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1

Density Functional Theory (DFT) Simulated Annealing (SA)  

E-Print Network (OSTI)

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

2

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

E-Print Network (OSTI)

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

Haule, Kristjan

3

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

E-Print Network (OSTI)

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

Grossman, Jeffrey C.

4

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

SciTech Connect

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

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

2014-05-14T23:59:59.000Z

5

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

E-Print Network (OSTI)

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

Botti, Silvana

6

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

E-Print Network (OSTI)

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

Jeremie Messud

2011-11-21T23:59:59.000Z

7

Assessing the density functional theory-based multireference configuration interaction (DFT/MRCI) method for transition metal complexes  

SciTech Connect

We report an assessment of the performance of density functional theory-based multireference configuration interaction (DFT/MRCI) calculations for a set of 3d- and 4d-transition metal (TM) complexes. The DFT/MRCI results are compared to published reference data from reliable high-level multi-configurational ab initio studies. The assessment covers the relative energies of different ground-state minima of the highly correlated CrF{sub 6} complex, the singlet and triplet electronically excited states of seven typical TM complexes (MnO{sub 4}{sup ?}, Cr(CO){sub 6}, [Fe(CN){sub 6}]{sup 4?}, four larger Fe and Ru complexes), and the corresponding electronic spectra (vertical excitation energies and oscillator strengths). It includes comparisons with results from different flavors of time-dependent DFT (TD-DFT) calculations using pure, hybrid, and long-range corrected functionals. The DFT/MRCI method is found to be superior to the tested TD-DFT approaches and is thus recommended for exploring the excited-state properties of TM complexes.

Escudero, Daniel, E-mail: escudero@kofo.mpg.de, E-mail: thiel@kofo.mpg.de; Thiel, Walter, E-mail: escudero@kofo.mpg.de, E-mail: thiel@kofo.mpg.de [Max-Planck-Institut fr Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mlheim an der Ruhr (Germany)] [Max-Planck-Institut fr Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mlheim an der Ruhr (Germany)

2014-05-21T23:59:59.000Z

8

MiniDFT  

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

MiniDFT MiniDFT MiniDFT Description MiniDFT is a plane-wave denstity functional theory (DFT) mini-app for modeling materials. Given an set of atomic coordinates and pseudopotentials, MiniDFT computes self-consistent solutions of the Kohn-Sham equations using either the LDA or PBE exchange-correlation functionals. For each iteration of the self-consistent field cycle, the Fock matrix is constructed and then diagonalized. To build the Fock matrix, Fast Fourier Transforms are used to tranform orbitals from the plane wave basis ( where the kinetic energy is most readily compted ) to real space (where the potential is evaluated ) and back. Davidson diagonalization is used to compute the orbital energies and update the orbital coefficients. The MiniDFT mini-app was excised from the general-purpose Quantum Espresso

9

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

Science Journals Connector (OSTI)

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

James P. Olivier; Mario L. Occelli

2000-12-23T23:59:59.000Z

10

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

E-Print Network (OSTI)

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

Bjørnstad, Ottar Nordal

11

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

SciTech Connect

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

12

http://chem.ps.uci.edu/~kieron/dft/book/ The ABC of DFT  

E-Print Network (OSTI)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 II Basics 55 6 Density functional theory 57 6.1 One electron1 http://chem.ps.uci.edu/~kieron/dft/book/ The ABC of DFT Kieron Burke and friends Department.6 Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 2 Functionals 27 2

Burke, Kieron

13

Monte Carlo simulation methodology of the ghost interface theory for the planar surface tension  

E-Print Network (OSTI)

Monte Carlo simulation methodology of the ghost interface theory for the planar surface tension October 2003 A novel ``ghost interface'' expression for the surface tension of a planar liquid coexisting phases. Results generated from the ghost interface theory for the surface tension are presented

Attard, Phil

14

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

SciTech Connect

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

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

2014-05-14T23:59:59.000Z

15

Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography  

E-Print Network (OSTI)

We compute the non-zero temperature conductivity of conserved flavor currents in conformal field theories (CFTs) in 2+1 spacetime dimensions. At frequencies much greater than the temperature, $\\hbar\\omega>> k_B T$, the $\\omega$ dependence can be computed from the operator product expansion (OPE) between the currents and operators which acquire a non-zero expectation value at T > 0. Such results are found to be in excellent agreement with quantum Monte Carlo studies of the O(2) Wilson-Fisher CFT. Results for the conductivity and other observables are also obtained in vector 1/N expansions. We match these large $\\omega$ results to the corresponding correlators of holographic representations of the CFT: the holographic approach then allows us to extrapolate to small $\\hbar \\omega/(k_B T)$. Other holographic studies implicitly only used the OPE between the currents and the energy-momentum tensor, and this yields the correct leading large $\\omega$ behavior for a large class of CFTs. However, for the Wilson-Fisher CFT a relevant "thermal" operator must also be considered, and then consistency with the Monte Carlo results is obtained without a previously needed ad hoc rescaling of the T value. We also establish sum rules obeyed by the conductivity of a wide class of CFTs.

Emanuel Katz; Subir Sachdev; Erik S. Sorensen; William Witczak-Krempa

2014-09-12T23:59:59.000Z

16

Ab Initio Geometry and Bright Excitation of Carotenoids: Quantum Monte Carlo and Many Body Green's Function Theory Calculations  

E-Print Network (OSTI)

Ab Initio Geometry and Bright Excitation of Carotenoids: Quantum Monte Carlo and Many Body Green state. Many Body Green's Function Theory (MBGFT) calculations of the vertical excitation energy and coupling with Qy of the chlorophyll.8-13 Measurements in several solvents have been reported

Guidoni, Leonardo

17

Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography  

E-Print Network (OSTI)

We compute the non-zero temperature conductivity of conserved flavor currents in conformal field theories (CFTs) in 2+1 spacetime dimensions. At frequencies much greater than the temperature, $\\hbar\\omega>> k_B T$, the $\\omega$ dependence can be computed from the operator product expansion (OPE) between the currents and operators which acquire a non-zero expectation value at T > 0. Such results are found to be in excellent agreement with quantum Monte Carlo studies of the O(2) Wilson-Fisher CFT. Results for the conductivity and other observables are also obtained in vector 1/N expansions. We match these large $\\omega$ results to the corresponding correlators of holographic representations of the CFT: the holographic approach then allows us to extrapolate to small $\\hbar \\omega/(k_B T)$. Other holographic studies implicitly only used the OPE between the currents and the energy-momentum tensor, and this yields the correct leading large $\\omega$ behavior for a large class of CFTs. However, for the Wilson-Fisher ...

Katz, Emanuel; Sorensen, Erik S; Witczak-Krempa, William

2014-01-01T23:59:59.000Z

18

A Monte Carlo simulation based two-stage adaptive resonance theory mapping approach for offshore oil spill vulnerability index classification  

Science Journals Connector (OSTI)

Abstract In this paper, a Monte Carlo simulation based two-stage adaptive resonance theory mapping (MC-TSAM) model was developed to classify a given site into distinguished zones representing different levels of offshore Oil Spill Vulnerability Index (OSVI). It consisted of an adaptive resonance theory (ART) module, an ART Mapping module, and a centroid determination module. Monte Carlo simulation was integrated with the TSAM approach to address uncertainties that widely exist in site conditions. The applicability of the proposed model was validated by classifying a large coastal area, which was surrounded by potential oil spill sources, based on 12 features. Statistical analysis of the results indicated that the classification process was affected by multiple features instead of one single feature. The classification results also provided the least or desired number of zones which can sufficiently represent the levels of offshore OSVI in an area under uncertainty and complexity, saving time and budget in spill monitoring and response.

Pu Li; Bing Chen; Zelin Li; Xiao Zheng; Hongjing Wu; Liang Jing; Kenneth Lee

2014-01-01T23:59:59.000Z

19

Propagation of uncertainties in the nuclear DFT models  

E-Print Network (OSTI)

Parameters of the nuclear density functional theory (DFT) models are usually adjusted to experimental data. As a result they carry certain theoretical error, which, as a consequence, carries out to the predicted quantities. In this work we address the propagation of theoretical error, within the nuclear DFT models, from the model parameters to the predicted observables. In particularly, the focus is set on the Skyrme energy density functional models.

Markus Kortelainen

2014-09-04T23:59:59.000Z

20

Monte Carlo fundamentals  

SciTech Connect

This report is composed of the lecture notes from the first half of a 32-hour graduate-level course on Monte Carlo methods offered at KAPL. These notes, prepared by two of the principle developers of KAPL`s RACER Monte Carlo code, cover the fundamental theory, concepts, and practices for Monte Carlo analysis. In particular, a thorough grounding in the basic fundamentals of Monte Carlo methods is presented, including random number generation, random sampling, the Monte Carlo approach to solving transport problems, computational geometry, collision physics, tallies, and eigenvalue calculations. Furthermore, modern computational algorithms for vector and parallel approaches to Monte Carlo calculations are covered in detail, including fundamental parallel and vector concepts, the event-based algorithm, master/slave schemes, parallel scaling laws, and portability issues.

Brown, F.B.; Sutton, T.M.

1996-02-01T23:59:59.000Z

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


21

Density Functional Theory (DFT) Rob Parrish  

E-Print Network (OSTI)

: ­ Nuclear-electron attraction (exact) ­ Classical Coulomb electron repulsion (exact) ­ Dynamical correlation ­ Nondynamical correlation ­ Dispersion 8 Dealbreaker! (Almost) #12;Breakthrough: The Kohn-Sham Witchcraft) Center Nucleus (k=3, naïve) Plots are of nuclear weights, wn. Black stars represent nuclear positions. 16

Sherrill, David

22

Density Functional Theory for Superconductors  

E-Print Network (OSTI)

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

Gross, E.K.U.

23

Density Functional Theory Approach to Nuclear Fission  

E-Print Network (OSTI)

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

N. Schunck

2013-01-20T23:59:59.000Z

24

Density Functional Theory applied to the solid state...  

E-Print Network (OSTI)

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

Adler, Joan

25

Quantum Monte Carlo calculations of electromagnetic moments and transitions in A{<=}9 nuclei including meson-exchange currents derived from chiral effective field theory  

SciTech Connect

Quantum Monte Carlo calculations of electromagnetic moments and transitions are reported for A{<=}9 nuclei. The realistic Argonne v{sub 18} two-nucleon and Illinois-7 three-nucleon potentials are used to generate the nuclear wave functions. Contributions of two-body meson-exchange current (MEC) operators are included for magnetic moments and M1 transitions. The MEC operators have been derived in both a standard nuclear physics approach and a chiral effective field theory formulation with pions and nucleons including up to one-loop corrections. The two-body MEC contributions provide significant corrections and lead to very good agreement with experiment. Their effect is particularly pronounced in the A=9, T=3/2 systems, in which they provide up to ~20% (~40%) of the total predicted value for the {sup 9}Li ({sup 9}C) magnetic moment.

Saori Pastore, S.C. Pieper, Rocco Schiavilla, Robert Wiringa

2013-03-01T23:59:59.000Z

26

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

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

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

27

Adsorption of silver dimer on graphene - A DFT study  

SciTech Connect

We performed a systematic density functional theory (DFT) study of the adsorption of silver dimer (Ag{sub 2}) on graphene using SIESTA (Spanish Initiative for Electronic Simulations with Thousands of Atoms) package, in the generalized gradient approximation (GGA). The adsorption energy, geometry, and charge transfer of Ag2-graphene system are calculated. The minimum energy configuration for a silver dimer is parallel to the graphene sheet with its two atoms directly above the centre of carbon-carbon bond. The negligible charge transfer between the dimer and the surface is also indicative of a weak bond. The methodology demonstrated in this paper may be applied to larger silver clusters on graphene sheet.

Kaur, Gagandeep, E-mail: gaganj1981@yahoo.com [Department of Physics and Centre of Advanced Studies in Physics, Panjab University, Chandigarh-160014, India and Chandigarh Engineering College, Landran, Mohali-140307, Punjab (India); Gupta, Shuchi [Department of Physics and Centre of Advanced Studies in Physics, Panjab University, Chandigarh-160014, India and University Institute of Engineering and Technology, Panjab University, Chandigarh -160014 (India); Rani, Pooja; Dharamvir, Keya [Department of Physics and Centre of Advanced Studies in Physics, Panjab University, Chandigarh-160014 (India)

2014-04-24T23:59:59.000Z

28

Screened Hybrid and DFT + U Studies of the Structural, Electronic...  

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

Screened Hybrid and DFT + U Studies of the Structural, Electronic, and Optical Properties of U3O8. Screened Hybrid and DFT + U Studies of the Structural, Electronic, and Optical...

29

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

30

DFT investigation on the electronic structure of Faujasite  

SciTech Connect

We report here first-principle pseudopotential DFT calculations to investigate relevant aspects of the electronic structure of zeolites based FAU. Fundamental molecular issues of the band-gap and electronic population analysis were reviewed under GGA/RPBE level of theory, corroborated with a DZP basis set and Troullier-Martins norm conserving pseudo-potentials. The atom-projected density of states and the analysis of HOMO-LUMO frontier orbitals at Gamma point were performed. Their electronic transfers are discussed through the alignment and relative positions of orbitals in order to determine the way that the molecule interacts with adsorbed molecules and other practical applications. Mulliken population analysis was employed for describing atomic charge distribution in the chosen systems.

Popeneciu, Horea; Calborean, Adrian; Tudoran, Cristian; Buimaga-Iarinca, Luiza [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)] [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)

2013-11-13T23:59:59.000Z

31

Triplet absorption in carbon nanotubes: a TD-DFT study  

E-Print Network (OSTI)

We predict properties of triplet excited states in single-walled carbon nanotubes (CNTs) using a time-dependent density-functional theory (TD-DFT). We show that the lowest triplet state energy in CNTs to be about 0.2-0.3 eV lower than the lowest singlet states. Like in $\\pi$-conjugated polymers, the lowest CNT triplets are spatially localized. These states show strong optical absorption at about 0.5-0.6 eV to the higher lying delocalized triplet states. These results demonstrate striking similarity of the electronic features between CNTs and $\\pi$-conjugated polymers and provide explicit guidelines for spectroscopic detection of CNT triplet states.

Sergei Tretiak

2007-02-13T23:59:59.000Z

32

ORBITAL-FREE KINETIC-ENERGY DENSITY FUNCTIONAL THEORY  

E-Print Network (OSTI)

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

Wang, Yan Alexander

33

Benchmark density functional theory calculations for nanoscale conductance  

E-Print Network (OSTI)

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

Thygesen, Kristian

34

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

35

Session #1: Cutting Edge Methodologies--Beyond Current DFT  

Energy.gov (U.S. Department of Energy (DOE))

Benchmarking state-of-the-art approaches, accurate energy landscape. Identify problems with the current DFT-LDA and GGA approaches and possible pathways to overcome these problems.

36

Density Functional Theory for Superconductors  

E-Print Network (OSTI)

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

Gross, E.K.U.

37

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

E-Print Network (OSTI)

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

Armiento, Rickard

38

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

E-Print Network (OSTI)

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

Lindgren, Ingvar

39

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

E-Print Network (OSTI)

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

Ortiz, Michael

40

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

E-Print Network (OSTI)

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

Wang, Yan Alexander

Note: This page contains sample records for the topic "theory dft monte" 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

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

42

The Dirac equation in electronic structure calculations: Accurate evaluation of DFT predictions for actinides  

SciTech Connect

Brooks, Johansson, and Skriver, using the LMTO-ASA method and considerable insight, were able to explain many of the ground state properties of the actinides. In the many years since this work was done, electronic structure calculations of increasing sophistication have been applied to actinide elements and compounds, attempting to quantify the applicability of DFT to actinides and actinide compounds and to try to incorporate other methodologies (i.e. DMFT) into DFT calculations. Through these calculations, the limits of both available density functionals and ad hoc methodologies are starting to become clear. However, it has also become clear that approximations used to incorporate relativity are not adequate to provide rigorous tests of the underlying equations of DFT, not to mention ad hoc additions. In this talk, we describe the result of full-potential LMTO calculations for the elemental actinides, comparing results obtained with a full Dirac basis with those obtained from scalar-relativistic bases, with and without variational spin-orbit. This comparison shows that the scalar relativistic treatment of actinides does not have sufficient accuracy to provide a rigorous test of theory and that variational spin-orbit introduces uncontrolled errors in the results of electronic structure calculations on actinide elements.

Wills, John M [Los Alamos National Laboratory; Mattsson, Ann E [Sandia National Laboratories

2012-06-06T23:59:59.000Z

43

Modeling of molecular gas adsorption isotherms on porous materials with hybrid PC-SAFTDFT  

Science Journals Connector (OSTI)

Abstract The developed hybrid PC-SAFTDFT model, a coupling of density functional theory (DFT) with perturbed-chain statistical associating fluid theory (PC-SAFT), was used to study the adsorption of pure- and mixed-fluids on nano-porous materials, and carbons and zeolites were chosen as examples of nano-porous materials in this work for model performance evaluation. In the PC-SAFTDFT model, the modified fundamental measure theory was used for the hard sphere contribution, the dispersion free energy functional was represented with a weighted density approximation, and the chain free energy functional from interfacial SAFT was used to account for the chain connectivity. The fluid was modeled as a chain molecule with molecular parameters taken from those in the bulk PC-SAFT. The external force field was used to describe the interaction between the solid surface of a nano-porous material and fluid. Application of this model was demonstrated on the gas adsorption on porous carbons and zeolites which were assumed to have slit- and cylinder-shaped pores with mean pore sizes, respectively. The parameters of the adsorption model were obtained by fitting to the pure-gas adsorption isotherms measured experimentally. With parameters of the model fitted to the pure-gas adsorption at one temperature, the model was used to predict the pure-gas adsorption at other temperatures as well as the adoption isotherms of mixtures. The model prediction was compared with the available experimental data, which shows that the predictions are reliable for most of the systems studied in this work. The effect of the pore size distribution on the model performance was further investigated, and it was found that the consideration of the pore size distribution (PSD) can improve the accuracy of the model results but the PSD analysis requires much more computing time.

Gulou Shen; Xiaohua Lu; Xiaoyan Ji

2014-01-01T23:59:59.000Z

44

Session #1: Cutting Edge Methodologies--Beyond Current DFT  

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

Session #1: Cutting Edge Methodologies (beyond Current DFT) Moderator: Shengbai Zhang (RPI/ REL) Topics to be addressed: Benchmarking state-of-the-art approaches, accurate energy landscape. Identify problems with the current DFT-LDA and GGA approaches and possible pathways to overcome these problems. PBE PBE How Bad is DFT for vdW Interactions? fcc Ar Benzene dimer PBE LDA Exp CCSD(T) LDA PBE vdW Interaction between H 2 and Carbon � PBE Graphene CCSD(T) LDA Benzene omitted in the LDA and GGA van der Walls (vdW)-DFT: Langreth, Kohn � Fully nonlocal � functional: � � Long-range nonlocal correlation energy functional (omitted in the LDA and GGA) ) ( � Computational cost considerably more than GGA � Added as post-GGA energy correction but force

45

Session #1: Cutting Edge Methodologies--Beyond Current DFT  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

dimer PBE LDA Exp CCSD(T) LDA PBE vdW Interaction between H 2 and Carbon PBE Graphene CCSD(T) LDA Benzene omitted in the LDA and GGA van der Walls (vdW)-DFT: Langreth,...

46

Self-assembly of patchy particles into polymer chains: A parameter-free comparison between Wertheim theory and Monte Carlo simulation  

E-Print Network (OSTI)

Self-assembly of patchy particles into polymer chains: A parameter-free comparison between Wertheim theory. This comparison offers a unique framework for the analytic prediction of the properties of self-assembling this basic form of self-assembly energy per particle, order parameter or average fraction of particles

Sciortino, Francesco

47

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

E-Print Network (OSTI)

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

Chu, Shih-I

48

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

E-Print Network (OSTI)

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

Baer, Roi

49

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

E-Print Network (OSTI)

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

Song, Xueyu

50

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

E-Print Network (OSTI)

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

Ceder, Gerbrand

51

Asymptotic Scaling and Monte Carlo Data  

E-Print Network (OSTI)

It is a generally known problem that the behaviour predicted from perturbation theory for asymptotically free theories like QCD, i.e. asymptotic scaling, has not been observed in Monte Carlo simulations when the series is expressed in terms of the bare coupling g_0. This discrepancy has been explained in the past with the poor convergence properties of the perturbative series in the g_0. An alternative point of view, called Lattice-Distorted Perturbation Theory proposes that lattice artifacts due to the finiteness of the lattice spacing, a, cause the disagreement between Monte Carlo data and perturbative scaling. Following this alternative scenario, we fit recent quenched data from different observables to fitting functions that include these cut-off effects, confirming that the lattice data are well reproduced by g_0-PT with the simple addition of terms O(a^n).

A. Trivini; C. R. Allton

2005-11-02T23:59:59.000Z

52

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

E-Print Network (OSTI)

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

Wu, Zhigang

53

Modeling Excited States in TiO2 Nanoparticles: On the Accuracy of a TD-DFT Based Description  

SciTech Connect

We have investigated the suitability of Time-Dependent Density Functional Theory (TD-DFT) to describe vertical low-energy excitations in naked and hydrated titanium dioxide nanoparticles through a comparison with results from Equation-of-Motion Coupled Cluster (EOM-CC) quantum chemistry methods. We demonstrate that for most TiO2 nanoparticles TD-DFT calculations with commonly used exchange-correlation (XC-)potentials (e.g. B3LYP) and EOM-CC methods give qualitatively similar results. Importantly, however, we also show that for an important subset of structures, TD-DFT gives qualitatively different results depending upon the XC-potential used and that in this case only TD-CAM-B3LYP and TD-BHLYP calculations yield results that are consistent with those obtained using EOM-CC theory. Moreover, we demonstrate that the discrepancies for such structures arise from a particular combination of defects, excitations involving which are charge-transfer excitations and hence are poorly described by XC-potentials that contain no or low fractions of Hartree-Fock like exchange. Finally, we discuss that such defects are readily healed in the presence of ubiquitously present water and that as a result the description of vertical low-energy excitations for hydrated TiO2 nanoparticles is hence non-problematic.

Berardo, Enrico; Hu, Hanshi; Shevlin, S. A.; Woodley, Scott M.; Kowalski, Karol; Zwijnenburg, Martijn A.

2014-03-11T23:59:59.000Z

54

Analyzing Data Streams by Online DFT Alexander Hinneburg1  

E-Print Network (OSTI)

University of Technology, Germany dirk.habich@tu-dresden.de 3 Technical University of Ilmenau, Germany marcel Martin-Luther University of Halle-Wittenberg, Germany hinneburg@informatik.uni-halle.de 2 Dresden DFT lead to a number of interesting applications, e.g., forecasting, clean- ing, and moni

Hinneburg, Alexander

55

Electronic Spectra and DFT Calculations of Hexanuclear Chalcocyanide Rhenium Clusters  

Science Journals Connector (OSTI)

Electronic Spectra and DFT Calculations of Hexanuclear Chalcocyanide Rhenium Clusters ... The good agreement with experiment obtained for the geometrical parameters gives the basis for comparing the calculated electronic transitions of these complexes with the experimental electronic spectra. ... On the calculation of bonding energies by the Hartree Fock Slater method. ...

S. G. Kozlova; S. P. Gabuda; K. A. Brylev; Yu. V. Mironov; V. E. Fedorov

2004-11-03T23:59:59.000Z

56

Monte Carlo event generators at nonleading order  

Science Journals Connector (OSTI)

A method to construct Monte Carlo event generators at arbitrarily nonleading order is explained for the case of a nongauge theory. A precise and correct treatment of parton kinematics is provided. Modifications of the conventional formalism are required: parton showering is not exactly the same as Dokshitzer-Gribov-Lipatov-Altarelli-Parisi evolution, and the external line prescription for the hard scattering differs from the Lehmann-Symanzik-Zimmermann prescription. The prospects for extending the results to QCD are discussed.

John Collins

2002-05-06T23:59:59.000Z

57

First principles DFT investigation of yttrium-doped graphene: Electronic structure and hydrogen storage  

SciTech Connect

The electronic structure and hydrogen storage capability of Yttrium-doped grapheme has been theoretically investigated using first principles density functional theory (DFT). Yttrium atom prefers the hollow site of the hexagonal ring with a binding energy of 1.40 eV. Doping by Y makes the system metallic and magnetic with a magnetic moment of 2.11 ?{sub B}. Y decorated graphene can adsorb up to four hydrogen molecules with an average binding energy of 0.415 eV. All the hydrogen atoms are physisorbed with an average desorption temperature of 530.44 K. The Y atoms can be placed only in alternate hexagons, which imply a wt% of 6.17, close to the DoE criterion for hydrogen storage materials. Thus, this system is potential hydrogen storage medium with 100% recycling capability.

Desnavi, Sameerah, E-mail: sameerah-desnavi@zhcet.ac.in [Department of Electronic Engineering, ZHCET, Aligarh Muslim University, Aligarh-202002 (India); Chakraborty, Brahmananda; Ramaniah, Lavanya M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

2014-04-24T23:59:59.000Z

58

Structural and Energetic Analysis of MgxM1?x(OH)2 (M = Zn, Cu or Ca) Brucite-Like Compounds by DFT Calculations  

Science Journals Connector (OSTI)

Structural and Energetic Analysis of MgxM1?x(OH)2 (M = Zn, Cu or Ca) Brucite-Like Compounds by DFT Calculations ... Brucite-like mixed hydroxides of the general formula MgxM1?x(OH)2 for M = Zn, Cu or Ca were studied by density functional theory within pseudopotential approximation, plane waves basis set, and periodic boundary conditions. ... Brucite, which is the mineral form of magnesium hydroxide, is a commonly occurring material. ...

Deyse G. Costa; Alexandre B. Rocha; Wladmir F. Souza; Sandra Shirley X. Chiaro; Alexandre A. Leito

2008-06-28T23:59:59.000Z

59

THE MANY-ELECTRON ENERGY IN DENSITY FUNCTIONAL THEORY  

E-Print Network (OSTI)

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

Armiento, Rickard

60

RELATIVISTIC DENSITY FUNCTIONAL THEORY: FOUNDATIONS AND BASIC FORMALISM  

E-Print Network (OSTI)

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

Engel, Eberhard

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


61

E-Print Network 3.0 - approximate dft method Sample Search Results  

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

D'Alberto Yahoo pdalbert@yahoo-inc.com Peter A... - tions of the discrete Fourier transform (DFT) in fixed point precision. The partitioning strategy Source: Moura, Jos -...

62

Center for Emergent Superconductivity (CES) | U.S. DOE Office...  

Office of Science (SC) Website

Methods X-ray diffraction and scattering, electron microscopy, scanning probe microscopy, neutron diffraction and scattering, density functional theory (DFT), monte carlo (MC),...

63

PHaSE | U.S. DOE Office of Science (SC)  

Office of Science (SC) Website

scanning probe microscopy, near-field scanning optical microscopy, surface science, neutron diffraction and scattering, density functional theory (DFT), monte carlo (MC),...

64

A Monte Carlo algorithm for degenerate plasmas  

SciTech Connect

A procedure for performing Monte Carlo calculations of plasmas with an arbitrary level of degeneracy is outlined. It has possible applications in inertial confinement fusion and astrophysics. Degenerate particles are initialised according to the FermiDirac distribution function, and scattering is via a Pauli blocked binary collision approximation. The algorithm is tested against degenerate electronion equilibration, and the degenerate resistivity transport coefficient from unmagnetised first order transport theory. The code is applied to the cold fuel shell and alpha particle equilibration problem of inertial confinement fusion.

Turrell, A.E., E-mail: a.turrell09@imperial.ac.uk; Sherlock, M.; Rose, S.J.

2013-09-15T23:59:59.000Z

65

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

E-Print Network (OSTI)

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

Bertsch George F.

66

Putting DFT to the Test: A First Principles Study of Electronic, Magnetic and Optical Properties of Co3O4  

Science Journals Connector (OSTI)

Putting DFT to the Test: A First Principles Study of Electronic, Magnetic and Optical Properties of Co3O4 ...

Vijay Singh; Monica Kosa; Koushik Majhi; Dan Thomas Major

2014-11-25T23:59:59.000Z

67

Hybrid DFT Functional-Based Static and Molecular Dynamics Studies of Excess Electron in Liquid Ethylene Carbonate  

SciTech Connect

We applied static and dynamic hybrid functional density functional theory (DFT) calculations to study the interactions of one and two excess electrons with ethylene carbonate (EC) liquid and clusters. Optimal structures of (EC){sub n} and (EC){sup ?}{sub n} clusters devoid of Li{sub +} ions, n?=?16, were obtained. The excess electron was found to be localized on a single EC in all cases, and the EC dimeric radical anion exhibits a reduced barrier associated with the breaking of the ethylene carbonoxygen covalent bond compared to EC{sub ?}. In ab initio molecular dynamics (AIMD) simulations of EC{sub ?} solvated in liquid EC, large fluctuations in the carbonyl carbonoxygen bond lengths were observed. AIMD simulations of a two-electron attack on EC in EC liquid and on Li metal surfaces yielded products similar to those predicted using nonhybrid DFT functionals, except that CO release did not occur for all attempted initial configurations in the liquid state.

Yu, J M; Balbuena, P B; Budzien, J L; Leung, Kevin

2011-01-01T23:59:59.000Z

68

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

SciTech Connect

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

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

2011-01-01T23:59:59.000Z

69

EERE PROJECT MANAGEMENT CENTER NFPA DFT1!lUIINATION  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

OFEN:rRGY OFEN:rRGY EERE PROJECT MANAGEMENT CENTER NFPA DFT1!lUIINATION Page 1 of2 RECIPIENT:Middlesex Community College STATE: MA PROJECf TITLE: Middlesex Community College - Geothermal Project Funding Opportunity Announcement Number Procurement Instrument Number NEPA Control Number CID Number N/A DE-EEOOOO323 GF0-0000323-002 EE323 Based on my review ofthe information concerning the proposed action, as NEPA Compliance Officer (authorized under DOE Order 4SI.IA), I have made the following determination: ex, EA, EIS APPENDIX AND NUMBER: Description: A9 Inf ormation gathering, analYSiS, and dissemination 82.1 Workplace enhancements B2.2 Building and equipment instrumentation Information gathering (including, but not limited to, literature surveys, inventories, site visits, and audils),

70

Interfacial tension of nonassociating pure substances and binary mixtures by density functional theory combined with PengRobinson equation  

E-Print Network (OSTI)

of the existing DFT versions can be reduced to the statistical associating fluid theory SAFT and its derivatives.6­11 Unfortunately, SAFT has not been widely used in petroleum production and reservoir engineering cal- culations

Firoozabadi, Abbas

71

Electronic structure and excitations in oxygen deficient CeO2?? from DFT calculations  

Science Journals Connector (OSTI)

The electronic structures of supercells of CeO2?? have been calculated within the density functional theory (DFT). The equilibrium properties such as lattice constants, bulk moduli, and magnetic moments are well reproduced by the generalized gradient approximation (GGA). Electronic excitations are simulated by robust total-energy calculations for constrained states with atomic core holes or valence holes. Pristine ceria CeO2 is found to be a nonmagnetic insulator with magnetism setting in as soon as oxygens are removed from the structure. In the ground state of defective ceria, the Ce-f majority band resides near the Fermi level but appears at about 2eV below the Fermi level in photoemission spectroscopy experiments due to final-state effects. We also tested our computational method by calculating threshold energies in Ce-M5 and O-K x-ray absorption spectroscopy and comparing theoretical predictions with the corresponding measurements. Our result that f electrons reside near the Fermi level in the ground state of oxygen-deficient ceria is crucial for understanding the catalytic properties of CeO2 and related materials.

T. Jarlborg; B. Barbiellini; C. Lane; Yung Jui Wang; R. S. Markiewicz; Zhi Liu; Zahid Hussain; A. Bansil

2014-04-01T23:59:59.000Z

72

First principles DFT study of dye-sensitized CdS quantum dots  

SciTech Connect

Dye-sensitized quantum dots (QDs) are considered promising candidates for dye-sensitized solar cells. In order to maximize their efficiency, detailed theoretical studies are important. Here, we report a first principles density functional theory (DFT) investigation of experimentally realized dye - sensitized QD / ligand systems, viz., Cd{sub 16}S{sub 16}, capped with acetate molecules and a coumarin dye. The hybrid B3LYP functional and a 6?311+G(d,p)/LANL2dz basis set are used to study the geometric, energetic and electronic properties of these clusters. There is significant structural rearrangement in all the clusters studied - on the surface for the bare QD, and in the positions of the acetate / dye ligands for the ligated QDs. The density of states (DOS) of the bare QD shows states in the band gap, which disappear on surface passivation with the acetate molecules. Interestingly, in the dye-sensitised QD, the HOMO is found to be localized mainly on the dye molecule, while the LUMO is on the QD, as required for photo-induced electron injection from the dye to the QD.

Jain, Kalpna; Singh, Kh. S. [Department of Physics, D. J. College, Baraut -250611, U.P. (India); Kishor, Shyam, E-mail: shyam387@gmail.com [Department of Chemistry, J. V. College, Baraut -250611, U.P. (India); Josefesson, Ida; Odelius, Michael [Fysikum, Albanova University Center, Stockholm University, S-106 91 Stockholm (Sweden); Ramaniah, Lavanya M. [High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, Mumbai-400085 (India)

2014-04-24T23:59:59.000Z

73

Methanol Synthesis from CO2 Hydrogenation over a Pd4/In2O3 Model Catalyst: A Combined DFT and Kinetic Study  

SciTech Connect

Methanol synthesis from CO2 hydrogenation on Pd4/In2O3 has been investigated using density functional theory (DFT) and microkinetic modeling. In this study, three possible routes in the reaction network of CO2 + H2 ? CH3OH + H2O have been examined. Our DFT results show that the HCOO route competes with the RWGS route whereas a high activation barrier kinetically blocks the HCOOH route. DFT results also suggest that H2COO* + H* ? H2CO* +OH* and cis-COOH* + H* ?CO* + H2O* are the rate limiting steps in the HCOO route and the RWGS route, respectively. Microkinetic modeling results demonstrate that the HCOO route is the dominant reaction route for methanol synthesis from CO2 hydrogenation. We found that the activation of H adatom on the small Pd cluster and the presence of H2O on the In2O3 substrate play important roles in promoting the methanol synthesis. The hydroxyl adsorbed at the interface of Pd4/In2O3 induces the transformation of the supported Pd4 cluster from a butterfly structure into a tetrahedron structure. This important structure change not only indicates the dynamical nature of the supported nanoparticle catalyst structure during the reaction but also shifts the final hydrogenation step from H2COH to CH3O.

Ye, Jingyun; Liu, Changjun; Mei, Donghai; Ge, Qingfeng

2014-08-01T23:59:59.000Z

74

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

E-Print Network (OSTI)

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

Lin, Xi

75

Multicomponent density-functional theory for electrons and nuclei Thomas Kreibich  

E-Print Network (OSTI)

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

Gross, E.K.U.

76

On the Floquet formulation of time-dependent density functional theory  

E-Print Network (OSTI)

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

77

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

E-Print Network (OSTI)

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

Gross, E.K.U.

78

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

E-Print Network (OSTI)

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

Gross, E.K.U.

79

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

E-Print Network (OSTI)

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

Sun, Sean

80

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

E-Print Network (OSTI)

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

Lorin, Emmanuel

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


81

Describing excited state relaxation and localization in TiO2 nanoparticles using TD-DFT  

SciTech Connect

We have investigated the description of excited state relaxation in naked and hydrated TiO2 nanoparticles using Time-Dependent Density Functional Theory (TD-DFT) with three common hybrid exchange-correlation (XC) potentials; B3LYP, CAM-B3LYP and BHLYP. Use of TD-CAM-B3LYP and TD-BHLYP yields qualitatively similar results for all structures, which are also consistent with predictions of coupled cluster theory for small particles. TD-B3LYP, in contrast, is found to make rather different predictions; including apparent conical intersections for certain particles that are not observed with TD-CAM-B3LYP nor with TD-BHLYP. In line with our previous observations for vertical excitations, the issue with TD-B3LYP appears to be the inherent tendency of TD-B3LYP, and other XC potentials with no or a low percentage of Hartree-Fock Like Exchange, to spuriously stabilize the energy of charge-transfer (CT) states. Even in the case of hydrated particles, for which vertical excitations are generally well described with all XC potentials, the use of TD-B3LYP appears to result in CT-problems for certain particles. We hypothesize that the spurious stabilization of CT-states by TD-B3LYP even may drive the excited state optimizations to different excited state geometries than those obtained using TD-CAM-B3LYP or TD-BHLYP. Finally, focusing on the TD-CAM-B3LYP and TD-BHLYP results, excited state relaxation in naked and hydrated TiO2 nanoparticles is predicted to be associated with a large Stokes shift.

Berardo, Enrico; Hu, Hanshi; van Dam, Hubertus JJ; Shevlin, S. A.; Woodley, Scott M.; Kowalski, Karol; Zwijnenburg, Martijn A.

2014-10-30T23:59:59.000Z

82

DFT calculations on nitrodiborane compounds as new potential high energy materials  

Science Journals Connector (OSTI)

We have used DFT methods to determine the structures and thermochemistry of several nitro-substituted diborane molecules in an attempt to rate their potential as high energy materials. The properties of nitrodibo...

John Abdelmalik; David W. Ball

2010-05-01T23:59:59.000Z

83

Generalized SAFT-DFT/DMT Model for the Thermodynamic, Interfacial, and Transport Properties of Associating Fluids:? Application for n-Alkanols  

Science Journals Connector (OSTI)

Generalized SAFT-DFT/DMT Model for the Thermodynamic, Interfacial, and Transport Properties of Associating Fluids:? Application for n-Alkanols ... We have developed a global crossover (GC) statistical associating fluid theory (SAFT) equation of state (EOS) for associating fluids that incorporates nonanalytic scaling laws in the critical region and in the limit of low densities, ? ? 0, is transformed into the ideal-gas equation EOS. ... Unlike the crossover SAFT EOS developed earlier, the new GC SAFT EOS contains a so-called kernel term and reproduces the asymptotic scaling behavior of the isochoric heat capacity in the one- and two-phase regions. ...

S. B. Kiselev; J. F. Ely; I. M. Abdulagatov; M. L. Huber

2005-07-02T23:59:59.000Z

84

DFT calculations of EPR parameters of transition metal complexes: Implications for catalysis  

SciTech Connect

Transition metal and ligand hyperfine coupling constants for paramagnetic vanadium and copper model complexes have been calculated using DFT methods that are available in commercial software packages. Variations in EPR parameters with ligand identity and ligand orientation are two of the trends that have been investigated with DFT calculations. For example, the systematic variation of the vanadium hyperfine coupling constant with orientation for an imidazole ligand in a VO2+ complex has been observed experimentally and has also been reproduced by DFT calculations. Similarly, changes in the vanadium hyperfine coupling constant with ligand binding have been calculated using model complexes and DFT methods. DFT methods were also used to calculate ligand hyperfine coupling constants in transition metal systems. The variation of the proton hyperfine coupling constant with water ligand orientation was investigated for [VO(H2O)5]2+ and the results were used to interpret high resolution EPR data of VO2+-exchanged zeolites. Nitrogen hyperfine and quadrupole coupling constants for VO2+ model complexes were calculated and compared with experimental data. The computational results were used to enhance the interpretation of the EPR data for vanadium-exchanged zeolites which are promising catalytic materials. The implications of the DFT calculations of EPR parameters with respect to catalysis will be discussed

Saladino, Alexander C.; Larsen, Sarah C.

2005-07-15T23:59:59.000Z

85

Intrinsic point-defect equilibria in tetragonal ZrO[subscript 2]: Density functional theory analysis with finite-temperature effects  

E-Print Network (OSTI)

We present a density functional theory (DFT) framework taking into account the finite temperature effects to quantitatively understand and predict charged defect equilibria in a metal oxide. Demonstration of this approach ...

Youssef, Mostafa Youssef Mahm

86

Monte Carlo for the LHC  

E-Print Network (OSTI)

I review the status of the general-purpose Monte Carlo event generators for the LHC, with emphasis on areas of recent physics developments. There has been great progress, especially in multi-jet simulation, but I mention some question marks that have recently arisen.

Michael H. Seymour

2010-08-17T23:59:59.000Z

87

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

E-Print Network (OSTI)

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

Thygesen, Kristian

88

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

E-Print Network (OSTI)

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

Ceder, Gerbrand

89

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

E-Print Network (OSTI)

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

Likos, Christos N.

90

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

E-Print Network (OSTI)

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

Gross, E.K.U.

91

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

E-Print Network (OSTI)

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

Hess, Daryl W.

92

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

E-Print Network (OSTI)

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

Gross, E.K.U.

93

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

E-Print Network (OSTI)

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

Gross, E.K.U.

94

A midway forward-adjoint coupling method for neutron and photon Monte Carlo transport  

SciTech Connect

The midway Monte Carlo method for calculating detector responses combines a forward and an adjoint Monte Carlo calculation. In both calculations, particle scores are registered at a surface to be chosen by the user somewhere between the source and detector domains. The theory of the midway response determination is developed within the framework of transport theory for external sources and for criticality theory. The theory is also developed for photons, which are generated at inelastic scattering or capture of neutrons. In either the forward or the adjoint calculation a so-called black absorber technique can be applied; i.e., particles need not be followed after passing the midway surface. The midway Monte Carlo method is implemented in the general-purpose MCNP Monte Carlo code. The midway Monte Carlo method is demonstrated to be very efficient in problems with deep penetration, small source and detector domains, and complicated streaming paths. All the problems considered pose difficult variance reduction challenges. Calculations were performed using existing variance reduction methods of normal MCNP runs and using the midway method. The performed comparative analyses show that the midway method appears to be much more efficient than the standard techniques in an overwhelming majority of cases and can be recommended for use in many difficult variance reduction problems of neutral particle transport.

Serov, I.V.; John, T.M.; Hoogenboom, J.E. [Delft Univ. of Technology (Netherlands). Interfaculty Reactor Inst.

1999-09-01T23:59:59.000Z

95

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

Science Journals Connector (OSTI)

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

B. Militzer

2009-04-08T23:59:59.000Z

96

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

E-Print Network (OSTI)

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

Armiento, Rickard

97

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

E-Print Network (OSTI)

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

Gross, E.K.U.

98

ORBITAL FUNCTIONALS IN STATIC AND TIME-DEPENDENT DENSITY FUNCTIONAL THEORY  

E-Print Network (OSTI)

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

Gross, E.K.U.

99

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

E-Print Network (OSTI)

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

Florian, Libisch

100

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

E-Print Network (OSTI)

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

Ramachandran, Bala (Ramu)

Note: This page contains sample records for the topic "theory dft monte" 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.


101

Mont Vista Capital LLC | Open Energy Information  

Open Energy Info (EERE)

Vista Capital LLC Vista Capital LLC Jump to: navigation, search Name Mont Vista Capital LLC Place New York, New York Zip 10167 Sector Services Product Mont Vista Capital is a leading global provider of services to clients in the alternative energy industry. Mont Vista also seeks proprietary trading and growth equity opportunities in alternative energy markets which add value for our stakeholders. References Mont Vista Capital LLC[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Mont Vista Capital LLC is a company located in New York, New York . References ↑ "Mont Vista Capital LLC" Retrieved from "http://en.openei.org/w/index.php?title=Mont_Vista_Capital_LLC&oldid=348916"

102

Monte Carlo methods in ICF  

SciTech Connect

Monte Carlo methods appropriate to simulate the transport of x-rays, neutrons, ion and electrons in Inertial Confinement Fusion targets are described and analyzed. The Implicit Monte Carlo method of x-ray transport handles symmetry within indirect drive ICF hohlraums well, but can be improved 50X in efficiency by angular biasing the x-rays towards the fuel capsule. Accurate simulation of thermonuclear burns nd burn diagnostics involves detailed particle source spectra, charged particle ranges, inflight reaction kinematics, corrections for bulk and thermal Doppler effects and variance reduction to obtain adequate statistics for rare events. It is found that the effects of angular Coulomb scattering must be included in models of charged particle transport through heterogeneous materials.

Zimmerman, G.B.

1997-06-24T23:59:59.000Z

103

Parallel Monte Carlo reactor neutronics  

SciTech Connect

The issues affecting implementation of parallel algorithms for large-scale engineering Monte Carlo neutron transport simulations are discussed. For nuclear reactor calculations, these include load balancing, recoding effort, reproducibility, domain decomposition techniques, I/O minimization, and strategies for different parallel architectures. Two codes were parallelized and tested for performance. The architectures employed include SIMD, MIMD-distributed memory, and workstation network with uneven interactive load. Speedups linear with the number of nodes were achieved.

Blomquist, R.N.; Brown, F.B.

1994-03-01T23:59:59.000Z

104

Atomistic force field for alumina fit to density functional theory  

SciTech Connect

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

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

2013-11-28T23:59:59.000Z

105

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

106

Hydrogenation of Acetylene-Ethylene Mixtures over Pd and Pd-Ag Alloys: First-Principles Based Kinetic Monte Carlo Simulations  

SciTech Connect

The kinetics for the selective hydrogenation of acetylene-ethylene mixtures over model Pd(111) and bimetallic Pd-Ag alloy surfaces were examined using first principles based kinetic Monte Carlo (KMC) simulations to elucidate the effects of alloying as well as process conditions (temperature and hydrogen partial pressure). The mechanisms that control the selective and unselective routes which included hydrogenation, dehydrogenation and C-?C bond breaking pathways were analyzed using first-principle density functional theory (DFT) calculations. The results were used to construct an intrinsic kinetic database that was used in a variable time step kinetic Monte Carlo simulation to follow the kinetics and the molecular transformations in the selective hydrogenation of acetylene-ethylene feeds over Pd and Pd-Ag surfaces. The lateral interactions between coadsorbates that occur through-surface and through-space were estimated using DFT-parameterized bond order conservation and van der Waal interaction models respectively. The simulation results show that the rate of acetylene hydrogenation as well as the ethylene selectivity increase with temperature over both the Pd(111) and the Pd-Ag/Pd(111) alloy surfaces. The selective hydrogenation of acetylene to ethylene proceeds via the formation of a vinyl intermediate. The unselective formation of ethane is the result of the over-hydrogenation of ethylene as well as over-hydrogenation of vinyl to form ethylidene. Ethylidene further hydrogenates to form ethane and dehydrogenates to form ethylidyne. While ethylidyne is not reactive, it can block adsorption sites which limit the availability of hydrogen on the surface and thus act to enhance the selectivity. Alloying Ag into the Pd surface decreases the overall rated but increases the ethylene selectivity significantly by promoting the selective hydrogenation of vinyl to ethylene and concomitantly suppressing the unselective path involving the hydrogenation of vinyl to ethylidene and the dehydrogenation ethylidene to ethylidyne. This is consistent with experimental results which suggest only the predominant hydrogenation path involving the sequential addition of hydrogen to form vinyl and ethylene exists over the Pd-Ag alloys. Ag enhances the desorption of ethylene and hydrogen from the surface thus limiting their ability to undergo subsequent reactions. The simulated apparent activation barriers were calculated to be 32-44 kJ/mol on Pd(111) and 26-31 kJ/mol on Pd-Ag/Pd(111) respectively. The reaction was found to be essentially first order in hydrogen over Pd(111) and Pd-Ag/Pd(111) surfaces. The results reveal that increases in the hydrogen partial pressure increase the activity but decrease ethylene selectivity over both Pd and Pd-Ag/Pd(111) surfaces. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

Mei, Donghai; Neurock, Matthew; Smith, C Michael

2009-10-22T23:59:59.000Z

107

Semiconductors Used in Photovoltaic and Photocatalytic Devices: Assessing Fundamental Properties from DFT  

Science Journals Connector (OSTI)

Semiconductors Used in Photovoltaic and Photocatalytic Devices: Assessing Fundamental Properties from DFT ... In a dielectric environment, the electrostatic force between the electron and the hole can be approximated by the eq 1. ... Madelung, O. Semiconductors: Data Handbook, 3rd ed.; Springer: New York, 2004. ...

Tangui Le Bahers; Michel Rrat; Philippe Sautet

2014-02-28T23:59:59.000Z

108

TEDTTC^/Dft Ris-R-641(pN) Methodology forJustification and  

E-Print Network (OSTI)

and optimization of protective mea- sures in case of a reactor accident situation with a large release of fissionTEDTTC^/Dft Risø-R-641(pN) Methodology forJustification and Optimization ofProtective Measures: *»***&*> Methodology forJustification and Optimization of Protective Measures Including a Case Study: Protective

109

A DFT Study of Ethanol Adsorption and Dehydrogenation on Cu/Cr2O3 Catalyst  

Science Journals Connector (OSTI)

In this work, DFT simulation method was used to study the adsorption and dehydrogenation of ethanol on Cu/Cr2O3 catalyst. Firstly, the stable configuration of Cu4 cluster adsorbed on Cr2O3...(001) surface was stu...

Minhua Zhang; Yanping Huang; Ruzhen Li; Guiming Li; Yingzhe Yu

2014-11-01T23:59:59.000Z

110

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

E-Print Network (OSTI)

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

Ceder, Gerbrand

111

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

E-Print Network (OSTI)

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

Herbert, John

112

Hybrid DFT study on the gas-phase SN2 reactions at neutral oxygen  

Science Journals Connector (OSTI)

The hybrid DFT method MPW1K, in conjunction with 6-31+G(d,p) basis sets, has been examined for the gas-phase reactions, Y?+HOX (Y, X=F, Cl, Br, I). Comparison of the results with the high-level G2(+) theory indicates that MPW1K/6-31+G(d,p) approach performs well in describing the potential energy surface for the identity SN2 reactions X?+HOX?HOX+X? (X=Cl, Br, I). The corresponding non-identity reactions (Y?X, Y, X=Cl, Br, I), are exothermic if the nucleophile is the heavier halide, in contrast to the corresponding reactions at carbon. The fluorine behaves different from the other halogens. The reactions Y?+HOF (Y=F, Cl, Br, I) are predicted to form the energetically favorable products YO?+HF with a large driving force(?H=?48.6, ?47.2, ?56.5, ?69.0kJ/mol for Y=F, Cl, Br, I, respectively) and lower reaction enthalpies than the corresponding SN2 reactions by about 60kJ/mol. Central barrier heights (?HYX?) for SN2 reactions in the exothermic directions vary from 52.5kJ/mol for Y=I, X=Br up to 76.6kJ/mol for Y=Br, X=Cl. Overall barriers (?HYXb) for reactions in the exothermic direction are all negative (varying from ?13.8kJ/mol for Y=I, X=Br to ?5.2kJ/mol for Y=Br, X=Cl). Complexation energies (?Hcomp) of the ionmolecule complexes Y??HOX vary from 66.3kJ/mol for Y=I, X=Br to 95.5kJ/mol for Y=Cl, X=Br. The central barrier heights ?HYX? and ?HXY? correlate well with the degree of the O?X and O?Y bond elongation in the transition structures. Both central and overall barriers can be interpreted with the aid of Marcus equation.

Yi Ren; Joel L. Wolk; Shmaryahu Hoz

2003-01-01T23:59:59.000Z

113

Llanto al pie del Monte Carmelo  

E-Print Network (OSTI)

llantos feroces, llorando al pie de aquella fuente te estoySpring, 1988) Monte Carmelo al pie del Hay tiempo que no por

Ferrer, Juan Jos Prat

1988-01-01T23:59:59.000Z

114

Analytic energy gradients for constrained DFT-configuration interaction  

SciTech Connect

The constrained density functional theory-configuration interaction (CDFT-CI) method has previously been used to calculate ground-state energies and barrier heights, and to describe electronic excited states, in particular conical intersections. However, the method has been limited to evaluating the electronic energy at just a single nuclear configuration, with the gradient of the energy being available only via finite difference. In this paper, we present analytic gradients of the CDFT-CI energy with respect to nuclear coordinates, which gives the potential for accurate geometry optimization and molecular dynamics on both the ground and excited electronic states, a realm which is currently quite challenging for electronic structure theory. We report the performance of CDFT-CI geometry optimization for representative reaction transition states as well as molecules in an excited state. The overall accuracy of CDFT-CI for computing barrier heights is essentially unchanged whether the energies are evaluated at geometries obtained from quadratic configuration-interaction singles and doubles (QCISD) or CDFT-CI, indicating that CDFT-CI produces very good reaction transition states. These results open up tantalizing possibilities for future work on excited states.

Kaduk, Benjamin; Tsuchimochi, Takashi; Van Voorhis, Troy, E-mail: tvan@mit.edu [Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 (United States)

2014-05-14T23:59:59.000Z

115

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

SciTech Connect

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

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

2014-05-14T23:59:59.000Z

116

DFT studies of Indium Nanoclusters (Inn where n=3-10) and Nanotube and their interaction with molecular hydrogen  

E-Print Network (OSTI)

Density functional theory calculations have been performed on Indium nanoclusters (Inn, n= 3 to 10) to explore the relative stability among their different isomers and interaction with H2. Geometry optimizations starting from initial candidate geometries were performed for each cluster size, so as to determine a few low energy isomers for each size. Clusters with planar configuration and high symmetry are found to be more stable. For n=8 there comes transition from 2D to 3D structures, which formed by stacking of planar rings are most stable. Energetically favorable isomers of indium nanoclusters for each size were considered to get H2 adsorbed. In general H2 interaction with these clusters is week but with odd index i.e. 5, 7 and 9 is significant. Indium nanotube also indicates H2 adsorption but Eads increases many folds on introduction of defect in the tube. On basis of these DFT studies we propose indium nanotubes and clusters of particular size appear to be good candidate for hydrogen storage materials.

Baig, Mirza Wasif; Ahmad, Idrees; Siddiq, Muhammad

2014-01-01T23:59:59.000Z

117

Multijet and single diffraction dissociation Monte Carlo generator  

Science Journals Connector (OSTI)

We have built a Monte Carlo generator for simulating propagation of cosmic ray particles in the atmosphere. The core of the generator is a p-air nuclear interaction model in which SD and NSD processes are included in the inelastic collisions. Based on QCD partonic theory, multiple minijet production is described in detail in the NSD process. A phase-space model is used for the SD process in our work. This generator reproduces cosmic ray experimental data well at very high energies.

J. C. Chen; Q. Q. Zhu; A. X. Huo

1997-05-01T23:59:59.000Z

118

Improved diffusion coefficients generated from Monte Carlo codes  

SciTech Connect

Monte Carlo codes are becoming more widely used for reactor analysis. Some of these applications involve the generation of diffusion theory parameters including macroscopic cross sections and diffusion coefficients. Two approximations used to generate diffusion coefficients are assessed using the Monte Carlo code MC21. The first is the method of homogenization; whether to weight either fine-group transport cross sections or fine-group diffusion coefficients when collapsing to few-group diffusion coefficients. The second is a fundamental approximation made to the energy-dependent P1 equations to derive the energy-dependent diffusion equations. Standard Monte Carlo codes usually generate a flux-weighted transport cross section with no correction to the diffusion approximation. Results indicate that this causes noticeable tilting in reconstructed pin powers in simple test lattices with L2 norm error of 3.6%. This error is reduced significantly to 0.27% when weighting fine-group diffusion coefficients by the flux and applying a correction to the diffusion approximation. Noticeable tilting in reconstructed fluxes and pin powers was reduced when applying these corrections. (authors)

Herman, B. R.; Forget, B.; Smith, K. [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Aviles, B. N. [Knolls Atomic Power Laboratory, Bechtel Marine Propulsion Corporation, P.O. Box 1072, Schenectady, NY 12301-1072 (United States)

2013-07-01T23:59:59.000Z

119

DFT studies of ethylene in femtosecond laser pulses  

E-Print Network (OSTI)

Using time-dependent density functional theory, applied to valence electrons, coupled non-adiabatically to molecular dynamics of the ions, we study the induced dynamics of ethylene subjected to the laser field. We demonstrate the reliable quality of such an approach in comparison to the experimental data on atomic and molecular properties. The impact of ionic motion on the ionization is discussed showing the importance of dealing with electronic and ionic degrees of freedom simultaneously. We explore the various excitation scenarios of ethylene as a function of the laser parameters. We find that the Coulomb fragmentation depends sensitively on the laser frequency. The high laser intensity can cause brute-force Coulomb explosion and the laser pulse length actually has influence on the excitation dynamics of ethylene.

Wang, Z P; Reinhard, P -G; Suraud, E; Zhang, F S

2009-01-01T23:59:59.000Z

120

Point-defect optical transitions and thermal ionization energies from quantum Monte Carlo methods: Application to the F-center defect in MgO  

E-Print Network (OSTI)

We present an approach to calculation of point-defect optical and thermal ionization energies based on the highly accurate quantum Monte Carlo methods. The use of an inherently many-body theory that directly treats electron ...

Ertekin, Elif

Note: This page contains sample records for the topic "theory dft monte" 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

A Monte Carlo algorithm for degenerate plasmas  

Science Journals Connector (OSTI)

A procedure for performing Monte Carlo calculations of plasmas with an arbitrary level of degeneracy is outlined. It has possible applications in inertial confinement fusion and astrophysics. Degenerate particles are initialised according to the Fermi-Dirac ... Keywords: Degenerate plasma, Monte Carlo

A. E. Turrell; M. Sherlock; S. J. Rose

2013-09-01T23:59:59.000Z

122

Monte Carlo Simulation of Isopentane Glass  

Science Journals Connector (OSTI)

...research-article Monte Carlo Simulation of Isopentane Glass S. Yashonath C. N. R. Rao Monte Carlo...quenching the liquid, we have obtained the glass-transition temperature from the temperature...distribution functions suggest a structure of the glass primarily influenced by geometrical factors...

1985-01-01T23:59:59.000Z

123

The MC21 Monte Carlo Transport Code  

SciTech Connect

MC21 is a new Monte Carlo neutron and photon transport code currently under joint development at the Knolls Atomic Power Laboratory and the Bettis Atomic Power Laboratory. MC21 is the Monte Carlo transport kernel of the broader Common Monte Carlo Design Tool (CMCDT), which is also currently under development. The vision for CMCDT is to provide an automated, computer-aided modeling and post-processing environment integrated with a Monte Carlo solver that is optimized for reactor analysis. CMCDT represents a strategy to push the Monte Carlo method beyond its traditional role as a benchmarking tool or ''tool of last resort'' and into a dominant design role. This paper describes various aspects of the code, including the neutron physics and nuclear data treatments, the geometry representation, and the tally and depletion capabilities.

Sutton TM, Donovan TJ, Trumbull TH, Dobreff PS, Caro E, Griesheimer DP, Tyburski LJ, Carpenter DC, Joo H

2007-01-09T23:59:59.000Z

124

Hydroxide Degradation Pathways for Substituted Trimethylammonium Cations: A DFT Study  

SciTech Connect

Substituted trimethylammonium cations serve as small molecule analogues for tetherable cations in anion exchange membranes. In turn, these membranes serve as the basis for alkaline membrane fuel cells by allowing facile conduction of hydroxide. As these cations are susceptible to hydroxide attack, they degrade over time and greatly limit the lifetime of the fuel cell. In this research, we performed density functional theory calculations to investigate the degradation pathways of substituted trimethylammonium cations to probe the relative durability of cation tethering strategies in alkyl and aromatic tethers. Our results show that significant changes in calculated energy barriers occur when substitution groups change. Specifically, we have found that, when available, the Hofmann elimination pathway is the most vulnerable pathway for degradation; however, this barrier is also found to depend on the carbon chain length and number of hydrogens susceptible to Hofmann elimination. S{sub N}2 barriers were also investigated for both methyl groups and substitution groups. The reported findings give important insight into potential tethering strategies for trimethylammonium cations in anion exchange membranes.

Long, H.; Kim, K.; Pivovar, B. S.

2012-05-03T23:59:59.000Z

125

Layered Tantalum Oxynitride Nanorod Array Carpets for Efficient Photoelectrochemical Conversion of Solar Energy: Experimental and DFT Insights  

Science Journals Connector (OSTI)

Layered Tantalum Oxynitride Nanorod Array Carpets for Efficient Photoelectrochemical Conversion of Solar Energy: Experimental and DFT Insights ... This difference in bond energy resulted in narrower band gap energies in oxynitrides compared to their metal oxide counterparts. ...

Nageh K. Allam; Basamat S. Shaheen; Ahmed M. Hafez

2014-03-25T23:59:59.000Z

126

How do vibrations change their composition upon electronic excitation? EXSY-T2D-IR measurements challenge DFT calculations.  

Science Journals Connector (OSTI)

The composition of excited state vibrations can be disentangled by projecting ground state vibrations on them using exchange transient two-dimensional IR spectroscopy. The results challenge excited state DFT c...

Andreas Messmer; Ana-Maria Blanco Rodrguez; Jakub ebera

2009-01-01T23:59:59.000Z

127

Molecular Binding in Post-KohnSham Orbital-Free DFT  

Science Journals Connector (OSTI)

Alex Borgoo *, James A. Green , and David J. Tozer * ... Molecular binding in post-KohnSham orbital-free DFT is investigated, using noninteracting kinetic energy functionals that satisfy the uniform electron gas condition and which are inhomogeneous under density scaling. ... A parameter is introduced that quantifies binding, and a series of functionals are determined from fits to near-exact effective homogeneities and/or KohnSham noninteracting kinetic energies. ...

Alex Borgoo; James A. Green; David J. Tozer

2014-10-30T23:59:59.000Z

128

Combined Investigation of Water Sorption on TiO2 Rutile (110) Single Crystal Face: XPS vs. Periodic DFT  

E-Print Network (OSTI)

1 Combined Investigation of Water Sorption on TiO2 Rutile (110) Single Crystal Face: XPS vs(0)169157150; e-mail: roques@ipno.in2p3.fr Keywords: water, sorption, rutile TiO2, (110), XPS, DFT. Abstract XPS and periodic DFT calculations have been used to investigate water sorption on the TiO2 rutile (110) face. Two

Paris-Sud XI, Université de

129

HILO: Quasi Diffusion Accelerated Monte Carlo on Hybrid Architectures  

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

HILO: Quasi Diffusion Accelerated Monte Carlo on Hybrid Architectures HILO: Quasi Diffusion Accelerated Monte Carlo on Hybrid Architectures The Boltzmann transport equation...

130

Monte Carlo simulation of quantum Zeno effect in the brain  

E-Print Network (OSTI)

Environmental decoherence appears to be the biggest obstacle for successful construction of quantum mind theories. Nevertheless, the quantum physicist Henry Stapp promoted the view that the mind could utilize quantum Zeno effect to influence brain dynamics and that the efficacy of such mental efforts would not be undermined by environmental decoherence of the brain. To address the physical plausibility of Stapp's claim, we modeled the brain using quantum tunneling of an electron in a multiple-well structure such as the voltage sensor in neuronal ion channels and performed Monte Carlo simulations of quantum Zeno effect exerted by the mind upon the brain in the presence or absence of environmental decoherence. The simulations unambiguously showed that the quantum Zeno effect breaks down for timescales greater than the brain decoherence time. To generalize the Monte Carlo simulation results for any n-level quantum system, we further analyzed the change of brain entropy due to the mind probing actions and proved a theorem according to which local projections cannot decrease the von Neumann entropy of the unconditional brain density matrix. The latter theorem establishes that Stapp's model is physically implausible but leaves a door open for future development of quantum mind theories provided the brain has a decoherence-free subspace.

Danko Georgiev

2014-12-11T23:59:59.000Z

131

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

SciTech Connect

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

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

2014-04-28T23:59:59.000Z

132

Self-interaction-free time-dependent density-functional theory for molecular processes in strong fields: High-order harmonic generation of H2 in intense laser fields  

E-Print Network (OSTI)

Self-interaction-free time-dependent density-functional theory for molecular processes in strong work of Hohenberg and Kohn 1 and Kohn and Sham 2 , the steady-state density-functional theory DFT has-electron systems, within the density-functional theory, is much less developed. The central theme of the modern

Chu, Shih-I

133

Resummed thermodynamic perturbation theory for bond cooperativity in associating fluids  

E-Print Network (OSTI)

We develop a resummed thermodynamic perturbation theory for bond cooperativity in associating fluids by extension of Wertheim's multi - density formalism. We specifically consider the case of an associating hard sphere with two association sites and both pairwise and triplet contributions to the energy. To test the theory we perform new monte carlo simulations. Theory and simulation are found to be in excellent agreement.

B. D. Marshall; W. G. Chapman

2013-09-18T23:59:59.000Z

134

THE BEGINNING of the MONTE CARLO METHOD  

E-Print Network (OSTI)

. For a whole host of 125 #12;Monte Carlo reasons, he had become seriously inter- ested in the thermonuclear a preliminary computational model of a thermonuclear reaction for the ENIAC. He felt he could convince

135

Monte Carlo, Colloids, and Public Health  

Science Journals Connector (OSTI)

Here we see in a snapshot the importance of the Monte Carlo algorithm which is used in recent work to simulate data on women's mortality in a specific health-screening program.

Charles Day

2013-01-01T23:59:59.000Z

136

IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS--PART A: SYSTEMS AND HUMANS, VOL. 36, NO. 5, SEPTEMBER 2006 943 Extending the Decision Field Theory to Model  

E-Print Network (OSTI)

, SEPTEMBER 2006 943 Extending the Decision Field Theory to Model Operators' Reliance on Automation by describing a quantitative model of trust in automation. We extend decision field theory (DFT) to describe the multiple sequential decisions that characterize reliance on au- tomation in supervisory control situations

Lee, John D.

137

Subsystem real-time Time Dependent Density Functional Theory  

E-Print Network (OSTI)

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

Krishtal, Alisa; Pavanello, Michele

2015-01-01T23:59:59.000Z

138

Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation  

E-Print Network (OSTI)

Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Aljoscha Rheinwalt 14. Januar 2009 Betreuender Professor: Prof. M. M¨uller-Preu?ker #12;Das Ising-Modell und Monte-Carlo-Simulation Gliederung Gliederung Ising-Modell Definition Anwendungen Numerische Analyse Statistische Beschreibung Monte

139

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

E-Print Network (OSTI)

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

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

2015-01-01T23:59:59.000Z

140

Density of Configurational States from First-Principles Calculations: The Phase Diagram of  

E-Print Network (OSTI)

(LGH) using interatomic interaction energies derived from density functional theory (DFT) calculations,[3­7] together with Monte Carlo (MC) simulations (called "ab initio LGH+ MC"). Once the LGH has been

Note: This page contains sample records for the topic "theory dft monte" 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

This is the user's manual for DEGAS 2 -A Monte Carlo code for the study of neutral atom and molecular transport in confined plasmas. It is intended to cover  

E-Print Network (OSTI)

. The theory of neutral particle kinetics[1] treats the transport of mass, momen- tum, and energy in a plasma;Monte Carlo neutral transport codes can build on the techniques developed for neutron transportAbstract This is the user's manual for DEGAS 2 - A Monte Carlo code for the study of neutral atom

Karney, Charles

142

Estimation of expected human attention weights based on a decision field theory model  

Science Journals Connector (OSTI)

Abstract Modeling human decision making behavior is of great interest in understanding how a decision maker weights different decision attributes when making a decision. Such knowledge is critically important in helping predict future decisions, evaluating human decision performance, and improving the design of human and machine interface systems. Decision field theory (DFT) provides a psychological representation of the cognitive deliberation process, which is driven by the fluctuations of a persons attention among decision attributes. In this research area, the most common use of a DFT model is to estimate or predict the human decisions by using a set of pre-specified expected attention weights (EAWs) in the DFT model. Unlike other research, this paper extends the capabilities of DFT in a complementary direction, showing how to fit or train a DFT model by estimating the EAW based on sequentially obtained samples of decision trials. Furthermore, the inherent connection between the EAW and the decision choice uncertainty is investigated. The proposed modeling method is discussed in detail for a two-alternative decision scenario based on two attributes. Both simulations and a case study are conducted in the paper to demonstrate the effectiveness of the proposed modeling approach.

Andres G. Abad; Jionghua (Judy) Jin; Young-Jun Son

2014-01-01T23:59:59.000Z

143

Adaptive kinetic Monte Carlo simulation of methanol decomposition on Cu(100)  

SciTech Connect

The adaptive kinetic Monte Carlo method was used to calculate the dynamics of methanol decomposition on Cu(100) at room temperature over a time scale of minutes. Mechanisms of reaction were found using min-mode following saddle point searches based upon forces and energies from density functional theory. Rates of reaction were calculated with harmonic transition state theory. The dynamics followed a pathway from CH3-OH, CH3-O, CH2-O, CH-O and finally C-O. Our calculations confirm that methanol decomposition starts with breaking the O-H bond followed by breaking C-H bonds in the dehydrogenated intermediates until CO is produced. The bridge site on the Cu(100) surface is the active site for scissoring chemical bonds. Reaction intermediates are mobile on the surface which allows them to find this active reaction site. This study illustrates how the adaptive kinetic Monte Carlo method can model the dynamics of surface chemistry from first principles.

Xu, Lijun; Mei, Donghai; Henkelman, Graeme A.

2009-12-31T23:59:59.000Z

144

Velocity renormalization in graphene from lattice Monte Carlo  

E-Print Network (OSTI)

We compute the Fermi velocity of the Dirac quasiparticles in clean graphene at the charge neutrality point for strong Coulomb coupling alpha_g. We perform a Lattice Monte Carlo calculation within the low-energy Dirac theory, which includes an instantaneous, long-range Coulomb interaction. We find a renormalized Fermi velocity v_FR > v_F, where v_F = c/300. Our results are consistent with a momentum-independent v_FR which increases approximately linearly with alpha_g, although a logarithmic running with momentum cannot be excluded at present. At the predicted critical coupling alpha_gc for the semimetal-insulator transition due to excitonic pair formation, we find v_FR/v_F = 3.3, which we discuss in light of experimental findings for v_FR/v_F at the charge neutrality point in ultra-clean suspended graphene.

Joaqun E. Drut; Timo A. Lhde

2014-03-26T23:59:59.000Z

145

Dynamic modeling and optimal control of DFIG wind energy systems using DFT and NSGA-II  

Science Journals Connector (OSTI)

Abstract Once a doubly-fed induction generator (DFIG) is subjected to a disturbance by a change in the wind speed, the stator flux cannot change instantly. Under this condition, rotor back-EMF voltages reflect the effects of stator dynamics on rotor current dynamics, and have an important role on the oscillations of the rotor current. These oscillations decrease the DFIG system reliability and gear lifetime. Moreover, by focusing only on small signal analysis, the dynamic damping performance immediately following such disturbances is often degraded. Additional improvement in performance will be achieved if discrete Fourier transform (DFT) is used to quantify damping characteristic of the rotor current during changes of the operating points. This paper introduces an optimization technique based on non-dominated sorting genetic algorithm-II (NSGA-II) incorporating DFT analysis to achieve better control performance for DFIG system stability. Considering small signal stability, the main purpose of the control system in the present paper is to increase the system damping ratio as well as to guarantee enough stability margin. Eigenvalue analysis and time-domain simulations have been presented to demonstrate that the proposed optimizing method yields better control performance in comparison with one designed using mere eigenvalue relocation.

M. Zamanifar; B. Fani; M.E.H. Golshan; H.R. Karshenas

2014-01-01T23:59:59.000Z

146

Localized Orbital Corrections for the Barrier Heights in Density Functional Theory  

Science Journals Connector (OSTI)

In these cases, we have had to make decisions concerning which data to employ, and the choices are described below. ... Therefore, we must decide upon one resonance structure for each in order to successfully apply the LOC scheme. ... From an assessment of G2 and d. functional theories (DFT) on this test set G2 theory is the most reliable method both in terms of av. ...

Michelle Lynn Hall; Dahlia A. Goldfeld; Arteum D. Bochevarov; Richard A. Friesner

2009-10-27T23:59:59.000Z

147

Hybrid Monte Carlo with Wilson Dirac operator on the Fermi GPU  

E-Print Network (OSTI)

In this article we present our implementation of a Hybrid Monte Carlo algorithm for Lattice Gauge Theory using two degenerate flavours of Wilson-Dirac fermions on a Fermi GPU. We find that using registers instead of global memory speeds up the code by almost an order of magnitude. To map the array variables to scalars, so that the compiler puts them in the registers, we use code generators. Our final program is more than 10 times faster than a generic single CPU.

Abhijit Chakrabarty; Pushan Majumdar

2012-07-10T23:59:59.000Z

148

Radiative transfer in the earth's atmosphere-ocean system using Monte Carlo techniques  

E-Print Network (OSTI)

are described in the next chapter. The books by Morgan and Hammersley and Handscomb describe the theory and some methods of variance reduction for general applications. One item that is required of any Monte Carlo simulation is a supply of randoni numbers... be checked through modification of the model since the same sequeiice of random numbers may be generated repeatedly. Discussions on the properties ot' random nuinbers and their generation may be found in the books by Morgan' and Hammersley and Handscomb...

Bradley, Paul Andrew

2012-06-07T23:59:59.000Z

149

A unified Monte Carlo approach to fast neutron cross section data evaluation.  

SciTech Connect

A unified Monte Carlo (UMC) approach to fast neutron cross section data evaluation that incorporates both model-calculated and experimental information is described. The method is based on applications of Bayes Theorem and the Principle of Maximum Entropy as well as on fundamental definitions from probability theory. This report describes the formalism, discusses various practical considerations, and examines a few numerical examples in some detail.

Smith, D.; Nuclear Engineering Division

2008-03-03T23:59:59.000Z

150

Using exploratory data analysis modified Box Plots to enhance Monte Carlo simulated Range Estimating Decision Technology  

E-Print Network (OSTI)

of the thesis is written with the intent of reviewing some of the significant pieces of literature relating to Monte Carlo simulated REDT and exploratory data analysis Box Plots. In 1964 David Hertz published an article in the Harvard Business Review... entitled, "Risk Analysis in Capital Investment" (Hertz 1964). While this article does not directly discuss range estimating, it is the foundation for the current REDT theory. In his atticle, Hertz discussed the problems associated with estimating...

Clutter, David John

1992-01-01T23:59:59.000Z

151

Monte Carlo event reconstruction implemented with artificial neural networks  

E-Print Network (OSTI)

I implemented event reconstruction of a Monte Carlo simulation using neural networks. The OLYMPUS Collaboration is using a Monte Carlo simulation of the OLYMPUS particle detector to evaluate systematics and reconstruct ...

Tolley, Emma Elizabeth

2011-01-01T23:59:59.000Z

152

The DFT+Umol method and its application to the adsorption of CO on platinum model clusters  

SciTech Connect

Semi-local DFT approximations are well-known for their difficulty with describing the correct site preference for the adsorption of CO molecules on (111) surfaces of several late transition metals. To address this problem originating from a residual self-interaction in the CO LUMO, we present the DFT+Umol approach which generalizes the empirical DFT+U correction to fragment molecular orbitals. This correction is applied to examine CO adsorption energies at various sites on the (111) facets of cuboctahedral clusters Pt{sub m}(CO){sub 8} (m = 79, 140, 225). The DFT+Umol correction leaves the electronic ground state of metal clusters, in particular their d-band structure, essentially unchanged, affecting almost exclusively the energy of the CO LUMO. As a result, that correction is significantly stronger for complexes at hollow sites, hence increases the propensity for adsorption at top sites. We also analyze competing edge effects on the (111) facets of the cluster models.

Soini, Thomas M.; Krger, Sven [Department Chemie and Catalysis Research Center, Technische Universitt Mnchen, 85747 Garching (Germany)] [Department Chemie and Catalysis Research Center, Technische Universitt Mnchen, 85747 Garching (Germany); Rsch, Notker, E-mail: roesch@mytum.de [Department Chemie and Catalysis Research Center, Technische Universitt Mnchen, 85747 Garching (Germany) [Department Chemie and Catalysis Research Center, Technische Universitt Mnchen, 85747 Garching (Germany); Institute of High Performance Computing, Agency for Science, Technology and Research, 1 Fusionopolis Way, No. 16-16 Connexis, Singapore 138632 (Singapore)

2014-05-07T23:59:59.000Z

153

Exploring the interaction between lithium ion and defective graphene surface using dispersion corrected DFT studies  

SciTech Connect

To analyze the lithium ion interaction with realistic graphene surfaces, we carried out dispersion corrected DFT-D3 studies on graphene with common point defects and chemisorbed oxygen containing functional groups along with defect free graphene surface. Our study reveals that, the interaction between lithium ion (Li+) and graphene is mainly through the delocalized ? electron of pure graphene layer. However, the oxygen containing functional groups pose high adsorption energy for lithium ion due to the Li-O ionic bond formation. Similarly, the point defect groups interact with lithium ion through possible carbon dangling bonds and/or cation-? type interactions. Overall these defect sites render a preferential site for lithium ions compared with pure graphene layer. Based on these findings, the role of graphene surface defects in lithium battery performance were discussed.

Vijayakumar, M.; Hu, Jian Z.

2013-10-15T23:59:59.000Z

154

An Efficient Arithmetic Sum-of-Product (SOP) based Multiplication Approach for FIR Filters and DFT  

E-Print Network (OSTI)

, the output of a FIR filter is the weighted sum of the current value and a finite number of previous values of the input. An important property of FIR filters is their inherent stability due to the lack of feedback from the output. Y (n) = N?1 ? l=0 x(n... . . . . . . +++ . . . . . .+ + + + MCM z?1 z?1 z?1 z?1 a) Direct Form Realization z?1 z?1 z?1 z?1 b) Transposed Direct Form Realization c0 c1 c2 c3 cN?1 cN?3cN?1 c0cN?2 x(n) x(n) SOP Y (n) Y (n) cN?4 Fig. I.1. Implementation of DFT The previous approaches for solving...

Kumar, Rajeev

2013-04-24T23:59:59.000Z

155

A survey of Monte Carlo methods Jonathan Weare  

E-Print Network (OSTI)

A survey of Monte Carlo methods Jonathan Weare University of Chicago April 5, 2011 Jonathan Weare?) problems are high dimensional so we need MC. Jonathan Weare A survey of Monte Carlo methods #12;Some high in the initial conditions for an evolutionary PDE propagate? and many more · · · Jonathan Weare A survey of Monte

Anisimov, Mikhail

156

Module 2: Monte Carlo Methods Prof. Mike Giles  

E-Print Network (OSTI)

, Bermudan options, optimal trading given transaction costs) MC Lecture 1 ­ p. 7 #12;Monte Carlo vs. finite 1 ­ p. 5 #12;Monte Carlo vs. finite differences Hard to get reliable figures, but my "guesstimate most heavily? . . . and will it stay that way in the future? MC Lecture 1 ­ p. 6 #12;Monte Carlo vs

Giles, Mike

157

John von Neumann Institute for Computing Monte Carlo Protein Folding  

E-Print Network (OSTI)

John von Neumann Institute for Computing Monte Carlo Protein Folding: Simulations of Met://www.fz-juelich.de/nic-series/volume20 #12;#12;Monte Carlo Protein Folding: Simulations of Met-Enkephalin with Solvent-Accessible Area difficulties in applying Monte Carlo methods to protein folding. The solvent-accessible area method, a popular

Hsu, Hsiao-Ping

158

Effective field theory for dilute fermions with pairing  

SciTech Connect

Effective field theory (EFT) methods for a uniform system of fermions with short-range, natural interactions are extended to include pairing correlations, as part of a program to develop a systematic Kohn-Sham density functional theory (DFT) for medium and heavy nuclei. An effective action formalism for local composite operators leads to a free-energy functional that includes pairing by applying an inversion method order by order in the EFT expansion. A consistent renormalization scheme is demonstrated for the uniform system through next-to-leading order, which includes induced-interaction corrections to pairing.

Furnstahl, R.J. [Department of Physics, Ohio State University, Columbus, OH 43210 (United States)], E-mail: furnstahl.1@osu.edu; Hammer, H.-W. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany)], E-mail: hammer@itkp.uni-bonn.de; Puglia, S.J. [SBIG PLC, Berkeley Square House, London W1J 6BR (United Kingdom)], E-mail: spuglia@sbiguk.com

2007-11-15T23:59:59.000Z

159

Mont Alto Borough | Open Energy Information  

Open Energy Info (EERE)

Alto Borough Alto Borough Jump to: navigation, search Name Mont Alto Borough Place Pennsylvania Utility Id 12817 Utility Location Yes Ownership M NERC Location RFC NERC RFC Yes Activity Buying Transmission Yes Activity Distribution Yes References EIA Form EIA-861 Final Data File for 2010 - File1_a[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Utility Rate Schedules Grid-background.png Commercial Commercial Residential Residential Average Rates Residential: $0.1460/kWh Commercial: $0.0899/kWh Industrial: $0.1480/kWh References ↑ "EIA Form EIA-861 Final Data File for 2010 - File1_a" Retrieved from "http://en.openei.org/w/index.php?title=Mont_Alto_Borough&oldid=411118"

160

Overview of Monte Carlo radiation transport codes  

SciTech Connect

The Radiation Safety Information Computational Center (RSICC) is the designated central repository of the United States Department of Energy (DOE) for nuclear software in radiation transport, safety, and shielding. Since the center was established in the early 60's, there have been several Monte Carlo particle transport (MC) computer codes contributed by scientists from various countries. An overview of the neutron transport computer codes in the RSICC collection is presented.

Kirk, Bernadette Lugue [ORNL] [ORNL

2010-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

New Monte Carlo Algorithm for Protein Folding  

Science Journals Connector (OSTI)

We demonstrate that the recently introduced pruned-enriched Rosenbluth method leads to extremely efficient algorithms for the folding of simple model proteins. We test them on several models for lattice heteropolymers, and compare the results to published Monte Carlo studies. In all cases our algorithms are faster than previous ones, and in several cases we find new minimal energy states. In addition, our algorithms give estimates for the partition sum at finite temperatures.

Helge Frauenkron; Ugo Bastolla; Erwin Gerstner; Peter Grassberger; Walter Nadler

1998-04-06T23:59:59.000Z

162

Monte Carlo Particle Transport: Algorithm and Performance Overview  

National Nuclear Security Administration (NNSA)

Monte Carlo Particle Transport: Monte Carlo Particle Transport: Algorithm and Performance Overview N. A. Gentile, R. J. Procassini and H. A. Scott Lawrence Livermore National Laboratory, Livermore, California, 94551 Monte Carlo methods are frequently used for neutron and radiation trans- port. These methods have several advantages, such as relative ease of programming and dealing with complex meshes. Disadvantages include long run times and statistical noise. Monte Carlo photon transport calcu- lations also often suffer from inaccuracies in matter temperature due to the lack of implicitness. In this paper we discuss the Monte Carlo algo- rithm as it is applied to neutron and photon transport, detail the differ- ences between neutron and photon Monte Carlo, and give an overview of the ways the numerical method has been modified to deal with issues that

163

Hybrid Monte Carlo and topological modes of full QCD  

E-Print Network (OSTI)

We investigate the performance of the hybrid Monte Carlo algorithm, the standard algorithm used for lattice QCD simulations involving fermions, in updating non-trivial global topological structures. We find that the hybrid Monte Carlo algorithm has serious problems decorrelating the global topological charge at the values of $\\beta$ and $m$ currently simulated, where continuum physics should be approximately realized. This represents a warning which must be seriously considered when simulating full QCD by hybrid Monte Carlo.

B. Alls; G. Boyd; M. D'Elia; A. Di Giacomo; E. Vicari

1996-07-22T23:59:59.000Z

164

Monte Carlo Simulations of the Corrosion of Aluminoborosilicate...  

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

Simulations of the Corrosion of Aluminoborosilicate Glasses. Monte Carlo Simulations of the Corrosion of Aluminoborosilicate Glasses. Abstract: Aluminum is one of the most common...

165

Posters Monte Carlo Simulation of Longwave Fluxes Through Broken...  

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

5 Posters Monte Carlo Simulation of Longwave Fluxes Through Broken Scattering Cloud Fields E. E. Takara and R. G. Ellingson University of Maryland College Park, Maryland To...

166

Binding and Diffusion of Lithium in Graphite: Quantum Monte Carlo...  

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

Binding and Diffusion of Lithium in Graphite: Quantum Monte Carlo Benchmarks and Validation of van der Waals Density Functional Methods P. Ganesh,* , Jeongnim Kim, Changwon...

167

An efficient approach to ab initio Monte Carlo simulation  

SciTech Connect

We present a Nested Markov chain Monte Carlo (NMC) scheme for building equilibrium averages based on accurate potentials such as density functional theory. Metropolis sampling of a reference system, defined by an inexpensive but approximate potential, was used to substantially decorrelate configurations at which the potential of interest was evaluated, thereby dramatically reducing the number needed to build ensemble averages at a given level of precision. The efficiency of this procedure was maximized on-the-fly through variation of the reference system thermodynamic state (characterized here by its inverse temperature ?{sup 0}), which was otherwise unconstrained. Local density approximation results are presented for shocked states of argon at pressures from 4 to 60 GPa, wheredepending on the quality of the reference system potentialacceptance probabilities were enhanced by factors of 1.228 relative to unoptimized NMC. The optimization procedure compensated strongly for reference potential shortcomings, as evidenced by significantly higher speedups when using a reference potential of lower quality. The efficiency of optimized NMC is shown to be competitive with that of standard ab initio molecular dynamics in the canonical ensemble.

Leiding, Jeff; Coe, Joshua D., E-mail: jcoe@lanl.gov [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2014-01-21T23:59:59.000Z

168

THE MCNPX MONTE CARLO RADIATION TRANSPORT CODE  

SciTech Connect

MCNPX (Monte Carlo N-Particle eXtended) is a general-purpose Monte Carlo radiation transport code with three-dimensional geometry and continuous-energy transport of 34 particles and light ions. It contains flexible source and tally options, interactive graphics, and support for both sequential and multi-processing computer platforms. MCNPX is based on MCNP4B, and has been upgraded to most MCNP5 capabilities. MCNP is a highly stable code tracking neutrons, photons and electrons, and using evaluated nuclear data libraries for low-energy interaction probabilities. MCNPX has extended this base to a comprehensive set of particles and light ions, with heavy ion transport in development. Models have been included to calculate interaction probabilities when libraries are not available. Recent additions focus on the time evolution of residual nuclei decay, allowing calculation of transmutation and delayed particle emission. MCNPX is now a code of great dynamic range, and the excellent neutronics capabilities allow new opportunities to simulate devices of interest to experimental particle physics; particularly calorimetry. This paper describes the capabilities of the current MCNPX version 2.6.C, and also discusses ongoing code development.

WATERS, LAURIE S. [Los Alamos National Laboratory; MCKINNEY, GREGG W. [Los Alamos National Laboratory; DURKEE, JOE W. [Los Alamos National Laboratory; FENSIN, MICHAEL L. [Los Alamos National Laboratory; JAMES, MICHAEL R. [Los Alamos National Laboratory; JOHNS, RUSSELL C. [Los Alamos National Laboratory; PELOWITZ, DENISE B. [Los Alamos National Laboratory

2007-01-10T23:59:59.000Z

169

Calculating Pi Using the Monte Carlo Method  

Science Journals Connector (OSTI)

During the summer of 2012 I had the opportunity to participate in a research experience for teachers at the center for sustainable energy at Notre Dame University (RET @ cSEND) working with Professor John LoSecco on the problem of using antineutrino detection to accurately determine the fuel makeup and operating power of nuclear reactors. During full power operation a reactor may produce 1021 antineutrinos per second with approximately 100 per day being detected. While becoming familiar with the design and operation of the detectors and how total antineutrino flux could be obtained from such a small sample I read about a simulation program called Monte Carlo. 1 Further investigation led me to the Monte Carlo method page of Wikipedia 2 where I saw an example of approximating pi using this simulation. Other examples where this method was applied were typically done with computer simulations 2 or purely mathematical. 3 It is my belief that this method may be easily related to the students by performing the simple activity of sprinkling rice on an arc drawn in a square. The activity that follows was inspired by those simulations and was used by my AP Physics class last year with very good results.

Timothy Williamson

2013-01-01T23:59:59.000Z

170

Quantum Monte Carlo methods for nuclear physics  

E-Print Network (OSTI)

Quantum Monte Carlo methods have proved very valuable to study the structure and reactions of light nuclei and nucleonic matter starting from realistic nuclear interactions and currents. These ab-initio calculations reproduce many low-lying states and transition moments in light nuclei, and simultaneously predict many properties of light nuclei and neutron matter over a rather wide range of energy and momenta. We review the nuclear interactions and currents, and describe the continuum Quantum Monte Carlo methods used in nuclear physics. These methods are similar to those used in condensed matter and electronic structure but naturally include spin-isospin, tensor, spin-orbit, and three-body interactions. We present a variety of results including the low-lying spectra of light nuclei, nuclear form factors, and transition matrix elements. We also describe low-energy scattering techniques, studies of the electroweak response of nuclei relevant in electron and neutrino scattering, and the properties of dense nucleonic matter as found in neutron stars. A coherent picture of nuclear structure and dynamics emerges based upon rather simple but realistic interactions and currents.

J. Carlson; S. Gandolfi; F. Pederiva; Steven C. Pieper; R. Schiavilla; K. E. Schmidt; R. B. Wiringa

2014-12-09T23:59:59.000Z

171

Energy Monte Carlo (EMCEE) | Open Energy Information  

Open Energy Info (EERE)

Energy Monte Carlo (EMCEE) Energy Monte Carlo (EMCEE) Jump to: navigation, search Tool Summary LAUNCH TOOL Name: EMCEE and Emc2 Agency/Company /Organization: United States Geological Survey Sector: Energy Focus Area: Non-renewable Energy Topics: Resource assessment Resource Type: Software/modeling tools User Interface: Spreadsheet Website: pubs.usgs.gov/pp/pp1713/26/ Country: United States Cost: Free Northern America Coordinates: 37.09024°, -95.712891° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":37.09024,"lon":-95.712891,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

172

MC21 analysis of the nuclear energy agency Monte Carlo performance benchmark problem  

SciTech Connect

Due to the steadily decreasing cost and wider availability of large scale computing platforms, there is growing interest in the prospects for the use of Monte Carlo for reactor design calculations that are currently performed using few-group diffusion theory or other low-order methods. To facilitate the monitoring of the progress being made toward the goal of practical full-core reactor design calculations using Monte Carlo, a performance benchmark has been developed and made available through the Nuclear Energy Agency. A first analysis of this benchmark using the MC21 Monte Carlo code was reported on in 2010, and several practical difficulties were highlighted. In this paper, a newer version of MC21 that addresses some of these difficulties has been applied to the benchmark. In particular, the confidence-interval-determination method has been improved to eliminate source correlation bias, and a fission-source-weighting method has been implemented to provide a more uniform distribution of statistical uncertainties. In addition, the Forward-Weighted, Consistent-Adjoint-Driven Importance Sampling methodology has been applied to the benchmark problem. Results of several analyses using these methods are presented, as well as results from a very large calculation with statistical uncertainties that approach what is needed for design applications. (authors)

Kelly, D. J.; Sutton, T. M. [Knolls Atomic Power Laboratory, Bechtel Marine Propulsion Corporation, P. O. Box 1072, Schenectady, NY 12301-1072 (United States); Wilson, S. C. [Bertis Atomic Power Laboratory, Bechtel Marine Propulsion Corporation, P. O. Box 79, West Mifflin, PA 15122-0079 (United States)

2012-07-01T23:59:59.000Z

173

Multiphoton Monte Carlo event generator for Bhabha scattering at small angles  

Science Journals Connector (OSTI)

We describe in this paper the application of the theory of Yennie, Frautschi, and Suura (YFS) to construct a Monte Carlo (MC) event generator with multiple-photon production for Bhabha scattering at low angles. The respective generator provides the four-momenta of the electron and positron and of all soft and hard photons with a proper treatment of the phase space and conservation of the total four-momentum. The final-state electron and positron are assumed to be visible above some minimum angle with respect to the beams (double tag). The QED matrix element in the algorithm is taken according to the YFS exponentiation scheme. The Monte Carlo program will be helpful in luminosity determination at experiments at the SLAC Linear Collider and the CERN collider LEP; it takes into account QED O(?) and the leading higher-order corrections. The important difference with the existing MC procedures is that the minimum energy above which photons are generated may be set arbitrarily low. Sample Monte Carlo data are illustrated in our discussion.

Stanislaw Jadach and B. F. L. Ward

1989-12-01T23:59:59.000Z

174

Taming Density Functional Theory by Coarse-Graining  

E-Print Network (OSTI)

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

Paul E. Lammert

2010-08-10T23:59:59.000Z

175

Dicarboxylate assisted synthesis of the monoclinic heterometallic tetrathiocyanato bridged copper(II) and mercury(II) coordination polymer {l_brace}Cu[Hg(SCN){sub 4}]{r_brace}{sub n}: Synthesis, structural, vibration, luminescence, EPR studies and DFT calculations  

SciTech Connect

The synthesis of the monoclinic polymorph of {l_brace}Cu[Hg(SCN){sub 4}]{r_brace}{sub n} is reported. The compound, as determined by X-ray diffraction of a twinned crystal, consists of mercury and copper atoms linked by {mu}{sub 1,3}-SCN bridges. The crystal packing shows a highly porous infinite 3D structure. Diagnostic resonances for the SCN{sup -} ligand and metal-ligand bonds in the IR, far-IR and Raman spectra are assigned and discussed. The electronic band structure along with density of states (DOS) calculated by the DFT method indicates that the compound is an indirect band gap semiconductor. The DFT calculations show that the observed luminescence of the compound arises mainly from an excited LLCT state with small MLCT contributions (from the copper to unoccupied {pi}{sup *} orbital of the thiocyanate groups). The X-band EPR spectrum of the powdered sample at room temperature reveals an axial signal with anisotropic g factors consistent with the unpaired electron of Cu(II) ion in the d{sub x}{sup 2}{sub -y}{sup 2} orbital. -- Graphical abstract: Synthesis and X-ray structure determination of the monoclinic {l_brace}Cu[Hg(SCN){sub 4}]{r_brace}{sub n} is reported. The IR, far-IR, Raman, photoluminescence as well as EPR spectra of the compound is discussed. Also, the emission and semiconducting behavior of the compound is illustrated through the density functional theory calculation of electronic band structure along with density of states. Display Omitted Research highlights: > The monoclinic {l_brace}Cu[Hg(SCN){sub 4}]{r_brace}{sub n} has been prepared. > The structure of the compound is determined by XRD of a twinned crystal. > The IR, far-IR, Raman, EPR and emission spectra of the compound is investigated. > As shown by DFT calculations, the emission bands of the compound are mainly LLCT. > Small MLCT from the copper to the thiocyanate groups contributes to these bands.

Khandar, Ali Akbar, E-mail: akhandar@yahoo.co [Department of Inorganic Chemistry, Faculty of Chemistry, University of Tabriz, 5166614766 Tabriz (Iran, Islamic Republic of); Klein, Axel [Institut fuer Anorganische Chemie, Universitaet zu Koeln, Greinstrasse 6, 50939 Koeln (Germany); Bakhtiari, Akbar [Department of Inorganic Chemistry, Faculty of Chemistry, University of Tabriz, 5166614766 Tabriz (Iran, Islamic Republic of); Institut fuer Anorganische Chemie, Universitaet zu Koeln, Greinstrasse 6, 50939 Koeln (Germany); Mahjoub, Ali Reza [Department of Chemistry, School of Science, Tarbiat Modares University, P.O. Box 14155-4838 Tehran (Iran, Islamic Republic of); Pohl, Roland W.H. [Institut fuer Anorganische Chemie, Universitaet zu Koeln, Greinstrasse 6, 50939 Koeln (Germany)

2011-02-15T23:59:59.000Z

176

Augmented Lagrangian Method for Constrained Nuclear Density Functional Theory  

E-Print Network (OSTI)

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

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

2010-07-21T23:59:59.000Z

177

RADIATIVE HEAT TRANSFER WITH QUASI-MONTE CARLO METHODS  

E-Print Network (OSTI)

RADIATIVE HEAT TRANSFER WITH QUASI-MONTE CARLO METHODS A. Kersch1 W. Moroko2 A. Schuster1 1Siemens of Quasi-Monte Carlo to this problem. 1.1 Radiative Heat Transfer Reactors In the manufacturing of the problems which can be solved by such a simulation is high accuracy modeling of the radiative heat transfer

178

Sequential Monte Carlo EM for multivariate probit models  

Science Journals Connector (OSTI)

Multivariate probit models have the appealing feature of capturing some of the dependence structure between the components of multidimensional binary responses. The key for the dependence modelling is the covariance matrix of an underlying latent multivariate ... Keywords: Adaptive sequential Monte Carlo, Maximum likelihood, Monte Carlo EM, Multivariate probit

Giusi Moffa; Jack Kuipers

2014-04-01T23:59:59.000Z

179

CERN-TH.6275/91 Monte Carlo Event Generation  

E-Print Network (OSTI)

CERN-TH.6275/91 Monte Carlo Event Generation for LHC T. Sj¨ostrand CERN -- Geneva Abstract The necessity of event generators for LHC physics studies is illustrated, and the Monte Carlo approach is outlined. A survey is presented of existing event generators, followed by a more detailed study

Sjöstrand, Torbjörn

180

Lattice field theory simulations of graphene  

E-Print Network (OSTI)

We discuss the Monte Carlo method of simulating lattice field theories as a means of studying the low-energy effective theory of graphene. We also report on simulational results obtained using the Metropolis and Hybrid Monte Carlo methods for the chiral condensate, which is the order parameter for the semimetal-insulator transition in graphene, induced by the Coulomb interaction between the massless electronic quasiparticles. The critical coupling and the associated exponents of this transition are determined by means of the logarithmic derivative of the chiral condensate and an equation-of-state analysis. A thorough discussion of finite-size effects is given, along with several tests of our calculational framework. These results strengthen the case for an insulating phase in suspended graphene, and indicate that the semimetal-insulator transition is likely to be of second order, though exhibiting neither classical critical exponents, nor the predicted phenomenon of Miransky scaling.

Joaqun E. Drut; Timo A. Lhde

2009-01-06T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" from the National Library of EnergyBeta (NLEBeta).
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181

A boot-strap PoissonBoltzmann theory for the structure and thermodynamics of charged colloidal solutions  

E-Print Network (OSTI)

A boot-strap Poisson­Boltzmann theory for the structure and thermodynamics of charged colloidal investigated by Monte Carlo simulation. A boot-strap Poisson­Boltzmann BSPB theory has been developed using a boot-strap Poisson­Boltzmann BSPB theory. Comparisons of the structure, internal en- ergy

Chan, Derek Y C

182

Monte Carlo stratified source-sampling  

SciTech Connect

In 1995, at a conference on criticality safety, a special session was devoted to the Monte Carlo {open_quotes}eigenvalue of the world{close_quotes} problem. Argonne presented a paper, at that session, in which the anomalies originally observed in that problem were reproduced in a much simplified model-problem configuration, and removed by a version of stratified source-sampling. The original test-problem was treated by a special code designed specifically for that purpose. Recently ANL started work on a method for dealing with more realistic eigenvalue of the world configurations, and has been incorporating this method into VIM. The original method has been modified to take into account real-world statistical noise sources not included in the model problem. This paper constitutes a status report on work still in progress.

Blomquist, R.N.; Gelbard, E.M.

1997-09-01T23:59:59.000Z

183

Monte Carlo Simulation of Joint Transport of Neutrons Monte Carlo Simulation of Joint Transport of Neutrons  

National Nuclear Security Administration (NNSA)

Monte Carlo Simulation of Joint Transport of Neutrons Monte Carlo Simulation of Joint Transport of Neutrons Monte Carlo Simulation of Joint Transport of Neutrons and Photons and Photons Zhitnik Zhitnik A A . . K K . . , , Artemeva Artemeva E.V., E.V., Bakanov Bakanov V.V., V.V., Donskoy Donskoy E.N., E.N., Zalyalov Zalyalov A.N., A.N., Ivanov Ivanov N.V., N.V., Ognev Ognev S.P., S.P., Ronzhin Ronzhin A.B., A.B., Roslov Roslov V.I., V.I., Semenova Semenova T.V. T.V. RFNC-VNIIEF, 607190, Sarov, RFNC-VNIIEF, 607190, Sarov, Nizhni Nizhni Novgorod region Novgorod region The approaches used at VNIIEF to simulate transport of neutrons and photons in standard (with The approaches used at VNIIEF to simulate transport of neutrons and photons in standard (with surface description of region interfaces) and grid geometries are considered in the paper.

184

E-Print Network 3.0 - all-atom monte carlo Sample Search Results  

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

Source: Collection: Engineering ; Computer Technologies and Information Sciences 17 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

185

E-Print Network 3.0 - accurate monte carlo Sample Search Results  

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

Tilburg University Collection: Computer Technologies and Information Sciences 59 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

186

E-Print Network 3.0 - adjoint monte carlo Sample Search Results  

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

Oxford Collection: Engineering ; Computer Technologies and Information Sciences 37 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

187

Accelerated rescaling of single Monte Carlo simulation runs with the Graphics Processing Unit (GPU)  

E-Print Network (OSTI)

and S. Andersson-Engels, Accelerated Monte Carlo models toAccelerated rescaling of single Monte Carlo simulation runsreported on online, GPU- accelerated MC simulations. Along

Yang, Owen; Choi, Bernard

2013-01-01T23:59:59.000Z

188

Fundamental measure theory for the electric double layer: applications to blue-energy harvesting and water desalination  

E-Print Network (OSTI)

Capacitive mixing (CAPMIX) and capacitive deionization (CDI) are promising candidates for harvesting clean, renewable energy and for the energy efficient production of potable water, respectively. Both CAPMIX and CDI involve water-immersed porous carbon electrodes at voltages of the order of hundreds of millivolts, such that counter-ionic packing is important. We propose a density functional theory (DFT) to model the electric double layer which forms near the surfaces of these porous materials. The White-Bear mark II fundamental measure theory (FMT) functional is combined with a mean-field Coulombic and a MSA-type correction to describe the interplay between dense packing and electrostatics, in good agreement with MD simulations. Compared to less elaborate mean-field models our DFT calculations reveal a higher work output for blue-energy cycles and a higher energy demand for desalination cycles.

Andreas Hrtel; Mathijs Janssen; Sela Samin; Ren van Roij

2014-11-20T23:59:59.000Z

189

Iterative acceleration methods for Monte Carlo and deterministic criticality calculations  

SciTech Connect

If you have ever given up on a nuclear criticality calculation and terminated it because it took so long to converge, you might find this thesis of interest. The author develops three methods for improving the fission source convergence in nuclear criticality calculations for physical systems with high dominance ratios for which convergence is slow. The Fission Matrix Acceleration Method and the Fission Diffusion Synthetic Acceleration (FDSA) Method are acceleration methods that speed fission source convergence for both Monte Carlo and deterministic methods. The third method is a hybrid Monte Carlo method that also converges for difficult problems where the unaccelerated Monte Carlo method fails. The author tested the feasibility of all three methods in a test bed consisting of idealized problems. He has successfully accelerated fission source convergence in both deterministic and Monte Carlo criticality calculations. By filtering statistical noise, he has incorporated deterministic attributes into the Monte Carlo calculations in order to speed their source convergence. He has used both the fission matrix and a diffusion approximation to perform unbiased accelerations. The Fission Matrix Acceleration method has been implemented in the production code MCNP and successfully applied to a real problem. When the unaccelerated calculations are unable to converge to the correct solution, they cannot be accelerated in an unbiased fashion. A Hybrid Monte Carlo method weds Monte Carlo and a modified diffusion calculation to overcome these deficiencies. The Hybrid method additionally possesses reduced statistical errors.

Urbatsch, T.J.

1995-11-01T23:59:59.000Z

190

Recent advances and future prospects for Monte Carlo  

SciTech Connect

The history of Monte Carlo methods is closely linked to that of computers: The first known Monte Carlo program was written in 1947 for the ENIAC; a pre-release of the first Fortran compiler was used for Monte Carlo In 1957; Monte Carlo codes were adapted to vector computers in the 1980s, clusters and parallel computers in the 1990s, and teraflop systems in the 2000s. Recent advances include hierarchical parallelism, combining threaded calculations on multicore processors with message-passing among different nodes. With the advances In computmg, Monte Carlo codes have evolved with new capabilities and new ways of use. Production codes such as MCNP, MVP, MONK, TRIPOLI and SCALE are now 20-30 years old (or more) and are very rich in advanced featUres. The former 'method of last resort' has now become the first choice for many applications. Calculations are now routinely performed on office computers, not just on supercomputers. Current research and development efforts are investigating the use of Monte Carlo methods on FPGAs. GPUs, and many-core processors. Other far-reaching research is exploring ways to adapt Monte Carlo methods to future exaflop systems that may have 1M or more concurrent computational processes.

Brown, Forrest B [Los Alamos National Laboratory

2010-01-01T23:59:59.000Z

191

Absolute Approximation of Tukey Depth: Theory and Experiments  

E-Print Network (OSTI)

Absolute Approximation of Tukey Depth: Theory and Experiments Dan Chen School of Computer Science¨ur Theoretische Informatik Abstract A Monte Carlo approximation algorithm for the Tukey depth problem in high. Keywords: Tukey depth, computational geometry 1. Introduction Tukey depth is also known as location depth

Morin, Pat

192

Increasing the applicability of density functional theory. IV. Consequences of ionization-potential improved exchange-correlation potentials  

SciTech Connect

This paper's objective is to create a consistent mean-field based Kohn-Sham (KS) density functional theory (DFT) meaning the functional should not only provide good total energy properties, but also the corresponding KS eigenvalues should be accurate approximations to the vertical ionization potentials (VIPs) of the molecule, as the latter condition attests to the viability of the exchange-correlation potential (V{sub XC}). None of the prominently used DFT approaches show these properties: the optimized effective potential V{sub XC} based ab initio dft does. A local, range-separated hybrid potential cam-QTP-00 is introduced as the basis for a consistent KS DFT approach. The computed VIPs as the negative of KS eigenvalue have a mean absolute error of 0.8 eV for an extensive set of molecule's electron ionizations, including the core. Barrier heights, equilibrium geometries, and magnetic properties obtained from the potential are in good agreement with experiment. A similar accuracy with less computational efforts can be achieved by using a non-variational global hybrid variant of the QTP-00 approach.

Verma, Prakash; Bartlett, Rodney J., E-mail: bartlett@ufl.edu [Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)

2014-05-14T23:59:59.000Z

193

Monte Carlo methods for the nuclear shell model  

E-Print Network (OSTI)

We present novel Monte Carlo methods for treating the interacting shell model that allow exact calculations much larger than those heretofore possible. The two-body interaction is linearized by an auxiliary field; Monte Carlo evaluation of the resulting functional integral gives ground-state or thermal expectation values of few-body operators. The ``sign problem'' generic to quantum Monte Carlo calculations is absent in a number of cases. We discuss the favorable scaling of these methods with nucleon numb er and basis size and their suitability to parallel computation.

C. W. Johnson; S. E. Koonin; G. H. Lang; W. E. Ormand

1992-10-20T23:59:59.000Z

194

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

E-Print Network (OSTI)

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

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

2014-01-01T23:59:59.000Z

195

Sequential Monte Carlo Methods for Protein Folding  

E-Print Network (OSTI)

We describe a class of growth algorithms for finding low energy states of heteropolymers. These polymers form toy models for proteins, and the hope is that similar methods will ultimately be useful for finding native states of real proteins from heuristic or a priori determined force fields. These algorithms share with standard Markov chain Monte Carlo methods that they generate Gibbs-Boltzmann distributions, but they are not based on the strategy that this distribution is obtained as stationary state of a suitably constructed Markov chain. Rather, they are based on growing the polymer by successively adding individual particles, guiding the growth towards configurations with lower energies, and using "population control" to eliminate bad configurations and increase the number of "good ones". This is not done via a breadth-first implementation as in genetic algorithms, but depth-first via recursive backtracking. As seen from various benchmark tests, the resulting algorithms are extremely efficient for lattice models, and are still competitive with other methods for simple off-lattice models.

Peter Grassberger

2004-08-26T23:59:59.000Z

196

Report of the Monte Rosa Expedition of 1911  

Science Journals Connector (OSTI)

1 January 1915 research-article Report of the Monte Rosa Expedition of 1911 J. Barcroft M. Camis C. G. Mathison Ff. Roberts J. H. Ryffel The Royal Society is collaborating...

1915-01-01T23:59:59.000Z

197

A Monte Carlo tool for multi-node reliability evaluation  

E-Print Network (OSTI)

-Area Reliability Program(NARP) is based on the random sampling of generator and transmission line status for each hour. Monte Carlo Approach for Estimating Contingency Statistics along with the Evaluation Subroutine(MACS-ES) advances the generation...

Thalasila, Chander Pravin

2012-06-07T23:59:59.000Z

198

An Analysis Tool for Flight Dynamics Monte Carlo Simulations  

E-Print Network (OSTI)

and analysis work to understand vehicle operating limits and identify circumstances that lead to mission failure. A Monte Carlo simulation approach that varies a wide range of physical parameters is typically used to generate thousands of test cases...

Restrepo, Carolina 1982-

2011-05-20T23:59:59.000Z

199

Variance Reduction Techniques for Implicit Monte Carlo Simulations  

E-Print Network (OSTI)

The Implicit Monte Carlo (IMC) method is widely used for simulating thermal radiative transfer and solving the radiation transport equation. During an IMC run a grid network is constructed and particles are sourced into the problem to simulate...

Landman, Jacob Taylor

2013-09-19T23:59:59.000Z

200

Brueckner-Goldstone quantum Monte Carlo for correlation energies and quasiparticle energy bands of one-dimensional solids  

Science Journals Connector (OSTI)

A quantum Monte Carlo method that combines the second-order many-body perturbation theory and Monte Carlo (MC) integration has been developed for correlation and correlation-corrected (quasiparticle) energy bands of one-dimensional solids. The sum-of-product expressions of correlation energy and self-energy are transformed, with the aid of a Laplace transform, into high-dimensional integrals, which are subject to a highly scalable MC integration with the Metropolis algorithm for importance sampling. The method can compute correlation energies of polyacetylene and polyethylene within a few mEh and quasiparticle energy bands within a few tenths of an eV. It does not suffer from the fermion sign problem and its description can be systematically improved by raising the perturbation order.

Soohaeng Yoo Willow; Kwang S. Kim; So Hirata

2014-11-18T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

Beyond chemical accuracy: The pseudopotential approximation in diffusion Monte Carlo calculations of the HCP to BCC phase transition in beryllium  

E-Print Network (OSTI)

Motivated by the disagreement between recent diffusion Monte Carlo calculations and experiments on the phase transition pressure between the ambient and beta-Sn phases of silicon, we present a study of the HCP to BCC phase transition in beryllium. This lighter element provides an oppor- tunity for directly testing many of the approximations required for calculations on silicon and may suggest a path towards increasing the practical accuracy of diffusion Monte Carlo calculations of solids in general. We demonstrate that the single largest approximation in these calculations is the pseudopotential approximation. After removing this we find excellent agreement with experiment for the ambient HCP phase and results similar to careful calculations using density functional theory for the phase transition pressure.

Shulenburger, Luke; Desjarlais, M P

2015-01-01T23:59:59.000Z

202

MOCABA: a general Monte Carlo-Bayes procedure for improved predictions of integral functions of nuclear data  

E-Print Network (OSTI)

MOCABA is a combination of Monte Carlo sampling and Bayesian updating algorithms for the prediction of integral functions of nuclear data, such as reactor power distributions or neutron multiplication factors. Similarly to the established Generalized Linear Least Squares (GLLS) methodology, MOCABA offers the capability to utilize integral experimental data to reduce the prior uncertainty of integral observables. The MOCABA approach, however, does not involve any series expansions and, therefore, does not suffer from the breakdown of first-order perturbation theory for large nuclear data uncertainties. This is related to the fact that, in contrast to the GLLS method, the updating mechanism within MOCABA is applied directly to the integral observables without having to "adjust" any nuclear data. A central part of MOCABA is the nuclear data Monte Carlo program NUDUNA, which performs random sampling of nuclear data evaluations according to their covariance information and converts them into libraries for transpor...

Hoefer, Axel; Hennebach, Maik; Schmid, Michael; Porsch, Dieter

2014-01-01T23:59:59.000Z

203

Implications of Monte Carlo Statistical Errors in Criticality Safety Assessments  

SciTech Connect

Most criticality safety calculations are performed using Monte Carlo techniques because of Monte Carlo's ability to handle complex three-dimensional geometries. For Monte Carlo calculations, the more histories sampled, the lower the standard deviation of the resulting estimates. The common intuition is, therefore, that the more histories, the better; as a result, analysts tend to run Monte Carlo analyses as long as possible (or at least to a minimum acceptable uncertainty). For Monte Carlo criticality safety analyses, however, the optimization situation is complicated by the fact that procedures usually require that an extra margin of safety be added because of the statistical uncertainty of the Monte Carlo calculations. This additional safety margin affects the impact of the choice of the calculational standard deviation, both on production and on safety. This paper shows that, under the assumptions of normally distributed benchmarking calculational errors and exact compliance with the upper subcritical limit (USL), the standard deviation that optimizes production is zero, but there is a non-zero value of the calculational standard deviation that minimizes the risk of inadvertently labeling a supercritical configuration as subcritical. Furthermore, this value is shown to be a simple function of the typical benchmarking step outcomes--the bias, the standard deviation of the bias, the upper subcritical limit, and the number of standard deviations added to calculated k-effectives before comparison to the USL.

Pevey, Ronald E.

2005-09-15T23:59:59.000Z

204

DFT+U Study of Polaronic Conduction in Li2O2 and Li2CO3: Implications for LiAir Batteries  

Science Journals Connector (OSTI)

DFT+U Study of Polaronic Conduction in Li2O2 and Li2CO3: Implications for LiAir Batteries ... The emission of greenhouse gases and the local pollution in the cities produced by the fossil fuel-powered vehicles (FFVs) is forcing the development of alternative power systems for automobiles. ... A delocalized solution was found. ...

J. M. Garcia-Lastra; J. S. G. Myrdal; R. Christensen; K. S. Thygesen; T. Vegge

2013-02-15T23:59:59.000Z

205

Basic physical and chemical information needed for development of Monte Carlo codes  

SciTech Connect

It is important to view track structure analysis as an application of a branch of theoretical physics (i.e., statistical physics and physical kinetics in the language of the Landau school). Monte Carlo methods and transport equation methods represent two major approaches. In either approach, it is of paramount importance to use as input the cross section data that best represent the elementary microscopic processes. Transport analysis based on unrealistic input data must be viewed with caution, because results can be misleading. Work toward establishing the cross section data, which demands a wide scope of knowledge and expertise, is being carried out through extensive international collaborations. In track structure analysis for radiation biology, the need for cross sections for the interactions of electrons with DNA and neighboring protein molecules seems to be especially urgent. Finally, it is important to interpret results of Monte Carlo calculations fully and adequately. To this end, workers should document input data as thoroughly as possible and report their results in detail in many ways. Workers in analytic transport theory are then likely to contribute to the interpretation of the results.

Inokuti, M.

1993-08-01T23:59:59.000Z

206

MONTE CARLO SIMULATION MODEL OF ENERGETIC PROTON TRANSPORT THROUGH SELF-GENERATED ALFVEN WAVES  

SciTech Connect

A new Monte Carlo simulation model for the transport of energetic protons through self-generated Alfven waves is presented. The key point of the model is that, unlike the previous ones, it employs the full form (i.e., includes the dependence on the pitch-angle cosine) of the resonance condition governing the scattering of particles off Alfven waves-the process that approximates the wave-particle interactions in the framework of quasilinear theory. This allows us to model the wave-particle interactions in weak turbulence more adequately, in particular, to implement anisotropic particle scattering instead of isotropic scattering, which the previous Monte Carlo models were based on. The developed model is applied to study the transport of flare-accelerated protons in an open magnetic flux tube. Simulation results for the transport of monoenergetic protons through the spectrum of Alfven waves reveal that the anisotropic scattering leads to spatially more distributed wave growth than isotropic scattering. This result can have important implications for diffusive shock acceleration, e.g., affect the scattering mean free path of the accelerated particles in and the size of the foreshock region.

Afanasiev, A.; Vainio, R., E-mail: alexandr.afanasiev@helsinki.fi [Department of Physics, University of Helsinki (Finland)

2013-08-15T23:59:59.000Z

207

DFT study on cysteine adsorption mechanism on Au(111) and Au(110)  

SciTech Connect

Periodic density functional theory calculations were used to investigate relevant aspects of adsorption mechanisms of cysteine dimers in protonated form on Au(111) and Au(110) surfaces. The projected densities of states are explicitly discussed for all main chemical groups of cysteine, i.e. the amino group (NH2), the thiol group (SH) and the carboxylic group (COOH) to identify differences in adsorption mechanism. Special emphasis is put on the analysis of changes in the electronic structure of molecules adsorbed on Au(111) and Au(110) surfaces as well as the accompanying charge transfer mechanisms at molecule-substrate interaction.

Buimaga-Iarinca, Luiza; Floare, Calin G.; Calborean, Adrian; Turcu, Ioan [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)] [National Institute for Research and Development of Isotopic and Molecular Technologies, 65-103 Donath, 400293 Cluj-Napoca (Romania)

2013-11-13T23:59:59.000Z

208

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

209

DOE Science Showcase - Monte Carlo Methods | OSTI, US Dept of Energy,  

Office of Scientific and Technical Information (OSTI)

Monte Carlo Methods Monte Carlo Methods Monte Carlo calculation methods are algorithms for solving various kinds of computational problems by using (pseudo)random numbers. Developed in the 1940s during the Manhattan Project, the Monte Carlo method signified a radical change in how scientists solved problems. Learn about the ways these methods are used in DOE's research endeavors today in "Monte Carlo Methods" by Dr. William Watson, Physicist, OSTI staff. Effects of static particle dispersions on grain growth are studied using SPPARKS simulations Image credit: Sandia National Laboratory Monte Carlo Results in DOE Databases Lab biophysicist invents improvement to Monte Carlo technique, LLNL News Monte Carlo Benchmark software, ESTSC Improved Monte Carlo Renormalization Group Method, DOE R&D

210

Stochastic models: theory and simulation.  

SciTech Connect

Many problems in applied science and engineering involve physical phenomena that behave randomly in time and/or space. Examples are diverse and include turbulent flow over an aircraft wing, Earth climatology, material microstructure, and the financial markets. Mathematical models for these random phenomena are referred to as stochastic processes and/or random fields, and Monte Carlo simulation is the only general-purpose tool for solving problems of this type. The use of Monte Carlo simulation requires methods and algorithms to generate samples of the appropriate stochastic model; these samples then become inputs and/or boundary conditions to established deterministic simulation codes. While numerous algorithms and tools currently exist to generate samples of simple random variables and vectors, no cohesive simulation tool yet exists for generating samples of stochastic processes and/or random fields. There are two objectives of this report. First, we provide some theoretical background on stochastic processes and random fields that can be used to model phenomena that are random in space and/or time. Second, we provide simple algorithms that can be used to generate independent samples of general stochastic models. The theory and simulation of random variables and vectors is also reviewed for completeness.

Field, Richard V., Jr.

2008-03-01T23:59:59.000Z

211

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

E-Print Network (OSTI)

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

Norbert Schuch; Frank Verstraete

2007-12-04T23:59:59.000Z

212

Monte Carlo study of living polymers with the bond-fluctuation method  

Science Journals Connector (OSTI)

The highly efficient bond-fluctuation method for Monte Carlo simulations of both static and dynamic properties of polymers is applied to a system of living polymers. Parallel to stochastic movements of monomers, which result in Rouse dynamics of the macromolecules, the polymer chains break, or associate at chain ends with other chains and single monomers, in the process of equilibrium polymerization. We study the changes in equilibrium properties, such as molecular-weight distribution, average chain length, and radius of gyration, and specific heat with varying density and temperature of the system. The results of our numeric experiments indicate a very good agreement with the recently suggested description in terms of the mean-field approximation. The coincidence of the specific heat maximum position at kBT=V/4 in both theory and simulation suggests the use of calorimetric measurements for the determination of the scission-recombination energy V in real experiments.

Yannick Rouault and Andrey Milchev

1995-06-01T23:59:59.000Z

213

Interfaces in partly compatible polymer mixtures: A Monte Carlo simulation approach  

E-Print Network (OSTI)

The structure of polymer coils near interfaces between coexisting phases of symmetrical polymer mixtures (AB) is discussed, as well as the structure of symmetric diblock copolymers of the same chain length N adsorbed at the interface. The problem is studied by Monte Carlo simulations of the bond fluctuation model on the simple cubic lattice, using massively parallel computers (CRAY T3D). While homopolymer coils in the strong segregation limit are oriented parallel to the interface, the diblocks form ``dumbbells'' oriented perpendicular to the interface. However, in the dilute case (``mushroom regime'' rather than ``brush regime''), the diblocks are only weakly stretched. Distribution functions for monomers at the chain ends and in the center of the polymer are obtained, and a comparison to the self consistent field theory is made.

K. Binder; M. Mueller; F. Schmid; A. Werner

1997-06-27T23:59:59.000Z

214

Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo  

E-Print Network (OSTI)

Despite liquid water is ubiquitous in chemical reactions at roots of life and climate on earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in excellent agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous Density Functional Theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab-initio simulations of complex chemical systems.

Zen, Andrea; Mazzola, Guglielmo; Guidoni, Leonardo; Sorella, Sandro

2014-01-01T23:59:59.000Z

215

Ab-initio molecular dynamics simulation of liquid water by Quantum Monte Carlo  

E-Print Network (OSTI)

Despite liquid water is ubiquitous in chemical reactions at roots of life and climate on earth, the prediction of its properties by high-level ab initio molecular dynamics simulations still represents a formidable task for quantum chemistry. In this article we present a room temperature simulation of liquid water based on the potential energy surface obtained by a many-body wave function through quantum Monte Carlo (QMC) methods. The simulated properties are in excellent agreement with recent neutron scattering and X-ray experiments, particularly concerning the position of the oxygen-oxygen peak in the radial distribution function, at variance of previous Density Functional Theory attempts. Given the excellent performances of QMC on large scale supercomputers, this work opens new perspectives for predictive and reliable ab-initio simulations of complex chemical systems.

Andrea Zen; Ye Luo; Guglielmo Mazzola; Leonardo Guidoni; Sandro Sorella

2014-12-09T23:59:59.000Z

216

Combined Monte Carlo and quantum mechanics study of the hydration of the guanine-cytosine base pair  

Science Journals Connector (OSTI)

We present a computer simulation study of the hydration of the guanine-cytosine (GC) hydrogen-bonded complex. Using first principles density-functional theory, with gradient-corrected exchange-correlation and Monte Carlo simulation, we include thermal contribution, structural effects, solvent polarization, and the water-water and water-GC hydrogen bond interaction to show that the GC interaction in an aqueous environment is weakened to about 70% of the value obtained for an isolated complex. We also analyze in detail the preferred hydration sites of the GC pair and show that on the average it makes around five hydrogen bonds with water.

Kaline Coutinho; Valdemir Ludwig; Sylvio Canuto

2004-06-01T23:59:59.000Z

217

Including screening in van der Waals corrected density functional theory calculations: The case of atoms and small molecules physisorbed on graphene  

SciTech Connect

The Density Functional Theory (DFT)/van der Waals-Quantum Harmonic Oscillator-Wannier function (vdW-QHO-WF) method, recently developed to include the vdW interactions in approximated DFT by combining the quantum harmonic oscillator model with the maximally localized Wannier function technique, is applied to the cases of atoms and small molecules (X=Ar, CO, H{sub 2}, H{sub 2}O) weakly interacting with benzene and with the ideal planar graphene surface. Comparison is also presented with the results obtained by other DFT vdW-corrected schemes, including PBE+D, vdW-DF, vdW-DF2, rVV10, and by the simpler Local Density Approximation (LDA) and semilocal generalized gradient approximation approaches. While for the X-benzene systems all the considered vdW-corrected schemes perform reasonably well, it turns out that an accurate description of the X-graphene interaction requires a proper treatment of many-body contributions and of short-range screening effects, as demonstrated by adopting an improved version of the DFT/vdW-QHO-WF method. We also comment on the widespread attitude of relying on LDA to get a rough description of weakly interacting systems.

Silvestrelli, Pier Luigi; Ambrosetti, Alberto [Dipartimento di Fisica e Astronomia, Universit di Padova, via Marzolo 8, I35131 Padova, Italy and DEMOCRITOS National Simulation Center of the Italian Istituto Officina dei Materiali (IOM) of the Italian National Research Council (CNR), Trieste (Italy)] [Dipartimento di Fisica e Astronomia, Universit di Padova, via Marzolo 8, I35131 Padova, Italy and DEMOCRITOS National Simulation Center of the Italian Istituto Officina dei Materiali (IOM) of the Italian National Research Council (CNR), Trieste (Italy)

2014-03-28T23:59:59.000Z

218

El Monte, California: Energy Resources | Open Energy Information  

Open Energy Info (EERE)

Monte, California: Energy Resources Monte, California: Energy Resources (Redirected from El Monte, CA) Jump to: navigation, search Equivalent URI DBpedia Coordinates 34.0686206°, -118.0275667° Loading map... {"minzoom":false,"mappingservice":"googlemaps3","type":"ROADMAP","zoom":14,"types":["ROADMAP","SATELLITE","HYBRID","TERRAIN"],"geoservice":"google","maxzoom":false,"width":"600px","height":"350px","centre":false,"title":"","label":"","icon":"","visitedicon":"","lines":[],"polygons":[],"circles":[],"rectangles":[],"copycoords":false,"static":false,"wmsoverlay":"","layers":[],"controls":["pan","zoom","type","scale","streetview"],"zoomstyle":"DEFAULT","typestyle":"DEFAULT","autoinfowindows":false,"kml":[],"gkml":[],"fusiontables":[],"resizable":false,"tilt":0,"kmlrezoom":false,"poi":true,"imageoverlays":[],"markercluster":false,"searchmarkers":"","locations":[{"text":"","title":"","link":null,"lat":34.0686206,"lon":-118.0275667,"alt":0,"address":"","icon":"","group":"","inlineLabel":"","visitedicon":""}]}

219

An Overview of Geometry Representation in Monte Carlo Codes  

National Nuclear Security Administration (NNSA)

Geometry Representation Geometry Representation in Monte Carlo Codes R.P. Kensek, * B.C. Franke, * T.W. Laub * , L.J. Lorence, * M. R. Martin, * S. Warren † * Sandia National Laboratories, P.O. Box 5800, MS 1179, Albuquerque, NM 87185 † Kansas State University, Manhattan, KS 66506 Geometry representations in production Monte Carlo radiation transport codes used for linear-transport simulations are traditionally limited to combinatorial geometry (CG) topologies. While CG representations of input geometries are efficient to query, they are difficult to construct. In the Integrated-TIGER-Series (ITS) Monte Carlo code suite, a new approach for radiation transport geometry engines has been implemented that allows for Computer Aided Design (CAD), facetted approximations, and other geometry types to simultaneously define an input geometry.

220

The Monte Carlo Independent Column Approximation Model Intercomparison  

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

The Monte Carlo Independent Column Approximation Model Intercomparison The Monte Carlo Independent Column Approximation Model Intercomparison Project (McMIP) Barker, Howard Meteorological Service of Canada Cole, Jason Meteorological Service of Canada Raisanen, Petri Finnish Meteorological Institute Pincus, Robert NOAA-CIRES Climate Diagnostics Center Morcrette, Jean-Jacques European Centre for Medium-Range Weather Forecasts Li, Jiangnan Canadian Center for Climate Modelling Stephens, Graeme Colorado State University Vaillancourt, Paul Environment Canada Oreopoulos, Lazaros JCET/UMBC and NASA/GSFC Siebesma, Pier KNMI Los, Alexander KNMI Clothiaux, Eugene The Pennsylvania State University Randall, David Colorado State University Iacono, Michael Atmospheric & Environmental Research, Inc. Category: Radiation The Monte Carlo Independent Column Approximation (McICA) method for

Note: This page contains sample records for the topic "theory dft monte" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
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We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

Coupling of kinetic Monte Carlo simulations of surface reactions to transport in a fluid for heterogeneous catalytic reactor modeling  

SciTech Connect

We have developed a method to couple kinetic Monte Carlo simulations of surface reactions at a molecular scale to transport equations at a macroscopic scale. This method is applicable to steady state reactors. We use a finite difference upwinding scheme and a gap-tooth scheme to efficiently use a limited amount of kinetic Monte Carlo simulations. In general the stochastic kinetic Monte Carlo results do not obey mass conservation so that unphysical accumulation of mass could occur in the reactor. We have developed a method to perform mass balance corrections that is based on a stoichiometry matrix and a least-squares problem that is reduced to a non-singular set of linear equations that is applicable to any surface catalyzed reaction. The implementation of these methods is validated by comparing numerical results of a reactor simulation with a unimolecular reaction to an analytical solution. Furthermore, the method is applied to two reaction mechanisms. The first is the ZGB model for CO oxidation in which inevitable poisoning of the catalyst limits the performance of the reactor. The second is a model for the oxidation of NO on a Pt(111) surface, which becomes active due to lateral interaction at high coverages of oxygen. This reaction model is based on ab initio density functional theory calculations from literature.

Schaefer, C.; Jansen, A. P. J. [Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

2013-02-07T23:59:59.000Z

222

UV-vis spectra of singlet state cationic polycyclic aromatic hydrocarbons: Time-dependent density functional theory study  

SciTech Connect

A theoretical study of singlet state cations of polycyclic aromatic hydrocarbons is performed. Appropriate symmetry suitable for further calculations is chosen for each of the systems studied. The excitation states of such species are obtained by the time dependent density functional theory (TD-DFT) method. The computations are performed using both Pople and electronic response properties basis sets. The results obtained with the use of different basis sets are compared. The electronic transitions are described and the relationships for the lowest-lying transitions states of different species are found. The properties of in-plane and out-of-plane transitions are also delineated. The TD-DFT results are compared with the experimental data available.

Dominikowska, Justyna, E-mail: justyna@uni.lodz.pl; Domagala, Malgorzata; Palusiak, Marcin [Department of Theoretical and Structural Chemistry, University of ?d?, Pomorska 163/165, 90-236 ?d? (Poland)] [Department of Theoretical and Structural Chemistry, University of ?d?, Pomorska 163/165, 90-236 ?d? (Poland)

2014-01-28T23:59:59.000Z

223

Density Functional Theory for Fractional Particle Number: Derivative Discontinuity of the Energy at the Maximum Number of Bound Electrons  

E-Print Network (OSTI)

The derivative discontinuity in the exact exchange-correlation potential of ensemble Density Functional Theory (DFT) is investigated at the specific integer number that corresponds to the maximum number of bound electrons, $J_{max}$. A recently developed complex-scaled analog of DFT is extended to fractional particle numbers and used to study ensembles of both bound and metastable states. It is found that the exact exchange-correlation potential experiences discontinuous jumps at integer particle numbers including $J_{max}$. For integers below $J_{max}$ the jump is purely real because of the real shift in the chemical potential. At $J_{max}$, the jump has a non-zero imaginary component reflecting the finite lifetime of the $(J_{max}+1)$ state.

Daniel L. Whitenack; Yu Zhang; Adam Wasserman

2011-11-08T23:59:59.000Z

224

Argonne Physics Division - Theory Group  

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

Division Seminar: R-150 @ 3:30pm Division Seminar: R-150 @ 3:30pm 14 April 2011 Stefano Gandolfi Los Alamos National Laboratory stefano@lanl.gov Quantum Monte Carlo Study of Strongly Correlated Fermions: Neutron Matter, Neutron Stars and Cold Atoms Division Seminar: R-150 @ 3:30pm 31 March 2011 Lucas Platter Chalmers University of Technology, Göteborg platter@chalmers.se Effective Field Theories for Nuclear Systems Division Seminar: R-150 @ 3:30pm 17 February 2011 Alexandros Gezerlis University of Washington gezerlis@uw.edu Bridging the Gap: Fermions in Nuclear Structure and Nuclear Astrophysics Special Day: Tuesday 15 February 2011 Louis H. Kauffman UIC kauffman@uic.edu Topological Quantum Information and the Jones Polynomial Division Seminar: R-150 @ 3:30pm 10 February 2011 JoaquÃ-n Drut

225

Fast neutron fluxes in pressure vessels using Monte Carlo methods  

SciTech Connect

The objective of this project is to determine the feasibility of calculating the fast neutron flux in the pressure vessel of a pressurized water reactor by Monte Carlo methods. Neutron reactions reduce the ductility of the steel and thus limit the useful life of this important reactor component. This work was performed for Virginia Power (VEPCO). VIM is a continuous-energy Monte Carlo code which provides a versatile geometrical capability and a neutron physics data base closely representing the EDNF/B-IV data from which it was derived.

Edlund, M.C.; Thomas, J.R.

1986-01-01T23:59:59.000Z

226

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

227

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

228

E-Print Network 3.0 - atlas monte carlo Sample Search Results  

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

di - Dipartimento di Fisica, Quantum Optics Group Collection: Physics 50 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

229

E-Print Network 3.0 - accelerated monte carlo Sample Search Results  

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

Nuclear Technologies ; Environmental Sciences and Ecology ; Biology and Medicine 36 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

230

E-Print Network 3.0 - applicator monte carlo Sample Search Results  

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

of Electrical and Computer Engineering, Virginia Tech Collection: Engineering 85 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

231

E-Print Network 3.0 - adaptive monte carlo Sample Search Results  

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

and Statistics, University of New South Wales Collection: Mathematics 47 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

232

E-Print Network 3.0 - accelerating monte carlo Sample Search...  

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

Nuclear Technologies ; Environmental Sciences and Ecology ; Biology and Medicine 36 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

233

E-Print Network 3.0 - anatomy monte carlo Sample Search Results  

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

de Lige Collection: Power Transmission, Distribution and Plants ; Engineering 19 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

234

E-Print Network 3.0 - absolute monte carlo Sample Search Results  

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

Engineering, University of California at San Diego Collection: Engineering 37 Das Ising-Modell und Monte-Carlo-Simulation Das Ising-Modell und Monte-Carlo-Simulation Summary:...

235

Bone Penetration of Amoxicillin and Clavulanic Acid Evaluated by Population Pharmacokinetics and Monte Carlo Simulation  

Science Journals Connector (OSTI)

...infusion. Simulations with our...equilibration by modeling and to derive...Monte Carlo simulations. Drusano...bone was rapid for both...using a fully automated extraction...pharmacokinetic modeling and Monte Carlo simulation. Antimicrob...

Cornelia B. Landersdorfer; Martina Kinzig; Jrgen B. Bulitta; Friedrich F. Hennig; Ulrike Holzgrabe; Fritz Srgel; Johannes Gusinde

2009-03-23T23:59:59.000Z

236

The theoretical development of a new high speed solution for Monte Carlo radiation transport computations  

E-Print Network (OSTI)

Advancements in parallel and cluster computing have made many complex Monte Carlo simulations possible in the past several years. Unfortunately, cluster computers are large, expensive, and still not fast enough to make the Monte Carlo technique...

Pasciak, Alexander Samuel

2007-04-25T23:59:59.000Z

237

Monte Carlo Simulations of Thermal Conductivity in Nanoporous Si Membranes  

E-Print Network (OSTI)

candidates for thermoelectric materials as they can provide extremely low thermal conductivity , relatively of boundary scattering on the thermal conductivity. We show that the material porosity strongly affects1 Monte Carlo Simulations of Thermal Conductivity in Nanoporous Si Membranes Stefanie Wolf1

238

Impact of random numbers on parallel Monte Carlo application  

SciTech Connect

A number of graduate students are involved at various level of research in this project. We investigate the basic issues in materials using Monte Carlo simulations with specific interest in heterogeneous materials. Attempts have been made to seek collaborations with the DOE laboratories. Specific details are given.

Pandey, Ras B.

2002-10-22T23:59:59.000Z

239

Observations of Comet b 1881 made at Monte Video  

Science Journals Connector (OSTI)

... 1881 Royal Astronomical Society. Provided by the NASA Astrophysics Data System 14 July 1881 research-article Articles Observations of Comet b 1881 made at Monte Video Lieut. B. E. W. Gwynne R.A. 1881MNRAS..41..438G...

B. E. W. Gwynne

1881-07-14T23:59:59.000Z

240

Monte Carlo calibration of avalanches described as Coulomb fluid flows  

Science Journals Connector (OSTI)

...different mathematical issues to invert a relationship in the form...crude current knowledge of snow rheology and avalanche physics as well...positioned on each side of 0 and a flat asymmetric tail extending over...Theoretical Monte Carlo Method Motion Rheology methods Snow chemistry Static...

2005-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

Difficulties in vector-parallel processing of Monte Carlo codes  

SciTech Connect

Experiences with vectorization of production-level Monte Carlo codes such as KENO-IV, MCNP, VIM, and MORSE have shown that it is difficult to attain high speedup ratios on vector processors because of indirect addressing, nests of conditional branches, short vector length, cache misses, and operations for realization of robustness and generality. A previous work has already shown that the first, second, and third difficulties can be resolved by using special computer hardware for vector processing of Monte Carlo codes. Here, the fourth and fifth difficulties are discussed in detail using the results for a vectorized version of the MORSE code. As for the fourth difficulty, it is shown that the cache miss-hit ratio affects execution times of the vectorized Monte Carlo codes and the ratio strongly depends on the number of the particles simultaneously tracked. As for the fifth difficulty, it is shown that remarkable speedup ratios are obtained by removing operations that are not essential to the specific problem being solved. These experiences have shown that if a production-level Monte Carlo code system had a capability to selectively construct source coding that complements the input data, then the resulting code could achieve much higher performance.

Higuchi, Kenji; Asai, Kiyoshi [Japan Atomic Energy Research Inst., Tokyo (Japan). Center for Promotion of Computational Science and Engineering; Hasegawa, Yukihiro [Research Organization for Information Science and Technology, Tokai, Ibaraki (Japan)

1997-09-01T23:59:59.000Z

242

Using random number generators in Monte Carlo simulations  

Science Journals Connector (OSTI)

One of the standard tests for Monte Carlo algorithms and for testing random number generators is the two-dimensional Ising model. We show that at least in the present case, where we study the two-state clock model, good random number generators can give inconsistent values for the critical temperature.

F. J. Resende and B. V. Costa

1998-10-01T23:59:59.000Z

243

Evolutionary Monte Carlo for protein folding simulations Faming Lianga)  

E-Print Network (OSTI)

Evolutionary Monte Carlo for protein folding simulations Faming Lianga) Department of Statistics to simulations of protein folding on simple lattice models, and to finding the ground state of a protein. In all structures in protein folding. The numerical results show that it is drastically superior to other methods

Liang, Faming

244

ccsd00003115, Coupled Electron Ion Monte Carlo Calculations of Atomic  

E-Print Network (OSTI)

ccsd­00003115, version 1 ­ 21 Oct 2004 Coupled Electron Ion Monte Carlo Calculations of Atomic state calculations where both electronic and protonic degrees of freedom are treated quantum­zero temperature with a QMC calculation for the electronic energies where the Born­Oppenheimer approximation helps

245

ENVIRONMENTAL MODELING: 1 APPLICATIONS: MONTE CARLO SENSITIVITY SIMULATIONS  

E-Print Network (OSTI)

SIMULATIONS TO THE PROBLEM OF AIR POLLUTION TRANSPORT 3 1.1 The Danish Eulerian Model #12;Chapter 1 APPLICATIONS: MONTE CARLO SENSITIVITY SIMULATIONS TO THE PROBLEM OF AIR POLLUTION of pollutants in a real-live scenario of air-pollution transport over Europe. First, the developed technique

Dimov, Ivan

246

Faster Fermions in the Tempered Hybrid Monte Carlo Algorithm  

E-Print Network (OSTI)

Tempering is used to change the quark mass while remaining in equilibrium between the trajectories of a standard hybrid Monte Carlo simulation of four flavours of staggered fermions. The algorithm is faster for small enough quark masses, and particularly so when more than one mass is required.

G. Boyd

1997-01-20T23:59:59.000Z

247

Monte Carlo sampling from the quantum state space. II  

E-Print Network (OSTI)

High-quality random samples of quantum states are needed for a variety of tasks in quantum information and quantum computation. Searching the high-dimensional quantum state space for a global maximum of an objective function with many local maxima or evaluating an integral over a region in the quantum state space are but two exemplary applications of many. These tasks can only be performed reliably and efficiently with Monte Carlo methods, which involve good samplings of the parameter space in accordance with the relevant target distribution. We show how the Markov-chain Monte Carlo method known as Hamiltonian Monte Carlo, or Hybrid Monte Carlo, can be adapted to this context. It is applicable when an efficient parameterization of the state space is available. The resulting random walk is entirely inside the physical parameter space, and the Hamiltonian dynamics enable us to take big steps, thereby avoiding strong correlations between successive sample points while enjoying a high acceptance rate. We use examples of single and double qubit measurements for illustration.

Yi-Lin Seah; Jiangwei Shang; Hui Khoon Ng; David John Nott; Berthold-Georg Englert

2014-07-29T23:59:59.000Z

248

Influence of Al doping on optical properties of CdS/PVA nanocomposites: Theory and experiment  

SciTech Connect

In the present work theoretical and experimental studies of aluminium doped cadmium sulphide polyvinyl alcohol (Al:CdS/PVA) nanocomposites have been carried out. Tetrahedral cluster AlCd{sub 9}S{sub 2}(SH){sub 18}]{sup 1?} has been encapsulated by small segments of polyvinyl alcohol (PVA) chains in order to simulate experimental environment of nanocomposites. Density functional theory (DFT) using local density approximation (LDA) functionals is employed to study the broadening of band gap upon ligation of nanoclusters. We have used in situ chemical route to synthesize nanocomposites. Optical band gap has been calculated from both experimental and theoretical approach.

Bala, Vaneeta, E-mail: vaneetabala@yahoo.com; Tripathi, S. K., E-mail: vaneetabala@yahoo.com; Kumar, Ranjan, E-mail: vaneetabala@yahoo.com [Department of Physics, Panjab University, Chandigarh (India)

2014-04-24T23:59:59.000Z

249

SciTech Connect: Fast Monte Carlo for radiation therapy: the...  

Office of Scientific and Technical Information (OSTI)

MEDICINE, BASIC STUDIES; RADIOTHERAPY; PLANNING; COMPUTER CALCULATIONS; RADIATION DOSE DISTRIBUTIONS; MONTE CARLO METHOD; THREE-DIMENSIONAL CALCULATIONS; COMPUTERIZED TOMOGRAPHY...

250

Interaction of the cesium cation with calix[4]arene-bis(t-octylbenzo-18-crown-6): Extraction and DFT study  

Science Journals Connector (OSTI)

From extraction experiments and ?-activity measurements, the extraction constant corresponding to the equilibrium Cs+ (aq)+I? (aq)+1 (org)?1?Cs+ (org)+I? (org) taking place in the two-phase water-phenyltrifluoromethyl sulfone (abbrev. FS 13) system (1=calix[4]arene-bis(t-octylbenzo-18-crown-6); aq=aqueous phase, org=FS 13 phase) was evaluated as logKex(1?Cs+,I?)=2.10.1. Further, the stability constant of the 1?Cs+ complex in FS 13 saturated with water was calculated for a temperature of 25C: log?org(1?Cs+)=9.90.1. Finally, by using quantum mechanical DFT calculations, the most probable structure of the cationic complex species 1?Cs+ was derived. In the resulting 1?Cs+ complex, the central cation Cs+ is bound by eight bond interactions to six oxygen atoms of the respective 18-crown-6 moiety and to two carbons of the corresponding two benzene rings of the parent ligand 1 via cation? interaction.

Emanuel Makrlk; Petr Toman; Petr Va?ura; Bruce A. Moyer

2013-01-01T23:59:59.000Z

251

Hydrologic data assimilation using particle Markov chain Monte Carlo simulation: Theory, concepts and applications  

E-Print Network (OSTI)

and applications Jasper A. Vrugt a,b, , Cajo J.F. ter Braak c , Cees G.H. Diks d , Gerrit Schoups e a Department

Vrugt, Jasper A.

252

An efficient Monte Carlo method for calculating ab initio transition state theory reaction rates in solution  

E-Print Network (OSTI)

an efficient method for sampling the relevant state space in condensed phase reactions. In the present method as in computational chemistry4,5 have made possible the study of most gas-phase and some condensed-phase reactions of explicit solvent molecules. The sampling algorithm uses a molecular mechanics guiding potential

Schofield, Jeremy

253

Monte Carol-based validation of neutronic methodology for EBR-II analyses  

SciTech Connect

The continuous-energy Monte Carlo code VIM (Ref. 1) has been validated extensively over the years against fast critical experiments and other neutronic analysis codes. A high degree of confidence in VIM for predicting reactor physics parameters has been firmly established. This paper presents a numerical validation of two conventional multigroup neutronic analysis codes, DIF3D (Ref. 4) and VARIANT (Ref. 5), against VIM for two Experimental Breeder Reactor II (EBR-II) core loadings in detailed three-dimensional hexagonal-z geometry. The DIF3D code is based on nodal diffusion theory, and it is used in calculations for day-today reactor operations, whereas the VARIANT code is based on nodal transport theory and is used with increasing frequency for specific applications. Both DIF3D and VARIANT rely on multigroup cross sections generated from ENDF/B-V by the ETOE-2/MC[sup 2]-II/SDX (Ref. 6) code package. Hence, this study also validates the multigroup cross-section processing methodology against the continuous-energy approach used in VIM.

Liaw, J.R.; Finck, P.J. (Argonne National Lab., IL (United States))

1993-01-01T23:59:59.000Z

254

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 this (more)

Danser, Mandelle Ann

2010-01-01T23:59:59.000Z

255

High density effective theory on the lattice  

E-Print Network (OSTI)

Long-range interactions in finite density QCD necessitate a non-perturbative approach in order to reliably map out the key features and spectrum of the QCD phase diagram. However, the complex nature of the fermion determinant in this sector prohibits the use of established Monte Carlo techniques that utilize importance sampling. Whilst significant progress has been made in the low density, high temperature region, this remains a considerable challenge at mid to high density. At large chemical potential, QCD can be approximated using high density effective theory which is free from the sign problem at leading order. We investigate the implementation of this theory on the lattice in conjunction with existing re-weighting techniques.

A. Dougall

2007-10-08T23:59:59.000Z

256

Load Balancing Of Parallel Monte Carlo Transport Calculations  

National Nuclear Security Administration (NNSA)

Load Balancing Of Parallel Load Balancing Of Parallel Monte Carlo Transport Calculations R.J. Procassini, M. J. O'Brien and J.M. Taylor Lawrence Livermore National Laboratory, P. O. Box 808, Livermore, CA 94551 The performance of parallel Monte Carlo transport calculations which use both spatial and particle parallelism is increased by dynamically assigning processors to the most worked domains. Since the particle work load varies over the course of the simulation, each cycle this algorithm determines if dynamic load balancing would speed up the calculation. If load balancing is required, a small number of particle communications are initiated in order to achieve load balance. This method has decreased the parallel run time by more than a factor of three for certain criticality

257

Beyond the Born-Oppenheimer approximation with quantum Monte Carlo  

E-Print Network (OSTI)

In this work we develop tools that enable the study of non-adiabatic effects with variational and diffusion Monte Carlo methods. We introduce a highly accurate wave function ansatz for electron-ion systems that can involve a combination of both fixed and quantum ions. We explicitly calculate the ground state energies of H$_{2}$, LiH, H$_{2}$O and FHF$^{-}$ using fixed-node quantum Monte Carlo with wave function nodes that explicitly depend on the ion positions. The obtained energies implicitly include the effects arising from quantum nuclei and electron-nucleus coupling. We compare our results to the best theoretical and experimental results available and find excellent agreement.

Tubman, Norm M; Hammes-Schiffer, Sharon; Ceperley, David M

2014-01-01T23:59:59.000Z

258

Monte Carlo simulation of gamma ray scanning gauge  

SciTech Connect

A gamma ray scanning gauge was simulated with Monte Carlo to study the properties of gamma scanning gauges and to resolve the counts coming from a {sup 235}U source from those coming from a contaminant ({sup 232}U) whose daughters emit high energy gamma rays. The simulation has been used to infer the amount of the {sup 232}U contaminant in a {sup 235}U source to select the best size for the NaI(Tl) detector crystal to minimize the effect of the contaminant. The results demonstrate that Monte Carlo simulation provides a systematic tool for designing a gauge with desired properties and for estimating properties of the gamma source from measured count rates.

Hartfield, G.L.; Freeman, L.B.; Dei, D.E.; Emert, C.J.; Glickstein, S.S.; Kahler, A.C.; Niedzwecki, P.F.

1990-12-31T23:59:59.000Z

259

Transport Theory for Shallow Water Propagation with Rough Boundaries  

SciTech Connect

At frequencies of about 1 kHz and higher, forward scattering from a rough sea surface (and/or a rough bottom) can strongly affect shallow water propagation and reverberation. The need exists for a fast, yet accurate method for modeling such propagation where multiple forward scattering occurs. A transport theory method based on mode coupling is described that yields the first and second moments of the field. This approach shows promise for accurately treating multiple forward scattering in one-way propagation. The method is presently formulated in two space dimensions, and Monte-Carlo rough surface PE simulations are used for assessing the accuracy of transport theory results.

Thorsos, Eric I.; Henyey, Frank S.; Elam, W. T.; Hefner, Brian T.; Reynolds, Stephen A.; Yang Jie [Applied Physics Laboratory, University of Washington, 1013 NE 40th Street, Seattle, WA 98105 (United States)

2010-09-06T23:59:59.000Z

260

The hybrid Monte Carlo Algorithm and the chiral transition  

SciTech Connect

In this talk the author describes tests of the Hybrid Monte Carlo Algorithm for QCD done in collaboration with Greg Kilcup and Stephen Sharpe. We find that the acceptance in the glubal Metropolis step for Staggered fermions can be tuned and kept large without having to make the step-size prohibitively small. We present results for the finite temperature transition on 4/sup 4/ and 4 x 6/sup 3/ lattices using this algorithm.

Gupta, R.

1987-01-01T23:59:59.000Z

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261

Topology and $\\theta$ dependence in finite temperature $G_2$ lattice gauge theory  

E-Print Network (OSTI)

In this work we study the topological properties of the $G_2$ lattice gauge theory by means of Monte Carlo simulations. We focus on the behaviour of topological quantities across the deconfinement transition and investigate observables related to the $\\theta$ dependence of the free energy. As in $SU(N)$ gauge theories, an abrupt change happens at deconfinement and an instanton gas behaviour rapidly sets in for $T>T_c$.

Bonati, Claudio

2015-01-01T23:59:59.000Z

262

Quantum Monte Carlo benchmark of exchange-correlation functionals for bulk water  

SciTech Connect

The accurate description of the thermodynamic and dynamical properties of liquid water from first-principles is a very important challenge to the theoretical community. This represents not only a critical test of the predictive capabilities of first-principles methods, but it will also shed light into the microscopic properties of such an important substance. Density Functional Theory, the main workhorse in the field of first-principles methods, has been so far unable to properly describe water and its unusual properties in the liquid state. With the recent introduction of exact exchange and an improved description of dispersion interaction, the possibility of an accurate description of the liquid is finally within reach. Unfortunately, there is still no way to systematically improve exchange-correlation functionals and the number of available functionals is very large. In this article we use highly accurate quantum Monte Carlo calculations to benchmark a selection of exchange-correlation functionals typically used in Density Functional Theory simulations of bulk water. This allows us to test the predictive capabilities of these functionals in water, giving us a way not only to choose optimal functionals for first-principles simulations, but also giving us a route for the optimization of the functionals for the system at hand. We compare and contrast the importance of different features of functionals, including the hybrid component, the vdW component, and their importance within different aspects of the PES. In addition, we test a recently introduce scheme that combines Density Functional Theory with Coupled Cluster Calculations through a Many-Body expansion of the energy, in order to correct the inaccuracies in the description of short range interactions in the liquid.

Morales, Miguel A [Lawrence Livermore National Laboratory (LLNL); Gergely, John [University of Illinois, Urbana-Champaign; McMinis, Jeremy [Lawrence Livermore National Laboratory (LLNL); McMahon, Jeffrey [University of Illinois, Urbana-Champaign; Kim, Jeongnim [ORNL; Ceperley, David M. [University of Illinois, Urbana-Champaign

2014-01-01T23:59:59.000Z

263

Development of multicomponent hybrid density functional theory with polarizable continuum model for the analysis of nuclear quantum effect and solvent effect on NMR chemical shift  

SciTech Connect

We have developed the multicomponent hybrid density functional theory [MC-(HF+DFT)] method with polarizable continuum model (PCM) for the analysis of molecular properties including both nuclear quantum effect and solvent effect. The chemical shifts and H/D isotope shifts of the picolinic acid N-oxide (PANO) molecule in chloroform and acetonitrile solvents are applied by B3LYP electron exchange-correlation functional for our MC-(HF+DFT) method with PCM (MC-B3LYP/PCM). Our MC-B3LYP/PCM results for PANO are in reasonable agreement with the corresponding experimental chemical shifts and isotope shifts. We further investigated the applicability of our method for acetylacetone in several solvents.

Kanematsu, Yusuke; Tachikawa, Masanori [Quantum Chemistry Division, Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027 (Japan)] [Quantum Chemistry Division, Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027 (Japan)

2014-04-28T23:59:59.000Z

264

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

SciTech Connect

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

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

2014-01-14T23:59:59.000Z

265

On the Calculation of Surface Tensions of n-Alkanes Using the Modified SAFT-BACK-DFT Approach  

Science Journals Connector (OSTI)

Density functional theory is combined with the modified SAFT-BACK EOS to investigate liquidvapor interfaces...n-alkanes. We evaluate the temperature dependence of the interfacial width and the surface tension. D...

Ali Maghari; Mohsen Najafi

2010-01-01T23:59:59.000Z

266

Report on International Collaboration Involving the FE Heater and HG-A Tests at Mont Terri  

SciTech Connect

Nuclear waste programs outside of the US have focused on different host rock types for geological disposal of high-level radioactive waste. Several countries, including France, Switzerland, Belgium, and Japan are exploring the possibility of waste disposal in shale and other clay-rich rock that fall within the general classification of argillaceous rock. This rock type is also of interest for the US program because the US has extensive sedimentary basins containing large deposits of argillaceous rock. LBNL, as part of the DOE-NE Used Fuel Disposition Campaign, is collaborating on some of the underground research laboratory (URL) activities at the Mont Terri URL near Saint-Ursanne, Switzerland. The Mont Terri project, which began in 1995, has developed a URL at a depth of about 300 m in a stiff clay formation called the Opalinus Clay. Our current collaboration efforts include two test modeling activities for the FE heater test and the HG-A leak-off test. This report documents results concerning our current modeling of these field tests. The overall objectives of these activities include an improved understanding of and advanced relevant modeling capabilities for EDZ evolution in clay repositories and the associated coupled processes, and to develop a technical basis for the maximum allowable temperature for a clay repository. The R&D activities documented in this report are part of the work package of natural system evaluation and tool development that directly supports the following Used Fuel Disposition Campaign (UFDC) objectives: ? Develop a fundamental understanding of disposal-system performance in a range of environments for potential wastes that could arise from future nuclear-fuel-cycle alternatives through theory, simulation, testing, and experimentation. ? Develop a computational modeling capability for the performance of storage and disposal options for a range of fuel-cycle alternatives, evolving from generic models to more robust models of performance assessment. For the purpose of validating modeling capabilities for thermal-hydro-mechanical (THM) processes, we developed a suite of simulation models for the planned full-scale FE Experiment to be conducted in the Mont Terri URL, including a full three-dimensional model that will be used for direct comparison to experimental data once available. We performed for the first time a THM analysis involving the Barcelona Basic Model (BBM) in a full three-dimensional field setting for modeling the geomechanical behavior of the buffer material and its interaction with the argillaceous host rock. We have simulated a well defined benchmark that will be used for codeto- code verification against modeling results from other international modeling teams. The analysis highlights the complex coupled geomechanical behavior in the buffer and its interaction with the surrounding rock and the importance of a well characterized buffer material in terms of THM properties. A new geomechanical fracture-damage model, TOUGH-RBSN, was applied to investigate damage behavior in the ongoing HG-A test at Mont Terri URL. Two model modifications have been implemented so that the Rigid-Body-Spring-Network (RBSN) model can be used for analysis of fracturing around the HG-A microtunnel. These modifications are (1) a methodology to compute fracture generation under compressive stress conditions and (2) a method to represent anisotropic elastic and strength properties. The method for computing fracture generation under compressive load produces results that roughly follow trends expected for homogeneous and layered systems. Anisotropic properties for the bulk rock were represented in the RBSN model using layered heterogeneity and gave bulk material responses in line with expectations. These model improvements were implemented for an initial model of fracture damage at the HG-A test. While the HG-A test model results show some similarities with the test observations, differences between the model results and observations remain.

Houseworth, Jim; Rutqvist, Jonny; Asahina, Daisuke; Chen, Fei; Vilarrasa, Victor; Liu, Hui-Hai; Birkholzer, Jens

2013-11-06T23:59:59.000Z

267

MiniDFT  

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

for bulk silicon, using the LDA functional and a 30 Ry plane-wave cutoff. mpirun -np 8 .minidft -in Si333.in > Si333.out The second test is a 2 x 2 x 2 super-cell for TiO2,...

268

MOCABA: a general Monte Carlo-Bayes procedure for improved predictions of integral functions of nuclear data  

E-Print Network (OSTI)

MOCABA is a combination of Monte Carlo sampling and Bayesian updating algorithms for the prediction of integral functions of nuclear data, such as reactor power distributions or neutron multiplication factors. Similarly to the established Generalized Linear Least Squares (GLLS) methodology, MOCABA offers the capability to utilize integral experimental data to reduce the prior uncertainty of integral observables. The MOCABA approach, however, does not involve any series expansions and, therefore, does not suffer from the breakdown of first-order perturbation theory for large nuclear data uncertainties. This is related to the fact that, in contrast to the GLLS method, the updating mechanism within MOCABA is applied directly to the integral observables without having to "adjust" any nuclear data. A central part of MOCABA is the nuclear data Monte Carlo program NUDUNA, which performs random sampling of nuclear data evaluations according to their covariance information and converts them into libraries for transport code systems like MCNP or SCALE. What is special about MOCABA is that it can be applied to any integral function of nuclear data, and any integral measurement can be taken into account to improve the prediction of an integral observable of interest. In this paper we present two example applications of the MOCABA framework: the prediction of the neutron multiplication factor of a water-moderated PWR fuel assembly based on 21 criticality safety benchmark experiments and the prediction of the power distribution within a toy model reactor containing 100 fuel assemblies.

Axel Hoefer; Oliver Buss; Maik Hennebach; Michael Schmid; Dieter Porsch

2014-11-12T23:59:59.000Z

269

Properties of Reactive Oxygen Species by Quantum Monte Carlo  

E-Print Network (OSTI)

The electronic properties of the oxygen molecule, in its singlet and triplet states, and of many small oxygen-containing radicals and anions have important roles in different fields of Chemistry, Biology and Atmospheric Science. Nevertheless, the electronic structure of such species is a challenge for ab-initio computational approaches because of the difficulties to correctly describe the statical and dynamical correlation effects in presence of one or more unpaired electrons. Only the highest-level quantum chemical approaches can yield reliable characterizations of their molecular properties, such as binding energies, equilibrium structures, molecular vibrations, charge distribution and polarizabilities. In this work we use the variational Monte Carlo (VMC) and the lattice regularized Monte Carlo (LRDMC) methods to investigate the equilibrium geometries and molecular properties of oxygen and oxygen reactive species. Quantum Monte Carlo methods are used in combination with the Jastrow Antisymmetrized Geminal Power (JAGP) wave function ansatz, which has been recently shown to effectively describe the statical and dynamical correlation of different molecular systems. In particular we have studied the oxygen molecule, the superoxide anion, the nitric oxide radical and anion, the hydroxyl and hydroperoxyl radicals and their corresponding anions, and the hydrotrioxyl radical. Overall, the methodology was able to correctly describe the geometrical and electronic properties of these systems, through compact but fully-optimised basis sets and with a computational cost which scales as $N^3-N^4$, where $N$ is the number of electrons. This work is therefore opening the way to the accurate study of the energetics and of the reactivity of large and complex oxygen species by first principles.

Andrea Zen; Bernhardt L. Trout; Leonardo Guidoni

2014-03-11T23:59:59.000Z

270

Monte Carlo Tools for charged Higgs boson production  

E-Print Network (OSTI)

In this short review we discuss two implementations of the charged Higgs boson production process in association with a top quark in Monte Carlo event generators at next-to-leading order in QCD. We introduce the MC@NLO and the POWHEG method of matching next-to-leading order matrix elements with parton showers and compare both methods analyzing the charged Higgs boson production process in association with a top quark. We shortly discuss the case of a light charged Higgs boson where the associated charged Higgs production interferes with the charged Higgs production via t tbar-production and subsequent decay of the top quark.

Kovarik, K

2014-01-01T23:59:59.000Z

271

Protein folding bottlenecks: A lattice Monte Carlo simulation  

Science Journals Connector (OSTI)

Results of Monte Carlo simulations of folding of a model protein, which is a freely joined 27-monomer chain on a simple cubic lattice with nearest-neighbor interactions, are reported. All compact self-avoiding conformations on this chain have been enumerated, and the conformation (native) corresponding to the global minimum of energy is known for each sequence. Only one out of thirty sequences folds and finds the global minimum. For this sequence, the folding process has a two-stage character, with a rapid noncooperative compactization followed by a slower transition over a free-energy barrier to the global minimum. The evolutionary implications of the results are discussed.

E. Shakhnovich; G. Farztdinov; A. M. Gutin; M. Karplus

1991-09-16T23:59:59.000Z

272

Monte Carlo Tools for charged Higgs boson production  

E-Print Network (OSTI)

In this short review we discuss two implementations of the charged Higgs boson production process in association with a top quark in Monte Carlo event generators at next-to-leading order in QCD. We introduce the MC@NLO and the POWHEG method of matching next-to-leading order matrix elements with parton showers and compare both methods analyzing the charged Higgs boson production process in association with a top quark. We shortly discuss the case of a light charged Higgs boson where the associated charged Higgs production interferes with the charged Higgs production via t tbar-production and subsequent decay of the top quark.

K. Kovarik

2014-12-18T23:59:59.000Z

273

GPU accelerated Monte Carlo simulations of lattice spin models  

E-Print Network (OSTI)

We consider Monte Carlo simulations of classical spin models of statistical mechanics using the massively parallel architecture provided by graphics processing units (GPUs). We discuss simulations of models with discrete and continuous variables, and using an array of algorithms ranging from single-spin flip Metropolis updates over cluster algorithms to multicanonical and Wang-Landau techniques to judge the scope and limitations of GPU accelerated computation in this field. For most simulations discussed, we find significant speed-ups by two to three orders of magnitude as compared to single-threaded CPU implementations.

Martin Weigel; Taras Yavors'kii

2011-07-27T23:59:59.000Z

274

Temperature and density extrapolations in canonical ensemble Monte Carlo simulations  

E-Print Network (OSTI)

We show how to use the multiple histogram method to combine canonical ensemble Monte Carlo simulations made at different temperatures and densities. The method can be applied to study systems of particles with arbitrary interaction potential and to compute the thermodynamic properties over a range of temperatures and densities. The calculation of the Helmholtz free energy relative to some thermodynamic reference state enables us to study phase coexistence properties. We test the method on the Lennard-Jones fluids for which many results are available.

A. L. Ferreira; M. A. Barroso

1999-06-14T23:59:59.000Z

275

Formalizing Synthetic Domain Theory  

Science Journals Connector (OSTI)

Synthetic Domain Theory (SDT) is a constructive variant of Domain Theory where all functions are continuous following Dana Scotts idea of domains as sets. Recently there have been suggested more abstract axiomatizations encompassing ... Keywords: LCF, domain theory, formal verification, programming logics, synthetic domain theory, type theory

Bernhard Reus

1999-11-01T23:59:59.000Z

276

Monte Carlo Fundamentals E B. BROWN and T M. S N  

Office of Scientific and Technical Information (OSTI)

e 32-64 X - Parallel & vector processing are now "routine" & necessary for high-performance computing I661 Vector & Parallel Monte Carlo - Introduction .. .. Characterize...

277

Investigation of Protein Folding by Using Combined Method of Molecular Dynamics and Monte Carlo Simulations.  

E-Print Network (OSTI)

??We used the combination of molecular dynamics and Monte Carlo method to investigate protein folding problems. The environments of proteins are very big, and often (more)

Liao, Jun-min

2006-01-01T23:59:59.000Z

278

Protein folding and phylogenetic tree reconstruction using stochastic approximation Monte Carlo.  

E-Print Network (OSTI)

??Recently, the stochastic approximation Monte Carlo algorithm has been proposed by Liang et al. (2005) as a general-purpose stochastic optimization and simulation algorithm. An annealing (more)

Cheon, Sooyoung

2007-01-01T23:59:59.000Z

279

Doppler effect's contribution to ultrasonic modulation of multiply scattered coherent light: Monte Carlo modeling  

Science Journals Connector (OSTI)

Modulation of light by ultrasound in turbid media is investigated by modified public domain software based on the Monte Carlo algorithm. Apart from the recognized modulation...

Elazar, Jovan M; Steshenko, Oleg

2008-01-01T23:59:59.000Z

280

Accelerating Markov chain Monte Carlo simulation by differential evolution with self-adaptive randomized subspace sampling  

SciTech Connect

Markov chain Monte Carlo (MCMC) methods have found widespread use in many fields of study to estimate the average properties of complex systems, and for posterior inference in a Bayesian framework. Existing theory and experiments prove convergence of well constructed MCMC schemes to the appropriate limiting distribution under a variety of different conditions. In practice, however this convergence is often observed to be disturbingly slow. This is frequently caused by an inappropriate selection of the proposal distribution used to generate trial moves in the Markov Chain. Here we show that significant improvements to the efficiency of MCMC simulation can be made by using a self-adaptive Differential Evolution learning strategy within a population-based evolutionary framework. This scheme, entitled DiffeRential Evolution Adaptive Metropolis or DREAM, runs multiple different chains simultaneously for global exploration, and automatically tunes the scale and orientation of the proposal distribution in randomized subspaces during the search. Ergodicity of the algorithm is proved, and various examples involving nonlinearity, high-dimensionality, and multimodality show that DREAM is generally superior to other adaptive MCMC sampling approaches. The DREAM scheme significantly enhances the applicability of MCMC simulation to complex, multi-modal search problems.

Vrugt, Jasper A [Los Alamos National Laboratory; Hyman, James M [Los Alamos National Laboratory; Robinson, Bruce A [Los Alamos National Laboratory; Higdon, Dave [Los Alamos National Laboratory; Ter Braak, Cajo J F [NETHERLANDS; Diks, Cees G H [UNIV OF AMSTERDAM

2008-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

Generation of an Covariance Matrix by Monte Carlo Sampling of the Phonon Frequency Spectrum  

Science Journals Connector (OSTI)

Abstract Formats and procedures are currently established for representing covariances in the ENDF library for many reaction types. However, no standard exists for thermal neutron inelastic scattering cross section covariance data. These cross sections depend on the material's dynamic structure factor, or S ( ? , ? ) . The structure factor is a function of the phonon density of states (DOS). Published ENDF thermal neutron scattering libraries are commonly produced by modeling codes, such as NJOY/LEAPR, which utilize the DOS as the fundamental input and directly output the S ( ? , ? ) matrix. To calculate covariances for the computed S ( ? , ? ) data, information about uncertainties in the DOS is required. The DOS may be viewed as a probability distribution function of available atomic vibrational energy states in a solid. In this work, density functional theory and lattice dynamics in the harmonic approximation were used to simulate the structure of silicon dioxide (?-quartz) to produce the DOS. A range for the variation in the partial DOS for silicon in ?-quartz was established based on limits of variation in the crystal lattice parameters. Uncertainty in an experimentally derived DOS may also be incorporated with the same methodology. A description of possible variation in the DOS allowed Monte Carlo generation of a set of perturbed DOS spectra which were sampled to produce the S ( ? , ? ) covariance matrix for scattering with silicon in ?-quartz. With appropriate sensitivity matrices, it is shown that the S ( ? , ? ) covariance matrix can be propagated to generate covariance matrices for integrated cross sections, secondary energy distributions, and coupled energy-angle distributions.

J.C. Holmes; A.I. Hawari

2014-01-01T23:59:59.000Z

282

Retrodictive derivation of the radical-ion-pair master equation and Monte-Carlo simulation with single-molecule quantum trajectories  

E-Print Network (OSTI)

Radical-ion-pair reactions, central in photosynthesis and the avian magnetic compass mechanism, have recently shown to be a paradigm system for applying quantum information science in a biochemical setting. The fundamental quantum master equation describing radical-ion-pair reactions is still under debate. We here use quantum retrodiction to produce a rigorous refinement of the theory put forward in Phys. Rev. E {\\bf 83}, 056118 (2011). We also provide a rigorous analysis of the measure of singlet-triplet coherence required for deriving the radical-pair master equation. A Monte-Carlo simulation with single-molecule quantum trajectories supports the self-consistency of our approach.

Kritsotakis, M

2014-01-01T23:59:59.000Z

283

Monte Carlo Domain Decomposition for Robust Nuclear Reactor Analyses  

Science Journals Connector (OSTI)

Abstract Monte Carlo (MC) neutral particle transport codes are considered the gold-standard for nuclear simulations, but they cannot be robustly applied to high-fidelity nuclear reactor analysis without accommodating several terabytes of materials and tally data. While this is not a large amount of aggregate data for a typical high performance computer, MC methods are only embarrassingly parallel when the key data structures are replicated for each processing element, an approach which is likely infeasible on future machines. The present work explores the use of spatial domain decomposition to make full-scale nuclear reactor simulations tractable with Monte Carlo methods, presenting a simple implementation in a production-scale code. Good performance is achieved for mesh-tallies of up to 2.39TB distributed across 512 compute nodes while running a full-core reactor benchmark on the Mira Blue Gene/Q supercomputer at the Argonne National Laboratory. In addition, the effects of load imbalances are explored with an updated performance model that is empirically validated against observed timing results. Several load balancing techniques are also implemented to demonstrate that imbalances can be largely mitigated, including a new and efficient way to distribute extra compute resources across coarse domain meshes.

Nicholas Horelik; Andrew Siegel; Benoit Forget; Kord Smith

2014-01-01T23:59:59.000Z

284

Improved criticality convergence via a modified Monte Carlo iteration method  

SciTech Connect

Nuclear criticality calculations with Monte Carlo codes are normally done using a power iteration method to obtain the dominant eigenfunction and eigenvalue. In the last few years it has been shown that the power iteration method can be modified to obtain the first two eigenfunctions. This modified power iteration method directly subtracts out the second eigenfunction and thus only powers out the third and higher eigenfunctions. The result is a convergence rate to the dominant eigenfunction being |k{sub 3}|/k{sub 1} instead of |k{sub 2}|/k{sub 1}. One difficulty is that the second eigenfunction contains particles of both positive and negative weights that must sum somehow to maintain the second eigenfunction. Summing negative and positive weights can be done using point detector mechanics, but this sometimes can be quite slow. We show that an approximate cancellation scheme is sufficient to accelerate the convergence to the dominant eigenfunction. A second difficulty is that for some problems the Monte Carlo implementation of the modified power method has some stability problems. We also show that a simple method deals with this in an effective, but ad hoc manner.

Booth, Thomas E [Los Alamos National Laboratory; Gubernatis, James E [Los Alamos National Laboratory

2009-01-01T23:59:59.000Z

285

Monte Carlo Simulation of Massive Absorbers for Cryogenic Calorimeters  

SciTech Connect

There is a growing interest in cryogenic calorimeters with macroscopic absorbers for applications such as dark matter direct detection and rare event search experiments. The physics of energy transport in calorimeters with absorber masses exceeding several grams is made complex by the anisotropic nature of the absorber crystals as well as the changing mean free paths as phonons decay to progressively lower energies. We present a Monte Carlo model capable of simulating anisotropic phonon transport in cryogenic crystals. We have initiated the validation process and discuss the level of agreement between our simulation and experimental results reported in the literature, focusing on heat pulse propagation in germanium. The simulation framework is implemented using Geant4, a toolkit originally developed for high-energy physics Monte Carlo simulations. Geant4 has also been used for nuclear and accelerator physics, and applications in medical and space sciences. We believe that our current work may open up new avenues for applications in material science and condensed matter physics.

Brandt, D.; Asai, M.; Brink, P.L.; /SLAC; Cabrera, B.; /Stanford U.; Silva, E.do Couto e; Kelsey, M.; /SLAC; Leman, S.W.; McArthy, K.; /MIT; Resch, R.; Wright, D.; /SLAC; Figueroa-Feliciano, E.; /MIT

2012-06-12T23:59:59.000Z

286

Monte Carlo source convergence and the Whitesides problem  

SciTech Connect

The issue of fission source convergence in Monte Carlo eigenvalue calculations is of interest because of the potential consequences of erroneous criticality safety calculations. In this work, the authors compare two different techniques to improve the source convergence behavior of standard Monte Carlo calculations applied to challenging source convergence problems. The first method, super-history powering, attempts to avoid discarding important fission sites between generations by delaying stochastic sampling of the fission site bank until after several generations of multiplication. The second method, stratified sampling of the fission site bank, explicitly keeps the important sites even if conventional sampling would have eliminated them. The test problems are variants of Whitesides' Criticality of the World problem in which the fission site phase space was intentionally undersampled in order to induce marginally intolerable variability in local fission site populations. Three variants of the problem were studied, each with a different degree of coupling between fissionable pieces. Both the superhistory powering method and the stratified sampling method were shown to improve convergence behavior, although stratified sampling is more robust for the extreme case of no coupling. Neither algorithm completely eliminates the loss of the most important fissionable piece, and if coupling is absent, the lost piece cannot be recovered unless its sites from earlier generations have been retained. Finally, criteria for measuring source convergence reliability are proposed and applied to the test problems.

Blomquist, R. N.

2000-02-25T23:59:59.000Z

287

Stratified source-sampling techniques for Monte Carlo eigenvalue analysis.  

SciTech Connect

In 1995, at a conference on criticality safety, a special session was devoted to the Monte Carlo ''Eigenvalue of the World'' problem. Argonne presented a paper, at that session, in which the anomalies originally observed in that problem were reproduced in a much simplified model-problem configuration, and removed by a version of stratified source-sampling. In this paper, stratified source-sampling techniques are generalized and applied to three different Eigenvalue of the World configurations which take into account real-world statistical noise sources not included in the model problem, but which differ in the amount of neutronic coupling among the constituents of each configuration. It is concluded that, in Monte Carlo eigenvalue analysis of loosely-coupled arrays, the use of stratified source-sampling reduces the probability of encountering an anomalous result over that if conventional source-sampling methods are used. However, this gain in reliability is substantially less than that observed in the model-problem results.

Mohamed, A.

1998-07-10T23:59:59.000Z

288

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

SciTech Connect

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

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

2013-11-15T23:59:59.000Z

289

Dark Matter Theory  

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

Dark Matter Theory Dark Matter Theory Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers Get Expertise Rajan Gupta (505) 667-7664 Email Bruce Carlsten (505)...

290

Quantum Field Theory & Gravity  

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

Field Theory & Gravity Quantum Field Theory & Gravity Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers Get Expertise Rajan Gupta (505) 667-7664 Email...

291

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

Science Journals Connector (OSTI)

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

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

2010-08-03T23:59:59.000Z

292

Monte Carlo simulations of free chains in end-linked polymer networks Nisha Gilra  

E-Print Network (OSTI)

be significantly altered.1­3 This occurs because the micro- scopic structure including network defectsMonte Carlo simulations of free chains in end-linked polymer networks Nisha Gilra School networks prepared in the presence of inert linear chain solvent were investigated with Monte Carlo

293

Self-assembly of surfactants in a supercritical solvent from lattice Monte Carlo simulations  

E-Print Network (OSTI)

Self-assembly of surfactants in a supercritical solvent from lattice Monte Carlo simulations Martin self-assembly of surfactants in a supercritical solvent by large-scale Monte Carlo simulations. CarbonCO2.3 Surfactant molecules used in scCO2 have two mutually incompatible components: a CO2-philic tail

Lisal, Martin

294

Effect of different genotypes of Phytophthora infestans (Mont. de Bary) and temperature on tuber disease development  

E-Print Network (OSTI)

Effect of different genotypes of Phytophthora infestans (Mont. de Bary) and temperature on tuber Lines (ABL) of potato with different genotypes of the potato late blight pathogen (Phytophthora Phytophthora infestans (Mont. de Bary) is the greatest threat to the potato crop, accounting for significant

Douches, David S.

295

Quantum Monte Carlo study of a disordered 2D Josephson junction array  

E-Print Network (OSTI)

Quantum Monte Carlo study of a disordered 2D Josephson junction array W.A. Al-Saidi *, D. Stroud reserved. PACS: 74.25.Dw; 05.30.Jp; 85.25.Cp Keywords: Josephson junctions; Quantum Monte Carlo; Disorder 1. Introduction A Josephson junction array (JJA) consists of a collection of superconducting islands connected

Stroud, David

296

Optimization of quantum Monte Carlo wave functions using analytical energy derivatives  

E-Print Network (OSTI)

Optimization of quantum Monte Carlo wave functions using analytical energy derivatives Xi Lin of the local energy, H^ / .5 If the wave function were the exact ground eigenstate, the local energy would November 1999 An algorithm is proposed to optimize quantum Monte Carlo QMC wave functions based on Newton

Lin, Xi

297

Status of the VIM Monte Carlo neutron/photon transport code.  

SciTech Connect

Recent work on the VIM Monte Carlo code has aimed at advanced data libraries, ease of use, availability to users outside of Argonne, and fission source convergence algorithms in eigenvalue calculations. VIM is one of three US Monte Carlo codes in the USDOE Nuclear Criticality Safety Program, and is available through RSICC and the NEA Data Bank.

Blomquist, R.N.

2002-01-22T23:59:59.000Z

298

Overview of Bayesian sequential Monte Carlo methods for group and extended object tracking  

Science Journals Connector (OSTI)

This work presents the current state-of-the-art in techniques for tracking a number of objects moving in a coordinated and interacting fashion. Groups are structured objects characterized with particular motion patterns. The group can be comprised of ... Keywords: Group and extended object tracking, Markov chain Monte Carlo methods, Metropolis Hastings, Nonlinear filtering, Reasoning over time, Sequential Monte Carlo methods

Lyudmila Mihaylova; Avishy Y. Carmi; Franois Septier; Amadou Gning; Sze Kim Pang; Simon Godsill

2014-02-01T23:59:59.000Z

299

Melting of Iron under Earth's Core Conditions from Diffusion Monte Carlo Free Energy Calculations  

E-Print Network (OSTI)

Melting of Iron under Earth's Core Conditions from Diffusion Monte Carlo Free Energy Calculations Ester Sola1 and Dario Alfe`1,2 1 Thomas Young Centre@UCL, and Department of Earth Sciences, UCL, Gower. Here we used quantum Monte Carlo techniques to compute the free energies of solid and liquid iron

Alfè, Dario

300

Fluid simulations with localized boltzmann upscaling by direct simulation Monte-Carlo  

Science Journals Connector (OSTI)

In the present work, we present a novel numerical algorithm to couple the Direct Simulation Monte Carlo method (DSMC) for the solution of the Boltzmann equation with a finite volume like method for the solution of the Euler equations. Recently we presented ... Keywords: Boltzmann equation, Kinetic-fluid coupling, Monte Carlo methods, Multiscale problems

Pierre Degond; Giacomo Dimarco

2012-03-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

Using Monte-Carlo simulation for risk assessment: application to occupational exposure during remediation works  

Science Journals Connector (OSTI)

The aim of this study was to apply the Monte-Carlo techniques to develop a probabilistic risk assessment. The risk resulting from the occupational exposure during the remediation activities of a uranium tailings disposal, in an abandoned uranium mining ... Keywords: Monte Carlo simulation, occupational exposure, risk and dose assessment, uranium tailings disposal

M. L. Dinis; A. Fiza

2010-08-01T23:59:59.000Z

302

Entanglement Distillation Protocols and Number Theory  

E-Print Network (OSTI)

We show that the analysis of entanglement distillation protocols for qudits of arbitrary dimension $D$ benefits from applying basic concepts from number theory, since the set $\\zdn$ associated to Bell diagonal states is a module rather than a vector space. We find that a partition of $\\zdn$ into divisor classes characterizes the invariant properties of mixed Bell diagonal states under local permutations. We construct a very general class of recursion protocols by means of unitary operations implementing these local permutations. We study these distillation protocols depending on whether we use twirling operations in the intermediate steps or not, and we study them both analitically and numerically with Monte Carlo methods. In the absence of twirling operations, we construct extensions of the quantum privacy algorithms valid for secure communications with qudits of any dimension $D$. When $D$ is a prime number, we show that distillation protocols are optimal both qualitatively and quantitatively.

H. Bombin; M. A. Martin-Delgado

2005-03-01T23:59:59.000Z

303

Entanglement distillation protocols and number theory  

SciTech Connect

We show that the analysis of entanglement distillation protocols for qudits of arbitrary dimension D benefits from applying basic concepts from number theory, since the set Z{sub D}{sup n} associated with Bell diagonal states is a module rather than a vector space. We find that a partition of Z{sub D}{sup n} into divisor classes characterizes the invariant properties of mixed Bell diagonal states under local permutations. We construct a very general class of recursion protocols by means of unitary operations implementing these local permutations. We study these distillation protocols depending on whether we use twirling operations in the intermediate steps or not, and we study them both analytically and numerically with Monte Carlo methods. In the absence of twirling operations, we construct extensions of the quantum privacy algorithms valid for secure communications with qudits of any dimension D. When D is a prime number, we show that distillation protocols are optimal both qualitatively and quantitatively.

Bombin, H.; Martin-Delgado, M.A. [Departamento de Fisica Teorica I, Universidad Complutense, 28040 Madrid (Spain)

2005-09-15T23:59:59.000Z

304

Markov-Chain Monte Carlo Methods for Simulations of Biomolecules  

E-Print Network (OSTI)

The computer revolution has been driven by a sustained increase of computational speed of approximately one order of magnitude (a factor of ten) every five years since about 1950. In natural sciences this has led to a continuous increase of the importance of computer simulations. Major enabling techniques are Markov Chain Monte Carlo (MCMC) and Molecular Dynamics (MD) simulations. This article deals with the MCMC approach. First basic simulation techniques, as well as methods for their statistical analysis are reviewed. Afterwards the focus is on generalized ensembles and biased updating, two advanced techniques, which are of relevance for simulations of biomolecules, or are expected to become relevant with that respect. In particular we consider the multicanonical ensemble and the replica exchange method (also known as parallel tempering or method of multiple Markov chains).

Bernd A. Berg

2007-09-04T23:59:59.000Z

305

Shell model Monte Carlo investigation of rare earth nuclei  

Science Journals Connector (OSTI)

We utilize the shell model Monte Carlo method to study the structure of rare earth nuclei. This work demonstrates the first systematic full oscillator shell with intruder calculations in such heavy nuclei. Exact solutions of a pairing plus quadrupole Hamiltonian are compared with the static path approximation in several dysprosium isotopes from A=152 to 162, including the odd mass A=153. Some comparisons are also made with Hartree-Fock-Bogoliubov results from Baranger and Kumar. Basic properties of these nuclei at various temperatures and spin are explored. These include energy, deformation, moments of inertia, pairing channel strengths, band crossing, and evolution of shell model occupation numbers. Exact level densities are also calculated and, in the case of 162Dy, compared with experimental data.

J. A. White; S. E. Koonin; D. J. Dean

2000-02-14T23:59:59.000Z

306

Hydrogen molecule ion: Path-integral Monte Carlo approach  

SciTech Connect

The path-integral Monte Carlo approach is used to study the coupled quantum dynamics of the electron and nuclei in hydrogen molecule ion. The coupling effects are demonstrated by comparing differences in adiabatic Born-Oppenheimer and nonadiabatic simulations, and inspecting projections of the full three-body dynamics onto the adiabatic Born-Oppenheimer approximation. Coupling of the electron and nuclear quantum dynamics is clearly seen. The nuclear pair correlation function is found to broaden by 0.040a{sub 0}, and the average bond length is larger by 0.056a{sub 0}. Also, a nonadiabatic correction to the binding energy is found. The electronic distribution is affected less than the nuclear one upon inclusion of nonadiabatic effects.

Kylaenpaeae, I.; Leino, M.; Rantala, T. T. [Institute of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere (Finland)

2007-11-15T23:59:59.000Z

307

Monte Carlo sampling of negative-temperature plasma states  

Science Journals Connector (OSTI)

A Monte Carlo procedure is used to generate N-particle configurations compatible with two-temperature canonical equilibria in two dimensions, with particular attention to nonlinear plasma gyrokinetics. An unusual feature of the problem is the importance of a nontrivial probability density function P0(?), the probability of realizing a set ? of Fourier amplitudes associated with an ensemble of uniformly distributed, independent particles. This quantity arises because the equilibrium distribution is specified in terms of ?, whereas the sampling procedure naturally produces particle states ?; ? and ? are related via a gyrokinetic Poisson equation, highly nonlinear in its dependence on ?. Expansion and asymptotic methods are used to calculate P0(?) analytically; excellent agreement is found between the large-N asymptotic result and a direct numerical calculation. The algorithm is tested by successfully generating a variety of states of both positive and negative temperature, including ones in which either the longest- or shortest-wavelength modes are excited to relatively large amplitudes.

John A. Krommes and Sharadini Rath

2003-06-09T23:59:59.000Z

308

Monte Carlo modeling of spallation targets containing uranium and americium  

E-Print Network (OSTI)

Neutron production and transport in spallation targets made of uranium and americium are studied with a Geant4-based code MCADS (Monte Carlo model for Accelerator Driven Systems). A good agreement of MCADS results with experimental data on neutron- and proton-induced reactions on $^{241}$Am and $^{243}$Am nuclei allows to use this model for simulations with extended Am targets. Several geometry options and material compositions (U, U+Am, Am, Am$_2$O$_3$) are considered for spallation targets to be used in Accelerator Driven Systems. It was demonstrated that MCADS model can be reliably used for calculating critical masses of fissile materials. All considered options operate as deep subcritical targets having neutron multiplication factor of $k \\sim 0.5$. It is found that more than 4 kg of Am can be burned in one spallation target during the first year of operation.

Malyshkin, Yury; Mishustin, Igor; Greiner, Walter

2013-01-01T23:59:59.000Z

309

Monte Carlo modeling of spallation targets containing uranium and americium  

E-Print Network (OSTI)

Neutron production and transport in spallation targets made of uranium and americium are studied with a Geant4-based code MCADS (Monte Carlo model for Accelerator Driven Systems). A good agreement of MCADS results with experimental data on neutron- and proton-induced reactions on $^{241}$Am and $^{243}$Am nuclei allows to use this model for simulations with extended Am targets. It was demonstrated that MCADS model can be used for calculating the values of critical mass for $^{233,235}$U, $^{237}$Np, $^{239}$Pu and $^{241}$Am. Several geometry options and material compositions (U, U+Am, Am, Am$_2$O$_3$) are considered for spallation targets to be used in Accelerator Driven Systems. All considered options operate as deep subcritical targets having neutron multiplication factor of $k \\sim 0.5$. It is found that more than 4 kg of Am can be burned in one spallation target during the first year of operation.

Yury Malyshkin; Igor Pshenichnov; Igor Mishustin; Walter Greiner

2014-05-02T23:59:59.000Z

310

Lifting -- A Nonreversible Markov Chain Monte Carlo Algorithm  

E-Print Network (OSTI)

Markov Chain Monte Carlo algorithms are invaluable numerical tools for exploring stationary properties of physical systems -- in particular when direct sampling is not feasible. They are widely used in many areas of physics and other sciences. Most common implementations are done with reversible Markov chains -- Markov chains that obey detailed balance. Reversible Markov chains are sufficient in order for the physical system to relax to equilibrium, but it is not necessary. Here we review several works that use "lifted" or nonreversible Markov chains, which violate detailed balance, yet still converge to the correct stationary distribution (they obey the global balance condition). In certain cases, the acceleration is a square root improvement at most, to the conventional reversible Markov chains. We introduce the problem in a way that makes it accessible to non-specialists. We illustrate the method on several representative examples (sampling on a ring, sampling on a torus, an Ising model on a complete graph...

Vucelja, Marija

2015-01-01T23:59:59.000Z

311

MONTE-CARLO BURNUP CALCULATION UNCERTAINTY QUANTIFICATION AND PROPAGATION DETERMINATION  

SciTech Connect

MONTEBURNS is a Monte-Carlo depletion routine utilizing MCNP and ORIGEN 2.2. Uncertainties exist in the MCNP transport calculation, but this information is not passed to the depletion calculation in ORIGEN or saved. To quantify this transport uncertainty and determine how it propagates between burnup steps, a statistical analysis of a multiple repeated depletion runs is performed. The reactor model chosen is the Oak Ridge Research Reactor (ORR) in a single assembly, infinite lattice configuration. This model was burned for a 25.5 day cycle broken down into three steps. The output isotopics as well as effective multiplication factor (k-effective) were tabulated and histograms were created at each burnup step using the Scott Method to determine the bin width. It was expected that the gram quantities and k-effective histograms would produce normally distributed results since they were produced from a Monte-Carlo routine, but some of results do not. The standard deviation at each burnup step was consistent between fission product isotopes as expected, while the uranium isotopes created some unique results. The variation in the quantity of uranium was small enough that, from the reaction rate MCNP tally, round off error occurred producing a set of repeated results with slight variation. Statistical analyses were performed using the {chi}{sup 2} test against a normal distribution for several isotopes and the k-effective results. While the isotopes failed to reject the null hypothesis of being normally distributed, the {chi}{sup 2} statistic grew through the steps in the k-effective test. The null hypothesis was rejected in the later steps. These results suggest, for a high accuracy solution, MCNP cell material quantities less than 100 grams and greater kcode parameters are needed to minimize uncertainty propagation and minimize round off effects.

Nichols, T.; Sternat, M.; Charlton, W.

2011-05-08T23:59:59.000Z

312

Polarized light propagation in highly scattering turbid media with a distribution of the particle size: a Monte Carlo study  

E-Print Network (OSTI)

The light propagation in highly scattering turbid media composed of the particles with different size distribution is studied using a Monte Carlo simulation model implemented in Standard C. Monte Carlo method has been widely utilized to study...

Koh, Wonshill

2013-02-22T23:59:59.000Z

313

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

SciTech Connect

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

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

2014-05-14T23:59:59.000Z

314

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

SciTech Connect

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

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

2013-03-15T23:59:59.000Z

315

Benchmarking and validation of a Geant4-SHADOW Monte Carlo simulation for dose calculations in microbeam radiation therapy  

Science Journals Connector (OSTI)

Benchmarking and validation of a new Monte Carlo code for dose calculations in microbeam radiation therapy are described.

Cornelius, I.

2014-04-03T23:59:59.000Z

316

Soci t d exploitation du parc olien de Mont d H z cques SARL | Open Energy  

Open Energy Info (EERE)

Soci t d exploitation du parc olien de Mont d H z cques SARL Soci t d exploitation du parc olien de Mont d H z cques SARL Jump to: navigation, search Name Société d'exploitation du parc éolien de Mont d'Hézècques SARL Place Madrid, Spain Sector Wind energy Product Special purpose vehicle for French wind farm project development. References Société d'exploitation du parc éolien de Mont d'Hézècques SARL[1] LinkedIn Connections CrunchBase Profile No CrunchBase profile. Create one now! This article is a stub. You can help OpenEI by expanding it. Société d'exploitation du parc éolien de Mont d'Hézècques SARL is a company located in Madrid, Spain . References ↑ "[ Société d'exploitation du parc éolien de Mont d'Hézècques SARL]" Retrieved from "http://en.openei.org/w/index.php?title=Soci_t_d_exploitation_du_parc_olien_de_Mont_d_H_z_cques_SARL&oldid=351211

317

Classical trajectory Monte Carlo model calculations for the antiproton-induced ionization of atomic hydrogen at low impact energy  

E-Print Network (OSTI)

The three-body dynamics of the ionization of the atomic hydrogen by 30 keV antiproton impact has been investigated by calculation of fully differential cross sections (FDCS) using the classical trajectory Monte Carlo (CTMC) method. The results of the calculations are compared with the predictions of quantum mechanical descriptions: The semi-classical time-dependent close-coupling theory, the fully quantal, time-independent close-coupling theory, and the continuum-distorted-wave-eikonal-initial-state model. In the analysis particular emphasis was put on the role of the nucleus-nucleus (NN) interaction played in the ionization process. For low-energy electron ejection CTMC predicts a large NN interaction effect on FDCS, in agreement with the quantum mechanical descriptions. By examining individual particle trajectories it was found that the relative motion between the electron and the nuclei is coupled very weakly with that between the nuclei, consequently the two motions can be treated independently. A simple ...

Sarkadi, L

2015-01-01T23:59:59.000Z

318

Electromagnetic Theory 1 /56 Electromagnetic Theory  

E-Print Network (OSTI)

Electromagnetic Theory 1 /56 Electromagnetic Theory Summary: · Maxwell's equations · EM Potentials · Equations of motion of particles in electromagnetic fields · Green's functions · Lienard-Weichert potentials · Spectral distribution of electromagnetic energy from an arbitrarily moving charge #12;Electromagnetic

Bicknell, Geoff

319

Generation of SFR few-group constants using the Monte Carlo code Serpent  

SciTech Connect

In this study, the Serpent Monte Carlo code was used as a tool for preparation of homogenized few-group cross sections for the nodal diffusion analysis of Sodium cooled Fast Reactor (SFR) cores. Few-group constants for two reference SFR cores were generated by Serpent and then employed by nodal diffusion code DYN3D in 2D full core calculations. The DYN3D results were verified against the references full core Serpent Monte Carlo solutions. A good agreement between the reference Monte Carlo and nodal diffusion results was observed demonstrating the feasibility of using Serpent for generation of few-group constants for the deterministic SFR analysis. (authors)

Fridman, E.; Rachamin, R. [Helmholz-Zentrum Dresden-Rossendorf, POB 510119, Dresden, 01314 (Germany); Shwageraus, E. [Ben-Gurion University, POB 653, 84105 Beer-Sheva (Israel)

2013-07-01T23:59:59.000Z

320

Coupled Electron-Ion Monte Carlo Calculations of Dense Metallic Hydrogen  

Science Journals Connector (OSTI)

We present an efficient new Monte Carlo method which couples path integrals for finite temperature protons with quantum Monte Carlo calculations for ground state electrons, and we apply it to metallic hydrogen for pressures beyond molecular dissociation. We report data for the equation of state for temperatures across the melting of the proton crystal. Our data exhibit more structure and higher melting temperatures of the proton crystal than do Car-Parrinello molecular dynamics results. This method fills the gap between high temperature electron-proton path integral and ground state diffusion Monte Carlo methods and should have wide applicability.

Carlo Pierleoni; David M. Ceperley; Markus Holzmann

2004-09-27T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

Quantum Monte Carlo for electronic structure: Recent developments and applications  

SciTech Connect

Quantum Monte Carlo (QMC) methods have been found to give excellent results when applied to chemical systems. The main goal of the present work is to use QMC to perform electronic structure calculations. In QMC, a Monte Carlo simulation is used to solve the Schroedinger equation, taking advantage of its analogy to a classical diffusion process with branching. In the present work the author focuses on how to extend the usefulness of QMC to more meaningful molecular systems. This study is aimed at questions concerning polyatomic and large atomic number systems. The accuracy of the solution obtained is determined by the accuracy of the trial wave function`s nodal structure. Efforts in the group have given great emphasis to finding optimized wave functions for the QMC calculations. Little work had been done by systematically looking at a family of systems to see how the best wave functions evolve with system size. In this work the author presents a study of trial wave functions for C, CH, C{sub 2}H and C{sub 2}H{sub 2}. The goal is to study how to build wave functions for larger systems by accumulating knowledge from the wave functions of its fragments as well as gaining some knowledge on the usefulness of multi-reference wave functions. In a MC calculation of a heavy atom, for reasonable time steps most moves for core electrons are rejected. For this reason true equilibration is rarely achieved. A method proposed by Batrouni and Reynolds modifies the way the simulation is performed without altering the final steady-state solution. It introduces an acceleration matrix chosen so that all coordinates (i.e., of core and valence electrons) propagate at comparable speeds. A study of the results obtained using their proposed matrix suggests that it may not be the optimum choice. In this work the author has found that the desired mixing of coordinates between core and valence electrons is not achieved when using this matrix. A bibliography of 175 references is included.

Rodriguez, M.M.S. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry]|[Lawrence Berkeley Lab., CA (United States). Chemical Sciences Div.

1995-04-01T23:59:59.000Z

322

Complete Monte Carlo Simulation of Neutron Scattering Experiments  

SciTech Connect

In the far past, it was not possible to accurately correct for the finite geometry and the finite sample size of a neutron scattering set-up. The limited calculation power of the ancient computers as well as the lack of powerful Monte Carlo codes and the limitation in the data base available then prevented a complete simulation of the actual experiment. Using e.g. the Monte Carlo neutron transport code MCNPX [1], neutron scattering experiments can be simulated almost completely with a high degree of precision using a modern PC, which has a computing power that is ten thousand times that of a super computer of the early 1970s. Thus, (better) corrections can also be obtained easily for previous published data provided that these experiments are sufficiently well documented. Better knowledge of reference data (e.g. atomic mass, relativistic correction, and monitor cross sections) further contributes to data improvement. Elastic neutron scattering experiments from liquid samples of the helium isotopes performed around 1970 at LANL happen to be very well documented. Considering that the cryogenic targets are expensive and complicated, it is certainly worthwhile to improve these data by correcting them using this comparatively straightforward method. As two thirds of all differential scattering cross section data of {sup 3}He(n,n){sup 3}He are connected to the LANL data, it became necessary to correct the dependent data measured in Karlsruhe, Germany, as well. A thorough simulation of both the LANL experiments and the Karlsruhe experiment is presented, starting from the neutron production, followed by the interaction in the air, the interaction with the cryostat structure, and finally the scattering medium itself. In addition, scattering from the hydrogen reference sample was simulated. For the LANL data, the multiple scattering corrections are smaller by a factor of five at least, making this work relevant. Even more important are the corrections to the Karlsruhe data due to the inclusion of the missing outgoing self-attenuation that amounts to up to 15%.

Drosg, M. [Faculty of Physics, University of Vienna, Boltzmanngasse 5, A-1090 Wien (Austria)

2011-12-13T23:59:59.000Z

323

Universality for SU(2) Yang-Mills theory in 2+1 dimensions  

Science Journals Connector (OSTI)

A comparison is made for SU(2) Yang-Mills theory in (2+1)D between various Hamiltonian results obtained by series expansions, linked cluster expansions, and coupled cluster methods, and the recent Euclidean Monte Carlo results of Teper. A striking demonstration of universality between the Hamiltonian and Euclidean formulations is obtained, once the difference in scales between the two formulations is taken into account.

C. J. Hamer; M. Sheppeard; Zheng Weihong; D. Schtte

1996-08-01T23:59:59.000Z

324

Elements of number theory  

E-Print Network (OSTI)

The dissertation argues for the necessity of a morphosemantic theory of number, that is, a theory of number serviceable both to semantics and morphology. The basis for this position, and the empirical core of the dissertation, ...

Harbour, Daniel, 1975-

2003-01-01T23:59:59.000Z

325

Essays on economic theory  

E-Print Network (OSTI)

These four essays concern the theory of games and its application to economic theory. The first two, closely linked, chapters are an investigation into the foundational question of the sensitivity of the predictions of ...

Weinstein, Jonathan

2005-01-01T23:59:59.000Z

326

Ensemble bayesian model averaging using markov chain Monte Carlo sampling  

SciTech Connect

Bayesian model averaging (BMA) has recently been proposed as a statistical method to calibrate forecast ensembles from numerical weather models. Successful implementation of BMA however, requires accurate estimates of the weights and variances of the individual competing models in the ensemble. In their seminal paper (Raftery etal. Mon Weather Rev 133: 1155-1174, 2(05)) has recommended the Expectation-Maximization (EM) algorithm for BMA model training, even though global convergence of this algorithm cannot be guaranteed. In this paper, we compare the performance of the EM algorithm and the recently developed Differential Evolution Adaptive Metropolis (DREAM) Markov Chain Monte Carlo (MCMC) algorithm for estimating the BMA weights and variances. Simulation experiments using 48-hour ensemble data of surface temperature and multi-model stream-flow forecasts show that both methods produce similar results, and that their performance is unaffected by the length of the training data set. However, MCMC simulation with DREAM is capable of efficiently handling a wide variety of BMA predictive distributions, and provides useful information about the uncertainty associated with the estimated BMA weights and variances.

Vrugt, Jasper A [Los Alamos National Laboratory; Diks, Cees G H [NON LANL; Clark, Martyn P [NON LANL

2008-01-01T23:59:59.000Z

327

Cohesion Energetics of Carbon Allotropes: Quantum Monte Carlo Study  

SciTech Connect

We have performed quantum Monte Carlo calculations to study the cohesion energetics of carbon allotropes, including sp3-bonded diamond, sp2-bonded graphene, sp-sp2 hybridized graphynes, and sp-bonded carbyne. The comput- ed cohesive energies of diamond and graphene are found to be in excellent agreement with the corresponding values de- termined experimentally for diamond and graphite, respectively, when the zero-point energies, along with the interlayer binding in the case of graphite, are included. We have also found that the cohesive energy of graphyne decreases system- atically as the ratio of sp-bonded carbon atoms increases. The cohesive energy of -graphyne, the most energetically- stable graphyne, turns out to be 6.766(6) eV/atom, which is smaller than that of graphene by 0.698(12) eV/atom. Experi- mental difficulty in synthesizing graphynes could be explained by their significantly smaller cohesive energies. Finally we conclude that the cohesive energy of a newly-proposed two-dimensional carbon network can be accurately estimated with the carbon-carbon bond energies determined from the cohesive energies of graphene and three different graphynes.

Shin, Hyeondeok [Konkuk University, South Korea] [Konkuk University, South Korea; Kang, Sinabro [Konkuk University, South Korea] [Konkuk University, South Korea; Koo, Jahyun [Konkuk University, South Korea] [Konkuk University, South Korea; Lee, Hoonkyung [Konkuk University, South Korea] [Konkuk University, South Korea; Kim, Jeongnim [ORNL] [ORNL; Kwon, Yongkyung [Konkuk University, South Korea] [Konkuk University, South Korea

2014-01-01T23:59:59.000Z

328

Random Number Generation for Petascale Quantum Monte Carlo  

SciTech Connect

The quality of random number generators can affect the results of Monte Carlo computations, especially when a large number of random numbers are consumed. Furthermore, correlations present between different random number streams in a parallel computation can further affect the results. The SPRNG software, which the author had developed earlier, has pseudo-random number generators (PRNGs) capable of producing large numbers of streams with large periods. However, they had been empirically tested on only thousand streams earlier. In the work summarized here, we tested the SPRNG generators with over a hundred thousand streams, involving over 10^14 random numbers per test, on some tests. We also tested the popular Mersenne Twister. We believe that these are the largest tests of PRNGs, both in terms of the numbers of streams tested and the number of random numbers tested. We observed defects in some of these generators, including the Mersenne Twister, while a few generators appeared to perform well. We also corrected an error in the implementation of one of the SPRNG generators.

Ashok Srinivasan

2010-03-16T23:59:59.000Z

329

Improving computational efficiency of Monte Carlo simulations with variance reduction  

SciTech Connect

CCFE perform Monte-Carlo transport simulations on large and complex tokamak models such as ITER. Such simulations are challenging since streaming and deep penetration effects are equally important. In order to make such simulations tractable, both variance reduction (VR) techniques and parallel computing are used. It has been found that the application of VR techniques in such models significantly reduces the efficiency of parallel computation due to 'long histories'. VR in MCNP can be accomplished using energy-dependent weight windows. The weight window represents an 'average behaviour' of particles, and large deviations in the arriving weight of a particle give rise to extreme amounts of splitting being performed and a long history. When running on parallel clusters, a long history can have a detrimental effect on the parallel efficiency - if one process is computing the long history, the other CPUs complete their batch of histories and wait idle. Furthermore some long histories have been found to be effectively intractable. To combat this effect, CCFE has developed an adaptation of MCNP which dynamically adjusts the WW where a large weight deviation is encountered. The method effectively 'de-optimises' the WW, reducing the VR performance but this is offset by a significant increase in parallel efficiency. Testing with a simple geometry has shown the method does not bias the result. This 'long history method' has enabled CCFE to significantly improve the performance of MCNP calculations for ITER on parallel clusters, and will be beneficial for any geometry combining streaming and deep penetration effects. (authors)

Turner, A. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon, 0X14 3DB (United Kingdom); Davis, A. [EURATOM/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxon, 0X14 3DB (United Kingdom); University of Wisconsin-Madison, Madison, WI 53706 (United States)

2013-07-01T23:59:59.000Z

330

Monte Carlo sampling from the quantum state space. I  

E-Print Network (OSTI)

High-quality random samples of quantum states are needed for a variety of tasks in quantum information and quantum computation. Searching the high-dimensional quantum state space for a global maximum of an objective function with many local maxima or evaluating an integral over a region in the quantum state space are but two exemplary applications of many. These tasks can only be performed reliably and efficiently with Monte Carlo methods, which involve good samplings of the parameter space in accordance with the relevant target distribution. We show how the standard strategies of rejection sampling, importance sampling, and Markov-chain sampling can be adapted to this context, where the samples must obey the constraints imposed by the positivity of the statistical operator. For a comparison of these sampling methods, we generate sample points in the probability space for two-qubit states probed with a tomographically incomplete measurement, and then use the sample for the calculation of the size and credibility of the recently-introduced optimal error regions [see New J. Phys. 15 (2013) 123026]. Another illustration is the computation of the fractional volume of separable two-qubit states.

Jiangwei Shang; Yi-Lin Seah; Hui Khoon Ng; David John Nott; Berthold-Georg Englert

2014-07-29T23:59:59.000Z

331

Hybrid Radiosity/Monte Carlo Methods Peter Shirley  

E-Print Network (OSTI)

important of which are: continuous random variable, probability density function, expected value an elementary probability theory book (particularly the sections on continuous, rather than discrete, random density function, p, associated with x (the relationship is denoted x p). If x ranges over some region S

Shirley, Peter

332

Game Theory Kenneth Prestwich  

E-Print Network (OSTI)

...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ......... . . . . . . ESS Game theory modeling: Hawks dashed line and Doves solid line. #12;Game Theory Kenneth Prestwich ...................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ............. ......... . . . . . . ESS Game theory modeling: Hawks dashed line and Doves solid line. #12;c 1999 by Kenneth Prestwich. All are available on-line at: http: science.holycross.edu departments biology kprestwi behavior ESS ESS index frmset

Prestwich, Ken

333

Decision Theory Mendoza, M.  

E-Print Network (OSTI)

1 MS 1319 Decision Theory Mendoza, M. Dept. Statistics, ITAM Rio Hondo 1, San Angel. México 01000 D of Decision Theory, the literature offers an account of the ways people actually make decisions and a discussion on the mechanisms underlying this behavior. This is called a "descriptive" decision theory

Mendoza Ramírez, Manuel

334

A Monte Carlo code describing the neutral gas transport in pipe configurations with attenuating media  

Science Journals Connector (OSTI)

A three-dimensional Monte Carlo description of the neutral gas transport in pipe configurations with almost arbitrary torsion and curvature is presented. To avoid quadratic or even transcendental expressions describing the pipe surfaces confining and ...

A. Nicolai

1993-06-01T23:59:59.000Z

335

Vectorization on Monte Carlo particle transport: an architectural study using the LANL benchmark GAMTEB  

Science Journals Connector (OSTI)

Fully vectorized versions of the Los Alamos National Laboratory benchmark code Gamteb, a Monte Carlo photon transport algorithm, were developed for the Cyber 205/ETA-10 and Cray X-MP/Y-MP architectures. Single-processor performance measurements ...

P. J. Burns; M. Christon; R. Schweitzer; O. M. Lubeck; H. J. Wasserman

1989-08-01T23:59:59.000Z

336

A semi Monte Carlo calculation of the flux of high-energy muons in air showers  

Science Journals Connector (OSTI)

A semi Monte Carlo method has been used to calculate the flux of muons of energy ?180 GeV associated with air showers at ... of nucleon and pion interactions at ultra-high energies. Various aspects of these muons

Siddheshwar Lal

1967-03-21T23:59:59.000Z

337

E-Print Network 3.0 - au code monte Sample Search Results  

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

ON APPLIED SUPERCONDUCTIVITY, VOL. 13, NO. 2, JUNE 2003 889 High Quality YBa2Cu3O7 Josephson Junctions Summary: been studied by Monte Carlo simulation using a mod- ified...

338

APR1400 LBLOCA uncertainty quantification by Monte Carlo method and comparison with Wilks' formula  

SciTech Connect

An analysis of the uncertainty quantification for the PWR LBLOCA by the Monte Carlo calculation has been performed and compared with the tolerance level determined by Wilks' formula. The uncertainty range and distribution of each input parameter associated with the LBLOCA accident were determined by the PIRT results from the BEMUSE project. The Monte-Carlo method shows that the 95. percentile PCT value can be obtained reliably with a 95% confidence level using the Wilks' formula. The extra margin by the Wilks' formula over the true 95. percentile PCT by the Monte-Carlo method was rather large. Even using the 3 rd order formula, the calculated value using the Wilks' formula is nearly 100 K over the true value. It is shown that, with the ever increasing computational capability, the Monte-Carlo method is accessible for the nuclear power plant safety analysis within a realistic time frame. (authors)

Hwang, M.; Bae, S.; Chung, B. D. [Korea Atomic Energy Research Inst., 150 Dukjin-dong, Yuseong-gu, Daejeon (Korea, Republic of)

2012-07-01T23:59:59.000Z

339

Observations of the Great Southern Comet 1880, I. made at Monte Video  

Science Journals Connector (OSTI)

... 1880 Royal Astronomical Society. Provided by the NASA Astrophysics Data System 12 March 1880 research-article Articles Observations of the Great Southern Comet 1880, I. made at Monte Video Lieut. B. Gwynne 1880MNRAS..40..295G...

B. Gwynne

1880-03-12T23:59:59.000Z

340

Sextant Observations of Comet Pons-Brooks made at Monte Video  

Science Journals Connector (OSTI)

... 1884 Royal Astronomical Society. Provided by the NASA Astrophysics Data System 14 March 1884 research-article Articles Sextant Observations of Comet Pons-Brooks made at Monte Video Rev. S. S. O. Morris 1884MNRAS..44..256M...

S. S. O. Morris

1884-03-14T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

Modeling of Asymmetry between Gasoline and Crude Oil Prices: A Monte Carlo Comparison  

Science Journals Connector (OSTI)

An EngleGranger two-step procedure is commonly used to estimate cointegrating vectors and consequently asymmetric error-correction models. This study uses Monte Carlo methods and demonstrates that the EngleG...

Afshin Honarvar

2010-10-01T23:59:59.000Z

342

Monte Carlo Simulations of Microchannel Plate Based, Fast-Gated X-Ray Imagers  

SciTech Connect

This is a chapter in a book titled Applications of Monte Carlo Method in Science and Engineering Edited by: Shaul Mordechai ISBN 978-953-307-691-1, Hard cover, 950 pages Publisher: InTech Publication date: February 2011

Wu., M., Kruschwitz, C.

2011-02-01T23:59:59.000Z

343

Protein folding and phylogenetic tree reconstruction using stochastic approximation Monte Carlo  

E-Print Network (OSTI)

folding problems. The numerical results indicate that it outperforms simulated annealing and conventional Monte Carlo algorithms as a stochastic optimization algorithm. We also propose one method for the use of secondary structures in protein folding...

Cheon, Sooyoung

2007-09-17T23:59:59.000Z

344

Probability Distributions and Threshold Selection for Monte CarloType Tropical Cyclone Wind Speed Forecasts  

Science Journals Connector (OSTI)

Probabilistic wind speed forecasts for tropical cyclones from Monte Carlotype simulations are assessed within a theoretical framework for a simple unbiased Gaussian system that is based on feature size and location error that mimic tropical ...

Michael E. Splitt; Steven M. Lazarus; Sarah Collins; Denis N. Botambekov; William P. Roeder

2014-10-01T23:59:59.000Z

345

MonteCarlo and Analytical Methods for Forced Outage Rate Calculations of Peaking Units  

E-Print Network (OSTI)

(unavailability) of such units. This thesis examines the representation of peaking units using a four-state model and performs the analytical calculations and Monte Carlo simulations to examine whether such a model does indeed represent the peaking units...

Rondla, Preethi 1988-

2012-10-26T23:59:59.000Z

346

A Monte Carlo Approach To Generator Portfolio Planning And Carbon Emissions  

Open Energy Info (EERE)

Monte Carlo Approach To Generator Portfolio Planning And Carbon Emissions Monte Carlo Approach To Generator Portfolio Planning And Carbon Emissions Assessments Of Systems With Large Penetrations Of Variable Renewables Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Journal Article: A Monte Carlo Approach To Generator Portfolio Planning And Carbon Emissions Assessments Of Systems With Large Penetrations Of Variable Renewables Details Activities (0) Areas (0) Regions (0) Abstract: A new generator portfolio planning model is described that is capable of quantifying the carbon emissions associated with systems that include very high penetrations of variable renewables. The model combines a deterministic renewable portfolio planning module with a Monte Carlo simulation of system operation that determines the expected least-cost

347

Monte Carlo simulation model for electromagnetic scattering from vegetation and inversion of vegetation parameters  

E-Print Network (OSTI)

In this thesis research, a coherent scattering model for microwave remote sensing of vegetation canopy is developed on the basis of Monte Carlo simulations. An accurate model of vegetation structure is essential for the ...

Wang, Li-Fang, Ph. D. Massachusetts Institute of Technology

2007-01-01T23:59:59.000Z

348

The Monte Carlo Independent Column Approximations Conditional Random Noise: Impact on Simulated Climate  

Science Journals Connector (OSTI)

The Monte Carlo Independent Column Approximation (McICA) method for computing domain-average radiative fluxes is unbiased with respect to the full ICA, but its flux estimates contain conditional random noise. Results for five experiments are used ...

P. Risnen; H. W. Barker; J. N. S. Cole

2005-11-01T23:59:59.000Z

349

The effect of load imbalances on the performance of Monte Carlo algorithms in LWR analysis  

SciTech Connect

A model is developed to predict the impact of particle load imbalances on the performance of domain-decomposed Monte Carlo neutron transport algorithms. Expressions for upper bound performance penalties are derived in terms of simple machine characteristics, material characterizations and initial particle distributions. The hope is that these relations can be used to evaluate tradeoffs among different memory decomposition strategies in next generation Monte Carlo codes, and perhaps as a metric for triggering particle redistribution in production codes.

Siegel, A.R., E-mail: siegela@mcs.anl.gov [Argonne National Laboratory, Nuclear Engineering Division (United States); Argonne National Laboratory, Mathematics and Computer Science Division (United States); Smith, K., E-mail: kord@mit.edu [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering (United States); Romano, P.K., E-mail: romano7@mit.edu [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering (United States); Forget, B., E-mail: bforget@mit.edu [Massachusetts Institute of Technology, Department of Nuclear Science and Engineering (United States); Felker, K., E-mail: felker@mcs.anl.gov [Argonne National Laboratory, Mathematics and Computer Science Division (United States)

2013-02-15T23:59:59.000Z

350

Monte Carlo techniques of simulation applied to a single item inventory system  

E-Print Network (OSTI)

MONTE CARI, O TECHNIQUES OF SIMULATION APPLIED TO A SINGLE ITEM INVENTORY SYSTEM A Thesis By WILLIAM MURRAY ALDRED, JR. Submitted to the Graduate College of the Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE August 1965 Major SubJect: Computer Science MONTE CARLO TECHNIQUES OF SIMULATION APPLIED TO A SINGLE ITEM INVENTORY SYSTEM A Thesis By WILLIAM MURRAY ALDRED, JR. Approved as to style and content by: (Chairman of Committee (Head...

Aldred, William Murray

2012-06-07T23:59:59.000Z

351

Preventing xenon oscillations in Monte Carlo burnup calculations by enforcing equilibrium xenon distribution  

Science Journals Connector (OSTI)

Abstract Existing Monte Carlo burnup codes suffer from instabilities caused by spatial xenon oscillations. These oscillations can be prevented by forcing equilibrium between the neutron flux and saturated xenon distribution. The equilibrium calculation can be integrated to Monte Carlo neutronics, which provides a simple and lightweight solution that can be used with any of the existing burnup calculation algorithms. The stabilizing effect of this approach, as well as its limitations are demonstrated using the reactor physics code Serpent.

A.E. Isotalo; J. Leppnen; J. Dufek

2013-01-01T23:59:59.000Z

352

Comparison of value-added models for school ranking and classification: a Monte Carlo study  

E-Print Network (OSTI)

COMPARISON OF VALUE-ADDED MODELS FOR SCHOOL RANKING AND CLASSIFICATION: A MONTE CARLO STUDY A Dissertation by ZHONGMIAO WANG Submitted to the Office of Graduate Studies of Texas A&M University... AND CLASSIFICATION: A MONTE CARLO STUDY A Dissertation by ZHONGMIAO WANG Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Co...

Wang, Zhongmiao

2009-05-15T23:59:59.000Z

353

Application of a modified generalized Flory dimer theory to normal alkanes  

SciTech Connect

The applicability of chain equations of state to real systems is discussed in this paper. For this purpose, the authors have compared four theories: the perturbed-hard-chain theory (PHCT) of Prausnitz and coworkers, the generalized Flory (GF) and generalized Flory dimer (GFD) theories of Hall and coworkers, and the statistical associating fluid theory (SAFT) of Radosz, Gubbins, and co-workers. In this comparison, the perturbation expansion in the attractive term was truncated after the first-order term for all theories. Comparison of these theories with Monte Carlo simulation data for hard chains and square-well chains showed that the GFD theory, which explicitly takes into account the effect of the formation of chains in both the repulsive and the attractive part of the equations, is in best agreement with the data. The GFD theory was further improved by using the simulations data directly to reevaluate the shape parameters c and q, which were found to be density dependent. The new simplified GFD theory gives a significantly better correlation of the properties of normal alkanes than the other four theories.

Bokis, C.P.; Donohue, M.D. (Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Chemical Engineering); Hall, C.K. (North Carolina State Univ., Raleigh, NC (United States). Dept. of Chemical Engineering)

1994-05-01T23:59:59.000Z

354

Nonextensive lattice gauge theories: algorithms and methods  

E-Print Network (OSTI)

High-energy phenomena presenting strong dynamical correlations, long-range interactions and microscopic memory effects are well described by nonextensive versions of the canonical Boltzmann-Gibbs statistical mechanics. After a brief theoretical review, we introduce a class of generalized heat-bath algorithms that enable Monte Carlo lattice simulations of gauge fields on the nonextensive statistical ensemble of Tsallis. The algorithmic performance is evaluated as a function of the Tsallis parameter q in equilibrium and nonequilibrium setups. Then, we revisit short-time dynamic techniques, which in contrast to usual simulations in equilibrium present negligible finite-size effects and no critical slowing down. As an application, we investigate the short-time critical behaviour of the nonextensive hot Yang-Mills theory at q- values obtained from heavy-ion collision experiments. Our results imply that, when the equivalence of statistical ensembles is obeyed, the long-standing universality arguments relating gauge theories and spin systems hold also for the nonextensive framework.

Rafael B. Frigori

2014-04-26T23:59:59.000Z

355

PyMercury: Interactive Python for the Mercury Monte Carlo Particle Transport Code  

SciTech Connect

Monte Carlo particle transport applications are often written in low-level languages (C/C++) for optimal performance on clusters and supercomputers. However, this development approach often sacrifices straightforward usability and testing in the interest of fast application performance. To improve usability, some high-performance computing applications employ mixed-language programming with high-level and low-level languages. In this study, we consider the benefits of incorporating an interactive Python interface into a Monte Carlo application. With PyMercury, a new Python extension to the Mercury general-purpose Monte Carlo particle transport code, we improve application usability without diminishing performance. In two case studies, we illustrate how PyMercury improves usability and simplifies testing and validation in a Monte Carlo application. In short, PyMercury demonstrates the value of interactive Python for Monte Carlo particle transport applications. In the future, we expect interactive Python to play an increasingly significant role in Monte Carlo usage and testing.

Iandola, F N; O'Brien, M J; Procassini, R J

2010-11-29T23:59:59.000Z

356

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

357

Comparison between Gaussian-type orbitals and plane wave ab initio density functional theory modeling of layer silicates: Talc [Mg{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}] as model system  

SciTech Connect

The quantum chemical characterization of solid state systems is conducted with many different approaches, among which the adoption of periodic boundary conditions to deal with three-dimensional infinite condensed systems. This method, coupled to the Density Functional Theory (DFT), has been proved successful in simulating a huge variety of solids. Only in relatively recent years this ab initio quantum-mechanic approach has been used for the investigation of layer silicate structures and minerals. In the present work, a systematic comparison of different DFT functionals (GGA-PBEsol and hybrid B3LYP) and basis sets (plane waves and all-electron Gaussian-type orbitals) on the geometry, energy, and phonon properties of a model layer silicate, talc [Mg{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}], is presented. Long range dispersion is taken into account by DFT+D method. Results are in agreement with experimental data reported in literature, with minimal deviation given by the GTO/B3LYP-D* method regarding both axial lattice parameters and interaction energy and by PW/PBE-D for the unit-cell volume and angular values. All the considered methods adequately describe the experimental talc infrared spectrum.

Ulian, Gianfranco; Valdr, Giovanni, E-mail: giovanni.valdre@unibo.it [Dipartimento di Scienze Biologiche e Geologico-Ambientali, Centro di Ricerca Interdisciplinare di Biomineralogia, Cristallografia e Biomateriali, Universit di Bologna Alma Mater Studiorum Piazza di Porta San Donato 1, 40126 Bologna (Italy)] [Dipartimento di Scienze Biologiche e Geologico-Ambientali, Centro di Ricerca Interdisciplinare di Biomineralogia, Cristallografia e Biomateriali, Universit di Bologna Alma Mater Studiorum Piazza di Porta San Donato 1, 40126 Bologna (Italy); Tosoni, Sergio [Departament de Qumica Fsica and Institut de Qumica Terica i Computacional (IQTCUB), Universitat de Barcelona, C/ Mart i Franqus 1, E-08028 Barcelona (Spain)] [Departament de Qumica Fsica and Institut de Qumica Terica i Computacional (IQTCUB), Universitat de Barcelona, C/ Mart i Franqus 1, E-08028 Barcelona (Spain)

2013-11-28T23:59:59.000Z

358

Weakly interacting two-dimensional system of dipoles: Limitations of the mean-field theory  

Science Journals Connector (OSTI)

We consider a homogeneous two-dimensional Bose gas with repulsive dipole-dipole interactions. The ground-state equation of state, calculated using the diffusion Monte Carlo method, shows quantitative differences from the predictions of the commonly used Gross-Pitaevskii mean-field theory. The static structure factor, pair distribution function, and condensate fraction are calculated in a wide range of the gas parameter. Differences from mean-field theory are reflected in the frequency of the lowest breathing mode for harmonically trapped systems.

G. E. Astrakharchik, J. Boronat, J. Casulleras, I. L. Kurbakov, and Yu. E. Lozovik

2007-06-29T23:59:59.000Z

359

Magnetism Theory Group / POSTECH Magnetism Theory Group / POSTECH  

E-Print Network (OSTI)

Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH #12;Magnetism Theory Group / POSTECH J.H . Park et al. #12;'s of FeinCsm e tal The chargeandorbitalordering geom etryin YB a C o 2 O 5 S. K. Kwon etal .Magnetism Theory

Min, Byung Il

360

A new class of accelerated kinetic Monte Carlo algorithms  

SciTech Connect

Kinetic (aka dynamic) Monte Carlo (KMC) is a powerful method for numerical simulations of time dependent evolution applied in a wide range of contexts including biology, chemistry, physics, nuclear sciences, financial engineering, etc. Generally, in a KMC the time evolution takes place one event at a time, where the sequence of events and the time intervals between them are selected (or sampled) using random numbers. While details of the method implementation vary depending on the model and context, there exist certain common issues that limit KMC applicability in almost all applications. Among such is the notorious 'flicker problem' where the same states of the systems are repeatedly visited but otherwise no essential evolution is observed. In its simplest form the flicker problem arises when two states are connected to each other by transitions whose rates far exceed the rates of all other transitions out of the same two states. In such cases, the model will endlessly hop between the two states otherwise producing no meaningful evolution. In most situation of practical interest, the trapping cluster includes more than two states making the flicker somewhat more difficult to detect and to deal with. Several methods have been proposed to overcome or mitigate the flicker problem, exactly [1-3] or approximately [4,5]. Of the exact methods, the one proposed by Novotny [1] is perhaps most relevant to our research. Novotny formulates the problem of escaping from a trapping cluster as a Markov system with absorbing states. Given an initial state inside the cluster, it is in principle possible to solve the Master Equation for the time dependent probabilities to find the walker in a given state (transient or absorbing) of the cluster at any time in the future. Novotny then proceeds to demonstrate implementation of his general method to trapping clusters containing the initial state plus one or two transient states and all of their absorbing states. Similar methods have been subsequently proposed in [refs] but applied in a different context. The most serious deficiency of the earlier methods is that size of the trapping cluster size is fixed and often too small to bring substantial simulation speedup. Furthermore, the overhead associated with solving for the probability distribution on the trapping cluster sometimes makes such simulations less efficient than the standard KMC. Here we report on a general and exact accelerated kinetic Monte Carlo algorithm generally applicable to arbitrary Markov models1. Two different implementations are attempted both based on incremental expansion of trapping sub-set of Markov states: (1) numerical solution of the Master Equation with absorbing states and (2) incremental graph reduction followed by randomization. Of the two implementations, the 2nd one performs better allowing, for the first time, to overcome trapping basins spanning several million Markov states. The new method is used for simulations of anomalous diffusion on a 2D substrate and of the kinetics of diffusive 1st order phase transformations in binary alloys. Depending on temperature and (alloy) super-saturation conditions, speedups of 3 to 7 orders of magnitude are demonstrated, with no compromise of simulation accuracy.

Bulatov, V V; Oppelstrup, T; Athenes, M

2011-11-30T23:59:59.000Z

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361

Liquid-state polaron theory of the hydrated electron revisited  

E-Print Network (OSTI)

The quantum path integral/classical liquid-state theory of Chandler and co-workers, created to describe an excess electron in solvent, is re-examined for the hydrated electron. The portion that models electron-water density correlations is replaced by two equations: the range optimized random phase approximation (RO-RPA), and the DRL approximation to the "two-chain" equation, both shown previously to describe accurately the static structure and thermodynamics of strongly charged polyelectrolyte solutions. The static equilibrium properties of the hydrated electron are analyzed using five different electron-water pseudopotentials. The theory is then compared with data from mixed quantum/classical Monte Carlo and molecular dynamics simulations using these same pseudopotentials. It is found that the predictions of the RO-RPA and DRL-based polaron theories are similar and improve upon previous theory, with values for almost all properties analyzed in reasonable quantitative agreement with the available simulation data. Also, it is found using the Larsen, Glover and Schwartz pseudopotential that the theories give values for the solvation free energy that are at least three times larger than that from experiment.

James P. Donley; David R. Heine; Caleb A. Tormey; David T. Wu

2014-12-25T23:59:59.000Z

362

Quantum Monte Carlo methods and lithium cluster properties  

SciTech Connect

Properties of small lithium clusters with sizes ranging from n = 1 to 5 atoms were investigated using quantum Monte Carlo (QMC) methods. Cluster geometries were found from complete active space self consistent field (CASSCF) calculations. A detailed development of the QMC method leading to the variational QMC (V-QMC) and diffusion QMC (D-QMC) methods is shown. The many-body aspect of electron correlation is introduced into the QMC importance sampling electron-electron correlation functions by using density dependent parameters, and are shown to increase the amount of correlation energy obtained in V-QMC calculations. A detailed analysis of D-QMC time-step bias is made and is found to be at least linear with respect to the time-step. The D-QMC calculations determined the lithium cluster ionization potentials to be 0.1982(14) [0.1981], 0.1895(9) [0.1874(4)], 0.1530(34) [0.1599(73)], 0.1664(37) [0.1724(110)], 0.1613(43) [0.1675(110)] Hartrees for lithium clusters n = 1 through 5, respectively; in good agreement with experimental results shown in the brackets. Also, the binding energies per atom was computed to be 0.0177(8) [0.0203(12)], 0.0188(10) [0.0220(21)], 0.0247(8) [0.0310(12)], 0.0253(8) [0.0351(8)] Hartrees for lithium clusters n = 2 through 5, respectively. The lithium cluster one-electron density is shown to have charge concentrations corresponding to nonnuclear attractors. The overall shape of the electronic charge density also bears a remarkable similarity with the anisotropic harmonic oscillator model shape for the given number of valence electrons.

Owen, R.K.

1990-12-01T23:59:59.000Z

363

Balance of Nanostructure and Bimetallic Interactions in Pt Model Fuel Cell Catalysts: An in Situ XAS and DFT Study  

SciTech Connect

We have studied the effect of nanostructuring in Pt monolayer model electrocatalysts on a Rh(111) single-crystal substrate on the adsorption strength of chemisorbed species. In situ high energy resolution fluorescence detection X-ray absorption spectroscopy at the Pt L(3) edge reveals characteristic changes of the shape and intensity of the 'white-line' due to chemisorption of atomic hydrogen (H(ad)) at low potentials and oxygen-containing species (O/OH(ad)) at high potentials. On a uniform, two-dimensional Pt monolayer grown by Pt evaporation in ultrahigh vacuum, we observe a significant destabilization of both H(ad) and O/OH(ad) due to strain and ligand effects induced by the underlying Rh(111) substrate. When Pt is deposited via a wet-chemical route, by contrast, three-dimensional Pt islands are formed. In this case, strain and Rh ligand effects are balanced with higher local thickness of the Pt islands as well as higher defect density, shifting H and OH adsorption energies back toward pure Pt. Using density functional theory, we calculate O adsorption energies and corresponding local ORR activities for fcc 3-fold hollow sites with various local geometries that are present in the three-dimensional Pt islands.

Friebel, Daniel; Viswanathan, Venkatasubramanian; Miller, Daniel James; Anniyev, Toyli; Ogasawara, Hirohito; Larsen, Ask Hjorth; O'Grady, Christopher P.; Norskov, Jens K.; Nilsson, Anders

2012-05-31T23:59:59.000Z

364

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

365

The Structure of Hydrated Electron. Part 1. Magnetic Resonance of Internally Trapping Water Anions: A Density Functional Theory Study  

E-Print Network (OSTI)

Density functional theory (DFT) is used to rationalize magnetic parameters of hydrated electron trapped in alkaline glasses as observed using Electron Paramagnetic Resonance (EPR) and Electron Spin Echo Envelope Modulation (ESEEM) spectroscopies. To this end, model water cluster anions (n=4-8 and n=20,24) that localize the electron internally are examined. It is shown that EPR parameters of such water anions (such as hyperfine coupling tensors of H/D nuclei in the water molecules) are defined mainly by the cavity size and the coordination number of the electron; the water molecules in the second solvation shell play a relatively minor role. An idealized model of hydrated electron (that is usually attributed to L. Kevan) in which six hydroxyl groups arranged in an octahedral pattern point towards the common center is shown to provide the closest match to the experimental parameters, such as isotropic and anisotropic hyperfine coupling constants for the protons (estimated from ESEEM), the second moment of the EPR spectra, and the radius of gyration. The salient feature of these DFT models is the significant transfer (10-20%) of spin density into the frontal O 2p orbitals of water molecules. Spin bond polarization involving these oxygen orbitals accounts for small, negative hyperfine coupling constants for protons in hydroxyl groups that form the electron-trapping cavity. In Part 2, these results are generalized for more realistic geometries of core anions obtained using a dynamic one-electron mixed qunatum/classical molecular dynamics model.

I. A. Shkrob

2006-07-25T23:59:59.000Z

366

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

E-Print Network (OSTI)

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

Davide Pini

2014-07-04T23:59:59.000Z

367

Density functional theory study of chemical sensing on surfaces of single-layer MoS{sub 2} and graphene  

SciTech Connect

In this work, density functional theory (DFT) calculations have been used to investigate chemical sensing on surfaces of single-layer MoS{sub 2} and graphene, considering the adsorption of the chemical compounds triethylamine, acetone, tetrahydrofuran, methanol, 2,4,6-trinitrotoluene, o-nitrotoluene, o-dichlorobenzene, and 1,5-dicholoropentane. Physisorption of the adsorbates on free-standing surfaces was analyzed in detail for optimized material structures, considering various possible adsorption sites. Similar adsorption characteristics for the two surface types were demonstrated, where inclusion of a correction to the DFT functional for London dispersion was shown to be important to capture interactions at the interface of molecular adsorbate and surface. Charge transfer analyses for adsorbed free-standing surfaces generally demonstrated very small effects. However, charge transfer upon inclusion of the underlying SiO{sub 2} substrate rationalized experimental observations for some of the adsorbates considered. A larger intrinsic response for the electron-donor triethylamine adsorbed on MoS{sub 2} as compared to graphene was demonstrated, which may assist in devising chemical sensors for improved sensitivity.

Mehmood, F.; Pachter, R., E-mail: ruth.pachter@us.af.mil [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio 45433 (United States)

2014-04-28T23:59:59.000Z

368

Which decision theory?  

Science Journals Connector (OSTI)

Abstract A new laboratory experiment is designed to identify the best theories for describing decisions under risk. The experimental design has two noteworthy features: a representative sample of binary choice problems (for fair comparison across theories) and a lottery set with a small number of outcomes and probabilities (for ease of non-parametric estimation). We find that a simple heuristic, rank-dependent utility and expected utility theory provide the best goodness of fit.

Pavlo Blavatskyy

2013-01-01T23:59:59.000Z

369

Automated Lattice Perturbation Theory  

SciTech Connect

I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.

Monahan, Christopher

2014-11-01T23:59:59.000Z

370

Monte Carlo Simulations of the Corrosion of Aluminoborosilicate Glasses  

SciTech Connect

Aluminum is one of the most common components included in nuclear waste glasses. Therefore, Monte Carlo (MC) simulations were carried out to investigate the influence of aluminum on the rate and mechanism of dissolution of sodium borosilicate glasses in static conditions. The glasses studied were in the compositional range (70 2x)% SiO2x% Al2O3 15% B2O3 (15 + x)% Na2O, where 0 x 15%. The simulation results show that increasing amounts of aluminum in the pristine glasses slow down the initial rate of dissolution as determined from the rate of boron release. However, the extent of corrosion as measured by the total amount of boron release initially increases with addition of Al2O3, up to 5 mol% Al2O3, but subsequently decreases with further Al2O3 addition. The MC simulations reveal that this behavior is due to the interplay between two opposing mechanisms: (1) aluminum slows down the kinetics of hydrolysis/condensation reactions that drive the reorganization of the glass surface and eventual formation of a blocking layer; and (2) aluminum strengthens the glass thereby increasing the lifetime of the upper part of its surface and allowing for more rapid formation of a blocking layer. Additional MC simulations were performed whereby a process representing the formation of a secondary aluminosilicate phase was included. Secondary phase formation draws dissolved glass components out of the aqueous solution, thereby diminishing the rate of condensation and delaying the formation of a blocking layer. As a result, the extent of corrosion is found to increase continuously with increasing Al2O3 content, as observed experimentally. For Al2O3 < 10 mol%, the MC simulations also indicate that, because the secondary phase solubility eventually controls the aluminum content in the part of the altered layer in contact with the bulk aqueous solution, the dissolved aluminum and silicon concentrations at steady state are not dependent on the Al2O3 content of the pristine aluminoborosilicate glass.

Kerisit, Sebastien [Pacific Northwest National Laboratory (PNNL); Ryan, Joseph V [Pacific Northwest National Laboratory (PNNL); Pierce, Eric M [ORNL

2013-01-01T23:59:59.000Z

371

Monte Carlo Simulations of the Corrosion of Aluminoborosilicate Glasses  

SciTech Connect

Aluminum is one of the most common components included in nuclear waste glasses. Therefore, Monte Carlo (MC) simulations were carried out to investigate the influence of aluminum on the rate and mechanism of dissolution of sodium borosilicate glasses in static conditions. The glasses studied were in the compositional range (70-2x)% SiO2 x% Al2O3 15% B2O3 (15+x)% Na2O, where 0 ? x ? 15%. The simulation results show that increasing amounts of aluminum in the pristine glasses slow down the initial rate of dissolution as determined from the rate of boron release. However, the extent of corrosion - as measured by the total amount of boron release - initially increases with addition of Al2O3, up to 5 Al2O3 mol%, but subsequently decreases with further Al2O3 addition. The MC simulations reveal that this behavior is due to the interplay between two opposing mechanisms: (1) aluminum slows down the kinetics of hydrolysis/condensation reactions that drive the reorganization of the glass surface and eventual formation of a blocking layer; and (2) aluminum strengthens the glass thereby increasing the lifetime of the upper part of its surface and allowing for more rapid formation of a blocking layer. Additional MC simulations were performed whereby a process representing the formation of a secondary aluminosilicate phase was included. Secondary phase formation draws dissolved glass components out of the aqueous solution, thereby diminishing the rate of condensation and delaying the formation of a blocking layer. As a result, the extent of corrosion is found to increase continuously with increasing Al2O3 content, as observed experimentally. For Al2O3 < 10 mol%, the MC simulations also indicate that, because the secondary phase solubility eventually controls the aluminum content in the part of the altered layer in contact with the bulk aqueous solution, the dissolved aluminum and silicon concentrations at steady state are not dependent on the Al2O3 content of the pristine aluminoborosilicate glass.

Kerisit, Sebastien N.; Ryan, Joseph V.; Pierce, Eric M.

2013-10-15T23:59:59.000Z

372

Theory and Software  

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

groups at several beam lines. At NIU, the theory effort is integrated with the nanoscience program of the Institute for Nanoscience, Engineering and Technology (INSET) at...

373

Effective medium theory  

SciTech Connect

New applications of the theory of homogenization for heterogeneous metamaterials, in particular for acoustic cloaking and for design and engineering of tunable phononic crystal.

Krokhin, Arkadii [Univ. of North Texas, Denton, TX (United States)

2014-04-18T23:59:59.000Z

374

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

375

Coupled forward-adjoint monte carlo simulations of radiative transport for the study of optical probe design in heterogeneous tissues  

E-Print Network (OSTI)

A new e?ective Monte Carlo midway coupling method in MCNPand J. E. Hoogenboom, A midway forward-adjoint couplingand described the midway forward- adjoint coupling method

Hayakawa, Carole K.; Spanier, Jerome; Venugopalan, Vasan

2007-01-01T23:59:59.000Z

376

Utility Theory Social Intelligence  

E-Print Network (OSTI)

Utility Theory Social Intelligence Daniel Polani Utility Theory ­ p.1/15 Utilities: Motivation Consider: game scenario For Instance: 2-or-more players Necessary: development of concept for utilities decisions sequential decisions (time) games Utility The Prototypical Scenario Consider: agent that can take

Polani, Daniel

377

Wilson loops to 20th order numerical stochastic perturbation theory  

Science Journals Connector (OSTI)

We calculate perturbative contributions of Wilson loops of various sizes up to order 20 in SU(3) pure lattice gauge theory at different lattice sizes for the Wilson gauge action using the technique of numerical stochastic perturbation theory. This allows us to investigate the perturbative series for various Wilson loops at high orders of the perturbation theory. We observe differences in the behavior of the series as a function of the loop order n. Up to n=20 we do not find evidence for the factorial growth of the expansion coefficients often assumed to characterize an asymptotic series. Based on the actually observed behavior we sum the series in a model parametrized by hypergeometric functions. For Wilson loops of moderate sizes the summed series in boosted perturbation theory reach stable plateaus for moderate perturbative order already. The coefficients in the boosted series become much more stable in the result of smoothing the coefficients of the original series effected by the hypergeometric model. We introduce generalized ratios of Wilson loops of different sizes. Together with the corresponding Wilson loops from standard MonteCarlo measurements they enable us to assess their nonperturbative parts.

R. Horsley; G. Hotzel; E.-M. Ilgenfritz; R. Millo; H. Perlt; P. E. L. Rakow; Y. Nakamura; G. Schierholz; A. Schiller

2012-09-06T23:59:59.000Z

378

Final Technical Report for DE-SC0001878 [Theory and Simulation of Defects in Oxide Materials  

SciTech Connect

We explored a wide variety of oxide materials and related problems, including materials at the nanoscale and generic problems associated with oxide materials such as the development of more efficient computational tools to examine these materials. We developed and implemented methods to understand the optical and structural properties of oxides. For ground state properties, our work is predominantly based on pseudopotentials and density functional theory (DFT), including new functionals and going beyond the local density approximation (LDA): LDA+U. To study excited state properties (quasiparticle and optical excitations), we use time dependent density functional theory, the GW approach, and GW plus Bethe-Salpeter equation (GW-BSE) methods based on a many-body Green function approaches. Our work focused on the structural, electronic, optical and magnetic properties of defects (such as oxygen vacancies) in hafnium oxide, titanium oxide (both bulk and clusters) and related materials. We calculated the quasiparticle defect states and charge transition levels of oxygen vacancies in monoclinic hafnia. we presented a milestone G0W0 study of two of the crystalline phases of dye-sensitized TiO{sub 2} clusters. We employed hybrid density functional theory to examine the electronic structure of sexithiophene/ZnO interfaces. To identify the possible effect of epitaxial strain on stabilization of the ferromagnetic state of LaCoO{sub 3} (LCO), we compare the total energy of the magnetic and nonmagnetic states of the strained theoretical bulk structure.

Chelikowsky, James R. [University of Texas at Austin] [University of Texas at Austin

2014-04-14T23:59:59.000Z

379

Tests of Monte Carlo Independent Column Approximation With a Mixed-Layer Ocean Model  

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

Tests of Monte Carlo Independent Column Tests of Monte Carlo Independent Column Approximation With a Mixed-Layer Ocean Model Petri Simo Järvenoja Heikki Järvinen Räisänen Finnish Meteorological Institute Figure 1. Root-mean-square sampling errors in local instant- aneous total (LW+SW) net flux at the surface and total radiative heating rate for the 1COL, CLDS, and REF approaches. Global rms values are given at the upper right hand corner of the plots. 1. Introduction The Monte Carlo Independent Column Approximation (McICA) separates the description of unresolved cloud structure from the radiative transfer solver very flexible ! unbiased with respect to ICA ! However, the radiative fluxes and heating rates contain conditional random errors ("McICA noise"). ? The topic of this poster: All previous tests of McICA

380

Tests of Monte Carlo Independent Column Approximation in the ECHAM5  

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

Tests of Monte Carlo Independent Column Approximation in the ECHAM5 Tests of Monte Carlo Independent Column Approximation in the ECHAM5 Atmospheric GCM Raisanen, Petri Finnish Meteoroligical Institute Jarvenoja, Simo Finnish Meteorological Institute Jarvinen, Heikki Finnish Meteorological Institute Category: Modeling The Monte Carlo Independent Column Approximation (McICA) was recently introduced as a new approach for parametrizing broadband radiative fluxes in global climate models (GCMs). The McICA allows a flexible description of unresolved cloud structure, and it is unbiased with respect to the full ICA, but its results contain conditional random errors (i.e., noise). In this work, McICA and a stochastic cloud generator have been implemented to the Max Planck Institute for Meteorology's ECHAM5 atmospheric GCM. The

Note: This page contains sample records for the topic "theory dft monte" 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

A Proposal for a Standard Interface Between Monte Carlo Tools And One-Loop Programs  

SciTech Connect

Many highly developed Monte Carlo tools for the evaluation of cross sections based on tree matrix elements exist and are used by experimental collaborations in high energy physics. As the evaluation of one-loop matrix elements has recently been undergoing enormous progress, the combination of one-loop matrix elements with existing Monte Carlo tools is on the horizon. This would lead to phenomenological predictions at the next-to-leading order level. This note summarises the discussion of the next-to-leading order multi-leg (NLM) working group on this issue which has been taking place during the workshop on Physics at TeV Colliders at Les Houches, France, in June 2009. The result is a proposal for a standard interface between Monte Carlo tools and one-loop matrix element programs.

Binoth, T.; /Edinburgh U.; Boudjema, F.; /Annecy, LAPP; Dissertori, G.; Lazopoulos, A.; /Zurich, ETH; Denner, A.; /PSI, Villigen; Dittmaier, S.; /Freiburg U.; Frederix, R.; Greiner, N.; Hoeche, Stefan; /Zurich U.; Giele, W.; Skands, P.; Winter, J.; /Fermilab; Gleisberg, T.; /SLAC; Archibald, J.; Heinrich, G.; Krauss, F.; Maitre, D.; /Durham U., IPPP; Huber, M.; /Munich, Max Planck Inst.; Huston, J.; /Michigan State U.; Kauer, N.; /Royal Holloway, U. of London; Maltoni, F.; /Louvain U., CP3 /Milan Bicocca U. /INFN, Turin /Turin U. /Granada U., Theor. Phys. Astrophys. /CERN /NIKHEF, Amsterdam /Heidelberg U. /Oxford U., Theor. Phys.

2011-11-11T23:59:59.000Z

382

A proposal for a standard interface between Monte Carlo tools and one-loop programs  

SciTech Connect

Many highly developed Monte Carlo tools for the evaluation of cross sections based on tree matrix elements exist and are used by experimental collaborations in high energy physics. As the evaluation of one-loop matrix elements has recently been undergoing enormous progress, the combination of one-loop matrix elements with existing Monte Carlo tools is on the horizon. This would lead to phenomenological predictions at the next-to-leading order level. This note summarizes the discussion of the next-to-leading order multi-leg (NLM) working group on this issue which has been taking place during the workshop on Physics at TeV colliders at Les Houches, France, in June 2009. The result is a proposal for a standard interface between Monte Carlo tools and one-loop matrix element programs.

Binoth, T.; Boudjema, F.; Dissertori, G.; Lazopoulos, A.; Denner, A.; Dittmaier, S.; Frederix, R.; Greiner, N.; Hoche, S.; Giele, W.; Skands, P.

2010-01-01T23:59:59.000Z

383

Adjoint and forward Monte Carlo coupled weight window generator for variance reduction  

SciTech Connect

Among the various variance-reduction methods in Monte Carlo calculations, one of the most widely used techniques is the weight window method. The MCNP code provides a weight window generator (WWG) option. In WWG of MCNP, the importance of a cell is estimated by the virtual sampling method during normal Monte Carlo calculation. But, the performance of WWG tends to deteriorate in deep penetration problems. To enhance the performance of the weight window method, importance estimation by the deterministic adjoint calculation has been proposed. However, this approach is possible only when the related deterministic code and interface program are available. The midway coupling method is a surface tally technique that calculates detector response based on the reciprocity theorem, but it does not provide an importance generator. In this paper, a new weight window generation method, called adjoint and forward Monte Carlo coupled WWG, is proposed to overcome the drawbacks of the current WWG in MCNP and the deterministic adjoint calculation method.

Ahn, J.G.; Cho, N.Z.

2000-07-01T23:59:59.000Z

384

Calculation of radiation therapy dose using all particle Monte Carlo transport  

DOE Patents (OSTI)

The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media.

Chandler, William P. (Tracy, CA); Hartmann-Siantar, Christine L. (San Ramon, CA); Rathkopf, James A. (Livermore, CA)

1999-01-01T23:59:59.000Z

385

A Model Collision Operator for Orbit Averaged Monte Carlo Codes  

SciTech Connect

Modelling of fast ion populations, e.g. during ion cyclotron resonance heating, requires accurate treatment of both the fast ions and the thermal populations, while retaining the effects of wide guiding centre orbits. Often the ion-ion collisions are modelled as test particles colliding against a Maxwellian background. However, this type of operator generates a transport of thermal ions on the time scale of ion-ion collisions, and not on the ion-electron time scale as suggested by neoclassical theory. Various approaches have been made to correct this defect. Here we introduce a radial electric field so that the friction between the trapped and passing ions balances the diffusion due to ion-ion collisions.

Hellsten, T.; Johnson, T. [Alfven Laboratory, School of Electrical Engineering, KTH, Association VR-Euratom (Sweden)

2006-11-30T23:59:59.000Z

386

Time and International Relations Theory  

E-Print Network (OSTI)

Eternal permutational theories: neorealism and world systems theory 19 Neorealism 20 World systems theory 24 Closed historical theories: liberal democratic peace theory and teleological constructivsm 29 Liberal... frequently characterizes them by their duration. 3 International institutions and regimes emerge over years, decades, or centuries rather than appearing instantaneously in the global milieu. Innovations such as telegraphs, telephones, televisions...

Hom, Andrew R.

2008-07-22T23:59:59.000Z

387

SEQUENTIAL ADOPTION THEORY: A Theory For Understanding Herding in Technology  

E-Print Network (OSTI)

SEQUENTIAL ADOPTION THEORY: A Theory For Understanding Herding in Technology Adoption Decisions, Sequential decision making, Signal detection theory, Imitative behavior, Simulation I. INTRODUCTION adoption often occurs sequentially, so that later potential adopters can see the decisions (adopt

Walden, Eric

388

Magnetic properties of carbon doped CdS: A first-principles and Monte Carlo study  

Science Journals Connector (OSTI)

Carbon doping of CdS is studied using first-principles calculations and Monte Carlo simulation. Our calculations predict ferromagnetism in C doped CdS, resulting from carbon substitution of sulfur. A single carbon substitution of sulfur favors a spin-polarized state with a magnetic moment of 1.22?B. Ferromagnetic coupling is generally observed between these magnetic moments. A transition temperature of 270K is predicted through Monte Carlo simulation. The ferromagnetism of C doped CdS can be explained by the hole-mediated double exchange mechanism.

Hui Pan; Yuan Ping Feng; Qin Yun Wu; Zhi Gao Huang; Jianyi Lin

2008-03-13T23:59:59.000Z

389

Pseudo-random number generators for Monte Carlo simulations on Graphics Processing Units  

E-Print Network (OSTI)

Basic uniform pseudo-random number generators are implemented on ATI Graphics Processing Units (GPU). The performance results of the realized generators (multiplicative linear congruential (GGL), XOR-shift (XOR128), RANECU, RANMAR, RANLUX and Mersenne Twister (MT19937)) on CPU and GPU are discussed. The obtained speed-up factor is hundreds of times in comparison with CPU. RANLUX generator is found to be the most appropriate for using on GPU in Monte Carlo simulations. The brief review of the pseudo-random number generators used in modern software packages for Monte Carlo simulations in high-energy physics is present.

Demchik, Vadim

2010-01-01T23:59:59.000Z

390

Pseudo-random number generators for Monte Carlo simulations on Graphics Processing Units  

E-Print Network (OSTI)

Basic uniform pseudo-random number generators are implemented on ATI Graphics Processing Units (GPU). The performance results of the realized generators (multiplicative linear congruential (GGL), XOR-shift (XOR128), RANECU, RANMAR, RANLUX and Mersenne Twister (MT19937)) on CPU and GPU are discussed. The obtained speed-up factor is hundreds of times in comparison with CPU. RANLUX generator is found to be the most appropriate for using on GPU in Monte Carlo simulations. The brief review of the pseudo-random number generators used in modern software packages for Monte Carlo simulations in high-energy physics is present.

Vadim Demchik

2010-03-09T23:59:59.000Z

391

Improved convergence of Monte Carlo generated multi-group scattering moments  

SciTech Connect

This paper introduces an improved method of obtaining multi-group scattering moments from a Monte Carlo neutron transport code for use in deterministic transport solvers. The new method increases the information obtained from scattering events and therefore has more useful convergence characteristics than the currently used analog techniques. A prototype of the improved method was implemented in the OpenMC Monte Carlo transport code to compare the accuracy and convergence characteristics of the new method. The prototype showed that accuracy was retained (or improved) while increasing the figure-of-merit for the generation of multi-group scattering moments. (authors)

Nelson, A. G.; Martin, W. R. [University of Michigan, Department of Nuclear Engineering and Radiological Sciences, 2355 Bonisteel Boulevard, Ann Arbor, MI 48104 (United States)

2013-07-01T23:59:59.000Z

392

Milagro Version 2 An Implicit Monte Carlo Code for Thermal Radiative Transfer: Capabilities, Development, and Usage  

SciTech Connect

We have released Version 2 of Milagro, an object-oriented, C++ code that performs radiative transfer using Fleck and Cummings' Implicit Monte Carlo method. Milagro, a part of the Jayenne program, is a stand-alone driver code used as a methods research vehicle and to verify its underlying classes. These underlying classes are used to construct Implicit Monte Carlo packages for external customers. Milagro-2 represents a design overhaul that allows better parallelism and extensibility. New features in Milagro-2 include verified momentum deposition, restart capability, graphics capability, exact energy conservation, and improved load balancing and parallel efficiency. A users' guide also describes how to configure, make, and run Milagro2.

T.J. Urbatsch; T.M. Evans

2006-02-15T23:59:59.000Z

393

A Monte Carlo synthetic-acceleration method for solving the thermal radiation diffusion equation  

SciTech Connect

We present a novel synthetic-acceleration-based Monte Carlo method for solving the equilibrium thermal radiation diffusion equation in three spatial dimensions. The algorithm performance is compared against traditional solution techniques using a Marshak benchmark problem and a more complex multiple material problem. Our results show that our Monte Carlo method is an effective solver for sparse matrix systems. For solutions converged to the same tolerance, it performs competitively with deterministic methods including preconditioned conjugate gradient and GMRES. We also discuss various aspects of preconditioning the method and its general applicability to broader classes of problems.

Evans, Thomas M., E-mail: evanstm@ornl.gov [Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37831 (United States); Mosher, Scott W., E-mail: moshersw@ornl.gov [Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37831 (United States); Slattery, Stuart R., E-mail: sslattery@wisc.edu [University of WisconsinMadison, 1500 Engineering Dr., Madison, WI 53716 (United States); Hamilton, Steven P., E-mail: hamiltonsp@ornl.gov [Oak Ridge National Laboratory, 1 Bethel Valley Rd., Oak Ridge, TN 37831 (United States)

2014-02-01T23:59:59.000Z

394

Zinc surface complexes on birnessite: A density functional theory study  

E-Print Network (OSTI)

of plane- wave electronic structure calculations of bulkJ. (2006) Electronic Structure Calculations for Solids andelectronic, and magnetic properties of Mn oxides, a spin-polarization treatment is essential in performing DFT calculations (

Kwon, Kideok D.

2009-01-01T23:59:59.000Z

395

Hamilton-Jacobi Theory in k-Symplectic Field Theories  

E-Print Network (OSTI)

In this paper we extend the geometric formalism of Hamilton-Jacobi theory for Mechanics to the case of classical field theories in the k-symplectic framework.

M. De Len; D. Martn De Diego; J. C. Marrero; M. Salgado; S. Vilario

2010-05-10T23:59:59.000Z

396

Monte Carlo study of a compressible Ising antiferromagnet on a triangular lattice Lei Gu and Bulbul Chakraborty  

E-Print Network (OSTI)

ARTICLES Monte Carlo study of a compressible Ising antiferromagnet on a triangular lattice Lei Gu the compressible antiferromagnetic Ising Model on a triangular lattice using Monte Carlo simulations. It is found broken symmetries: the Ising symmetry and a three-state Potts symmetry characteristic of the triangular

Garrido, Pedro L.

397

Inverted List Kinetic Monte Carlo with Rejection ap-plied to Directed Self-Assembly of Epitaxial Growth  

E-Print Network (OSTI)

Inverted List Kinetic Monte Carlo with Rejection ap- plied to Directed Self-Assembly of Epitaxial of subsequently deposited material using a kinetic Monte Carlo algorithm that combines the use of inverted lists finding is that the relative performance of the inverted list algorithm improves with increasing system

Schulze, Tim

398

Quasi-Monte Carlo simulation of the light environment of plants Mikolaj CieslakA,E,F  

E-Print Network (OSTI)

Quasi-Monte Carlo simulation of the light environment of plants Mikolaj CieslakA,E,F , Christiane-based CARIBU software (Chelle et al. 2004),and we showthat thesetwo programs produceconsistent results. Wealso assessed theperformance oftheRQMCpath tracing algorithm by comparing it with Monte Carlo path tracing

Prusinkiewicz, Przemyslaw

399

Large-scale simulations on multiple Graphics Processing Units (GPUs) for the direct simulation Monte Carlo method  

Science Journals Connector (OSTI)

In this study, the application of the two-dimensional direct simulation Monte Carlo (DSMC) method using an MPI-CUDA parallelization paradigm on Graphics Processing Units (GPUs) clusters is presented. An all-device (i.e. GPU) computational approach is ... Keywords: Graphics Processing Unit (GPU), MPI-CUDA, Parallel direct simulation Monte Carlo, Rarefied gas dynamics, Very large-scale simulation

C. -C. Su; M. R. Smith; F. -A. Kuo; J. -S. Wu; C. -W. Hsieh; K. -C. Tseng

2012-10-01T23:59:59.000Z

400

Energetics of carbon clusters C8 and C10 from all-electron quantum Monte Carlo calculations  

E-Print Network (OSTI)

Energetics of carbon clusters C8 and C10 from all-electron quantum Monte Carlo calculations Yuri calculations. The total electronic energies obtained are 0.4­1.2 hartrees lower than those of the lowest of the scaling of computational effort with the number of electrons Ne for these quantum Monte Carlo calculations

Anderson, James B.

Note: This page contains sample records for the topic "theory dft monte" 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

Application of collision-based two dimensional Monte Carlo method in a simulated microscale ground water model  

E-Print Network (OSTI)

While the use of Monte Carlo method has been prevalent in nuclear engineering, it has yet to fully blossom in the study of solute transport in porous media. By using an etched-glass micromodel, an attempt is made to apply Monte Carlo method...

Chung, Kiwhan

2012-06-07T23:59:59.000Z

402

The Bulk Channel in Thermal Gauge Theories  

E-Print Network (OSTI)

We investigate the thermal correlator of the trace of the energy-momentum tensor in the SU(3) Yang-Mills theory. Our goal is to constrain the spectral function in that channel, whose low-frequency part determines the bulk viscosity. We focus on the thermal modification of the spectral function, $\\rho(\\omega,T)-\\rho(\\omega,0)$. Using the operator-product expansion we give the high-frequency behavior of this difference in terms of thermodynamic potentials. We take into account the presence of an exact delta function located at the origin, which had been missed in previous analyses. We then combine the bulk sum rule and a Monte-Carlo evaluation of the Euclidean correlator to determine the intervals of frequency where the spectral density is enhanced or depleted by thermal effects. We find evidence that the thermal spectral density is non-zero for frequencies below the scalar glueball mass $m$ and is significantly depleted for $m\\lesssim\\omega\\lesssim 3m$.

Harvey B. Meyer

2010-02-17T23:59:59.000Z

403

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

SciTech Connect

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

Lopata, Kenneth A.; Govind, Niranjan

2013-11-12T23:59:59.000Z

404

Density Functional Theory and Reaction Kinetics Studies of the WaterGas Shift Reaction on PtRe Catalysts  

SciTech Connect

Periodic, self-consistent density functional theory calculations (DFT-GGA-PW91) on Pt(111) and Pt3Re(111) surfaces, reaction kinetics measurements, and microkinetic modeling are employed to study the mechanism of the watergas shift (WGS) reaction over Pt and PtRe catalysts. The values of the reaction rates and reaction orders predicted by the model are in agreement with the ones experimentally determined; the calculated apparent activation energies are matched to within 6% of the experimental values. The primary reaction pathway is predicted to take place through adsorbed carboxyl (COOH) species, whereas formate (HCOO) is predicted to be a spectator species. We conclude that the clean Pt(111) is a good representation of the active site for the WGS reaction on Pt catalysts, whereas the active sites on the PtRe alloy catalyst likely contain partially oxidized metal ensembles.

Carrasquillo-Flores, Ronald; Gallo, Jean Marcel R.; Hahn, Konstanze; Dumesic, James A.; Mavrikakis, Manos

2013-12-01T23:59:59.000Z

405

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.

406

Gauge Theory and Renormalization  

Science Journals Connector (OSTI)

Early developments leading to renormalizable non-Abelian gauge theories for the weak, electromagnetic and strong interactions, are discussed from a personal viewpoint. They drastically improved our view of the...

Gerardt Hooft

1996-01-01T23:59:59.000Z

407

Theories of Truth  

Science Journals Connector (OSTI)

A theory of truth is supposed to tell us what it ... issue here? What are the bearers of truth and falsehood? Philosophical discussions of truth tend to revolve around four broad categories...truth bearers...: se...

Marian David

2004-01-01T23:59:59.000Z

408

Theory of nuclear reactions  

SciTech Connect

The book presents a theory of nuclear reaction. An account is given of the nonrelativistic nuclear reaction theory. The R - matrix description of nuclear reactions is considered and the dispersion method is formulated. Mechanisms of nuclear reactions and their relationship are studied in detail. Attention is paid to nuclear reactions involving the compound nuclear formation and to direct nuclear processes. The optical model the diffraction approach and high - energy diffraction nuclear processes involving composite particles are discussed.

Sitenko, A.G.

1990-01-01T23:59:59.000Z

409

Monte-Carlo simulation of Ising droplets in correlated site-bond percolation  

E-Print Network (OSTI)

L-99 Monte-Carlo simulation of Ising droplets in correlated site-bond percolation D. Stauffer ordinateur la définition de Coniglio et Klein pour les gouttes du modèle Ising, sur les réseaux carré et doublé. Abstract. 2014 The definition of droplets in the Ising model by Coniglio and Klein

Paris-Sud XI, Université de

410

Ising nematic phase in ultrathin magnetic films: A Monte Carlo study Sergio A. Cannas,1,  

E-Print Network (OSTI)

Ising nematic phase in ultrathin magnetic films: A Monte Carlo study Sergio A. Cannas,1, * Mateus F-dimensional Ising model with competing ferromagnetic exchange and dipolar interactions, which models an ultrathin at different temperatures with an intermediate Ising nematic phase between the stripe and the tetragonal ones

Stariolo, Daniel Adrián

411

Simulating and Visualising Phase Transitions: Small-World Effects on the Monte Carlo Ising Model  

E-Print Network (OSTI)

Simulating and Visualising Phase Transitions: Small-World Effects on the Monte Carlo Ising Model K Science, Institute of Information & Mathematical Sciences, Massey University, Albany The Ising Model Many temperature and the material becomes magnetic. A simulation model such as the Ising model has been widely used

Hawick, Ken

412

Monte-Carlo Simulations of Linear Polarization in Clumpy OB-Star Winds  

E-Print Network (OSTI)

Monte-Carlo Simulations of Linear Polarization in Clumpy OB-Star Winds Rich Townsend & Nick Mast Department of Astronomy, University of Wisconsin-Madison Observations of linear polarization in OB-star winds can in principle be used to constrain the characteristics of wind clumping. However, models exploring

Townsend, Richard

413

MONT 109N Mathematics Across Cultures Discussion/Problem Set 5 Indian Mathematics  

E-Print Network (OSTI)

MONT 109N ­ Mathematics Across Cultures Discussion/Problem Set 5 ­ Indian Mathematics April 8, 2011 Background and Assignment In this assignment, we want to look at a sample of Indian mathematics from. Use the formula above to express 17 + 240 as a sum of two square roots. C. Probably the high point

Little, John B.

414

Path-Integral Monte Carlo And The Squeezed Trapped Bose-Einstein Gas  

E-Print Network (OSTI)

Path-Integral Monte Carlo And The Squeezed Trapped Bose-Einstein Gas Juan Pablo Fernández1 the gas becomes effectively two-dimensional (2D). We confirm the plausibility of this result by performing different estimates for the condensate fraction. For the ideal gas, we find that the PIMC column density

Mullin, William J.

415

Quantum Monte Carlo for large chemical systems: Implementing efficient strategies for petascale platforms and beyond  

E-Print Network (OSTI)

Quantum Monte Carlo for large chemical systems: Implementing efficient strategies for petascale platforms and beyond Anthony Scemama, Michel Caffarel Laboratoire de Chimie et Physique Quantiques, CNRS efficiently QMC simulations for large chemical systems are pre- sented. These include: i.) the introduction

Paris-Sud XI, Université de

416

Passive revolution in the green economy: activism and the Belo Monte dam  

Science Journals Connector (OSTI)

Belo Monte is slated to be the worlds third largest dam, and it is Brazils largest infrastructure project, at a cost of at least USD 13 billion. It is forecast to produce around 11,000 GW of energy

Eve Bratman

2014-11-01T23:59:59.000Z

417

Multi-level Monte-Carlo Wiener-Hopf simulation for Lvy processes.  

E-Print Network (OSTI)

Multi-level Monte-Carlo Wiener-Hopf simulation for Lévy processes. Andreas Kyprianou University of Bath Friday May 23, 2014 15:00-16:00 Salle/Room PK-5115, Pavillon Président-Kennedy Building UQAM for a large family of Lévy processes that is based on the Wiener-Hopf decomposition. We pursue this idea

Leclercq, Remi

418

Monte Carlo Electromagnetic Cross Section Production Method for Low Energy Charged Particle Transport Through Single Molecules  

E-Print Network (OSTI)

to the many-body Schrdinger equation and proceeds to use Monte Carlo methods to calculate the perturbations in the internal electron field to determine the aforementioned processes. Results are computed for molecular water in the form of linear energy loss...

Madsen, Jonathan R

2013-08-13T23:59:59.000Z

419

A Java-Based Direct Monte Carlo Simulation of a Nano-Scale Pulse Detonation Engine  

E-Print Network (OSTI)

A Java-Based Direct Monte Carlo Simulation of a Nano- Scale Pulse Detonation Engine Darryl J. Here, the pulse detonation engine is proposed as a means of propulsion for micro-air vehicles and nano attempting to implement the pulse detonation engine at such small length scales is the dominance of the wall

420

Composition of Fish Communities in a European Macrotidal Salt Marsh (the Mont Saint-Michel Bay,  

E-Print Network (OSTI)

Composition of Fish Communities in a European Macrotidal Salt Marsh (the Mont Saint-Michel Bay At least 100 fish species are known to be present in the intertidal areas (estuaries, mudflats and salt, such as estuaries and lagoons, play a nursery role for many fish species. However, in Europe little attention has

Boyer, Edmond

Note: This page contains sample records for the topic "theory dft monte" 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

Dose point kernel simulation for monoenergetic electrons and radionuclides using Monte Carlo techniques  

Science Journals Connector (OSTI)

......Figure-1. Scaled DPKs in water calculated using MCNP5...Figure-2. Scaled DPKs in water calculated using MCNP5...from LHC to ICARUS and atmospheric showers. (1997) Proceedings...dose point kernels in water generated by the Monte...database, random number generator and statistical error......

J. Wu; Y. L. Liu; S. J. Chang; M. M. Chao; S. Y. Tsai; D. E. Huang

2012-11-01T23:59:59.000Z

422

Monte-Carlo simulations of light propagation in luminescent solar concentrators based on semiconductor nanoparticles  

E-Print Network (OSTI)

wavelengths, which can be more efficiently converted to electricity by a PV cell. To achieve this, most-remission events. This is also a big advantage over conventional single material semiconductor nanopar- ticles of semiconductor-based LSCs in detail we employ Monte Carlo simulations (see Sec. II) using the measured data

Ilan, Boaz

423

Monte Carlo Estimation of Time Mismatch Effect in an OFDM EER Architecture  

E-Print Network (OSTI)

Monte Carlo Estimation of Time Mismatch Effect in an OFDM EER Architecture J-F.Bercher, A.Diet, C technique due to non-linearities of the power amplification operation. EER architecture can be used to solve-linearities in the radio- frequency transmitter. Linearization methods are necessary. EER (Envelope Elimination

Baudoin, Geneviève

424

Monte Carlo charged-particle tracking and energy deposition on a Lagrangian mesh  

Science Journals Connector (OSTI)

A Monte Carlo algorithm for alpha particle tracking and energy deposition on a RZ cylindrical computational mesh in a Lagrangian hydrodynamics code used for inertial confinement fusion (ICF) simulations is presented. The straight line approximation is used to follow propagation of Monte Carlo particles which represent collections of alpha particles generated from thermonuclear deuterium-tritium (DT) reactions. Energy deposition in the plasma is modeled by the continuous slowing down approximation. The scheme addresses various aspects arising in the coupling of Monte Carlo tracking with Lagrangian hydrodynamics; such as non-orthogonal severely distorted mesh cells, particle relocation on the moving mesh and particle relocation after rezoning. A comparison with the flux-limited multi-group diffusion transport method is presented for a polar direct drive target design for the National Ignition Facility. Simulations show the Monte Carlo transport method predicts about 30picosecond earlier ignition than predicted by the diffusion method, and generates higher hot spot temperature. Nearly linear speed-up is achieved for multi-processor parallel simulations.

J. Yuan; G. A. Moses; P. W. McKenty

2005-10-10T23:59:59.000Z

425

Quasi-Monte Carlo Simulation of the Light Environment of Plants Mikolaj Cieslak1,5  

E-Print Network (OSTI)

Quasi-Monte Carlo Simulation of the Light Environment of Plants Mikolaj Cieslak1,5 , Christiane and Food Research Institute of New Zealand Limited Running Title: QMC Simulation of the Light Environment. In this paper, we will outline the RQMC path tracing algorithm that we use in our light environment program

Lemieux, Christiane

426

Uncertainty of Oil Field GHG Emissions Resulting from Information Gaps: A Monte Carlo Approach  

Science Journals Connector (OSTI)

Uncertainty of Oil Field GHG Emissions Resulting from Information Gaps: A Monte Carlo Approach ... Regulations on greenhouse gas (GHG) emissions from liquid fuel production generally work with incomplete data about oil production operations. ... We study the effect of incomplete information on estimates of GHG emissions from oil production operations. ...

Kourosh Vafi; Adam R. Brandt

2014-08-10T23:59:59.000Z

427

Use of single scatter electron monte carlo transport for medical radiation sciences  

DOE Patents (OSTI)

The single scatter Monte Carlo code CREEP models precise microscopic interactions of electrons with matter to enhance physical understanding of radiation sciences. It is designed to simulate electrons in any medium, including materials important for biological studies. It simulates each interaction individually by sampling from a library which contains accurate information over a broad range of energies.

Svatos, Michelle M. (Oakland, CA)

2001-01-01T23:59:59.000Z

428

Monte Carlo Study of the Spin Transport in Magnetic Materials , K. Akablia,b  

E-Print Network (OSTI)

Monte Carlo Study of the Spin Transport in Magnetic Materials Y. Magnina , K. Akablia,b , H. T of Natural Science and Technology, Okayama University 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.. Abstract The resistivity in magnetic materials has been theoretically shown to depend on the spin

429

VIM Monte Carlo versus CASMO comparisons for BWR advanced fuel designs  

SciTech Connect

Eigenvalues and two-dimensional fission rate distributions computed with the CASMO-3G lattice physics code and the VIM Monte Carlo Code are compared. The cases assessed are two advanced commercial BWR pin bundle designs. Generally, the two codes show good agreement in K{sub inf}, fission rate distributions, and control rod worths.

Pallotta, A.S. [Commonwealth Edison Co., Chicago, IL (United States); Blomquist, R.N. [Argonne National Lab., IL (United States)

1994-03-01T23:59:59.000Z

430

Quantum Monte Carlo calculations of electronic excitation energies: the case of the singlet n  

E-Print Network (OSTI)

) transition in acrolein Julien Toulouse1 , Michel Caffarel2 , Peter Reinhardt1 , Philip E. Hoggan3 , and C. J-of-the-art quantum Monte Carlo calculations of the singlet n (CO) vertical excitation energy in the acrolein in the acrolein molecule without reoptimization of the determinantal part of the wave function. The acrolein

Paris-Sud XI, Université de

431

Monte Carlo Simulation of Electromagnetic Interactions of Radiation with Liquid Water in  

E-Print Network (OSTI)

; nevertheless the concept of dose is not adequate to estimate the radiation effects when microscopic entitiesMonte Carlo Simulation of Electromagnetic Interactions of Radiation with Liquid Water. They address a physics domain relevant to the simulation of radiation effects in biological systems, where

Paris-Sud XI, Université de

432

Monte Carlo calculations of pair production in high-intensity laser-plasma interactions  

E-Print Network (OSTI)

Gamma-ray and electron-positron pair production will figure prominently in laser-plasma experiments with next generation lasers. Using a Monte Carlo approach we show that straggling effects arising from the finite recoil an electron experiences when it emits a high energy photon, increase the number of pairs produced on further interaction with the laser fields.

Roland Duclous; John Kirk; Anthony Bell

2010-10-21T23:59:59.000Z

433

Monte Carlo Characterization of a Pulsed Laser-Wakefield Driven Monochromatic  

E-Print Network (OSTI)

Monte Carlo Characterization of a Pulsed Laser-Wakefield Driven Monochromatic X-Ray Source S. D determination of the incident X-ray energy by using unfolding techniques. I. INTRODUCTION HE Diocles laser light from the same laser system, producing monochromatic X-rays with energy and spectral width

Umstadter, Donald

434

Direct Simulation Monte Carlo of Inductively Coupled Plasma and Comparison with Experiments  

E-Print Network (OSTI)

Direct Simulation Monte Carlo of Inductively Coupled Plasma and Comparison with Experiments Justine of Chemical Engineering, University of Houston, Houston, Texas 77204-4 792, USA ABSTRACT Direct simulation-density inductively coupled reactor with chlorine (electronegative) chemistry. Electron density and temperature were

Economou, Demetre J.

435

Optimisation of masked ion irradiation damage profiles in YBCO thin films by Monte Carlo simulation  

E-Print Network (OSTI)

Optimisation of masked ion irradiation damage profiles in YBCO thin films by Monte Carlo simulation production with a given mask structure. The results suggest that minimum ion scattering broadening tails with beam energy up to a few hundred keV, though the throughput is intrinsically low [1]. A combination

Webb, Roger P.

436

Interactive design of neutron beam collimators using the Monte Carlo technique in APL  

Science Journals Connector (OSTI)

The scattering and absorption of a neutron beam in a system of collimation rings is simulated step by step under user's control. In the APL notation, the expression of a parallel Monte Carlo simulation scheme is straightforward. Coupled with a fullscreen ...

C. Bastian

1982-07-01T23:59:59.000Z

437

Collective enhancement of nuclear state densities by the shell model Monte Carlo approach  

E-Print Network (OSTI)

The shell model Monte Carlo (SMMC) approach allows for the microscopic calculation of statistical and collective properties of heavy nuclei using the framework of the configuration-interaction shell model in very large model spaces. We present recent applications of the SMMC method to the calculation of state densities and their collective enhancement factors in rare-earth nuclei.

zen, C; Nakada, H

2015-01-01T23:59:59.000Z

438

E-Print Network 3.0 - anharmonic vibrator description Sample...  

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

constructed at the DFT... functional theory DFT calculations of the entire pep- tide. We have constructed anharmonic vibrational... anharmonic effects on fundamen- tal...

439

Bayesian decision theoryBayesian decision theory Jean Daunizeau  

E-Print Network (OSTI)

Bayesian decision theoryBayesian decision theory Jean Daunizeau Wellcome Trust CentreFromstatisticalinferencetostatisticaldecision...... estimationmotivationmotivation conclusionBayesian Decision Theory (i) What do we do with posterior pdfs? (ii) How can we learn:Expectedutilitytheory: existenceofautilityfunctionexistenceofautilityfunction estimationmotivationmotivation conclusionBayesian Decision Theory hypothesis testing

Daunizeau, Jean

440

The effects of mapping CT images to Monte Carlo materials on GEANT4 proton simulation accuracy  

SciTech Connect

Purpose: Monte Carlo simulations of radiation therapy require conversion from Hounsfield units (HU) in CT images to an exact tissue composition and density. The number of discrete densities (or density bins) used in this mapping affects the simulation accuracy, execution time, and memory usage in GEANT4 and other Monte Carlo code. The relationship between the number of density bins and CT noise was examined in general for all simulations that use HU conversion to density. Additionally, the effect of this on simulation accuracy was examined for proton radiation. Methods: Relative uncertainty from CT noise was compared with uncertainty from density binning to determine an upper limit on the number of density bins required in the presence of CT noise. Error propagation analysis was also performed on continuously slowing down approximation range calculations to determine the proton range uncertainty caused by density binning. These results were verified with Monte Carlo simulations. Results: In the presence of even modest CT noise (5 HU or 0.5%) 450 density bins were found to only cause a 5% increase in the density uncertainty (i.e., 95% of density uncertainty from CT noise, 5% from binning). Larger numbers of density bins are not required as CT noise will prevent increased density accuracy; this applies across all types of Monte Carlo simulations. Examining uncertainty in proton range, only 127 density bins are required for a proton range error of <0.1 mm in most tissue and <0.5 mm in low density tissue (e.g., lung). Conclusions: By considering CT noise and actual range uncertainty, the number of required density bins can be restricted to a very modest 127 depending on the application. Reducing the number of density bins provides large memory and execution time savings in GEANT4 and other Monte Carlo packages.

Barnes, Samuel; McAuley, Grant; Slater, James [Department of Radiation Medicine, Loma Linda University, Loma Linda, California 92350 (United States); Wroe, Andrew [Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, California 92350 (United States)

2013-04-15T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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

Physics as Information Theory  

SciTech Connect

The experience from Quantum Information of the last twenty years has lead theorists to look at Quantum Theory and the whole of Physics from a different angle. A new information-theoretic paradigm is emerging, long time ago prophesied by John Archibald Wheeler with his popular coinage 'It from bit'. Theoretical groups are now addressing the problem of deriving Quantum Theory from informational principles, and similar lines are investigated in new approaches to Quantum Gravity. In my talk I will review some recent advances on these lines. The general idea synthesizing the new paradigm is that there is only Quantum Theory (without quantization rules): the whole Physics--including space-time and relativity--is emergent from quantum-information processing. And, since Quantum Theory itself is made with purely informational principles, the whole Physics must be reformulated in information-theoretical terms. The review is divided into the following parts: (a) The informational axiomatization of Quantum Theory; (b) How space-time and relativistic covariance emerge from the quantum computation; (c) What is the information-theoretical meaning of inertial mass and Planck constant, and how the quantum field emerges; (d) Observational consequences: mass-dependent refraction index of vacuum. I then conclude with some possible future research lines.

D'Ariano, Giacomo Mauro (University of Pavia) [University of Pavia

2010-10-20T23:59:59.000Z

442

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 Zusammenhänge zwischen elektrischen und magnetischen Feldern und vereinigt diese zur Theorie des Elektromagnetismus. Das führte zu den heute berühmten 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 des W Bosons, welches schwache Wechselwirkung - z.B.

443

Perspective: Nonadiabatic dynamics theory  

Science Journals Connector (OSTI)

Nonadiabatic dynamicsnuclear motion evolving on multiple potential energy surfaceshas captivated the interest of chemists for decades. Exciting advances in experimentation and theory have combined to greatly enhance our understanding of the rates and pathways of nonadiabatic chemical transformations. Nevertheless there is a growing urgency for further development of theories that are practical and yet capable of reliable predictions driven by fields such as solar energy interstellar and atmospheric chemistry photochemistry vision single molecule electronics radiation damage and many more. This Perspective examines the most significant theoretical and computational obstacles to achieving this goal and suggests some possible strategies that may prove fruitful.

John C. Tully

2012-01-01T23:59:59.000Z

444

Theories with Memory  

E-Print Network (OSTI)

Dimensionally reduced supersymmetric theories retain a great deal of information regarding their higher dimensional origins. In superspace, this "memory" allows us to restore the action governing a reduced theory to that describing its higher-dimensional progenitor. We illustrate this by restoring four-dimensional N=4 Yang-Mills to its six-dimensional parent, N=(1,1) Yang-Mills. Supersymmetric truncation is introduced into this framework and used to obtain the N=1 action in six dimensions. We work in light-cone superspace, dealing exclusively with physical degrees of freedom.

Sudarshan Ananth

2005-10-07T23:59:59.000Z

445

Fortran MPI Checkerboard Code for SU(3) Lattice Gauge Theory I  

E-Print Network (OSTI)

We document Fortran MPI checkerboard code for Markov Chain Monte Carlo simulations of pure SU(3) lattice gauge theory with the Wilson action on a D-dimensional double-layered torus. This includes the usual torus with periodic boundary conditions as an optional case. We use Cabibbo-Marinari heatbath checkerboard updating. Parallelization on sublattices is implemented in all D directions and can be restricted to less than D directions. The parallelization techniques of this paper can be used for any model with interactions of link variables defined on plaquettes.

Bernd A. Berg

2009-04-03T23:59:59.000Z

446

Surface tension of isotropic-nematic interfaces: Fundamental Measure Theory for hard spherocylinders  

E-Print Network (OSTI)

A fluid constituted of hard spherocylinders is studied using a density functional theory for non-spherical hard particles, which can be written as a function of weighted densities. This is based on an extended deconvolution of the Mayer $f$-function for arbitrarily shaped convex hard bodies in tensorial weight functions, which depend each only on the shape and orientation of a single particle. In the course of an examination of the isotropic- nematic interface at coexistence the functional is applied to anisotropic and inhomogeneous problems for the first time. We find good qualitative agreement with other theoretical predictions and also with Monte-Carlo simulations.

Ren Wittmann; Klaus Mecke

2014-03-10T23:59:59.000Z

447

Fluctuation effects in first-order phase transitions: Theory and model for martensitic transformations  

Science Journals Connector (OSTI)

We discuss central questions in weak, first-order structural transitions by means of a magnetic analog model. A theory including fluctuation effects is developed for the model, showing a dynamical response with softening, fading modes and a growing central peak. The model is also analyzed by a two-dimensional Monte Carlo simulation, showing clear precursor phenomena near the first-order transition and spontaneous nucleation. The kinetics of the domain growth is studied and found to be exceedingly slow. The results are applicable for martensitic transformations and structural surface-reconstructive transitions.

Per-Anker Lindgrd and Ole G. Mouritsen

1990-01-01T23:59:59.000Z

448

The Temperature Dependence of the SU(N) Gluon Condensate from Lattice Gauge Theory  

E-Print Network (OSTI)

An analysis of the temperature dependence of the leading contributions to the gluon condensate for SU(N) lattice gauge theory is presented using the data from recent Monte Carlo simulations. The gluon condensate is calculated directly from the new lattice calculations of the interaction measure. It is shown how these computations provide a simple picture for the melting of the condensate around the deconfinement temperature, and the fact that it is negative, and increases in magnitude, above Tc. We close with a discussion of the implications for full QCD of recent results from simulations including fermions.

Graham Boyd; David E. Miller

1996-08-29T23:59:59.000Z

449

Non-Relativistic Superstring Theories  

SciTech Connect

We construct a supersymmetric version of the 'critical' non-relativistic bosonic string theory [1] with its manifest global symmetry. We introduce the anticommuting bc CFT which is the super partner of the {beta}{gamma} CFT. The conformal weights of the b and c fields are both 1/2. The action of the fermionic sector can be transformed into that of the relativistic superstring theory. We explicitly quantize the theory with manifest SO(8) symmetry and find that the spectrum is similar to that of Type IIB superstring theory. There is one notable difference: the fermions are non-chiral. We further consider 'noncritical' generalizations of the supersymmetric theory using the superspace formulation. There is an infinite range of possible string theories similar to the supercritical string theories. We comment on the connection between the critical non-relativistic string theory and the lightlike Linear Dilaton theory.

Kim, Bom Soo

2007-12-14T23:59:59.000Z

450

Variational transition state theory  

SciTech Connect

This research program involves the development of variational transition state theory (VTST) and semiclassical tunneling methods for the calculation of gas-phase reaction rates and selected applications. The applications are selected for their fundamental interest and/or their relevance to combustion.

Truhlar, D.G. [Univ. of Minnesota, Minneapolis (United States)

1993-12-01T23:59:59.000Z

451

Hightlights in Proof Theory  

Science Journals Connector (OSTI)

This is a survey of some of the principal developments in proof theory from its inception in the 1920s, at the hands of David Hilbert, up to the 1960s. Hilberts aim was to use this as a tool in his finitary c...

Solomon Feferman Lec. 1.

2000-01-01T23:59:59.000Z

452

Update on Charmonium Theory  

SciTech Connect

In this invited presentation, I review some recent developments in the theory of charmonium that appear likely to be of importance for future experimental studies in this field. The specific areas considered are double charmonium production. LQCD studies of charmonium, recent results for hadron loops, cc{bar} production cross sections at PANDA, charm molecules, and two recent developments, "charmiscelleny".

Barnes, Ted {F E } [ORNL

2010-01-01T23:59:59.000Z

453

In the OSTI Collections: Monte Carlo Methods | OSTI, US Dept of Energy,  

Office of Scientific and Technical Information (OSTI)

Monte Carlo Methods Monte Carlo Methods "The first thoughts and attempts I made ... were suggested by a question which occurred to me in 1946 as I was convalescing from an illness and playing solitaires. The question was what are the chances that a Canfield solitaire laid out with 52 cards will come out successfully? After spending a lot of time trying to estimate them by pure combinatorial calculations, I wondered whether a more practical method than 'abstract thinking' might not be to lay it out say one hundred times and simply observe and count the number of successful plays. This was already possible to envisage with the beginning of the new era of fast computers, and I immediately thought of problems of neutron diffusion and other questions of mathematical physics,

454

Monte-Carlo Simulations for the optimisation of a TOF-MIEZE Instrument  

E-Print Network (OSTI)

The MIEZE (Modulation of Intensity with Zero Effort) technique is a variant of neutron resonance spin echo (NRSE), which has proven to be a unique neutron scattering technique for measuring with high energy resolution in magnetic fields. Its limitations in terms of flight path differences have already been investigated analytically for neutron beams with vanishing divergence. In the present work Monte-Carlo simulations for quasi-elastic MIEZE experiments taking into account beam divergence as well as the sample dimensions are presented. One application of the MIEZE technique could be a dedicated NRSE-MIEZE instrument at the European Spallation Source (ESS) in Sweden. The optimisation of a particular design based on Montel mirror optics with the help of Monte Carlo simulations will be discussed here in detail.

Weber, T; Georgii, R; Huler, W; Weichselbaumer, S; Bni, P; 10.1016/j.nima.2013.03.010

2013-01-01T23:59:59.000Z

455

Calculating alpha Eigenvalues in a Continuous-Energy Infinite Medium with Monte Carlo  

SciTech Connect

The {alpha} eigenvalue has implications for time-dependent problems where the system is sub- or supercritical. We present methods and results from calculating the {alpha}-eigenvalue spectrum for a continuous-energy infinite medium with a simplified Monte Carlo transport code. We formulate the {alpha}-eigenvalue problem, detail the Monte Carlo code physics, and provide verification and results. We have a method for calculating the {alpha}-eigenvalue spectrum in a continuous-energy infinite-medium. The continuous-time Markov process described by the transition rate matrix provides a way of obtaining the {alpha}-eigenvalue spectrum and kinetic modes. These are useful for the approximation of the time dependence of the system.

Betzler, Benjamin R. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Brown, Forrest B. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory

2012-09-04T23:59:59.000Z

456

Monte Carlo study of the performance of a time-of-flight multichopper spectrometer  

SciTech Connect

The Monte Carlo method is a powerful technique for neutron transport studies. While it has been applied for many years to the study of nuclear systems, there are few codes available for neutron transport in the optical regime. The recent surge of interest in so-called next generation spallation neutron sources and the desire to design new and optimized instruments for these facilities has led us to develop a Monte Carlo code geared toward the simulation of neutron scattering instruments. The time-of-flight multichopper spectrometer, of which IN5 at the ILL is the prototypical example, is the first spectrometer studied with the code. Some of the results of a comparison between the IN5 performance at a reactor and at a Long Pulse Spallation Source (LPSS) are summarized here.

Daemen, L.L.; Eckert, J.; Pynn, R. [and others

1995-12-01T23:59:59.000Z

457

A new effective Monte Carlo Midway coupling method in MCNP applied to a well logging problem  

Science Journals Connector (OSTI)

The background of the Midway forwardadjoint coupling method including the black absorber technique for efficient Monte Carlo determination of radiation detector responses is described. The method is implemented in the general purpose MCNP Monte Carlo code. The utilization of the method is fairly straightforward and does not require any substantial extra expertise. The method was applied to a standard neutron well logging porosity tool problem. The results exhibit reliability and high efficiency of the Midway method. For the studied problem the efficiency gain is considerably higher than for a normal forward calculation, which is already strongly optimized by weight-windows. No additional effort is required to adjust the Midway model if the position of the detector or the porosity of the formation is changed. Additionally, the Midway method can be used with other variance reduction techniques if extra gain in efficiency is desired.

I.V. Serov; T.M. John; J.E. Hoogenboom

1998-01-01T23:59:59.000Z

458

Study of Monte Carlo approach to experimental uncertainty propagation with MSTW 2008 PDFs  

E-Print Network (OSTI)

We investigate the Monte Carlo approach to propagation of experimental uncertainties within the context of the established "MSTW 2008" global analysis of parton distribution functions (PDFs) of the proton at next-to-leading order in the strong coupling. We show that the Monte Carlo approach using replicas of the original data gives PDF uncertainties in good agreement with the usual Hessian approach using the standard Delta(chi^2) = 1 criterion, then we explore potential parameterisation bias by increasing the number of free parameters, concluding that any parameterisation bias is likely to be small, with the exception of the valence-quark distributions at low momentum fractions x. We motivate the need for a larger tolerance, Delta(chi^2) > 1, by making fits to restricted data sets and idealised consistent or inconsistent pseudodata. Instead of using data replicas, we alternatively produce PDF sets randomly distributed according to the covariance matrix of fit parameters including appropriate tolerance values,...

Watt, G

2012-01-01T23:59:59.000Z

459

MCAMC: An Advanced Algorithm for Kinetic Monte Carlo Simulations: from Magnetization Switching to Protein Folding  

E-Print Network (OSTI)

We present the Monte Carlo with Absorbing Markov Chains (MCAMC) method for extremely long kinetic Monte Carlo simulations. The MCAMC algorithm does not modify the system dynamics. It is extremely useful for models with discrete state spaces when low-temperature simulations are desired. To illustrate the strengths and limitations of this algorithm we introduce a simple model involving random walkers on an energy landscape. This simple model has some of the characteristics of protein folding and could also be experimentally realizable in domain motion in nanoscale magnets. We find that even the simplest MCAMC algorithm can speed up calculations by many orders of magnitude. More complicated MCAMC simulations can gain further increases in speed by orders of magnitude.

M. A. Novotny; Shannon M. Wheeler

2002-11-02T23:59:59.000Z

460

A comparison of maximum likelihood and other estimators of eigenvalues from several correlated Monte Carlo samples  

SciTech Connect

The maximum likelihood method for the multivariate normal distribution is applied to the case of several individual eigenvalues. Correlated Monte Carlo estimates of the eigenvalue are assumed to follow this prescription and aspects of the assumption are examined. Monte Carlo cell calculations using the SAM-CE and VIM codes for the TRX-1 and TRX-2 benchmark reactors, and SAM-CE full core results are analyzed with this method. Variance reductions of a few percent to a factor of 2 are obtained from maximum likelihood estimation as compared with the simple average and the minimum variance individual eigenvalue. The numerical results verify that the use of sample variances and correlation coefficients in place of the corresponding population statistics still leads to nearly minimum variance estimation for a sufficient number of histories and aggregates.

Beer, M.

1980-12-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" 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.


461

Photon energy absorption coefficients for nuclear track detectors using Geant4 Monte Carlo simulation  

Science Journals Connector (OSTI)

Abstract Geant4 Monte Carlo code simulations were used to solve experimental and theoretical complications for calculation of mass energy-absorption coefficients of elements, air, and compounds. The mass energy-absorption coefficients for nuclear track detectors were computed first time using Geant4 Monte Carlo code for energy 1keV20MeV. Very good agreements for simulated results of mass energy-absorption coefficients for carbon, nitrogen, silicon, sodium iodide and nuclear track detectors were observed on comparison with the values reported in the literatures. Kerma relative to air for energy 1keV20MeV and energy absorption buildup factors for energy 50keV10MeV up to 10mfp penetration depths of the selected nuclear track detectors were also calculated to evaluate the absorption of the gamma photons. Geant4 simulation can be utilized for estimation of mass energy-absorption coefficients in elements and composite materials.

Vishwanath P. Singh; M.E. Medhat; N.M. Badiger

2015-01-01T23:59:59.000Z

462

Geometric representations in the developmental Monte Carlo transport code MC21  

SciTech Connect

The geometry kernel of the developmental Monte Carlo transport code MC21 is designed as a combination of the geometry capabilities of several existing Monte Carlo codes. This combination of capabilities is intended to meet efficiently the general requirements associated with in-core design products and, at the same time, be flexible enough to support highly general geometric models. This paper provides a description of the different geometry representations of MC21 and outlines how the geometric data is stored internally through the use of Fortran-90 data structures. Finally, two alternative geometric representations of a published BWR unit assembly model are discussed. Results for the two representations are contrasted, including k-effective results, relative memory footprints, and relative computational speeds. While total memory footprint is not noticeably reduced, results show significant speed advantages of one representation. (authors)

Donovan, T. [KAPL, Inc. - A Lockheed Martin Company, Schenectady, NY (United States); Tyburski, L. [Bechtel Bettis, Inc., West Mifflin, PA (United States)

2006-07-01T23:59:59.000Z

463

Unbiased Reduced Density Matrices and Electronic Properties from Full Configuration Interaction Quantum Monte Carlo  

E-Print Network (OSTI)

Properties that are necessarily formulated within pure (symmetric) expectation values are difficult to calculate for projector quantum Monte Carlo approaches, but are critical in order to compute many of the important observable properties of electronic systems. Here, we investigate an approach for the sampling of unbiased reduced density matrices within the Full Configuration Interaction Quantum Monte Carlo dynamic, which requires only small computational overheads. This is achieved via an independent replica population of walkers in the dynamic, sampled alongside the original population. The resulting reduced density matrices are free from systematic error (beyond those present via constraints on the dynamic itself), and can be used to compute a variety of expectation values and properties, with rapid convergence to an exact limit. A quasi-variational energy estimate derived from these density matrices is proposed as an accurate alternative to the projected estimator for multiconfigurational wavefunctions, ...

Overy, Catherine; Blunt, N S; Shepherd, James; Cleland, Deidre; Alavi, Ali

2014-01-01T23:59:59.000Z

464

Validation of a Monte Carlo Based Depletion Methodology Using HFIR Post-Irradiation Measurements  

SciTech Connect

Post-irradiation uranium isotopic atomic densities within the core of the High Flux Isotope Reactor (HFIR) were calculated and compared to uranium mass spectrographic data measured in the late 1960s and early 70s [1]. This study was performed in order to validate a Monte Carlo based depletion methodology for calculating the burn-up dependent nuclide inventory, specifically the post-irradiation uranium

Chandler, David [ORNL; Maldonado, G Ivan [ORNL; Primm, Trent [ORNL

2009-11-01T23:59:59.000Z

465

SU?FF?T?109: Automation of Monte Carlo Simulations For A Proton Therapy System  

Science Journals Connector (OSTI)

Purpose: To develop a code system to automate the processes associated with Monte Carlo simulations of a clinical proton therapy system. Method and Materials: A software system was developed that accepts a clinical prescription (beam range range modulation and field size) and generates a complete Monte Carlo simulation input file that includes all major components in the M. D. Anderson passively scattered treatment head plus one of several user?selectable phantoms. The simulations are automatically submitted to a 130 dual?CPU cluster. Post processing scripts were also developed to analyze the simulation results and generate required configuration data for the Varian Eclipse treatment planning system. Quality assurance procedures such as design inspection unit test incremental integration test regression test and integration test were performed to ensure the code system produces correct results. The code system was written in mainly C language with some shell scripts and it runs on the LINUX operating system. Results: A code system has been developed to automatically generate MCNPX input files run simulations and perform post?processing of simulation results for a proton therapy system. The code system has been used to simulate dose profiles and generate required data for commissioning the M. D. Anderson proton therapy system. Over one thousand dose profiles were generated for different beam configurations by the code system in two months. Example beam data will be presented. Conclusion: The automated Monte Carlo code system has proved to be a useful tool for simulations of clinical applications in proton therapy. It allows for rapid modeling of proton therapy systems and the results of this study suggest that data from Monte Carlo simulations will play an increasingly prominent role in proton therapy projects i.e. pre?clinical design commissioning studies and routine clinical tasks.

Y Zheng; J Fontenot; N Koch

2006-01-01T23:59:59.000Z

466

The Metropolis Monte Carlo method with CUDA enabled Graphic Processing Units  

SciTech Connect

We present a CPUGPU system for runtime acceleration of large molecular simulations using GPU computation and memory swaps. The memory architecture of the GPU can be used both as container for simulation data stored on the graphics card and as floating-point code target, providing an effective means for the manipulation of atomistic or molecular data on the GPU. To fully take advantage of this mechanism, efficient GPU realizations of algorithms used to perform atomistic and molecular simulations are essential. Our system implements a versatile molecular engine, including inter-molecule interactions and orientational variables for performing the Metropolis Monte Carlo (MMC) algorithm, which is one type of Markov chain Monte Carlo. By combining memory objects with floating-point code fragments we have implemented an MMC parallel engine that entirely avoids the communication time of molecular data at runtime. Our runtime acceleration system is a forerunner of a new class of CPUGPU algorithms exploiting memory concepts combined with threading for avoiding bus bandwidth and communication. The testbed molecular system used here is a condensed phase system of oligopyrrole chains. A benchmark shows a size scaling speedup of 60 for systems with 210,000 pyrrole monomers. Our implementation can easily be combined with MPI to connect in parallel several CPUGPU duets. -- Highlights: We parallelize the Metropolis Monte Carlo (MMC) algorithm on one CPUGPU duet. The Adaptive Tempering Monte Carlo employs MMC and profits from this CPUGPU implementation. Our benchmark shows a size scaling-up speedup of 62 for systems with 225,000 particles. The testbed involves a polymeric system of oligopyrroles in the condensed phase. The CPUGPU parallelization includes dipoledipole and MieJones classic potentials.

Hall, Clifford [Computational Materials Science Center, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States) [Computational Materials Science Center, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States); School of Physics, Astronomy, and Computational Sciences, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States); Ji, Weixiao [Computational Materials Science Center, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States)] [Computational Materials Science Center, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States); Blaisten-Barojas, Estela, E-mail: blaisten@gmu.edu [Computational Materials Science Center, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States) [Computational Materials Science Center, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States); School of Physics, Astronomy, and Computational Sciences, George Mason University, 4400 University Dr., Fairfax, VA 22030 (United States)

2014-02-01T23:59:59.000Z

467

Path-integral Monte Carlo calculation of the kinetic energy of condensed lithium  

Science Journals Connector (OSTI)

We report path-integral Monte Carlo calculations of the kinetic energy of condensed lithium for several temperatures in both the solid and liquid phases. The excess kinetic energy of lithium decreases from about 10.4% of the classical value at 300 K to 3.2% at 520 K indicating a very slow decay with temperature. A Wigner-Kirkwood perturbation treatment of quantum effects to order ?2 gives a satisfactory agreement with the path-integral results.

Claudia Filippi and David M. Ceperley

1998-01-01T23:59:59.000Z

468

Modular, object-oriented redesign of a large-scale Monte Carlo neutron transport program  

SciTech Connect

This paper describes the modular, object-oriented redesign of a large-scale Monte Carlo neutron transport program. This effort represents a complete 'white sheet of paper' rewrite of the code. In this paper, the motivation driving this project, the design objectives for the new version of the program, and the design choices and their consequences will be discussed. The design itself will also be described, including the important subsystems as well as the key classes within those subsystems.

Moskowitz, B.S.

2000-02-01T23:59:59.000Z

469

A Geometric Hamilton-Jacobi Theory for Classical Field Theories  

E-Print Network (OSTI)

In this paper we extend the geometric formalism of the Hamilton-Jacobi theory for hamiltonian mechanics to the case of classical field theories in the framework of multisymplectic geometry and Ehresmann connections.

M. de Leon; J. C. Marrero; D. Martin de Diego

2008-01-08T23:59:59.000Z

470

Experimental validation and evaluation of uncertainty in the monte carlo modeling of electron irradiation of complex objects  

E-Print Network (OSTI)

Monte Carlo method is an invaluable tool in the field of radiation protection, used to calculate shielding effectiveness, as well as dose for medical applications. With few exceptions, most of the objects currently simulated have been homogeneous...

Tutt, Teresa Elizabeth

2009-05-15T23:59:59.000Z

471

Monte Carlo Simulation of Solid-State Thermionic Energy Conversion Devices Based on Non-Planar Heterostructure Interfaces  

Science Journals Connector (OSTI)

In this paper, electron emission from non-planar potential barrier structures is analyzed using a Monte Carlo electron transport model. Compared to the planar structures, about twice bigger emission current ca...

Z. Bian; A. Shakouri

2006-01-01T23:59:59.000Z

472

Monte Carlo Study of Patchy Nanostructures Self-Assembled from a Single Multiblock Chain  

E-Print Network (OSTI)

We present a lattice Monte Carlo simulation for a multiblock copolymer chain of length N=240 and microarchitecture $(10-10)_{12}$.The simulation was performed using the Monte Carlo method with the Metropolis algorithm. We measured average energy, heat capacity, the mean squared radius of gyration, and the histogram of cluster count distribution. Those quantities were investigated as a function of temperature and incompatibility between segments, quantified by parameter {\\omega}. We determined the temperature of the coil-globule transition and constructed the phase diagram exhibiting a variety of patchy nanostructures. The presented results yield a qualitative agreement with those of the off-lattice Monte Carlo method reported earlier, with a significant exception for small incompatibilities,{\\omega}, and low temperatures, where 3-cluster patchy nanostructures are observed in contrast to the 2-cluster structures observed for the off-lattice $(10-10)_{12}$ chain. We attribute this difference to a considerable stiffness of lattice chains in comparison to that of the off-lattice chains.

Jakub Krajniak; Michal Banaszak

2014-10-15T23:59:59.000Z

473

Spatial homogenization of thermal feedback regions in Monte Carlo reactor calculations  

SciTech Connect

An integrated thermal-hydraulic feedback module has previously been developed for the Monte Carlo transport solver, MC21. The module incorporates a flexible input format that allows the user to describe heat transfer and coolant flow paths within the geometric model at any level of spatial detail desired. The effect that the varying levels of spatial homogenization of thermal regions has on the accuracy of the Monte Carlo simulations is examined in this study. Six thermal feedback mappings are constructed from the same geometric model of the Calvert Cliffs core. The spatial homogenization of the thermal regions is varied, giving each scheme a different level of detail, and the adequacy of the spatial homogenization is determined based on the eigenvalue produced by each Monte Carlo calculation. The purpose of these numerical experiments is to determine the level of detail necessarily to accurately capture the thermal feedback effect on reactivity. Several different core models are considered: axial-flow only, axial and lateral flow, asymmetry due to control rod insertion, and fuel heating (temperature -dependent cross sections). The thermal results generated by the MC21 thermal feedback module are consistent with expectations. Based upon the numerical experiments conducted it is concluded that the amount of spatial detail necessary to accurately capture the feedback effect on reactivity is relatively small. Homogenization at the assembly level for the Calvert Cliffs PWR model results in a similar power defect to that calculated with individual pin-cells modeled as explicit thermal regions. (authors)

Hanna, B. R.; Gill, D. F.; Griesheimer, D. P. [Bertis Atomic Power Laboratory, Bechtel Marine Propulsion Corporation, P.O. Box 79, West Mifflin, PA 15122 (United States)

2012-07-01T23:59:59.000Z

474

Movable geometry and eigenvalue search capability in the MC21 Monte Carlo code  

SciTech Connect

A description of a robust and flexible movable geometry implementation in the Monte Carlo code MC21 is described along with a search algorithm that can be used in conjunction with the movable geometry capability to perform eigenvalue searches based on the position of some geometric component. The natural use of the combined movement and search capability is searching to critical through variation of control rod (or control drum) position. The movable geometry discussion provides the mathematical framework for moving surfaces in the MC21 combinatorial solid geometry description. A discussion of the interface between the movable geometry system and the user is also described, particularly the ability to create a hierarchy of movable groups. Combined with the hierarchical geometry description in MC21 the movable group framework provides a very powerful system for inline geometry modification. The eigenvalue search algorithm implemented in MC21 is also described. The foundations of this algorithm are a regula falsi search though several considerations are made in an effort to increase the efficiency of the algorithm for use with Monte Carlo. Specifically, criteria are developed to determine after each batch whether the Monte Carlo calculation should be continued, the search iteration can be rejected, or the search iteration has converged. These criteria seek to minimize the amount of time spent per iteration. Results for the regula falsi method are shown, illustrating that the method as implemented is indeed convergent and that the optimizations made ultimately reduce the total computational expense. (authors)

Gill, D. F.; Nease, B. R.; Griesheimer, D. P. [Bettis Atomic Power Laboratory, PO Box 79, West Mifflin, PA 15122 (United States)

2013-07-01T23:59:59.000Z

475

MCNPX Monte Carlo burnup simulations of the isotope correlation experiments in the NPP obrigheim.  

SciTech Connect

This paper describes the simulation work of the Isotope Correlation Experiment (ICE) using the MCNPX Monte Carlo computer code package. The Monte Carlo simulation results are compared with the ICE-Experimental measurements for burnup up to 30 GWD/t. The comparison shows the good capabilities of the MCNPX computer code package for predicting the depletion of the uranium fuel and the buildup of the plutonium isotopes in a PWR thermal reactor. The Monte Carlo simulation results show also good agreements with the experimental data for calculating several long-lived and stable fission products. However, for the americium and curium actinides, it is difficult to judge the predication capabilities for these actinides due to the large uncertainties in the ICE-Experimental data. In the MCNPX numerical simulations, a pin cell model is utilized to simulate the fuel lattice of the nuclear power reactor. Temperature dependent libraries based on JEFF3.1 nuclear data files are utilized for the calculations. In addition, temperature dependent libraries based ENDF/B-VII nuclear data files are utilized and the obtained results are very close to the JEFF3.1 results, except for {approx}10% differences in the prediction of the minor actinide isotopes buildup.

Cao, Y.; Gohar, Y.; Broeders, C. (Nuclear Engineering Division); (Inst. for Neutron Physics and Reactor Technology)

2010-10-01T23:59:59.000Z

476

Monte Carlo depletion calculations using VESTA 2.1 new features and perspectives  

SciTech Connect

VESTA is a Monte Carlo depletion interface code that is currently under development at IRSN. With VESTA, the emphasis lies on both accuracy and performance, so that the code will be capable of providing accurate and complete answers in an acceptable amount of time compared to other Monte Carlo depletion codes. From its inception, VESTA is intended to be a generic interface code so that it will ultimately be capable of using any Monte-Carlo code or depletion module and that can be tailored to the users needs. A new version of the code (version 2.1.x) will be released in 2012. The most important additions to the code are a burn up dependent isomeric branching ratio treatment to improve the prediction of metastable nuclides such as {sup 242m}Am and the integration of the PHOENIX point depletion module (also developed at IRSN) to overcome some of the limitations of the ORIGEN 2.2 module. The task of extracting and visualising the basic results and also the calculation of physical quantities or other data that can be derived from the basic output provided by VESTA will be the task of the AURORA depletion analysis tool which will be released at the same time as VESTA 2.1.x. The experimental validation database was also extended for this new version and it now contains a total of 35 samples with chemical assay data and 34 assembly decay heat measurements. (authors)

Haeck, W.; Cochet, B.; Aguiar, L. [Institut de Radioprotection et de Surete Nucleaire IRSN, BP 17, 92262 Fontenay-aux-Roses Cedex (France)

2012-07-01T23:59:59.000Z

477

Quantum probability from decision theory?  

Science Journals Connector (OSTI)

...128. Cox, R. T. 1946 Probability, frequency, and reasonable...Finetti, B. 1972 Theory of probability, vols I and II. Wiley...1999 Quantum theory of probability and decisions. Proc. R...1972 The foundations of statistics. Dover. Von Neumann, J...

2000-01-01T23:59:59.000Z

478

Decision Theory and Real Decisions:  

Science Journals Connector (OSTI)

Decision theory has been extremely successful in various ways. As a theory per se..., it has provided interesting research opportunities stemming from an elegant central core. It has served as a basis for identif...

Kenneth R. MacCrimmon

1999-01-01T23:59:59.000Z

479

Theory Seminar Schedule  

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

6-2007 6-2007 Click on a title to read an abstract, if available (underlined). 10 July 2007 Special Day: Tuesday, 3:00pm Robert Wiringa Argonne National Laboratory wiringa@theory.phy.anl.gov Dependence of nuclear binding on hadronic mass variation 3 July 2007 Special Day and Time: Tuesday, 10:30am Renato Higa University of Bonn, Germany higa@itkp.uni-bonn.de Coulomb interactions within Halo EFT 5 June 2007 Special Day and Time: Tuesday, 10.30am Omar Benhar Istituto Nazionale di Fisica Nucleare, Rome, Italy benhar@roma1.infn.it The equation of state of neutron star matter and gravitational wave emission 29 May 2007 Special Day: Tuesday Ulrich Mosel Giessen University, Germany Ulrich.Mosel@theo.physik.uni-giessen.de Hadrons in Medium - Theory meets experiment 10 May 2007

480

Salinas : theory manual.  

SciTech Connect

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 "theory dft monte" from the National Library of EnergyBeta (NLEBeta).
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481

A proposed gravitodynamic theory  

E-Print Network (OSTI)

This paper proposes a gravitodynamic theory because there are similarities between gravitational theory and electrodynamics. Based on Einstein's principle of equivalence, two coordinate conditions are proposed into the four-dimensional line element and transformations. As a consequence,the equation of motion for gravitational force or inertial force has a form similar to the equation of Lorentz force on a charge in electrodynamics. The inertial forces in auniformly rotating system are calculated, which show that the Coriolis force is produced by a magnetic-type gravitational field. We have also calculated the Sagnac effect due to the rotation. These experimental facts strongly support our proposed coordinate conditions. In addition, the gravitodynamic field equations are briefly discussed. Since only four gravitational potentials (3 + 1 split) enter the metric tensor, the gravitodynamic field equations in ``3+1 split" form would be analogous to Maxwell's equations.

T. Chang

1997-03-18T23:59:59.000Z

482

Field Theory of Matter  

Science Journals Connector (OSTI)

A speculative field theory of matter is developed. Simple computational methods are used in a preliminary survey of its consequences. The theory exploits the known properties of leptons by means of a principle of symmetry between electrical and nucleonic charge. There are fundamental fields with spins 0, , 1. The spinless field is neutral. Spin and 1 fields can carry both electrical and nucleonic charge. The multiplicity of any nonzero charge is 3. Explicit dynamical mechanisms for the breakdown of unitary symmetry and for the muon-electron mass difference are given. A more general view of lepton properties is proposed. Mass relations for baryon and meson multiplets are derived, together with approximate couplings among the multiplets. The weakness of ? production in ?-N collisions and the suppression of the ???+? decay is explained.

Julian Schwinger

1964-08-10T23:59:59.000Z

483

Nonlocal theory of accelerated observers  

Science Journals Connector (OSTI)

A nonlocal theory of accelerated observers is developed on the basis of the hypothesis that an electromagnetic wave can never stand completely still with respect to an observer. In the eikonal approximation, the nonlocal theory reduces to the standard extension of Lorentz invariance to accelerated observers. The validity of the nonlocal theory would exclude the possibility of existence of any basic scalar field in nature. The observational consequences of this theory are briefly discussed.

Bahram Mashhoon

1993-05-01T23:59:59.000Z

484

Measured and Monte Carlo calculated k{sub Q} factors: Accuracy and comparison  

SciTech Connect

Purpose: The journal Medical Physics recently published two papers that determine beam quality conversion factors, k{sub Q}, for large sets of ion chambers. In the first paper [McEwen Med. Phys. 37, 2179-2193 (2010)], k{sub Q} was determined experimentally, while the second paper [Muir and Rogers Med. Phys. 37, 5939-5950 (2010)] provides k{sub Q} factors calculated using Monte Carlo simulations. This work investigates a variety of additional consistency checks to verify the accuracy of the k{sub Q} factors determined in each publication and a comparison of the two data sets. Uncertainty introduced in calculated k{sub Q} factors by possible variation of W/e with beam energy is investigated further. Methods: The validity of the experimental set of k{sub Q} factors relies on the accuracy of the NE2571 reference chamber measurements to which k{sub Q} factors for all other ion chambers are correlated. The stability of NE2571 absorbed dose to water calibration coefficients is determined and comparison to other experimental k{sub Q} factors is analyzed. Reliability of Monte Carlo calculated k{sub Q} factors is assessed through comparison to other publications that provide Monte Carlo calculations of k{sub Q} as well as an analysis of the sleeve effect, the effect of cavity length and self-consistencies between graphite-walled Farmer-chambers. Comparison between the two data sets is given in terms of the percent difference between the k{sub Q} factors presented in both publications. Results: Monitoring of the absorbed dose calibration coefficients for the NE2571 chambers over a period of more than 15 yrs exhibit consistency at a level better than 0.1%. Agreement of the NE2571 k{sub Q} factors with a quadratic fit to all other experimental data from standards labs for the same chamber is observed within 0.3%. Monte Carlo calculated k{sub Q} factors are in good agreement with most other Monte Carlo calculated k{sub Q} factors. Expected results are observed for the sleeve effect and the effect of cavity length on k{sub Q}. The mean percent differences between experimental and Monte Carlo calculated k{sub Q} factors are -0.08, -0.07, and -0.23% for the Elekta 6, 10, and 25 MV nominal beam energies, respectively. An upper limit on the variation of W/e in photon beams from cobalt-60 to 25 MV is determined as 0.4% with 95% confidence. The combined uncertainty on Monte Carlo calculated k{sub Q} factors is reassessed and amounts to between 0.40 and 0.49% depending on the wall material of the chamber. Conclusions: Excellent agreement (mean percent difference of only 0.13% for the entire data set) between experimental and calculated k{sub Q} factors is observed. For some chambers, k{sub Q} is measured for only one chamber of each type--the level of agreement observed in this study would suggest that for those chambers the measured k{sub Q} values are generally representative of the chamber type.

Muir, B. R.; McEwen, M. R.; Rogers, D. W. O. [Ottawa Medical Physics Institute (OMPI), Ottawa Carleton Institute for Physics, Carleton University Campus, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6 (Canada); Institute for National Measurement Standards, National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada); Ottawa Medical Physics Institute (OMPI), Ottawa Carleton Institute for Physics, Carleton University Campus, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6 (Canada)

2011-08-15T23:59:59.000Z

485

Probabilistic theories with purification  

SciTech Connect

We investigate general probabilistic theories in which every mixed state has a purification, unique up to reversible channels on the purifying system. We show that the purification principle is equivalent to the existence of a reversible realization of every physical process, that is, to the fact that every physical process can be regarded as arising from a reversible interaction of the system with an environment, which is eventually discarded. From the purification principle we also construct an isomorphism between transformations and bipartite states that possesses all structural properties of the Choi-Jamiolkowski isomorphism in quantum theory. Such an isomorphism allows one to prove most of the basic features of quantum theory, like, e.g., existence of pure bipartite states giving perfect correlations in independent experiments, no information without disturbance, no joint discrimination of all pure states, no cloning, teleportation, no programming, no bit commitment, complementarity between correctable channels and deletion channels, characterization of entanglement-breaking channels as measure-and-prepare channels, and others, without resorting to the mathematical framework of Hilbert spaces.

Chiribella, Giulio; D'Ariano, Giacomo Mauro; Perinotti, Paolo [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Ontario, Ontario N2L 2Y5 (Canada); QUIT Group, Dipartimento di Fisica ''A. Volta'' and INFN Sezione di Pavia, via Bassi 6, 27100 Pavia (Italy)

2010-06-15T23:59:59.000Z

486

Informational derivation of quantum theory  

SciTech Connect

We derive quantum theory from purely informational principles. Five elementary axioms - causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning - define a broad class of theories of information processing that can be regarded as standard. One postulate - purification - singles out quantum theory within this class.

Chiribella, Giulio; D'Ariano, Giacomo Mauro; Perinotti, Paolo [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Ontario, N2L 2Y5 (Canada); QUIT Group, Dipartimento di Fisica ''A. Volta'' and INFN Sezione di Pavia, via Bassi 6, I-27100 Pavia (Italy)

2011-07-15T23:59:59.000Z

487

Quantum Probability from Decision Theory?  

E-Print Network (OSTI)

In a recent paper (quant-ph/9906015), Deutsch claims to derive the "probabilistic predictions of quantum theory" from the "non-probabilistic axioms of quantum theory" and the "non-probabilistic part of classical decision theory." We show that his derivation fails because it includes hidden probabilistic assumptions.

H. Barnum; C. M. Caves; J. Finkelstein; C. A. Fuchs; R. Schack

1999-07-07T23:59:59.000Z

488

Epistemic Decision Theory Hilary Greaves  

E-Print Network (OSTI)

Epistemic Decision Theory Hilary Greaves Faculty of Philosophy, University of Oxford hilary an epistemic decision theory, in a consequentialist spirit. Previous work has focused on cases in which and causal decision theory, and of the Newcomb Problem and `Psychopath Button' Problem. A variant of causal

Fitelson, Branden

489

Applying Effective Theories to Collider Phenomenology  

E-Print Network (OSTI)

Theories to Collider Phenomenology by Grigol GagikovichTheories to Collider Phenomenology Copyright 2010 by GrigolTheories to Collider Phenomenology by Grigol Gagikovich

Ovanesyan, Grigol

2010-01-01T23:59:59.000Z

490

Electronic and magnetic properties of Co_n Mo_m nanoclusters with n+m = x and 2<=x<=6 atoms from DFT calculations  

E-Print Network (OSTI)

We present the results of the density functional theory study of Co_n Mo_m nanoclusters with n+m=x and 2content and increases with increasing n. The magnetic anisotropy on the other hand becomes smaller for larger magnetic moments S. We observe an increase in the binding energy, electron affinity, and average bond length with increasing cluster size as well as a decrease in the ionization potential, chemical potential, molecular hardness and the HOMO-LUMO gap.

Liebing, Simon; Trepte, Kai; Kortus, Jens

2014-01-01T23:59:59.000Z

491

Complex higher order derivative theories  

SciTech Connect

In this work is considered a complex scalar field theory with higher order derivative terms and interactions. A procedure is developed to quantize consistently this system avoiding the presence of negative norm states. In order to achieve this goal the original real scalar high order field theory is extended to a complex space attaching a complex total derivative to the theory. Next, by imposing reality conditions the complex theory is mapped to a pair of interacting real scalar field theories without the presence of higher derivative terms.

Margalli, Carlos A.; Vergara, J. David [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico 04510 DF (Mexico)

2012-08-24T23:59:59.000Z

492

Structure and properties of nanoscale materials: theory and atomistic computer simulation  

Science Journals Connector (OSTI)

We present a review of a few research topics developed within the "Theory and Atomistic Computer Simulation" Department at CINaM. The bottom line of the scientific activity is to use up-to-date theoretical and computer simulation techniques to address physics and materials science problems, often at the nanometric scale, in close contact with experimental groups. It ranges from the study of the structure and properties of molecular systems for organic electronics to metallic clusters and alloys, magnetic oxides, nuclear fuels and carbon-based nanostructures. These studies are motivated by fundamental research questions as well as more applied goals including environmental and energy issues, or information technologies. This broad spectrum of activities requires a large range of techniques, from theory and ab initio calculations to semi-empirical models incorporated in Monte Carlo or molecular dynamics simulations.

C. Bichara; P. Marsal; C. Mottet; R. Pellenq; F. Ribeiro; A. Saú l; G. Tré glia; H.-Ch. Weissker

2012-01-01T23:59:59.000Z

493

Resummed thermodynamic perturbation theory for bond cooperativity in associating fluids with small bond angles: Effects of steric hindrance and ring formation  

E-Print Network (OSTI)

In this paper we develop a thermodynamic perturbation theory for two site associating fluids which exhibit bond cooperativity. We include both steric hindrance and ring formation such that the equation of state is bond angle dependent. Here the bond angle is the angle separating the centers of the two association sites. As a test, new Monte Carlo simulations are performed, and the theory is found to accurately predict the internal energy as well as the distribution of associated clusters as a function of bond angle and bond cooperativity.

B. D. Marshall; Amin Haghmoradi; W. G. Chapman

2014-04-03T23:59:59.000Z

494

Observer Localization in Multiverse Theories Marcus Hutter  

E-Print Network (OSTI)

battle; and the ongoing discussion of whether string theory is a theory of everything or more a theory's oscillating universe, Smolin's baby universe theory, Everett's many-worlds interpretation of quantum mechanics

Hutter, Marcus

495

Quantum Decision Theory  

E-Print Network (OSTI)

We argue that, contrary to conventional wisdom, decision theory is not invariant to the physical environment in which a decision is made. Specifically, we show that a decision maker (DM) with access to quantum information resources may be able to do strictly better than a DM with access only to classical information resources. In this respect, our findings are somewhat akin to those in computer science that have established the superiority of quantum over classical algorithms for certain problems. We treat three kinds of decision tree (Kuhn [1950], [1953]): Kuhn trees in which the DM does or does not have perfect recall, and non-Kuhn trees.

Adam Brandenburger; Pierfrancesco La Mura

2011-07-01T23:59:59.000Z

496

Neutrinos: Theory and Phenomenology  

SciTech Connect

The theory and phenomenology of neutrinos will be addressed, especially that relating to the observation of neutrino flavor transformations. The current status and implications for future experiments will be discussed with special emphasis on the experiments that will determine the neutrino mass ordering, the dominant flavor content of the neutrino mass eigenstate with the smallest electron neutrino content and the size of CP violation in the neutrino sector. Beyond the neutrino Standard Model, the evidence for and a possible definitive experiment to confirm or refute the existence of light sterile neutrinos will be briefly discussed.

Parke, Stephen

2013-10-22T23:59:59.000Z

497

An Interpretive, Multilevel Theory of Scenario Planning: Advancing Human Resource Development Theory Building  

E-Print Network (OSTI)

This study advances theory building as the process of modeling real-world phenomena and uses a theory-to-research strategy in the theory building process. A five-step theory building methodology constitutes applied theory building in general...

Matlock, James 1958-

2012-12-01T23:59:59.000Z

498

The applicability of certain Monte Carlo methods to the analysis of interacting polymers  

SciTech Connect

The authors consider polymers, modeled as self-avoiding walks with interactions on a hexagonal lattice, and examine the applicability of certain Monte Carlo methods for estimating their mean properties at equilibrium. Specifically, the authors use the pivoting algorithm of Madras and Sokal and Metroplis rejection to locate the phase transition, which is known to occur at {beta}{sub crit} {approx} 0.99, and to recalculate the known value of the critical exponent {nu} {approx} 0.58 of the system for {beta} = {beta}{sub crit}. Although the pivoting-Metropolis algorithm works well for short walks (N < 300), for larger N the Metropolis criterion combined with the self-avoidance constraint lead to an unacceptably small acceptance fraction. In addition, the algorithm becomes effectively non-ergodic, getting trapped in valleys whose centers are local energy minima in phase space, leading to convergence towards different values of {nu}. The authors use a variety of tools, e.g. entropy estimation and histograms, to improve the results for large N, but they are only of limited effectiveness. Their estimate of {beta}{sub crit} using smaller values of N is 1.01 {+-} 0.01, and the estimate for {nu} at this value of {beta} is 0.59 {+-} 0.005. They conclude that even a seemingly simple system and a Monte Carlo algorithm which satisfies, in principle, ergodicity and detailed balance conditions, can in practice fail to sample phase space accurately and thus not allow accurate estimations of thermal averages. This should serve as a warning to people who use Monte Carlo methods in complicated polymer folding calculations. The structure of the phase space combined with the algorithm itself can lead to surprising behavior, and simply increasing the number of samples in the calculation does not necessarily lead to more accurate results.

Krapp, D.M. Jr. [Univ. of California, Berkeley, CA (United States)

1998-05-01T23:59:59.000Z

499

Charged-Particle Thermonuclear Reaction Rates: I. Monte Carlo Method and Statistical Distributions  

E-Print Network (OSTI)

A method based on Monte Carlo techniques is presented for evaluating thermonuclear reaction rates. We begin by reviewing commonly applied procedures and point out that reaction rates that have been reported up to now in the literature have no rigorous statistical meaning. Subsequently, we associate each nuclear physics quantity entering in the calculation of reaction rates with a specific probability density function, including Gaussian, lognormal and chi-squared distributions. Based on these probability density functions the total reaction rate is randomly sampled many times until the required statistical precision is achieved. This procedure results in a median (Monte Carlo) rate which agrees under certain conditions with the commonly reported recommended "classical" rate. In addition, we present at each temperature a low rate and a high rate, corresponding to the 0.16 and 0.84 quantiles of the cumulative reaction rate distribution. These quantities are in general different from the statistically meaningless "minimum" (or "lower limit") and "maximum" (or "upper limit") reaction rates which are commonly reported. Furthermore, we approximate the output reaction rate probability density function by a lognormal distribution and present, at each temperature, the lognormal parameters miu and sigma. The values of these quantities will be crucial for future Monte Carlo nucleosynthesis studies. Our new reaction rates, appropriate for bare nuclei in the laboratory, are tabulated in the second paper of this series (Paper II). The nuclear physics input used to derive our reaction rates is presented in the third paper of this series (Paper III). In the fourth paper of this series (Paper IV) we compare our new reaction rates to previous results.

Richard Longland; Christian Iliadis; Art Champagne; Joe Newton; Claudio Ugalde; Alain Coc; Ryan Fitzgerald

2010-04-23T23:59:59.000Z

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Solvatochromism in a Pyridinium Cyclopentadienylide: Insights from a Sequential CarParrinello QM/MM and TD-DFT/Semicontinuum Approach  

Science Journals Connector (OSTI)

In particular, the structure modeling has been carried out using a CarParrinello hybrid QM/MM molecular dynamics approach, while the excitation energies were computed using time dependent density functional theory. ... We also aim to investigate the contribution from solvent-induced geometry (indirect solvent effect) and the direct solvent effect on the excitation energy and to characterize the nature of the solvatochromic band. ... This takes into account the polarization of the QM region due to the instantaneous electric field generated by the atomic charges of MM atoms. ...

N. Arul Murugan

2014-06-06T23:59:59.000Z