the definition of quantum fields $\\phi(x)\\to\\phi^{(A)}(x)$ and appropriate change of Feynman rules results in finite values of the Green functions. The Euclidean $\\phi^4$-field theory is taken as an example.

M. V. Altaisky

2010-02-12T23:59:59.000Z

310

[CuCln](2-n) Ion-Pair Species in 1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid-Water Mixtures: Ultraviolet-Visible, X-ray Absorbtion Fine Structure, and Density Functional Theory Characterization  

DOE Green Energy (OSTI)

We report details of the coordination environment about Cu(II) in a pure ionic liquid, 1- ethyl-3-methylimidazolium chloride ([EMIM]Cl) and in mixtures containing varying amounts of water from 0-100% of the [EMIM]Cl. There are many stages in the ion pairing of the divalent cation, Cu(II) including the contact ion pairing of Cu2+ with multiple Cl- to form various CuCln (2-n) polyanions. Thereis also the subsequent solvation and ion pairing of the polychlorometallate anion with the EMIM+ cation. Using a combination of x-ray absorption fine structure (XAFS), UV-Vis spectroscopy and electronic structure calculations (TDDFT) we are able to follow the detailed structural changes about Cu(II). Ion pair formation is strongly promoted in [EMIM]Cl by the low dielectric constant and by the extensive breakdown of the water hydrogen bond network in [EMIM]Cl/water mixtures. In the [EMIM]Cl solvent the CuCl4 2- species dominates and itís geometry is quite similar to gas-phase structure. These results are important in understanding catalysis and separation processes involving transition metals in ionic liquid systems.

Li, Guosheng; Camaioni, Donald M.; Amonette, James E.; Zhang, Z. Conrad; Johnson, Timothy J.; Fulton, John L.

2010-10-07T23:59:59.000Z

311

Functions and fixed types: Biological and other functions in the post-adaptationist era  

Science Conference Proceedings (OSTI)

Among naturalistic theories of biological functions, only those that do not reduce functions to actual causal roles allow for a distinction of function and dysfunction. Most prominent among those theories are etiological theories of function, which refer ... Keywords: Adaptationism, Millikan, dysfunction, function, naturalization of norms, type fixation

Ulrich Krohs

2011-04-01T23:59:59.000Z

312

Orthobaric Density: A Thermodynamic Variable for Ocean Circulation Studies  

Science Conference Proceedings (OSTI)

A new density variable, empirically corrected for pressure, is constructed. This is done by first fitting compressibility (or sound speed) computed from global ocean datasets to an empirical function of pressure and in situ density (or specific ...

Roland A. de Szoeke; Scott R. Springer; David M. Oxilia

2000-11-01T23:59:59.000Z

313

Theory and Software  

NLE Websites -- All DOE Office Websites (Extended Search)

Theory and Software Home People Science Highlights Publications Seminars & Meetings Opportunities Advisory Committee Theory and Software Group (X-ray Science Division) The Theory...

314

Alternative representation of N \\times N density matrix  

E-Print Network (OSTI)

We use polarization operators known from quantum theory of angular momentum to expand the $N \\times N$ dimensional density operators. Thereby, we construct generalized Bloch vectors representing density matrices. We study their properties and derive positivity conditions for any $N$. We also apply the procedure to study Bloch vector space for a qubit and a qutrit.

Stanislaw Kryszewski; Mateusz Zachcial

2006-02-06T23:59:59.000Z

315

Generalized Look-Ahead Methods for Computing Stationary Densities  

Science Conference Proceedings (OSTI)

The look-ahead estimator is used to compute densities associated with Markov processes via simulation. We study a framework that extends the look-ahead estimator to a broader range of applications. We provide a general asymptotic theory for the estimator, ... Keywords: densities, numerical methods, simulation

R. Anton Braun; Huiyu Li; John Stachurski

2012-08-01T23:59:59.000Z

316

On the Velocity in the Effective Field Theory of Large Scale Structures  

E-Print Network (OSTI)

We compute the renormalized two-point functions of density, divergence and vorticity of the velocity in the Effective Field Theory of Large Scale Structures. We show that the mass-weighted velocity, as opposed to the volume-weighted velocity, is the natural variable to use. We then prove that, Because of momentum and mass conservation, the corrections from short scales to the large-scale power spectra of density, divergence and vorticity must start at order $k^{4}$. For the vorticity this constitutes the leading term. Exact (approximated) self-similarity of an Einstein-de Sitter ($\\Lambda$CDM) background fixes the time dependence so that the vorticity power spectrum at leading order is uniquely determined, up to a normalization, by the symmetries of the problem. Focusing on density and velocity divergence, we show that the current formulation of the theory does not have enough counterterms to cancel all divergences. At the lowest order, the missing terms are a new stochastic noise and a heat conduction term in the continuity equation. For an Einstein de Sitter universe, we show that all three renormalized cross- and auto-correlation functions have the same structure but different numerical coefficients, which we compute. Using momentum instead of velocity, one can re-absorb the new terms and work with an uncorrected continuity equation but at the cost of having uncancelled IR divergences in equal-time correlators and a more complicated perturbation theory.

Lorenzo Mercolli; Enrico Pajer

2013-07-11T23:59:59.000Z

317

Variational Two-electron Reduced Density Matrix Theory for Many ...  

E-Print Network (OSTI)

Consider ąC to be a product of two fundamental second-quantized operators. ..... geometries for molecules are taken from the Handbook of Chemistry and†...

318

Minimizers for the Hartree-Fock-Bogoliubov Theory of Neutron Stars and White Dwarfs  

E-Print Network (OSTI)

We prove the existence of minimizers for Hartree-Fock-Bogoliubov (HFB) energy functionals with attractive two-body interactions given by Newtonian gravity. This class of HFB functionals serves as model problem for self-gravitating relativistic Fermi systems, which are found in neutron stars and white dwarfs. Furthermore, we derive some fundamental properties of HFB minimizers such as a decay estimate for the minimizing density. A decisive feature of the HFB model in gravitational physics is its failure of weak lower semicontinuity. This fact essentially complicates the analysis compared to the well-studied Hartree-Fock theories in atomic physics.

Enno Lenzmann; Mathieu Lewin

2008-09-15T23:59:59.000Z

319

A kinematic wave theory of capacity drop  

E-Print Network (OSTI)

Capacity drop at active bottlenecks is one of the most puzzling traffic phenomena, but a thorough understanding is practically important for designing variable speed limit and ramp metering strategies. In this study, we attempt to develop a simple model of capacity drop within the framework of kinematic wave theory based on the observation that capacity drop occurs when an upstream queue forms at an active bottleneck. In addition, we assume that the fundamental diagrams are continuous in steady states. This assumption is consistent with observations and can avoid unrealistic infinite characteristic wave speeds in discontinuous fundamental diagrams. A core component of the new model is an entropy condition defined by a discontinuous boundary flux function. For a lane-drop area, we demonstrate that the model is well-defined, and its Riemann problem can be uniquely solved. We theoretically discuss traffic stability with this model subject to perturbations in density, upstream demand, and downstream supply. We clarify that discontinuous flow-density relations, or so-called "discontinuous" fundamental diagrams, are caused by incomplete observations of traffic states. Theoretical results are consistent with observations in the literature and are verified by numerical simulations and empirical observations. We finally discuss potential applications and future studies.

Wen-Long Jin; Qi-Jian Gan; Jean-Patrick Lebacque

2013-10-09T23:59:59.000Z

320

Salinas : theory manual.  

Science Conference Proceedings (OSTI)

Salinas provides a massively parallel implementation of structural dynamics finite element analysis, required for high fidelity, validated models used in modal, vibration, static and shock analysis of structural systems. This manual describes the theory behind many of the constructs in Salinas. For a more detailed description of how to use Salinas, we refer the reader to Salinas, User's Notes. Many of the constructs in Salinas are pulled directly from published material. Where possible, these materials are referenced herein. However, certain functions in Salinas are specific to our implementation. We try to be far more complete in those areas. The theory manual was developed from several sources including general notes, a programmer notes manual, the user's notes and of course the material in the open literature.

Walsh, Timothy Francis; Reese, Garth M.; Bhardwaj, Manoj Kumar

2011-11-01T23:59:59.000Z

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


321

Two new proofs of the test particle superposition principle of plasma kinetic theory  

SciTech Connect

The test particle superposition principle of plasma kinetic theory is discussed in relation to the recent theory of two-time fluctuations in plasma given by Williams and Oberman. Both a new deductive and a new inductive proof of the principle are presented. The fundamental observation is that two-time expectations of one-body operators are determined completely in terms of the (x,v) phase space density autocorrelation, which to lowest order in the discreteness parameter obeys the linearized Vlasov equation with singular initial condition. For the deductive proof, this equation is solved formally using time- ordered operators, and the solution then rearranged into the superposition principle. The inductive proof is simpler than Rostoker's, although similar in some ways; it differs in that first order equations for pair correlation functions need not be invoked. It is pointed out that the superposition principle is also applicable to the short-time theory of neutral fluids. (auth)

Krommes, J.A.

1975-12-01T23:59:59.000Z

322

A statistical field theory approach applied to the liquid vapor interface  

E-Print Network (OSTI)

Last years, there has been a renewed interest in the utilization of statistical field theory methods for the description of systems at equilibrium both in the vicinity and away from critical points, in particular in the field of liquid state physics. These works deal in general with homogeneous systems, although recently the study of liquids in the vicinity of hard walls has also been considered in this way. On the other hand, effective Hamiltonian pertaining to the $\\phi^4$ theory family have been written and extensively used for the description of inhomogeneous systems either at the simple interface between equilibrium phases or for the description of wetting. In the present work, we focus on a field theoretical description of the liquid vapor interface of simple fluids. We start from the representation of the grand partition function obtained from the Hubbard-Stratonovich transform leading to an exact formulation of the problem, namely neither introducing an effective Hamiltonian nor associating the field to the one-body density of the liquid. Using as a reference system the hard sphere fluid and imposing the coexistence condition, the expansion of the Hamiltonian obtained yields a usual $\\phi^4$ theory without unknown parameter. An important point is that the so-called capillary wave theory appears as an approximation of the one-loop theory in the functional expansion of the Hamiltonian, without any need to an underlying phenomenology.

Vincent Russier; Jean-Michel Caillol

2009-07-16T23:59:59.000Z

323

Low density, resorcinol-formaldehyde aerogels  

DOE Patents (OSTI)

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.

Pekala, R.W.

1989-10-10T23:59:59.000Z

324

Low density, resorcinol-formaldehyde aerogels  

DOE Patents (OSTI)

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 {le}100 mg/cc; cell size {le}0.1 microns). The aerogels are transparent, dark red in color and consist of interconnected colloidal-like particles with diameters of about 100 A{degrees}. These aerogels may be further carbonized to form low density carbon foams with cell size of about 0.1 micron. 1 ref., 1 tab.

Pekala, R.W.

1989-09-12T23:59:59.000Z

325

Low density, resorcinol-formaldehyde aerogels  

DOE Patents (OSTI)

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.

Pekala, Richard W. (Pleasant Hill, CA)

1989-01-01T23:59:59.000Z

326

Low density, resorcinol-formaldehyde aerogels  

DOE Patents (OSTI)

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.

Pekala, Richard W. (Pleasant Hill, CA)

1991-01-01T23:59:59.000Z

327

An Alternative f(R,T) Gravity Theory : A probable Solution to Dark Energy  

E-Print Network (OSTI)

Recently, a generalized gravity theory was proposed by Harko etal where the Lagrangian density is an arbitrary function of the Ricci scalar R and the trace of the stress-energy tensor T, known as F(R,T) gravity. In their derivation of the field equations, they have not considered conservation of the stress-energy tensor. In the present work, we have shown that a part of the arbitrary function f(R,T) can be determined if we take into account of the conservation of stress-energy tensor, although the form of the field equations remain similar. For homogeneous and isotropic model of the universe the field equations are solved and corresponding cosmological aspects has been discussed. Finally, we have studied the energy conditions in this modified gravity theory both generally and a particular case of perfect fluid with constant equation of state.

Chakraborty, Subenoy

2012-01-01T23:59:59.000Z

328

The equilibrium state of hydrogen in gallium nitride: Theory and experiment  

DOE Green Energy (OSTI)

Formation energies and vibrational frequencies for H in wurtzite GaN were calculated from density functional theory and used to predict equilibrium state occupancies and solid solubilities for p-type, intrinsic, and n-type material. The solubility of deuterium (D) was measured at 600--800 C as a function of D{sub 2} pressure and doping and compared with theory. Agreement was obtained by reducing the H formation energies 0.2 eV from ab-initio theoretical values. The predicted stretch-mode frequency for H bound to the Mg acceptor lies 5% above an observed infrared absorption attributed to this complex. It is concluded that currently recognized H states and physical processes account for the equilibrium behavior of H examined in this work.

MYERS JR.,SAMUEL M.; WRIGHT,ALAN F.; PETERSEN,GARY A.; SEAGER,CARLETON H.; WAMPLER,WILLIAM R.; CRAWFORD,MARY H.; HAN,JUNG

2000-04-17T23:59:59.000Z

329

An Alternative f (R, T) Gravity Theory and the Dark Energy Problem  

E-Print Network (OSTI)

Recently, a generalized gravity theory was proposed by Harko etal where the Lagrangian density is an arbitrary function of the Ricci scalar R and the trace of the stress-energy tensor T, known as F(R,T) gravity. In their derivation of the field equations, they have not considered conservation of the stress-energy tensor. In the present work, we have shown that a part of the arbitrary function f(R,T) can be determined if we take into account of the conservation of stress-energy tensor, although the form of the field equations remain similar. For homogeneous and isotropic model of the universe the field equations are solved and corresponding cosmological aspects has been discussed. Finally, we have studied the energy conditions in this modified gravity theory both generally and a particular case of perfect fluid with constant equation of state.

Subenoy Chakraborty

2012-12-13T23:59:59.000Z

330

VOLUME 78, NUMBER 25 P H Y S I C A L R E V I E W L E T T E R S 23 JUNE 1997 Charge Density of MgO: Implications of Precise New Measurements for Theory  

E-Print Network (OSTI)

in the crystal charge density. We consider only the l 4 Kubic harmonic term (the lowest nonzero term

Zuo, Jian-Min "Jim"

331

Theory of space charge limited currents  

SciTech Connect

Space-charge-limited currents are important in energy devices such as solar cells and light-emitting diodes, but the available theory from the 1950's finds it necessary to postulate an exponential density of defect energy levels to match data. Here we revisit the theory and show that this postulate is not warranted. Instead, we demonstrate that dopants and the concomitant Frenkel effect, which have been neglected, control the shape of measured current-voltage characteristics. We also account for the observed peak in the noise power. Finally, the new theory can anchor efforts to develop experimental techniques to measure deep-trap levels.

Zhang, Xiaoguang [ORNL; Pantelides, Sokrates T. [Vanderbilt University

2012-01-01T23:59:59.000Z

332

Extended Chaos Theory and Multiparticle Production  

E-Print Network (OSTI)

First, using the method of the soliton-solution, the fermion probability density equation, which corresponds to the Dirac equation, is derived. Next, we extend the chaos theory, in which the period bifurcation is equivalent to the particle production. Then this extended chaos theory can be used for description of the multiparticle production and the extensive air showers at high energy. Let the parameter takes a suitable value, the quantitative results will be obtained, and an approximate formula will be derived. Many properties of the multiparticle production and of the chaos theory are universal.

Yi-Fang Chang

2008-08-02T23:59:59.000Z

333

BNL | CFN: Theory & Computation  

NLE Websites -- All DOE Office Websites (Extended Search)

Theory and Computation Contact: Mark Hybertsen Advances in theory, numerical algorithms and computational capabilities have enabled an unprecedented opportunity for fundamental...

334

Grand Unified Theory  

NLE Websites -- All DOE Office Websites (Extended Search)

Grand Unified Theory Ungelste Rtsel Grand Unified Theory Heute besteht eines der Hauptziele der Teilchenphysik darin, die verschiedenen fundamentalen Krfte in einer Grossen...

335

String (Faden) Theorie  

NLE Websites -- All DOE Office Websites (Extended Search)

String Theory Ungelste Rtsel String (Faden) Theorie Die heutige Physik kennt gute Theorien wie Quantenmechanik, Relativittstheorie und Gravitation. Aber diese Theorien passen...

336

A unified theory of superconductivity  

E-Print Network (OSTI)

In this paper, we study the reliability of BCS theory as a scientific explanation of the mystery of superconductivity. It is shown clearly that the phonon-mediated BCS theory is fundamentally incorrect. Two kinds of glues, pairing (pseudogap) glue and superconducting glue, are suggested based on a real space Coulomb confinement effect. The scenarios provide a unified explanation of the pairing symmetry, pseudogap and superconducting states, charge stripe order, spin density wave (SDW), checkerboard-type charge-ordered phase, magic doping fractions and vortex structures in conventional and unconventional (the high-Tc cuprates and MgB2) superconductors. The theory agrees with the existence of a pseudogap in high-temperature superconductors, while no pseudogap feature could be observed in MgB2 and most of the conventional superconductors. Our results indicate that the superconducting phase can coexist with a inclined hexagonal vortex lattice in pure MgB2 single crystal with a charge carrier density ps=1.49*10^{22}/cm^{3}. Finally, the physical reasons why the good conductors (for example, Ag, Au, and Cu) and the overdoped high-Tc superconductors are non-superconducting are also explored.

Xiuqing Huang

2008-04-10T23:59:59.000Z

337

Density | OpenEI  

Open Energy Info (EERE)

Density Density Dataset Summary Description This dataset is part of a larger internal dataset at the National Renewable Energy Laboratory (NREL) that explores various characteristics of large solar electric (both PV and CSP) facilities around the United States. This dataset focuses on the land use characteristics for solar facilities that are either under construction or currently in operation. Source Land-Use Requirements for Solar Power Plants in the United States Date Released June 25th, 2013 (5 months ago) Date Updated Unknown Keywords acres area average concentrating solar power csp Density electric hectares km2 land land requirements land use land-use mean photovoltaic photovoltaics PV solar statistics Data application/vnd.openxmlformats-officedocument.spreadsheetml.sheet icon Master Solar Land Use Spreadsheet (xlsx, 1.5 MiB)

338

Applicability of Effective-Medium Theories to problems of Scattering and Absorption by Nonhomogeneous Atmospheric Particles  

Science Conference Proceedings (OSTI)

Effective-medium theories yield effective dielectric functions (or, equivalently, refractive indices) of composite media. Such theories have been formulated that go beyond the Maxwell-Garnett and Bruggeman theories, which art restricted to media ...

Craig F. Bohren

1986-03-01T23:59:59.000Z

339

Spaces of Quantum Field Theories  

E-Print Network (OSTI)

The concept of a "space of quantum field theories" or "theory space" was set out in the 1970's in work of Wilson, Friedan and others. This structure should play an important role in organizing and classifying QFTs, and in the study of the string landscape, allowing us to say when two theories are connected by finite variations of the couplings or by RG flows, when a sequence of QFTs converges to another QFT, and bounding the amount of information needed to uniquely specify a QFT, enabling us to estimate their number. As yet we do not have any definition of theory space which can be used to make such arguments. In this talk, we will describe various concepts and tools which should be developed for this purpose, inspired by the analogous mathematical problem of studying the space of Riemannian manifolds. We state two general conjectures about the space of two-dimensional conformal field theories, and we define a distance function on this space, which gives a distance between any pair of theories, whether or not they are connected by varying moduli. Based on talks given at QTS6 (University of Kentucky), Erice, Texas A& M, and Northwestern University. To appear in the proceedings of QTS6.

Michael R. Douglas

2010-05-16T23:59:59.000Z

340

1 String field theory  

E-Print Network (OSTI)

This elementary introduction to string field theory highlights the features and the limitations of this approach to quantum gravity as it is currently understood. String field theory is a formulation of string theory as a field theory in space-time with an infinite number of massive fields. Although existing constructions of string field theory require expanding around a fixed choice of space-time background, the theory is in principle background-independent, in the sense that different backgrounds can be realized as different field configurations in the theory. String field theory is the only string formalism developed so far which, in principle, has the potential to systematically address questions involving multiple asymptotically distinct string backgrounds. Thus, although it is not yet well defined as a quantum theory, string field theory may eventually be helpful for understanding questions related to cosmology in string theory. 1.1

W. Taylor

2006-01-01T23:59:59.000Z

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


341

Synchrotron radiation in strongly coupled conformal field theories  

E-Print Network (OSTI)

Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled N=4 supersymmetric Yang-Mills theory. We compare the strong ...

Athanasiou, Christiana

342

Multiple density layered insulator  

DOE Patents (OSTI)

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.

Alger, T.W.

1994-09-06T23:59:59.000Z

343

Multiple density layered insulator  

DOE Patents (OSTI)

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.

Alger, Terry W. (Tracy, CA)

1994-01-01T23:59:59.000Z

344

Local Atomic Density of Microporous Carbons  

DOE Green Energy (OSTI)

We investigated the structure of two disordered carbons: activated carbon fibers (ACF) and ultramicroporous carbon (UMC). These carbons have highly porous structure with large surface areas and consequently low macroscopic density that should enhance adsorption of hydrogen. We used the atomic pair distribution function to probe the local atomic arrangements. The results show that the carbons maintain an in-plane local atomic structure similar to regular graphite, but the stacking of graphitic layers is strongly disordered. Although the local atomic density of these carbons is lower than graphite, it is only {approx}20% lower and is much higher than the macroscopic density due to the porosity of the structure. For this reason, the density of graphene sheets that have optimum separation for hydrogen adsorption is lower than anticipated.

Dmowski, Wojtek; Contescu, Cristian I.; Llobet, Anna; Gallego, Nidia C.; Egami, Takeskhi (Tennessee-K); (ORNL); (LANL)

2012-07-12T23:59:59.000Z

345

Cosmological singularities and modified theories of gravity  

Science Conference Proceedings (OSTI)

We consider perturbative modifications of the Friedmann equations in terms of energy density corresponding to modified theories of gravity proposed as an alternative route to comply with the observed accelerated expansion of the universe. Assuming that the present matter content of the universe is a pressureless fluid

Leonardo FernŠndez?Jambrina; Ruth Lazkoz

2009-01-01T23:59:59.000Z

346

Plasma Kinetic Theory  

Science Conference Proceedings (OSTI)

Kinetic Theory / Proceedings of the Ninth Carolus Magnus Summer School on Plasma and Fusion Energy Physics

B. Weyssow

347

Theory decision by decomposition  

Science Conference Proceedings (OSTI)

The topic of this article is decision procedures for satisfiability modulo theories (SMT) of arbitrary quantifier-free formulae. We propose an approach that decomposes the formula in such a way that its definitional part, including the theory, can be ... Keywords: Automated theorem proving: Rewriting, superposition, paramodulation, Satisfiability modulo theories: Decision procedures, combination of theories

Maria Paola Bonacina; Mnacho Echenim

2010-02-01T23:59:59.000Z

348

Model Theory and Quantum  

E-Print Network (OSTI)

Model Theory and Quantum Groups Sonia L'Innocente Model Theory and Quantum Groups Sonia L'Innocente (University of Mons) Model Theory and Quantum Groups 1 / 40 #12;Model Theory and Quantum Groups Sonia L quantum plane, submitted. This work is inspired by Ivo Herzog's paper: The pseudo-finite dimensional

Mons-Hainaut, Université de

349

Nonlinear spectral density estimation: thresholding the correlogram  

E-Print Network (OSTI)

in a nonlinear way. The rate of convergence of the new estimators is quantified, and practical issues estimation of the spectral density function; examples include astronomy, economics, electrical engineering Einstein (1914); see Brillinger (1993) for a historical perspective. The prevalent spectral estimation

Politis, Dimitris N.

350

Thermodynamics and Structural Properties of the High Density Gaussian Core Model  

E-Print Network (OSTI)

We numerically study thermodynamic and structural properties of the one-component Gaussian core model (GCM) at very high densities. The solid-fluid phase boundary is carefully determined. We find that the density dependence of both the freezing and melting temperatures obey the asymptotic relation, $\\log T_f$, $\\log T_m \\propto -\\rho^{2/3}$, where $\\rho$ is the number density, which is consistent with Stillinger's conjecture. Thermodynamic quantities such as the energy and pressure and the structural functions such as the static structure factor are also investigated in the fluid phase for a wide range of temperature above the phase boundary. We compare the numerical results with the prediction of the liquid theory with the random phase approximation (RPA). At high temperatures, the results are in almost perfect agreement with RPA for a wide range of density, as it has been already shown in the previous studies. In the low temperature regime close to the phase boundary line, although RPA fails to describe the structure factors and the radial distribution functions at the length scales of the interparticle distance, it successfully predicts their behaviors at shorter length scales. RPA also predicts thermodynamic quantities such as the energy, pressure, and the temperature at which the thermal expansion coefficient becomes negative, almost perfectly. Striking ability of RPA to predict thermodynamic quantities even at high densities and low temperatures is understood in terms of the decoupling of the length scales which dictate thermodynamic quantities from the interparticle distance which dominates the peak structures of the static structure factor due to the softness of the Gaussian core potential.

Atsushi Ikeda; Kunimasa Miyazaki

2011-04-18T23:59:59.000Z

351

QUANTIZATION OF THE GENERAL THEORY OF RELATIVITY  

SciTech Connect

It is possible to quantize most classical field theories by identifying the group of canonical transformations that maintain the covariance properties with a group of unitary transformations in Hilbert space that has the same commutator algebra. The computators among the canonical field variables are equal to the Dirac delta function times a factor that may be zero. But in the general theory of relativity the classical group of the canonical transformations that maintain the covariance properties of the theory has an invariance subgroup. The ambiguities thus introduced by the usual process of quantization can be avoided by the use of the Dirac quantization procedure for theories with constraints. An analogy between classical Dirac brackets and commutators is established, and an intrinsic coordinate system is fixed. This choice of local intrinsic coordinate conditions leads to commutators among the canonical field variables of the general theory of relativity that depend upon the Dirac delta function and its flrst seven derivatives. (auth)

Boardman, J.M.

1962-01-01T23:59:59.000Z

352

A symmetrical theory of nonrelativistic quantum mechanics  

E-Print Network (OSTI)

This paper presents a new Symmetrical Theory (ST) of nonrelativistic quantum mechanics which postulates: quantum mechanics is a theory about complete experiments, not particles; a complete experiment is maximally described by a complex transition amplitude density; and this transition amplitude density never collapses. This new ST is compared to the Conventional Theory (CT) of nonrelativistic quantum mechanics for the analysis of a beam-splitter experiment. The ST makes several experimentally testable predictions that differ from the CT, which can be checked using existing technology. The ST also solves one part of the CT measurement problem, and resolves some of the paradoxes of the CT. This nonrelativistic ST is the low energy limit of a relativistic ST presented in an earlier paper \\cite{Heaney1}.

Michael B. Heaney

2013-10-20T23:59:59.000Z

353

Theory Seminar Schedule  

NLE Websites -- All DOE Office Websites (Extended Search)

7-2008 7-2008 Click on a title to read an abstract, if available (underlined). 12 June 2008 Kristina Sviratcheva Louisiana State University kristina@rouge.phys.lsu.edu Symplectic Ab Initio No-Core Shell Model - Taming the Model Space Dilemma 5 June 2008 Wick Haxton INT, University of Washington haxton@u.washington.edu Probing Time-odd Moments in Atoms and Nuclei 1 May 2008 Wolfgang Bentz Tokai University, Japan bentz@keyaki.cc.u-tokai.ac.jp Fragmentation functions in an effective quark theory 17 April 2008 Special Time: 10:30am Dmitry G. Yakovlev Ioffe Physico-Technical Institute, St.Petersburg yak@astro.ioffe.rssi.ru Landau and Neutron Stars Tuesday 15 April 2008 Special Day Jochen Wambach GSI and TU Darmstadt J.Wambach@gsi.de Viscosity in the Nambu--Jona-Lasinio Model Tuesday 8 April 2008

354

NREL: Energy Sciences - Solid-State Theory  

NLE Websites -- All DOE Office Websites (Extended Search)

Solid-State Theory Solid-State Theory Image showing a roughly spherical red shape that looks like an apple that is floating within a yellow hemispherical shell. The shell is floating over a square below that shows an orange ring pattern bordered by yellow, then light blue, then darker blue. Square of the wave function (red) of a hole state in a spherical CdSe colloidal quantum dot (shape in yellow). The main research activities of the Solid-State Theory team within NREL's Theoretical Materials Science Group include the following: Theory of photovoltaic semiconductors Statistical and electronic theory of metal and semiconductor alloys Semiconductor nanostructures Inverse design of materials Computational methods in first-principles theories. This team provides the main theoretical thrust in the Center for Inverse

355

Raman Scattering from 1,3-Propanedithiol at a Hot Spot: Theory Meets Experiment  

SciTech Connect

We compute the Raman spectra of 1,3-propanedithiol (PDT) in the gas phase, in methanol, linked either to the face or vertex of a finite tetrahedral Ag20 cluster, and linking two Ag20 clusters using tools of density functional theory. The calculated normal mode-dependent molecular polarizability derivative tensors are employed to simulate single molecule surface-enhanced Raman (SERS) spectra. This is achieved by rotating the polarizability tensors of an individual molecule with respect to explicitly defined vector components of the incident and scattered radiation. Our results provide a basis for understanding commonly observed phenomena in single molecule SERS spectroscopy.

El-Khoury, Patrick Z.; Hess, Wayne P.

2013-08-21T23:59:59.000Z

356

Infrared Behavior of Scalar Condensates in Effective Holographic Theories  

E-Print Network (OSTI)

We investigate the infrared behavior of the spectrum of scalar-dressed, asymptotically Anti de Sitter (AdS) black brane (BB) solutions of effective holographic models. These solutions describe scalar condensates in the dual field theories. We show that for zero charge density the ground state of these BBs must be degenerate with the AdS vacuum, must satisfy conformal boundary conditions for the scalar field and it is isolated from the continuous part of the spectrum. When a finite charge density is switched on, the ground state is not anymore isolated and the degeneracy is removed. Depending on the coupling functions, the new ground state may possibly be energetically preferred with respect to the extremal Reissner-Nordstrom AdS BB. We derive several properties of BBs near extremality and at finite temperature. As a check and illustration of our results we derive and discuss several analytic and numerical, BB solutions of Einstein-scalar-Maxwell AdS gravity with different coupling functions and different potentials. We also discuss how our results can be used for understanding holographic quantum critical points, in particular their stability and the associated quantum phase transitions leading to superconductivity or hyperscaling violation.

Mariano Cadoni; Paolo Pani; Matteo Serra

2013-04-11T23:59:59.000Z

357

Stable and metastable hard sphere crystals in Fundamental Measure Theory  

E-Print Network (OSTI)

Using fully minimized fundamental measure functionals, we investigate free energies, vacancy concentrations and density distributions for bcc, fcc and hcp hard-sphere crystals. Results are complemented by an approach due to Stillinger which is based on expanding the crystal partition function in terms of the number n of free particles while the remaining particles are frozen at their ideal lattice positions. The free energies of fcc/hcp and one branch of bcc agree well with Stillinger's approach truncated at n=2. A second branch of bcc solutions features rather spread-out density distributions around lattice sites and large equilibrium vacancy concentrations and is presumably linked to the shear instability of the bcc phase. Within fundamental measure theory and the Stillinger approach (n=2), hcp is more stable than fcc by a free energy per particle of about 0.001 k_{B}T. In previous simulation work, the reverse situation has been found which can be rationalized in terms of effects due to a correlated motion of at least 5 particles in the Stillinger picture.

Mohammad Hossein Yamani; Martin Oettel

2013-04-22T23:59:59.000Z

358

Phase Diagram of Amorphous Solid Water: Low-Density, High-Density, and Very-High-Density Amorphous Ices  

E-Print Network (OSTI)

We describe the phase diagram of amorphous solid water by performing molecular dynamics simulations. Our simulations follow different paths in the phase diagram: isothermal compression/decompression, isochoric cooling/heating and isobaric cooling/heating. We are able to identify low-density amorphous (LDA), high-density amorphous (HDA), and very-high density amorphous (VHDA) ices. The density $\\rho$ of these glasses at different pressure $P$ and temperature $T$ agree well with experimental values. We also study the radial distribution functions of glassy water. We obtain VHDA by isobaric heating of HDA, as in experiment. We also find that ``other forms'' of glassy water can be obtained upon isobaric heating of LDA, as well as amorphous ices formed during the transformation of LDA to HDA. We argue that these other forms of amorphous ices, as well as VHDA, are not altogether new glasses but rather are the result of aging induced by heating. Samples of HDA and VHDA with different densities are recovered at normal $P$, showing that there is a continuum of glasses. Furthermore, the two ranges of densities of recovered HDA and recovered VHDA overlap at ambient $P$. Our simulations are consistent with the possibility of HDA$\\to$LDA and VHDA$\\to$LDA transformations, reproducing the experimental findings. We do not observe a VHDA$\\to$HDA transformation.

Nicolas Giovambattista; H. Eugene Stanley; Francesco Sciortino

2005-02-22T23:59:59.000Z

359

Turbulent Density Spectrum in Solar Wind Plasma  

E-Print Network (OSTI)

The density fluctuation spectrum in the solar wind reveals a Kolmogorov-like scaling with a spectral slope of -5/3 in wavenumber space. The energy transfer process in the magnetized solar wind, characterized typically by MHD turbulence, over extended length-scales remains an unresolved paradox of modern turbulence theories, raising the question of how a compressible magnetofluid exhibits a turbulent spectrum that is characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma fluid. It is shown that a Kolmogorov-like density spectrum can develop by plasma motions that are dominated by Alfv\\'enic cascades whereas compressive modes are dissipated.

Shaikh, Dastgeer

2009-01-01T23:59:59.000Z

360

Density Spectrum in the Solar Wind Plasma  

E-Print Network (OSTI)

The density fluctuation spectrum in the solar wind reveals a Kolmogorov-like scaling with a spectral slope of -5/3 in wavenumber space. The energy transfer process in the magnetized solar wind, characterized typically by MHD turbulence, over extended length-scales remains an unresolved paradox of modern turbulence theories, raising the question of how a compressible magnetofluid exhibits a turbulent spectrum that is characteristic of an incompressible hydrodynamic fluid. To address these questions, we have undertaken three-dimensional time dependent numerical simulations of a compressible magnetohydrodynamic fluid describing super-Alfv\\'enic, supersonic and strongly magnetized plasma fluid. It is shown that a Kolmogorov-like density spectrum can develop by plasma motions that are dominated by Alfv\\'enic cascades whereas compressive modes are dissipated.

Shaikh, Dastgeer

2009-01-01T23:59:59.000Z

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


361

Reconstructing f(R) theory according to holographic dark energy  

E-Print Network (OSTI)

In this paper a connection between the holographic dark energy model and the $f(R)$ theory is established. We treat the $f(R)$ theory as an effective description for the holographic dark energy and reconstruct the function $f(R)$ with the parameter $c>1$, $c=1$ and $cR)$ theory, especially for the future evolution.

Xing Wu; Zong-Hong Zhu

2007-12-21T23:59:59.000Z

362

Synthesis modulo recursive functions  

Science Conference Proceedings (OSTI)

We describe techniques for synthesis and verification of recursive functional programs over unbounded domains. Our techniques build on top of an algorithm for satisfiability modulo recursive functions, a framework for deductive synthesis, and complete ... Keywords: inductive learning, satisfiability modulo theories, software synthesis

Etienne Kneuss, Ivan Kuraj, Viktor Kuncak, Philippe Suter

2013-10-01T23:59:59.000Z

363

Energy in the Einstein-Aether Theory  

E-Print Network (OSTI)

We investigate the energy of a theory with a unit vector field (the "aether") coupled to gravity. Both the Weinberg and Einstein type energy-momentum pseudotensors are employed. In the linearized theory we find expressions for the energy density of the 5 wave modes. The requirement that the modes have positive energy is then used to constrain the theory. In the fully non-linear theory we compute the total energy of an asymptotically flat spacetime. The resulting energy expression is modified by the presence of the aether due to the non-zero value of the unit vector at infinity and its 1/r falloff. The question of non-linear energy positivity is also discussed, but not resolved.

Christopher Eling

2005-07-14T23:59:59.000Z

364

High Energy Density Capacitors  

SciTech Connect

BEEST Project: Recapping is developing a capacitor that could rival the energy storage potential and price of todayís 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.

None

2010-07-01T23:59:59.000Z

365

ABJM theory as a Fermi gas  

E-Print Network (OSTI)

The partition function on the three-sphere of many supersymmetric Chern-Simons-matter theories reduces, by localization, to a matrix model. We develop a new method to study these models in the M-theory limit, but at all orders in the 1/N expansion. The method is based on reformulating the matrix model as the partition function of an ideal Fermi gas with a non-trivial, one-particle quantum Hamiltonian. This new approach leads to a completely elementary derivation of the N^{3/2} behavior for ABJM theory and N=3 quiver Chern-Simons-matter theories. In addition, the full series of 1/N corrections to the original matrix integral can be simply determined by a next-to-leading calculation in the WKB or semiclassical expansion of the quantum gas, and we show that, for several quiver Chern-Simons-matter theories, it is given by an Airy function. This generalizes a recent result of Fuji, Hirano and Moriyama for ABJM theory. It turns out that the semiclassical expansion of the Fermi gas corresponds to a strong coupling expansion in type IIA theory, and it is dual to the genus expansion. This allows us to calculate explicitly non-perturbative effects due to D2-brane instantons in the AdS background.

Marcos Marino; Pavel Putrov

2011-10-18T23:59:59.000Z

366

Thin liquid lithium targets for high power density  

E-Print Network (OSTI)

Thin liquid lithium targets for high power density applications: heavy ion beam strippers and beta Hilton Malmö City #12;Outline Liquid Lithium Stripper idea for FRIB Brief theory of film stability Thickness measurement results Next Steps Beta-beams 2 #12;Liquid Lithium Stripper for FRIB: Advantages

McDonald, Kirk

367

Density-metric unimodular gravity: Vacuum maximal symmetry  

SciTech Connect

We have investigated the vacuum maximally symmetric solutions of recently proposed density-metric unimodular gravity theory. The results are widely different from inflationary scenario. The exponential dependence on time in deSitter space is substituted by a power law. Open space-times with non-zero cosmological constant are excluded.

Abbassi, A.H., E-mail: ahabbasi@modares.ac.ir [Department of Physics, School of Sciences, Tarbiat Modares University, P.O. Box 14155-4838, Tehran (Iran, Islamic Republic of); Abbassi, A.M., E-mail: amabasi@khayam.ut.ac.ir [Department of Physics, University of Tehran, P.O. Box 14155-6455, Tehran (Iran, Islamic Republic of)

2011-05-15T23:59:59.000Z

368

On the Energy-Momentum Tensor of the Scalar Field in Scalar--Tensor Theories of Gravity  

E-Print Network (OSTI)

We study the dynamical description of gravity, the appropriate definition of the scalar field energy-momentum tensor, and the interrelation between them in scalar-tensor theories of gravity. We show that the quantity which one would naively identify as the energy-momentum tensor of the scalar field is not appropriate because it is spoiled by a part of the dynamical description of gravity. A new connection can be defined in terms of which the full dynamical description of gravity is explicit, and the correct scalar field energy-momentum tensor can be immediately identified. Certain inequalities must be imposed on the two free functions (the coupling function and the potential) that define a particular scalar-tensor theory, to ensure that the scalar field energy density never becomes negative. The correct dynamical description leads naturally to the Einstein frame formulation of scalar-tensor gravity which is also studied in detail.

David I. Santiago; Alexander S. Silbergleit

1999-04-02T23:59:59.000Z

369

Scalar Quantum Field Theory in Disordered Media  

E-Print Network (OSTI)

A free massive scalar field in inhomogeneous random media is investigated. The coefficients of the Klein-Gordon equation are taken to be random functions of the spatial coordinates. The case of an annealed-like disordered medium, modeled by centered stationary and Gaussian processes, is analyzed. After performing the averages over the random functions, we obtain the two-point causal Green's function of the model up to one-loop. The disordered scalar quantum field theory becomes qualitatively similar to a $\\lambda\\phi^{4}$ self-interacting theory with a frequency-dependent coupling.

Arias, E; Krein, G; Menezes, G; Svaiter, N F

2011-01-01T23:59:59.000Z

370

The generalized van der Waals theory of pure fluids and mixtures  

Science Conference Proceedings (OSTI)

This report discusses functional group analysis and partition function analysis of pure fluids and mixtures using generalized van der waals theory. (LSP)

Sandler, S.I.

1990-06-01T23:59:59.000Z

371

Minority Influence Theory  

E-Print Network (OSTI)

The psychology of social impact. American Psychologist, 36,that later embodied in social impact theory (Latane, 1981)

Nemeth, Charlan Jeanne

2010-01-01T23:59:59.000Z

372

Plasma Kinetic Theory  

Science Conference Proceedings (OSTI)

Basic and Kinetic Theory / Proceedings of the Tenth Carolus Magnus Summer School on Plasma and Fusion Energy Physics

B. Weyssow

373

Quantum Physics Theory  

Science Conference Proceedings (OSTI)

Quantum Physics Theory. Summary: Theoretical work ... constant. The database is available at http://physics.nist.gov/hdel. Precise ...

2010-10-05T23:59:59.000Z

374

A Numerical Modeling Study of the Propagation of Idealized Sea-Breeze Density Currents  

Science Conference Proceedings (OSTI)

Sea breezes are often modeled as a wave response to transient heating in a stratified environment. They occur, however, as density currents with well-defined fronts, the understanding of which rests primarily on experiments and theory that do not ...

F. J. Robinson; M. D. Patterson; S. C. Sherwood

2013-02-01T23:59:59.000Z

375

Anomalous evolution of Ar metastable density with electron density in high density Ar discharge  

SciTech Connect

Recently, an anomalous evolution of argon metastable density with plasma discharge power (electron density) was reported [A. M. Daltrini, S. A. Moshkalev, T. J. Morgan, R. B. Piejak, and W. G. Graham, Appl. Phys. Lett. 92, 061504 (2008)]. Although the importance of the metastable atom and its density has been reported in a lot of literature, however, a basic physics behind the anomalous evolution of metastable density has not been clearly understood yet. In this study, we investigated a simple global model to elucidate the underlying physics of the anomalous evolution of argon metastable density with the electron density. On the basis of the proposed simple model, we reproduced the anomalous evolution of the metastable density and disclosed the detailed physics for the anomalous result. Drastic changes of dominant mechanisms for the population and depopulation processes of Ar metastable atoms with electron density, which take place even in relatively low electron density regime, is the clue to understand the result.

Park, Min; Chang, Hong-Young [Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 305-701 (Korea, Republic of); You, Shin-Jae; Kim, Jung-Hyung [Center for Vacuum Technology, Korea Research Institute of Standards and Science, Daejeon, 305-306 (Korea, Republic of); Shin, Yong-Hyeon

2011-10-15T23:59:59.000Z

376

Low density, resorcinol-formaldehyde aerogels  

DOE Patents (OSTI)

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.

Pekala, R.W.

1988-05-26T23:59:59.000Z

377

Empirical models for Dark Matter Halos. I. Nonparametric Construction of Density Profiles and Comparison with Parametric Models  

E-Print Network (OSTI)

We use techniques from nonparametric function estimation theory to extract the density profiles, and their derivatives, from a set of N-body dark matter halos. We consider halos generated from LCDM simulations of gravitational clustering, as well as isolated, spherical collapses. The logarithmic density slopes gamma = d(log rho)/d(log r) of the LCDM halos are found to vary as power-laws in radius, reaching values of gamma ~ -1 at the innermost resolved radii (~0.01 r_virial). This behavior is significantly different from that of broken power-law models like the NFW profile, but similar to that of models like de Vaucouleurs'. Accordingly, we compare the N-body density profiles with various parametric models to find which provide the best fit. We consider an NFW-like model with arbitrary inner slope; Dehnen & McLaughlin's anisotropic model; Einasto's model (identical in functional form to Sersic's model but fit to the space density); and the density model of Prugniel & Simien that was designed to match the deprojected form of Sersic's R^{1/n} law. Overall, the best-fitting model to the LCDM halos is Einasto's, although the Prugniel-Simien and Dehnen-McLaughlin models also perform well. With regard to the spherical collapse halos, both the Prugniel-Simien and Einasto models describe the density profiles well, with an rms scatter some four times smaller than that obtained with either the NFW-like model or the 3-parameter Dehnen-McLaughlin model. Finally, we confirm recent claims of a systematic variation in profile shape with halo mass.

David Merritt; Alister W. Graham; Ben Moore; Juerg Diemand; Balsa Terzic

2005-09-15T23:59:59.000Z

378

Energy density for chiral lattice fermions with chemical potential  

E-Print Network (OSTI)

We study a recently proposed formulation of overlap fermions at finite density. In particular we compute the energy density as a function of the chemical potential and the temperature. It is shown that overlap fermions with chemical potential reproduce the correct continuum behavior.

Gattringer, Christof

2007-01-01T23:59:59.000Z

379

Charge Density Wave Compounds  

NLE Websites -- All DOE Office Websites (Extended Search)

Fisher Research Group Fisher Research Group Layered Chalcogenides 29 February 2008 Controlling the Wave by Brad Plummer, SLAC Communications Stanford University researchers working in part at SSRL have discovered a novel set of properties pertaining to a compound of materials called tritellurides. These compounds, composed of three atoms of tellurium and a single atom of one of the rare earth elements, demonstrate unique electronic properties that can be controlled by altering the temperature of the material. The tritellurides display phenomena known as charge density waves (CDW). In a normal conductive metal, electrons persist in a "sea" wherein they are evenly distributed and equally available, or conductive. A CDW occurs under certain circumstances and causes the electrons to clump together, lowering their availability, and thereby lowering the compound's conductivity. Tellurium, when crystallized into quasi-two-dimensional planes and combined with rare earth elements, produces a material with CDWs that can be manipulated and controlled.

380

Low density microcellular foams  

DOE Patents (OSTI)

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.

LeMay, James D. (Castro Valley, CA)

1992-01-01T23:59:59.000Z

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


381

Low density microcellular foams  

DOE Patents (OSTI)

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.

LeMay, James D. (Castro Valley, CA)

1991-01-01T23:59:59.000Z

382

Density Coordinate Mixed Layer Models  

Science Conference Proceedings (OSTI)

The development of mixed layer models in so-called density coordinates is discussed. Density coordinates, or isopycnal coordinates as they are sometimes called, are becoming increasingly popular for use in ocean models due to their highly ...

William K. Dewar

2001-02-01T23:59:59.000Z

383

Reduced-Memory Decoding of Low-Density Lattice Codes  

E-Print Network (OSTI)

This letter describes a belief-propagation decoder for low-density lattice codes of finite dimension, in which the messages are represented as single Gaussian functions. Compared to previously-proposed decoders, memory is ...

Kurkoski, Brian

384

Free Field Theory as a String Theory?  

E-Print Network (OSTI)

An approach to systematically implement open-closed string duality for free large $N$ gauge theories is summarised. We show how the relevant closed string moduli space emerges from a reorganisation of the Feynman diagrams contributing to free field correlators. We also indicate why the resulting integrand on moduli space has the right features to be that of a string theory on $AdS$.

Rajesh Gopakumar

2004-09-23T23:59:59.000Z

385

ELECTROSPINNING APPLICATIONS IN MECHANOCHEMISTRY AND MULTI-FUNCTIONAL HYDROGEL MATERIALS  

E-Print Network (OSTI)

function (EWF). Under the assumptions of this theory the Schrödinger equation for the EWF is given by

Braun, Paul

386

Asymptotically Free Gauge Theories. I  

DOE R&D Accomplishments (OSTI)

Asymptotically free gauge theories of the strong interactions are constructed and analyzed. The reasons for doing this are recounted, including a review of renormalization group techniques and their application to scaling phenomena. The renormalization group equations are derived for Yang-Mills theories. The parameters that enter into the equations are calculated to lowest order and it is shown that these theories are asymptotically free. More specifically the effective coupling constant, which determines the ultraviolet behavior of the theory, vanishes for large space-like momenta. Fermions are incorporated and the construction of realistic models is discussed. We propose that the strong interactions be mediated by a "color" gauge group which commutes with SU(3)xSU(3). The problem of symmetry breaking is discussed. It appears likely that this would have a dynamical origin. It is suggested that the gauge symmetry might not be broken, and that the severe infrared singularities prevent the occurrence of non-color singlet physical states. The deep inelastic structure functions, as well as the electron position total annihilation cross section are analyzed. Scaling obtains up to calculable logarithmic corrections, and the naive lightcone or parton model results follow. The problems of incorporating scalar mesons and breaking the symmetry by the Higgs mechanism are explained in detail.

Wilczek, Frank; Gross, David J.

1973-07-00T23:59:59.000Z

387

1992 Trieste Lectures on Topological Gauge Theory and Yang-Mills Theory  

E-Print Network (OSTI)

In these lecture notes we explain a connection between Yang-Mills theory on arbitrary Riemann surfaces and two types of topological field theory, the so called $BF$ and cohomological theories. The quantum Yang-Mills theory is solved exactly using path integral techniques. Explicit expressions, in terms of group representation theory, are obtained for the partition function and various correlation functions. In a particular limit the Yang-Mills theory devolves to the topological models and the previously determined correlation functions give topological information about the moduli spaces of flat connections. In particular, the partition function yields the volume of the moduli space for which an explicit expression is derived. These notes are self contained, with a basic introduction to the various ideas underlying the topological field theories. This includes some relatively new work on handling problems that arise in the presence of reducible connections which in turn forms the bridge between the various models under consideration. These notes are identical to those made available to participants of the 1992 summer school in Trieste, except for one or two additions added circa January 1993.

George Thompson

1993-05-24T23:59:59.000Z

388

Three approaches to classical thermal field theory  

SciTech Connect

Research Highlights: > Classical thermal field theory admits three equivalent path integral formulations. > Classical Feynman rules can be derived for all three formulations. > Quantum Feynman rules reduce to classical ones at high temperatures. > Classical Feynman rules become much simpler when superfields are introduced. - Abstract: In this paper we study three different functional approaches to classical thermal field theory, which turn out to be the classical counterparts of three well-known different formulations of quantum thermal field theory: the closed-time path (CTP) formalism, the thermofield dynamics (TFD) and the Matsubara approach.

Gozzi, E., E-mail: gozzi@ts.infn.it [Department of Physics, University of Trieste, Strada Costiera 11, Miramare - Grignano, 34151 Trieste (Italy); INFN, Sezione di Trieste (Italy); Penco, R., E-mail: rpenco@syr.edu [Department of Physics, Syracuse University, Syracuse, NY 13244-1130 (United States)

2011-04-15T23:59:59.000Z

389

Dissipative Effects in the Effective Field Theory of Inflation  

SciTech Connect

We generalize the effective field theory of single clock inflation to include dissipative effects. Working in unitary gauge we couple a set of composite operators, {Omicron}{sub {mu}{nu}}..., in the effective action which is constrained solely by invariance under time-dependent spatial diffeomorphisms. We restrict ourselves to situations where the degrees of freedom responsible for dissipation do not contribute to the density perturbations at late time. The dynamics of the perturbations is then modified by the appearance of 'friction' and noise terms, and assuming certain locality properties for the Green's functions of these composite operators, we show that there is a regime characterized by a large friction term {gamma} >> H in which the {zeta}-correlators are dominated by the noise and the power spectrum can be significantly enhanced. We also compute the three point function <{zeta}{zeta}{zeta}> for a wide class of models and discuss under which circumstances large friction leads to an increased level of non-Gaussianities. In particular, under our assumptions, we show that strong dissipation together with the required non-linear realization of the symmetries implies |f{sub NL}| {approx} {gamma}/c{sub s}{sup 2} H >> 1. As a paradigmatic example we work out a variation of the 'trapped inflation' scenario with local response functions and perform the matching with our effective theory. A detection of the generic type of signatures that result from incorporating dissipative effects during inflation, as we describe here, would teach us about the dynamics of the early universe and also extend the parameter space of inflationary models.

Lopez Nacir, Diana; /Buenos Aires, CONICET /Buenos Aires U.; Porto, Rafael A.; /Princeton, Inst. Advanced Study /ISCAP, New York /Columbia U.; Senatore, Leonardo; /Stanford U., ITP /SLAC /KIPAC, Menlo Park; Zaldarriaga, Matias; /Princeton, Inst. Advanced Study

2012-09-14T23:59:59.000Z

390

An Algorithm for Lidar Mapping of Aerosol Concentrations in a Varying Atmospheric Background Density  

Science Conference Proceedings (OSTI)

An algorithm for the determination of the number density profiles of a specific aerosol as a function of time and space is developed and discussed. The algorithm is applicable to atmospheric conditions in which a varying density particulate ...

Moshe Kleiman; Smadar Egert; Ariel Cohen

1986-12-01T23:59:59.000Z

391

Symmetry analysis for anisotropic field theories  

Science Conference Proceedings (OSTI)

The purpose of this paper is to study with the help of Noether's theorem the symmetries of anisotropic actions for arbitrary fields which generally depend on higher order spatial derivatives, and to find the corresponding current densities and the Noether charges. We study in particular scale invariance and consider the cases of higher derivative extensions of the scalar field, electrodynamics and Chern-Simons theory.

Parra, Lorena; Vergara, J. David [Instituto de Ciencias Nucleares, UNAM, Circuito Exterior s/n, Ciudad Universitaria. Delg. Coyoacan. C.P. 04510 Mexico DF (Mexico)

2012-08-24T23:59:59.000Z

392

IAEA advisory group meeting on basic and applied problems of nuclear level densities  

Science Conference Proceedings (OSTI)

Separate entries were made in the data base for 17 of the 19 papers included. Two papers were previously included in the data base. Workshop reports are included on (1) nuclear level density theories and nuclear model reaction cross-section calculations and (2) extraction of nuclear level density information from experimental data. (WHK)

Bhat, M.R. (ed.)

1983-06-01T23:59:59.000Z

393

Lectures on String Theory  

E-Print Network (OSTI)

This is a one semester course on bosonic string theory aimed at beginning graduate students. The lectures assume a working knowledge of quantum field theory and general relativity. Contents: 1. The Classical String 2. The Quantum String 3. Open Strings and D-Branes 4. Introducing Conformal Field Theory 5. The Polyakov Path Integral and Ghosts 6. String Interactions 7. The Low-Energy Effective Action 8. Compactification and T-Duality

Tong, David

2009-01-01T23:59:59.000Z

394

Theory Modeling and Simulation  

SciTech Connect

Los Alamos has a long history in theory, modeling and simulation. We focus on multidisciplinary teams that tackle complex problems. Theory, modeling and simulation are tools to solve problems just like an NMR spectrometer, a gas chromatograph or an electron microscope. Problems should be used to define the theoretical tools needed and not the other way around. Best results occur when theory and experiments are working together in a team.

Shlachter, Jack [Los Alamos National Laboratory

2012-08-23T23:59:59.000Z

395

Theory and Software Science  

NLE Websites -- All DOE Office Websites (Extended Search)

Science Goals The Theory and Software Group connects to the experimental programs at the Advanced Photon Source by the development of theoretical methodologies that provide new...

396

Atomic Theory of Lithium  

Science Conference Proceedings (OSTI)

... polarization-adjusted data were an excellent fit to theory, and the team's results agree with the latest and presumably best theoretical predictions. ...

2011-10-06T23:59:59.000Z

397

Introduction to String Theory  

E-Print Network (OSTI)

The aim of these notes is to give recent developments in string theory. In particular, we discuss the string spectrums, compactifications, brane physics and dualities.

Belhaj, Adil

2008-01-01T23:59:59.000Z

398

Paramagnetic form factors from itinerant electron theory  

Science Conference Proceedings (OSTI)

Elastic neutron scattering experiments performed over the past two decades have provided accurate information about the magnetic form factors of paramagnetic transition metals. These measurements have traditionally been analyzed in terms of an atomic-like theory. There are, however, some cases where this procedure does not work, and there remains the overall conceptual problem of using an atomistic theory for systems where the unpaired-spin electrons are itinerant. We have recently developed computer codes for efficiently evaluating the induced magnetic form factors of fcc and bcc itinerant electron paramagnets. Results for the orbital and spin contributions have been obtained for Cr, Nb, V, Mo, Pd and Rh based on local density bands. By using calculated spin enhancement parameters, we find reasonable agreement between theory and neutron form factor data. In addition, these zero parameter calculations yield predictions for the bulk susceptibility on an absolute scale which are in reasonable agreement with experiment in all treated cases except palladium.

Cooke, J.F.; Liu, S.H.; Liu, A.J.

1984-09-01T23:59:59.000Z

399

More is the Same; Phase Transitions and Mean Field Theories  

E-Print Network (OSTI)

This paper looks at the early theory of phase transitions. It considers a group of related concepts derived from condensed matter and statistical physics. The key technical ideas here go under the names of "singularity", "order parameter", "mean field theory", and "variational method". In a less technical vein, the question here is how can matter, ordinary matter, support a diversity of forms. We see this diversity each time we observe ice in contact with liquid water or see water vapor, "steam", come up from a pot of heated water. Different phases can be qualitatively different in that walking on ice is well within human capacity, but walking on liquid water is proverbially forbidden to ordinary humans. These differences have been apparent to humankind for millennia, but only brought within the domain of scientific understanding since the 1880s. A phase transition is a change from one behavior to another. A first order phase transition involves a discontinuous jump in a some statistical variable of the system. The discontinuous property is called the order parameter. Each phase transitions has its own order parameter that range over a tremendous variety of physical properties. These properties include the density of a liquid gas transition, the magnetization in a ferromagnet, the size of a connected cluster in a percolation transition, and a condensate wave function in a superfluid or superconductor. A continuous transition occurs when that jump approaches zero. This note is about statistical mechanics and the development of mean field theory as a basis for a partial understanding of this phenomenon.

Leo P. Kadanoff

2009-06-03T23:59:59.000Z

400

Density Inhomogeneities and Electron Mobility in Supercritical Xenon  

NLE Websites -- All DOE Office Websites (Extended Search)

Density Inhomogeneities and Electron Mobility in Supercritical Xenon Density Inhomogeneities and Electron Mobility in Supercritical Xenon Richard A. Holroyd, Kengo Itoh, and Masaru Nishikawa J. Chem. Phys. 118, 706-710 (2003) [Find paper at Scitation] Abstract: The low-field mobility of electrons in supercritical Xe has been measured isothermally as a function of density above the critical temperature (289.7 K). At 293 K the mobility varies from a high of 890 cm2/Vs at 9.2 x 1021 atoms/cm3 to a minimum value of 4.6 cm2/Vs at a density of 3.5 x 1021 atoms/cm3, which is just below the critical density. The density dependence of the mobility is reasonably well predicted by the deformation potential model if the adiabatic compressibility is used to characterize the electron-medium interactions. Approximate agreement indicates that

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


401

Thermodynamics in Modified Gravity Theories  

E-Print Network (OSTI)

We demonstrate that there does exist an equilibrium description of thermodynamics on the apparent horizon in the expanding cosmological background for a wide class of modified gravity theories with the Lagrangian density $f(R, \\phi, X)$, where $R$ is the Ricci scalar and $X$ is the kinetic energy of a scalar field $\\phi$. This comes from a suitable definition of an energy momentum tensor of the "dark" component obeying the local energy conservation law in the Jordan frame. It is shown that the equilibrium description in terms of the horizon entropy $S$ is convenient because it takes into account the contribution of the horizon entropy $\\hat{S}$ in non-equilibrium thermodynamics as well as an entropy production term.

Kazuharu Bamba; Chao-Qiang Geng; Shinji Tsujikawa

2011-01-19T23:59:59.000Z

402

Aging Logarithmic Galilean Field Theories  

E-Print Network (OSTI)

We analytically compute correlation and response functions of scalar operators for the systems with Galilean and corresponding aging symmetries for general spatial dimensions $d$ and dynamical exponent $z$, along with their logarithmic and logarithmic squared extensions, using the gauge/gravity duality. These non-conformal extensions of the aging geometry are marked by two dimensionful parameters, eigenvalue $\\mathcal M$ of an internal coordinate and aging parameter $\\alpha$. We further perform systematic investigations on two-time response functions for general $d$ and $z$, and identify the growth exponent as a function of the scaling dimensions $\\Delta$ of the dual field theory operators and aging parameter $\\alpha$ in our theory. The initial growth exponent is only controlled by $\\Delta$, while its late time behavior by $\\alpha$ as well as $\\Delta$. These behaviors are separated by a time scale order of the waiting time. We attempt to make contact our results with some field theoretical growth models, such as Kim-Kosterlitz model at higher number of spatial dimensions $d$.

Seungjoon Hyun; Jaehoon Jeong; Bom Soo Kim

2013-03-29T23:59:59.000Z

403

Density rise experiment on PLT  

SciTech Connect

The evolution of the density profile in PLT during intense gas puffing is documented and analyzed. Measurements of the spectrum of low energy edge neutrals and of the change in central neutral density indicate that charge-exchange processes alone cannot account for the central density rise. The transient density profile changes can be reproduced numerically by a diffusivity of approx. 10/sup 4/ cm/sup 2//s, and a spatially averaged inward flow of 10/sup 3/ cm/s. These transport coefficients are 10 ..-->.. 10/sup 2/ times larger than neoclassical. The ion energy confinement is reduced, the small scale density fluctuations are increased, and runaway electrons losses are increased during the density rise.

Strachan, J.D.; Bretz, N.; Mazzucato, E.

1982-05-01T23:59:59.000Z

404

A perturbative approach to the spectral zeta functions of strings, drums, and quantum billiards  

Science Conference Proceedings (OSTI)

We show that the spectral zeta functions of inhomogeneous strings and drums can be calculated using Rayleigh-Schroedinger perturbation theory. The inhomogeneities that can be treated with this method are small but otherwise arbitrary and include the previously studied case of a piecewise constant density. In two dimensions the method can be used to derive the spectral zeta function of a domain obtained from the small deformation of a square. We also obtain exact sum rules that are valid for arbitrary densities and that correspond to the values taken by the spectral zeta function at integer positive values; we have tested numerically these sum rules in specific examples. We show that the Dirichlet or Neumann Casimir energies of an inhomogeneous string, evaluated to first order in perturbation theory, contain in some cases an irremovable divergence, but that the combination of the two is always free of divergences. Finally, our calculation of the Casimir energies of a string with piecewise constant density and of two perfectly conducting concentric cylinders, of similar radius, reproduce the results previously published.

Amore, Paolo [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal Diaz del Castillo 340, Colima, Colima (Mexico)

2012-12-15T23:59:59.000Z

405

Optimization of a hybrid exchange-correlation functional for silicon carbides  

SciTech Connect

A hybrid exchange-correlation functional is optimized in order to accurately describe the nature of silicon carbides (SiC) in the framework of ab-initio calculations based on density functional theory (DFT), especially with an aim toward future applications in defect studies. It is shown that the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional with the screening parameter of 0.15 -1 outperforms conventional exchange-correlation functionals and other popular hybrid functionals regarding description of band structures in SiC. High transferability is proven through assessment over various SiC polytypes, silicon and diamond. Excellent performance is also confirmed for other fundamental material properties including elastic constants and phonon frequency.

Oda, Takuji [University of Tennessee, Knoxville (UTK); Zhang, Yanwen [ORNL; Weber, William J [ORNL

2013-01-01T23:59:59.000Z

406

Energy Densities for LLNL EMB  

Summary of Projected Power and Energy Density Parameters for the ďNew GenerationĒ LLNL Electromechanical Batteries R.F. Post June 24, 2013

407

Investigations in gauge theories, topological solitons and string theories. Final report  

SciTech Connect

This is the Final Report on a supported research project on theoretical particle physics entitled ``Investigations in Gauge Theories, Topological Solitons and String Theories.`` The major theme of particle theory pursued has been within the rubric of the standard model, particularly on the interplay between symmetries and dynamics. Thus, the research has been carried out primarily in the context of gauge with or without chiral fermions and in effective chiral lagrangian field theories. The topics studied include the physical implications of abelian and non-abelian anomalies on the spectrum and possible dynamical symmetry breaking in a wide range of theories. A wide range of techniques of group theory, differential geometry and function theory have been applied to probe topological and conformal properties of quantum field theories in two and higher dimensions, the breaking of global chiral symmetries by vector-like gauge theories such as QCD,the phenomenology of a possibly strongly interacting Higgs sector within the minimal standard model, and the relevance of solitonic ideas to non-perturbative phenomena at SSC energies.

Not Available

1993-06-01T23:59:59.000Z

408

Yield Strength as a Function of Dislocation Density  

E-Print Network (OSTI)

.Vander Voort, George. Metallography Principles and Practices. New York: McGraw-Hill, 1984. 2.Shackelford

Collins, Gary S.

409

Surface Symmetry Energy of Nuclear Energy Density Functionals.  

E-Print Network (OSTI)

??The thesis studies the bulk deformation properties of the Skyrme nuclear energy densityfunctionals. Following simple arguments based on the leptodermous expansion andliquid drop model, theÖ (more)

Nikolov, Nikola Iliev

2011-01-01T23:59:59.000Z

410

Recovering Risk-Neutral Probability Density Functions from Options ...  

E-Print Network (OSTI)

Theorem 2 provides us with a simple mechanism to eliminate "artificial" arbitrage ..... options prices: An application to crude oil during theI≤ ulfcw risis. © o£ rd®.

411

Nonlocal exchange correlation in screened-exchange density functional methods  

E-Print Network (OSTI)

sX-)LDA and the self-energy matrix elements of GW. We ?rstGW results, where the self-energy matrix elements of GW are

Lee, Byounghak; Wang, Lin-Wang; Spataru, Catalin D.; Louie, Steven G.

2007-01-01T23:59:59.000Z

412

D12: Density Functional Study of Uranium-Niobium System  

Science Conference Proceedings (OSTI)

Calculation results show that the ? phase in U-Nb system tends to be stabilized ... A18: Effect of Local Alendronate Delivery on In Vivo Osteogenesis From PCL Coated .... C19: Dissolution Behavior of Cu Under Bump Metallization in Ball Grid Array ... Volume and Fast Turnaround Automated Inline TEM Sample Preparation

413

Angular momentum dependence of the nuclear level density parameter  

SciTech Connect

Dependence of nuclear level density parameter on the angular momentum and temperature is investigated in a theoretical framework using the statistical theory of hot rotating nuclei. The structural effects are incorporated by including shell correction, shape, and deformation. The nuclei around Zapprox =50 with an excitation energy range of 30 to 40 MeV are considered. The calculations are in good agreement with the experimentally deduced inverse level density parameter values especially for {sup 109}In, {sup 113}Sb, {sup 122}Te, {sup 123}I, and {sup 127}Cs nuclei.

Aggarwal, Mamta [UM-DAE Centre for Excellence in Basic Sciences, University of Mumbai-Kalina Campus, Mumbai 400 098 (India); Kailas, S. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

2010-04-15T23:59:59.000Z

414

The gravitational field energy density for symmetrical and asymmetrical systems  

E-Print Network (OSTI)

The relativistic theory of gravitation has the considerable difficulties by description of the gravitational field energy. Pseudotensor t00 in the some cases cannot be interpreted as energy density of the gravitational field. In [1] the approach was proposed, which allow to express the energy density of such a field through the components of a metric tensor. This approach based on the consideration of the isothermal compression of the layer consisted of the incoherent matter. It was employ to the cylindrically and spherically symmetrical static gravitational field. In presented paper the approach is developed.

Roald Sosnovskiy

2006-07-25T23:59:59.000Z

415

Quantum critical transport, duality, and M-theory  

E-Print Network (OSTI)

We consider charge transport properties of 2+1 dimensional conformal field theories at non-zero temperature. For theories with only Abelian U(1) charges, we describe the action of particle-vortex duality on the hydrodynamic-to-collisionless crossover function: this leads to powerful functional constraints for self-dual theories. For the n=8 supersymmetric, SU(N) Yang-Mills theory at the conformal fixed point, exact hydrodynamic-to-collisionless crossover functions of the SO(8) R-currents can be obtained in the large N limit by applying the AdS/CFT correspondence to M-theory. In the gravity theory, fluctuating currents are mapped to fluctuating gauge fields in the background of a black hole in 3+1 dimensional anti-de Sitter space. The electromagnetic self-duality of the 3+1 dimensional theory implies that the correlators of the R-currents obey a functional constraint similar to that found from particle-vortex duality in 2+1 dimensional Abelian theories. Thus the 2+1 dimensional, superconformal Yang Mills theory obeys a "holographic self duality" in the large N limit, and perhaps more generally.

Christopher P. Herzog; Pavel Kovtun; Subir Sachdev; Dam Thanh Son

2007-01-05T23:59:59.000Z

416

Introduction to string theory and conformal field theory  

Science Conference Proceedings (OSTI)

A concise survey of noncritical string theory and two-dimensional conformal field theory is presented. A detailed derivation of a conformal anomaly and the definition and general properties of conformal field theory are given. Minimal string theory, which is a special version of the theory, is considered. Expressions for the string susceptibility and gravitational dimensions are derived.

Belavin, A. A., E-mail: belavin@itp.ac.ru; Tarnopolsky, G. M., E-mail: Hetzif@yandex.r [Russian Academy of Sciences, Landau Institute for Theoretical Physics (Russian Federation)

2010-05-15T23:59:59.000Z

417

Density-based logistic regression  

Science Conference Proceedings (OSTI)

This paper introduces a nonlinear logistic regression model for classification. The main idea is to map the data to a feature space based on kernel density estimation. A discriminative model is then learned to optimize the feature weights as well as ... Keywords: density estimation, logistic regression, medical prediction, nonlinear classification

Wenlin Chen, Yixin Chen, Yi Mao, Baolong Guo

2013-08-01T23:59:59.000Z

418

Computing 1-D atomic densities in macromolecular simulations: the Density Profile Tool for VMD  

E-Print Network (OSTI)

Molecular dynamics simulations have a prominent role in biophysics and drug discovery due to the atomistic information they provide on the structure, energetics and dynamics of biomolecules. Specialized software packages are required to analyze simulated trajectories, either interactively or via scripts, to derive quantities of interest and provide insight for further experiments. This paper presents the Density Profile Tool, a package that enhances the Visual Molecular Dynamics environment with the ability to interactively compute and visualize 1-D projections of various density functions of molecular models. We describe how the plugin is used to perform computations both via a graphical interface and programmatically. Results are presented for realistic examples, all-atom bilayer models, showing how mass and electron densities readily provide measurements such as membrane thickness, location of structural elements, and how they compare to X-ray diffraction experiments.

Giorgino, Toni

2013-01-01T23:59:59.000Z

419

Density Log | Open Energy Information  

Open Energy Info (EERE)

Density Log Density Log Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Technique: Density Log Details Activities (6) Areas (6) Regions (0) NEPA(0) Exploration Technique Information Exploration Group: Downhole Techniques Exploration Sub Group: Well Log Techniques Parent Exploration Technique: Well Log Techniques Information Provided by Technique Lithology: provides data on the bulk density of the rock surrounding the well Stratigraphic/Structural: Stratigraphic correlation between well bores. Hydrological: Porosity of the formations loggesd can be calculated for the Density log andprovide an indication potential aquifers. Thermal: Cost Information Low-End Estimate (USD): 0.4040 centUSD 4.0e-4 kUSD 4.0e-7 MUSD 4.0e-10 TUSD / foot Median Estimate (USD): 0.6868 centUSD

420

Bayesian Methods for Parameter Estimation in Effective Field Theories  

E-Print Network (OSTI)

We demonstrate and explicate Bayesian methods for fitting the parameters that encode the impact of short-distance physics on observables in effective field theories (EFTs). We use Bayes' theorem together with the principle of maximum entropy to account for the prior information that these parameters should be natural, i.e.O(1) in appropriate units. Marginalization can then be employed to integrate the resulting probability density function (pdf) over the EFT parameters that are not of specific interest in the fit. We also explore marginalization over the order of the EFT calculation, M, and over the variable, R, that encodes the inherent ambiguity in the notion that these parameters are O(1). This results in a very general formula for the pdf of the EFT parameters of interest given a data set, D. We use this formula and the simpler "augmented chi-squared" in a toy problem for which we generate pseudo-data. These Bayesian methods, when used in combination with the "naturalness prior", facilitate reliable extractions of EFT parameters in cases where chi-squared methods are ambiguous at best. We also examine the problem of extracting the nucleon mass in the chiral limit, M_0, and the nucleon sigma term, from pseudo-data on the nucleon mass as a function of the pion mass. We find that Bayesian techniques can provide reliable information on M_0, even if some of the data points used for the extraction lie outside the region of applicability of the EFT.

Matthias R. Schindler; Daniel R. Phillips

2008-08-27T23:59:59.000Z

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


421

Gravitational Energy-Momentum Density in Teleparallel Gravity  

E-Print Network (OSTI)

In the context of a gauge theory for the translation group, a conserved energy-momentum gauge current for the gravitational field is obtained. It is a true spacetime and gauge tensor, and transforms covariantly under global Lorentz transformations. By rewriting the gauge gravitational field equation in a purely spacetime form, it becomes the teleparallel equivalent of Einstein's equation, and the gauge current reduces to the M{\\o}ller's canonical energy-momentum density of the gravitational field.

V. C. de Andrade; L. C. T. Guillen; J. G. Pereira

2000-03-27T23:59:59.000Z

422

Analytical theory of intensity fluctuations in SASE  

SciTech Connect

Recent advances in SASE experiments stimulate interest in quantitative comparison of measurements with theory. Extending the previous analysis of the SASE intensity in guided modes, the authors provide an analytical description of the intensity fluctuations by calculating intensity correlation functions in the frequency domain. Comparison of the results with experiment yields new insight into the SASE process.

Yu, L.H.; Krinsky, S. [Brookhaven National Lab., Upton, NY (United States). National Synchrotron Light Source

1997-07-01T23:59:59.000Z

423

Dirac Kirchhoff diffraction theory  

E-Print Network (OSTI)

Kirchhoff's scalar diffraction theory is applied throughout photon and electron optics. It is based on the stationary electromagnetic or Schr\\"odinger wave equation, and is useful in describing interference phenomena for both light and matter waves. Here, Kirchhoff's diffraction theory is derived from the relativistic Dirac equation, thus reformulated to work on Dirac spinors. The parallels with the "classic" scalar theory are highlighted, and a basic interpretation of the result obtained for the Fraunhofer diffraction limit is given. The goal of this paper is to emphasize the similarity between the two equations on the most fundamental level.

Ruben Van Boxem; Bart Partoens; Jo Verbeeck

2013-03-05T23:59:59.000Z

424

Dirac Kirchhoff diffraction theory  

E-Print Network (OSTI)

Kirchhoff's scalar diffraction theory is applied throughout photon and electron optics. It is based on the stationary electromagnetic or Schr\\"odinger wave equation, and is useful in describing interference phenomena for both light and matter waves. Here, Kirchhoff's diffraction theory is derived from the relativistic Dirac equation, thus reformulated to work on Dirac spinors. The parallels with the "classic" scalar theory are highlighted, and a basic interpretation of the result obtained for the Fraunhofer diffraction limit is given. The goal of this paper is to emphasize the similarity between the two equations on the most fundamental level.

Van Boxem, Ruben; Verbeeck, Jo

2013-01-01T23:59:59.000Z

425

Chern-Simons Theory on Seifert 3-Manifolds  

E-Print Network (OSTI)

We study Chern-Simons theory on 3-manifolds M that are circle-bundles over 2-dimensional orbifolds S by the method of Abelianisation. This method, which completely sidesteps the issue of having to integrate over the moduli space of non-Abelian flat connections, reduces the complete partition function of the non-Abelian theory on M to a 2-dimensional Abelian theory on the orbifold S which is easily evaluated.

Matthias Blau; George Thompson

2013-06-14T23:59:59.000Z

426

Finite BRST Transformations for the Bagger-Lambert-Gustavasson Theory  

E-Print Network (OSTI)

In this paper we analyse the Bagger-Lambert-Gustavsson (BLG) theory in $\\mathcal{N} =1$ superspace. Furthermore, we will construct the BRST transformations for this theory. These BRST transformations will be integrated out to obtain the finite field dependent version of BRST (FFBRST) transformations. We will also analyse the effect of the FFBRST transformations on the effective action. We will thus show that the FFBRST transformations can be used to relate generating functionals of the BLG theory in two different gauges.

Mir Faizal; Bhabani P Mandal; Sudhaker Upadhyay

2012-12-22T23:59:59.000Z

427

The Solar pp and hep Processes in Effective Field Theory  

E-Print Network (OSTI)

The strategy of modern effective field theory is exploited to pin down accurately the flux $S$ factors for the $pp$ and $hep$ processes in the Sun. The technique used is to combine the high accuracy established in few-nucleon systems of the "standard nuclear physics approach" (SNPA) and the systematic power counting of chiral perturbation theory (ChPT) into a consistent effective field theory framework. Using highly accurate wave functions obtained in the SNPA and working to \

T. -S. Park; K. Kubodera; D. -P. Min; M. Rho

2001-08-21T23:59:59.000Z

428

Joint Theory Institute  

NLE Websites -- All DOE Office Websites (Extended Search)

Program General Info Program General Info Registration Info Directions to Argonne Dynamics of Symmetry Breaking A Workshop sponsored by the ANL/UChicago Joint Theory Institute April 13-17, 2009 Argonne National Laboratory, IL The Joint Theory Institute (JTI) is a multi-disciplinary research institution jointly supported at the University of Chicago and Argonne National Laboratory to enhance collaborative research between both institutions in the broad area of theory. This year JTI sponsors a workshop the aim of which is to explore the dynamics of symmetry breaking in a broad range of systems from nuclear physics to string theory, using theoretical insights such as Dyson-Schwinger equations formalism, gauge/gravity duality and lattice QCD. We will focus on systems which exhibit dynamical symmetry breaking and will cover topics essential for understanding nonperturbative QCD and physics of quark-gluon plasma.

429

Adhesive contact of rough surfaces: comparison between numerical calculations and analytical theories  

E-Print Network (OSTI)

We have employed a numerical procedure to analyze the adhesive contact between a soft elastic layer and a rough rigid substrate. The solution of the problem is obtained by calculating the Green's function which links the pressure distribution to the normal displacements at the interface. The problem is then formulated in the form of a Fredholm integral equation of the first kind with a logarithmic kernel, and the boundaries of the contact area are calculated by requiring that the energy of the system is stationary. The methodology has been employed to study the adhesive contact between an elastic semi-infinite solid and a randomly rough rigid profile with a self-affine fractal geometry. We show that, even in presence of adhesion, the true contact area still linearly depends on the applied load. The numerical results are then critically compared with the prediction of an extended version of the Persson's contact mechanics theory, able to handle anisotropic surfaces, as 1D interfaces. It is shown that, for any given load, Persson's theory underestimates the contact area of about 50% in comparison with our numerical calculations. We find that this discrepancy is larger than what is found for 2D rough surfaces in case of adhesionless contact. We argue that this increased difference might be explained, at least partially, by considering that Persson's theory is a mean field theory in spirit, so it should work better for 2D rough surfaces rather than for 1D rough surfaces. We also observe, that the predicted value of separation is in very good agreement with our numerical results as well as the exponent of the power spectral density of the contact pressure distribution and of the elastic displacement of the solid. Therefore, we conclude that Persson's theory captures almost exactly the main qualitative behavior of the rough contact phenomena.

Giuseppe Carbone; Michele Scaraggi; Ugo Tartaglino

2010-06-03T23:59:59.000Z

430

Low-Energy Charge-Density Excitations in MgB2: Striking Interplay Between Single-Particle and Collective Behavior for Large Momenta  

Science Conference Proceedings (OSTI)

A sharp feature in the charge-density excitation spectra of single-crystal MgB{sub 2}, displaying a remarkable cosinelike, periodic energy dispersion with momentum transfer (q) along the c* axis, has been observed for the first time by high-resolution nonresonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-q collective mode residing in the single-particle excitation gap of the B {pi} bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB{sub 2}.

Cai,Y.; Chow, P.; Restrepo, O.; Takano, Y.; Kito, H.; Ishii, H.; Chen, C.; Liang, K.; Chen, C.; et al.

2006-01-01T23:59:59.000Z

431

ERGODIC THEORY OF PARABOLIC HORSESHOES MARIUSZ URBANSKI AND CHRISTIAN WOLF  

E-Print Network (OSTI)

ERGODIC THEORY OF PARABOLIC HORSESHOES MARIUSZ URBA¬īNSKI AND CHRISTIAN WOLF Abstract. In this paper parabolic fixed point and possibly also on Ws (). We call f a parabolic horseshoe map. In order to analyze of an embedded parabolic iterated function system and to apply the developed theory of the symbolic -finite

Urbanski, Mariusz

432

Dyson-Schwinger equations in the theory of computation  

E-Print Network (OSTI)

Following Manin's approach to renormalization in the theory of computation, we investigate Dyson-Schwinger equations on Hopf algebras, operads and properads of flow charts, as a way of encoding self-similarity structures in the theory of algorithms computing primitive and partial recursive functions and in the halting problem.

Colleen Delaney; Matilde Marcolli

2013-02-20T23:59:59.000Z

433

Description of Induced Nuclear Fission with Skyrme Energy Functionals: I. Static Potential Energy Surfaces and Fission Fragment Properties  

E-Print Network (OSTI)

Eighty years after its experimental discovery, a microscopic description of induced nuclear fission based solely on the interactions between neutrons and protons and quantum many-body methods still poses formidable challenges. The goal of this paper is to contribute to the development of a predictive microscopic framework for the accurate calculation of static properties of fission fragments for hot fission and thermal or slow neutrons. To this end, we focus on the 239Pu(n,f) reaction and employ nuclear density functional theory with Skyrme energy densities. Potential energy surfaces are computed at the Hartree-Fock-Bogoliubov approximation with up to five collective variables. We find that the triaxial degree of freedom plays an important role, both near the fission barrier and at scission. The impact of the parameterization of the Skyrme energy density on deformation properties from the ground-state up to scission is also quantified. We introduce a general template for the detailed description of fission fragment properties. It is based on the careful analysis of the scission point, using both advanced topological methods and recently proposed quantum many-body techniques. We conclude that an accurate prediction of fission fragment properties at low incident neutron energies, although technologically demanding, should be within the reach of current nuclear density functional theory.

N. Schunck; D. Duke; H. Carr; A. Knoll

2013-11-11T23:59:59.000Z

434

Low density carbonized composite foams  

DOE Patents (OSTI)

A carbonized composite foam having a density less than about 50 mg/cm{sup 3} and individual cell sizes no greater than about 1 {mu}m in diameter is described, and the process of making it. 3 figs.

Kong, Fung-Ming.

1989-12-07T23:59:59.000Z

435

Quarkonium at nonzero isospin density  

E-Print Network (OSTI)

We calculate the energies of quarkonium bound states in the presence of a medium of nonzero isospin density using lattice QCD. The medium, created using a canonical (fixed isospin charge) approach, induces a reduction of ...

Detmold, William

436

Continuous Wavelet Transform in Quantum Field Theory  

E-Print Network (OSTI)

We describe the application of the continuous wavelet transform to calculation of the Green functions in quantum field theory: scalar $\\phi^4$ theory, quantum electrodynamics, quantum chromodynamics. The method of continuous wavelet transform in quantum field theory presented in M.Altaisky Phys. Rev. D81(2010)125003 for the scalar $\\phi^4$ theory, consists in substitution of the local fields $\\phi(x)$ by those dependent on both the position $x$ and the resolution $a$. The substitution of the action $S[\\phi(x)]$ by the action $S[\\phi_a(x)]$ makes the local theory into nonlocal one, and implies the causality conditions related to the scale $a$, the region causality C. Christensen and L. Crane, J.Math. Phys 46 (2005) 122502. These conditions make the Green functions $G(x_1,a_1,..., x_n,a_n)= $ finite for any given set of regions by means of an effective cutoff scale $A=\\min (a_1,...,a_n)$.

Altaisky, Mikhail V

2013-01-01T23:59:59.000Z

437

Argonne Physics Division - Theory Group  

NLE Websites -- All DOE Office Websites (Extended Search)

23rd Annual Midwest Theory Get-Together 2010 Theory Group Theoretical research in Argonne's Physics Division addresses a broad range of problems involving the stucture and dynamics...

438

Argonne Physics Division - Theory Group  

NLE Websites -- All DOE Office Websites (Extended Search)

Argonne Theory Group: Postdoctoral Position The Theory Group in the Physics Division at Argonne National Laboratory is seeking exceptional candidates for a postdoctoral position...

439

Contact Transformations and Hamiltonian Dynamics in Generalized Semigeostrophic Theories  

Science Conference Proceedings (OSTI)

This paper is concerned with the fundamental role played by contact transformations and their corresponding generating functions in determining the structure and dynamical properties of a very general class of semigeostrophic theories possessing ...

R. J. Purser

1993-06-01T23:59:59.000Z

440

The Particle Adventure | Unsolved Mysteries | String theory  

NLE Websites -- All DOE Office Websites (Extended Search)

String theory String theory Modern physics has good theories for quantum mechanics, relativity, and gravity. But these theories do not quite work with each other. There are...

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


441

The string of variable density: Further results  

Science Conference Proceedings (OSTI)

We analyze the problem of calculating the solutions and the spectrum of a string with arbitrary density and fixed ends. We build a perturbative scheme which uses a basis of WKB-type functions and obtain explicit expressions for the eigenvalues and eigenfunctions of the string. Using this approach we show that it is possible to derive the asymptotic (high energy) behavior of the string, obtaining explicit expressions for the first three coefficients (the first two can also be obtained with the WKB method). Finally, using an iterative approach we also obtain analytical expressions for the low energy behavior of the eigenvalues and eigenfunctions of a string with rapidly oscillating density, recovering (in a simpler way) results in the literature. - Highlights: > We devise a perturbative approach to finding the modes of a string with arbitrary density. > We obtain explicitly the first three coefficients of the asymptotic high energy expansion. > We apply our findings to a series of examples, obtaining both analytical and numerical results.

Amore, Paolo, E-mail: paolo.amore@gmail.com

2011-09-15T23:59:59.000Z

442

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Use of Composting · Composting has ­ British Columbia 2009 #12;Disposal: Science and Theory · Initial farm linked to NY LBM · Two additional and pile procedure Delmarva 2004 #12;Disposal: Science and Theory Delmarva 2004 · Composting used

Benson, Eric R.

443

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Foam Used in Actual Outbreak · Water #12;Disposal: Science and Theory Water Based Foam Culling Demo · First large scale comparison · Two:46 (m:s) #12;Disposal: Science and Theory WV H5N2 AIV 2007 · AIV positive turkeys ­ 25,000 turkey farm

Benson, Eric R.

444

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · El compostaje se ha usado como Virginia (2007) ­ British Columbia (2009) Uso del compostaje #12;Disposal: Science and Theory · Primera apilamiento Delmarva (2004) #12;Disposal: Science and Theory · El compostaje se usó para proteger una densa

Benson, Eric R.

445

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Previous Research · Composting, et.al. 2005; Bendfeldt et al., 2006; DeRouchey et al., 2005) #12;Disposal: Science and Theory: Science and Theory Scientific Validation of Composting · Experiment 1 Impact of foam on composting

Benson, Eric R.

446

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Poultry Farm Daily Disposal Methods 0;Disposal: Science and Theory First Composter in Delaware ¬∑ Delmarva was of the first daily composting ¬∑ 120 in USA over next 10 years #12;Disposal: Science and Theory Composting Procedure ¬∑ Mixture ¬≠ 1 ¬Ĺ to 2

Benson, Eric R.

447

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Brief History of Foam 2004 ­ Bud and foam 2009 ­ No advantage for gas #12;Disposal: Science and Theory What is foam? · What is fire fighting system. #12;Disposal: Science and Theory Foam Composition · Foam can include ­ Mixture of surfactants

Benson, Eric R.

448

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Compostaje de aves de corralRouchey et al., 2005) Investigación previa #12;Disposal: Science and Theory · Se ha evaluado y documentado el, bovino Investigación previa #12;Disposal: Science and Theory · Experimento nro. 1 Impacto de la espuma en

Benson, Eric R.

449

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory ¬∑ Se ubica el carret√≥n con el enfriamiento Ventiladores de t√ļnel de viento #12;Disposal: Science and Theory ¬∑ Se estaciona el remolque en uno: Science and Theory ¬∑ Se usa un equipo de dos personas para hacer funcionar el sistema: ¬≠ Operario del

Benson, Eric R.

450

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory ¬∑ Opciones para la eliminaci√≥n ¬∑ ¬ŅQu√© compostaje durante brotes de enfermedades Lista de contenido #12;Disposal: Science and Theory "Ante un brote brotes de IIAP #12;Disposal: Science and Theory ¬∑ En 2004, se despoblaron 100 millones de aves en todo el

Benson, Eric R.

451

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory ¬∑ Las recomendaciones de campo se la espuma #12;Disposal: Science and Theory ¬∑ M√ļltiples especies de aves pueden despoblarse con espuma cesaci√≥n #12;Disposal: Science and Theory ¬∑ Dentro de una especie, pueden existir variaciones ¬≠ Los √°nades

Benson, Eric R.

452

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Summary · Foam is currently a viable ­ Foam application directly to cage #12;Disposal: Science and Theory Legal Status of Foam · Procedure depopulation, culling, and euthanasia #12;Disposal: Science and Theory Acknowledgements · USDA AICAP2 · USDA

Benson, Eric R.

453

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Mass Emergency Composting · Basic ­ Create carcass and litter windrow #12;Disposal: Science and Theory Mass Emergency Composting · Basic cover ­ Clean and disinfect house ­ Sample for virus again #12;Disposal: Science and Theory Mass

Benson, Eric R.

454

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Gassing is a preferred #12;Disposal: Science and Theory Carbon Dioxide Gassing · Carbon dioxide (CO2) one of the standard sensitivity time #12;Disposal: Science and Theory · Argon-CO2 gas depopulation evaluated under laboratory

Benson, Eric R.

455

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · El compostaje se define como la: Science and Theory · Compostaje óptimo ­ Relación carbono/nitrógeno (C:N): 20:1 a 35:1 ­ Contenido de Compostaje #12;Disposal: Science and Theory · Se ha utilizado satisfactoriamente una variedad de materiales

Benson, Eric R.

456

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Foam Generator Setup · Drop off foam generator cart at one end of house #12;Disposal: Science and Theory Foam Generator Setup · Trailer parked generator attached to hose #12;Disposal: Science and Theory Foam Generation Begins · Team of two to operate

Benson, Eric R.

457

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Foaming Options · Compressed Air Foam Systems (CAFS) · Foam Blower · Foam Generator · Nozzle Systems #12;Disposal: Science and Theory Compressed ­ Industry owned response team #12;Disposal: Science and Theory Commercial CAFS for Poultry · Poultry

Benson, Eric R.

458

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory 0 20 40 60 80 100 Compostaje #12;Disposal: Science and Theory ¬∑ Delmarva fue de las primeras granjas en realizar el compostaje de en EE.UU. en los pr√≥ximos 10 a√Īos. Pionera en compostaje en Delaware #12;Disposal: Science and Theory

Benson, Eric R.

459

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Procedimiento básico ­ Desarrollar una pila de carcasas y lecho. Compostaje masivo de emergencia #12;Disposal: Science and Theory de emergencia #12;Disposal: Science and Theory · Desarrollar planes antes de que ocurra una

Benson, Eric R.

460

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Composting · Composting is defined drop #12;Disposal: Science and Theory Composting · Optimal composting ­ Carbon to nitrogen ratio (C;Disposal: Science and Theory Compost Composition · A variety of supplemental carbon materials have been

Benson, Eric R.

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461

Radiation of a circulating quark in strongly coupled N = 4 super Yang-Mills theory  

E-Print Network (OSTI)

The energy density and angular distribution of power radiated by a quark undergoing circular motion in strongly coupled N? = ?4 supersymmetric Yang?Mills (SYM) theory is computed using gauge?gravity duality. The results ...

Athanasiou, Christiana

462

Vacuum Energy Problem, Fundamental Length and Deformed Quantum Field Theory  

E-Print Network (OSTI)

The cosmological constant (vacuum energy) problem is analyzed within the scope of quantum theories with UV-cut-off or fundamental length. Various cases associated with the appearance of the latter are considered both using the Generalized Uncertainty Relations and the deformed density matrix,previously introduced in the author's works. The use of the deformed density matrix is examined in detail. It is demonstrated that, provided the Fischler-Susskind cosmic holographic conjecture is valid, the Vacuum Energy Density takes a value close to the experimental one. The arguments supporting the validity of this conjecture are given on the basis of the recently obtained results on Gravitational Holography.

A. E. Shalyt-Margolin

2007-12-19T23:59:59.000Z

463

Fock exchange in meson theories of nuclei  

Science Conference Proceedings (OSTI)

The Fock exchange term in meson field theories of nuclear systems is shown to arise from a two-loop ground-state self-energy diagram. Evaluation of this diagram gives the relativistic or semirelativistic analog of the Fock exchange energy; it differs from the nucleon-nucleon Fock energy in including retardation effects. In finite meson-field theories of nuclear systems, the variational nature of the meson-field analog of the Hartree-Fock energy functional can be further elucidated. 4 refs.

Bolsterli, M.

1986-01-01T23:59:59.000Z

464

Creating a systemic functional grammar corpus from the Penn treebank  

Science Conference Proceedings (OSTI)

The lack of a large annotated systemic functional grammar (SFG) corpus has posed a significant challenge for the development of the theory. Automating SFG annotation is challenging because the theory uses a minimal constituency model, allocating as much ...

Matthew Honnibal; James R. Curran

2007-06-01T23:59:59.000Z

465

Star Polymers Confined in a Nanoslit: A Simulation Test of Scaling and Self-Consistent Field Theories  

E-Print Network (OSTI)

The free energy cost of confining a star polymer where $f$ flexible polymer chains containing $N$ monomeric units are tethered to a central unit in a slit with two parallel repulsive walls a distance $D$ apart is considered, for good solvent conditions. Also the parallel and perpendicular components of the gyration radius of the star polymer, and the monomer density profile across the slit are obtained. Theoretical descriptions via Flory theory and scaling treatments are outlined, and compared to numerical self-consistent field calculations (applying the Scheutjens-Fleer lattice theory) and to Molecular Dynamics results for a bead-spring model. It is shown that Flory theory and self-consistent field (SCF) theory yield the correct scaling of the parallel linear dimension of the star with $N$, $f$ and $D$, but cannot be used for estimating the free energy cost reliably. We demonstrate that the same problem occurs already for the confinement of chains in cylindrical tubes. We also briefly discuss the problem of a free or grafted star polymer interacting with a single wall, and show that the dependence of confining force on the functionality of the star is different for a star confined in a nanoslit and a star interacting with a single wall, which is due to the absence of a symmetry plane in the latter case.

J. Paturej; A. Milchev; S. A. Egorov; K. Binder

2013-07-08T23:59:59.000Z

466

OPTIMIZATION OF LAYER DENSITIES FOR MULTILAYERED INSULATION SYSTEMS  

Science Conference Proceedings (OSTI)

Numerous tests of various multilayer insulation systems have indicated that there are optimal densities for these systems. However, the only method of calculating this optimal density was by a complex physics based algorithm developed by McIntosh. In the 1970's much data were collected on the performance of these insulation systems with many different variables analyzed. All formulas generated included number of layers and layer density as geometric variables in solving for the heat flux, none of them was in a differentiable form for a single geometric variable. It was recently discovered that by converting the equations from heat flux to thermal conductivity using Fourier's Law, the equations became functions of layer density, temperatures, and material properties only. The thickness and number of layers of the blanket were merged into a layer density. These equations were then differentiated with respect to layer density. By setting the first derivative equal to zero, and solving for the layer density, the critical layer density was determined. This method was checked and validated using test data from the Multipurpose Hydrogen Testbed which was designed using Mcintosh's algorithm.

Johnson, W. L. [NASA Kennedy Space Center, KT-E Kennedy Space Center, FL 32899 (United States)

2010-04-09T23:59:59.000Z

467

Near the sill of the conformal window: gauge theories with fermions in two-index representations  

E-Print Network (OSTI)

We apply Schroedinger functional methods to two gauge theories with fermions in two-index representations: the SU(3) theory with Nf=2 adjoint fermions, and the SU(4) theory with Nf=6 fermions in the two-index antisymmetric representation. Each theory is believed to lie near the bottom of the conformal window for its respective representation. In the SU(3) theory we find a small beta function in strong coupling but we cannot confirm or rule out an infrared fixed point. In the SU(4) theory we find a hint of walking - a beta function that approaches the axis and then turns away from it. In both theories the mass anomalous dimension remains small even at the strongest couplings, much like the theories with fermions in the two-index symmetric representation investigated earlier.

Thomas DeGrand; Yigal Shamir; Benjamin Svetitsky

2013-07-09T23:59:59.000Z

468

An application of neutrix calculus to quantum field theory  

E-Print Network (OSTI)

Neutrices are additive groups of negligible functions that do not contain any constants except 0. Their calculus was developed by van der Corput and Hadamard in connection with asymptotic series and divergent integrals. We apply neutrix calculus to quantum field theory, obtaining finite renormalizations in the loop calculations. For renormalizable quantum field theories, we recover all the usual physically observable results. One possible advantage of the neutrix framework is that effective field theories can be accommodated. Quantum gravity theories appear to be more manageable.

Y. Jack Ng; H. van Dam

2005-02-17T23:59:59.000Z

469

Dynamic microscopic theory of fusion using DC-TDHF  

Science Conference Proceedings (OSTI)

The density-constrained time-dependent Hartree-Fock (DC-TDHF) theory is a fully microscopic approach for calculating heavy-ion interaction potentials and fusion cross sections below and above the fusion barrier. We discuss recent applications of DC-TDHF method to fusion of light and heavy systems.

Umar, A. S.; Oberacker, V. E.; Keser, R.; Maruhn, J. A.; Reinhard, P.-G. [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); RTE University, Science and Arts Faculty, Department of Physics, 53100, Rize (Turkey); Institut fuer Theoretische Physik, Goethe-Universitaet, D-60438 Frankfurt am Main (Germany); Institut fur Theoretische Physik, Universitat Erlangen, D-91054 Erlangen (Germany)

2012-10-20T23:59:59.000Z

470

History of Unified Theories  

NLE Websites -- All DOE Office Websites (Extended Search)

Jahrelang haben Physiker nach vereinheitlichten Theorien gesucht - und Jahrelang haben Physiker nach vereinheitlichten Theorien gesucht - und diese auch gefunden. 1861-1865 James Maxwell, beschreibt in einem Artikel die Zusammenh√§nge zwischen elektrischen und magnetischen Feldern und vereinigt diese zur Theorie des Elektromagnetismus. Das f√ľhrte zu den heute ber√ľhmten Maxwell'schen Gleichungen. 1881-1884 Heinrich Hertz demonstriert im Experiment die Existenz von Radiowellen und zeigt, dass Radiowellen und Licht elektromagnetische Wellen unterschiedlicher Frequenz darstellen - ein Faktum, das bereits von Maxwell in seiner Theorie vorhergesagt wurde. 1967-1970 Glashow, Salam und Weinberg schlagen eine Theorie vor, welche die elektromagnetische Wechselwirkung mit der schwachen WW vereinigt. Sie sagen die Masse