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1

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

2

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

DOE Green Energy (OSTI)

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

Liu, P.; Choi, Y.M.

2011-05-16T23:59:59.000Z

3

Uncertainty quantification of few group diffusion theory constants generated by the B1 theory-augmented Monte Carlo method  

SciTech Connect

The purpose of this paper is to quantify uncertainties of fuel pin cell or fuel assembly (FA) homogenized few group diffusion theory constants generated from the B1 theory-augmented Monte Carlo (MC) method. A mathematical formulation of the first kind is presented to quantify uncertainties of the few group constants in terms of the two major sources of the MC method; statistical and nuclear cross section and nuclide number density input data uncertainties. The formulation is incorporated into the Seoul National Univ. MC code McCARD. It is then used to compute the uncertainties of the burnup-dependent homogenized two group constants of a low-enriched UO{sub 2} fuel pin cell and a PWR FA on the condition that nuclear cross section input data of U-235 and U-238 from JENDL 3.3 library and nuclide number densities from the solution to fuel depletion equations have uncertainties. The contribution of the MC input data uncertainties to the uncertainties of the two group constants of the two fuel systems is separated from that of the statistical uncertainties. The utilities of uncertainty quantifications are then discussed from the standpoints of safety analysis of existing power reactors, development of new fuel or reactor system design, and improvement of covariance files of the evaluated nuclear data libraries. (authors)

Park, H. J. [Korea Atomic Energy Research Inst., Daedeokdaero 989-111, Yuseong-gu, Daejeon (Korea, Republic of); Shim, H. J.; Joo, H. G.; Kim, C. H. [Dept. of Nuclear Engineering, Seoul National Univ., 1 Gwanak-ro, Gwanak-gu, Seoul (Korea, Republic of)

2012-07-01T23:59:59.000Z

4

Electron energy and charge albedos - calorimetric measurement vs Monte Carlo theory  

SciTech Connect

A new calorimetric method has been employed to obtain saturated electron energy albedos for Be, C, Al, Ti, Mo, Ta, U, and UO/sub 2/ over the range of incident energies from 0.1 to 1.0 MeV. The technique was so designed to permit the simultaneous measurement of saturated charge albedos. In the cases of C, Al, Ta, and U the measurements were extended down to about 0.025 MeV. The angle of incidence was varied from 0/sup 0/ (normal) to 75/sup 0/ in steps of 15/sup 0/, with selected measurements at 82.5/sup 0/ in Be and C. In each case, state-of-the-art predictions were obtained from a Monte Carlo model. The generally good agreement between theory and experiment over this extensive parameter space represents a strong validation of both the theoretical model and the new experimental method. Nevertheless, certain discrepancies at low incident energies, especially in high-atomic-number materials, and at all energies in the case of the U energy albedos are not completely understood.

Lockwood, G.J.; Ruggles, L.E.; Miller, G.H.; Halbleib, J.A.

1981-11-01T23:59:59.000Z

5

Joint International Conference on Supercomputing in Nuclear Applications and Monte Carlo 2013 (SNA + MC 2013) La Cit des Sciences et de l'Industrie, Paris, France, October 27-31, 2013  

E-Print Network (OSTI)

Joint International Conference on Supercomputing in Nuclear Applications and Monte Carlo 2013 (SNA-Cr alloys are investigated using Density Functional Theory (DFT) formalism, in the form of constrained non temperature, represent the key unknown entities critical to the development of viable fusion reactor design

6

Radius of influence for a cosmic-ray soil moisture probe : theory and Monte Carlo simulations.  

Science Conference Proceedings (OSTI)

The lateral footprint of a cosmic-ray soil moisture probe was determined using diffusion theory and neutron transport simulations. The footprint is radial and can be described by a single parameter, an e-folding length that is closely related to the slowing down length in air. In our work the slowing down length is defined as the crow-flight distance traveled by a neutron from nuclear emission as a fast neutron to detection at a lower energy threshold defined by the detector. Here the footprint is defined as the area encompassed by two e-fold distances, i.e. the area from which 86% of the recorded neutrons originate. The slowing down length is approximately 150 m at sea level for neutrons detected over a wide range of energies - from 10{sup 0} to 10{sup 5} eV. Both theory and simulations indicate that the slowing down length is inversely proportional to air density and linearly proportional to the height of the sensor above the ground for heights up to 100 m. Simulations suggest that the radius of influence for neutrons >1 eV is only slightly influenced by soil moisture content, and depends weakly on the energy sensitivity of the neutron detector. Good agreement between the theoretical slowing down length in air and the simulated slowing down length near the air/ground interface support the conclusion that the footprint is determined mainly by the neutron scattering properties of air.

Desilets, Darin

2011-02-01T23:59:59.000Z

7

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

8

A DFT Approach to Non-Covalent Interactions via Monomer Polarization and Pauli Blockade  

E-Print Network (OSTI)

We propose a "DFT+dispersion" treatment which avoids double counting of dispersion terms by deriving the dispersion-free density functional theory (DFT) interaction energy and combining it with DFT-based dispersion. The formalism involves self-consistent polarization of DFT monomers restrained by the exclusion principle via the Pauli blockade technique. Any exchange-correlation potential can be used within monomers, but only the exchange operates between them. The applications to rare-gas dimers, ion-rare gas interactions and hydrogen bonds demonstrate that the interaction energies agree with benchmark values.

Rajchel, Lukasz; Szczesniak, Malgorzata M; Chalasinski, Grzegorz

2009-01-01T23:59:59.000Z

9

DFT-based molecular dynamics as a new tool for computational biology: first applications and perspective  

Science Conference Proceedings (OSTI)

Static and molecular dynamics (MD) calculations based on density-functional theory (DFT) are emerging as a valuable means for simulations in the field of biology, especially when coupled with classical simulations. In this contribution, we point out ...

W. Andreoni; A. Curioni; T. Mordasini

2001-05-01T23:59:59.000Z

10

Density Functional Theory Approach to Nuclear Fission  

E-Print Network (OSTI)

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

N. Schunck

2012-12-13T23:59:59.000Z

11

Thermal Density Functional Theory in Context  

E-Print Network (OSTI)

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

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

2013-01-01T23:59:59.000Z

12

Parallel Implementation of Gamma-Point Pseudopotential Plane-Wave DFT with Exact Exchange  

Science Conference Proceedings (OSTI)

One of the more persistent failures of conventional density functional theory (DFT) methods has been their failure to yield localized charge states such as polarons, excitons and solitons in solid-state and extended systems. It has been suggested that conventional DFT functionals, which are not self-interaction free, tend to favor delocalized electronic states since self-interaction creates a Coulomb barrier to charge localization. Pragmatic approaches in which the exchange correlation functionals are augmented with small amount of exact exchange (hybrid-DFT, e.g. B3LYP and PBE0) have shown promise in localizing charge states and predicting accurate band gaps and reaction barriers. We have developed a parallel algorithm for implementing exact exchange into pseudopotential plane-wave density functional theory and we have implemented it in the NWChem program package. The technique developed can readily be employed in plane-wave DFT programs. Furthermore, atomic forces and stresses are straightforward to implement, making it applicable to both confined and extended systems, as well as to Car-Parrinello ab initio molecular dynamic simulations. This method has been applied to several systems for which conventional DFT methods do not work well, including calculations for band gaps in oxides and the electronic structure of a charge trapped state in the Fe(II) containing mica, annite.

Bylaska, Eric J.; Tsemekhman, Kiril L.; Baden, Scott B.; Weare, John H.; Jonsson, Hannes

2011-01-15T23:59:59.000Z

13

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

14

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

E-Print Network (OSTI)

This thesis relates to the emerging field of high-throughput density functional theory (DFT) computation for materials design and optimization. Although highthroughput DFT is a promising new method for materials discovery, ...

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

2011-01-01T23:59:59.000Z

15

Hexakis(4-phormylphenoxy)cyclotriphosphazene: X-ray and DFT-calculated structures  

SciTech Connect

The crystal structure of hexakis(4-phormylphenoxy)cyclotriphosphazene is determined by using X-ray diffraction and then the molecular structure is investigated with density functional theory (DFT). X-Ray study shows that the title compound has C-H-{pi} interaction with phosphazene ring. The molecules in the unit cell are packed with Van der Waals and dipole-dipole interactions and the molecules are packed in zigzag shaped. Optimized molecular geometry is calculated with DFT at B3LYP/6-311G(d,p) level. The results from both experimental and theoretical calculations are compared in this study.

Albayrak, Cigdem, E-mail: calbayrak@sinop.edu.tr; Kosar, Basak [Sinop University, Faculty of Education (Turkey); Odabasoglu, Mustafa [Pamukkale University, Chemical Technology Program (Turkey); Bueyuekguengoer, Orhan [Ondokuz Mayis University, Faculty of Arts and Sciences (Turkey)

2010-12-15T23:59:59.000Z

16

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

17

Adaptive DFT-based interferometer fringe tracking  

Science Conference Proceedings (OSTI)

An automatic interferometer fringe tracking system has been developed, implemented, and tested at the Infrared Optical Telescope Array (IOTA) Observatory at Mount Hopkins, Arizona. The system can minimize the optical path differences (OPDs) for all three ... Keywords: DFT, IOTA, fringe tracking, interferometry, real time

Edward Wilson; Ettore Pedretti; Jesse Bregman; Robert W. Mah; Wesley A. Traub

2005-01-01T23:59:59.000Z

18

A DFT investigation of methanolysis and hydrolysis of triacetin  

E-Print Network (OSTI)

The thermodynamic and kinetic aspects of the methanolysis and hydrolysis reactions of glycerol triacetate or triacetin, a model triacylglycerol compound, were investigated by using Density Functional Theory (DFT) at the B3LYP/6-31++G(d,p) level of calculation. Twelve elementary steps of triacetin methanolysis were studied under acid-catalyzed and base-catalyzed conditions. The mechanism of acid-catalyzed methanolysis reaction which has not been reported yet for any esters was proposed. The effects of substitution, methanolysis/hydrolysis position, solvent and face of nucleophilic attack on the free energy of reaction and activation energy were examined. The prediction confirmed the facile position at the middle position of glycerol observed by NMR techniques. The calculated activation energy and the trends of those factors agree with existing experimental observations in biodiesel production.

Limpanuparb, Taweetham; Tantirungrotechai, Yuthana; 10.1016/j.theochem.2010.05.022

2012-01-01T23:59:59.000Z

19

Sequential Circuit Testing: From DFT to SFT  

Science Conference Proceedings (OSTI)

Sequential circuit testing is an active research area due to its applicability, its practicality, and its complexity. This paper gives an overview of the sequential automatic test pattern generation approaches and the classical and more recent design-for-testability ... Keywords: logic testing, sequential circuit testing, DFT techniques, automatic test pattern generation, design-for-testability methods, synthesis-for-testability, SFT techniques, large sequential circuits, ATPG

R. M. Chou; K. K. Saluja

1997-01-01T23:59:59.000Z

20

Tb0.5Bi0.5MnO3: New material. A DFT study  

Science Conference Proceedings (OSTI)

In the present work we have determined the band structure and the densities of states (DOS) of Tb0.5Bi0.5MnO3 in cubic phase using the density functional theory (DFT). The determination of the lattice constant was ... Keywords: 61.50.-f, 62.20.-x, 71.15.Nc, 71.20.-b, 71.55.Ht, 75.20.En, Band structure, DFT, Density of states, Magnetic properties, Mechanical and structural properties, Tb1-xBixMnO3

Miguel Grizalez; M. Jairo Arbey Rodríguez; Jesús Heiras; P. Prieto

2008-03-01T23:59:59.000Z

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.


21

Population Monte Carlo algorithms  

E-Print Network (OSTI)

We give a cross-disciplinary survey on ``population'' Monte Carlo algorithms. In these algorithms, a set of ``walkers'' or ``particles'' is used as a representation of a high-dimensional vector. The computation is carried out by a random walk and split/deletion of these objects. The algorithms are developed in various fields in physics and statistical sciences and called by lots of different terms -- ``quantum Monte Carlo'', ``transfer-matrix Monte Carlo'', ``Monte Carlo filter (particle filter)'',``sequential Monte Carlo'' and ``PERM'' etc. Here we discuss them in a coherent framework. We also touch on related algorithms -- genetic algorithms and annealed importance sampling.

Yukito IBA

2000-08-16T23:59:59.000Z

22

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

23

Monte Carlo Renormalization Group: a review  

Science Conference Proceedings (OSTI)

The logic and the methods of Monte Carlo Renormalization Group (MCRG) are reviewed. A status report of results for 4-dimensional lattice gauge theories derived using MCRG is presented. Existing methods for calculating the improved action are reviewed and evaluated. The Gupta-Cordery improved MCRG method is described and compared with the standard one. 71 refs., 8 figs.

Gupta, R.

1985-01-01T23:59:59.000Z

24

Quantum Monte Carlo for  

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

Quantum Monte Carlo for the Electronic Structure of Atoms and Molecules Brian Austin Lester Group, U.C. Berkeley BES Requirements Workshop Rockville, MD February 9, 2010 Outline...

25

A sequential Monte Carlo/Quantum Mechanics study of the dipole polarizability of liquid benzene  

Science Conference Proceedings (OSTI)

Metropolis Monte Carlo classical simulation and quantum mechanical calculations are performed to obtain the dipole polarizability of liquid benzene. Super-molecular configurations are sampled from NVT Monte Carlo simulation of liquid benzene at room ... Keywords: Monte Carlo simulation, density-functional theory, intermediate-neglect of differential overlap (INDO), liquid benzene, polarizability

Eudes E. Fileti; Sylvio Canuto

2004-12-01T23:59:59.000Z

26

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

27

(E)-2-[(2-Bromophenylimino)methyl]-5-methoxyphenol: X-ray and DFT-calculated structures  

SciTech Connect

The crystal structure of (E)-2-[(2-Bromophenylimino)methyl]-5-methoxyphenol is determined by using X-ray diffraction and then the molecular structure is investigated with density functional theory (DFT). X-Ray study shows that the title compound has a strong intramolecular O-H-N hydrogen bond and three dimensional crystal structure is primarily determined by C-H-{pi} and weak van der Waals interactions. The strong O-H-N bond is an evidence of the preference for the phenol-imine tautomeric form in the solid state. Optimized molecular geometry is calculated with DFT at the B3LYP/6-31G(d,p) level. The IR spectra of compound were recorded experimentally and calculated to compare with each other. The results from both experiment and theoretical calculations are compared in this study.

Kosar, B., E-mail: bkosar@omu.edu.tr; Albayrak, C. [Sinop University, Faculty of Education (Turkey); Odabasoglu, M. [Pamukkale University, Chemistry Program (Turkey); Bueyuekguengoer, O. [Ondokuz Mayis University, Faculty of Arts and Sciences (Turkey)

2010-12-15T23:59:59.000Z

28

Guideline of Monte Carlo calculation. Neutron/gamma ray transport simulation by Monte Carlo method  

E-Print Network (OSTI)

This report condenses basic theories and advanced applications of neutron/gamma ray transport calculations in many fields of nuclear energy research. Chapters 1 through 5 treat historical progress of Monte Carlo methods, general issues of variance reduction technique, cross section libraries used in continuous energy Monte Carlo codes. In chapter 6, the following issues are discussed: fusion benchmark experiments, design of ITER, experiment analyses of fast critical assembly, core analyses of JMTR, simulation of pulsed neutron experiment, core analyses of HTTR, duct streaming calculations, bulk shielding calculations, neutron/gamma ray transport calculations of the Hiroshima atomic bomb. Chapters 8 and 9 treat function enhancements of MCNP and MVP codes, and a parallel processing of Monte Carlo calculation, respectively. An important references are attached at the end of this report.

2002-01-01T23:59:59.000Z

29

Monte Carlo Neutrino Oscillations  

E-Print Network (OSTI)

We demonstrate that the effects of matter upon neutrino propagation may be recast as the scattering of the initial neutrino wavefunction. Exchanging the differential, Schrodinger equation for an integral equation for the scattering matrix S permits a Monte Carlo method for the computation of S that removes many of the numerical difficulties associated with direct integration techniques.

James P. Kneller; Gail C. McLaughlin

2005-09-29T23:59:59.000Z

30

Multi-Determinant Wave-functions in Quantum Monte Carlo  

Science Conference Proceedings (OSTI)

Quantum Monte Carlo methods have received considerable attention over the last decades due to the great promise they have for the direct solution to the many-body Schrodinger equation for electronic systems. Thanks to a low scaling with number of particles, they present one of the best alternatives in the accurate study of large systems and solid state calculations. In spite of such promise, the method has not become popular in the quantum chemistry community, mainly due to the lack of control over the fixed-node error which can be large in many cases. In this article we present the application of large multi-determinant expansions in quantum Monte Carlo, studying its performance with first row dimers and the 55 molecules of the G1 test set. We demonstrate the potential of the wave-function to systematically reduce the fixed-node error in the calculations, achieving chemical accuracy in almost all cases studied. When compared to traditional methods in quantum chemistry, the results show a marked improvement over most methods including MP2, CCSD(T) and DFT with various functionals; in fact the only method able to produce better results is the explicitly-correlated CCSD(T) method with a large basis set. With recent developments in trial wave functions and algorithmic improvements in Quantum Monte Carlo, we are quickly approaching a time where the method can become the standard in the study of large molecular systems and solids.

Morales, Miguel A [Lawrence Livermore National Laboratory (LLNL); Mcminis, Jeremy [University of Illinois, Urbana-Champaign; Clark, Bryan K. [Princeton University; Kim, Jeongnim [ORNL; Scuseria, Gustavo E [Rice University

2012-01-01T23:59:59.000Z

31

Ru L[subscript 2,3] XANES theoretical simulation with DFT: A test of the core-hole treatment  

SciTech Connect

Density functional theory (DFT)-based relativistic calculations were performed to model the Ru L-edge X-ray absorption near edge structure (XANES) spectra of the hexaammineruthenium complex [Ru(NH{sub 3}){sub 6}]{sup 3+} and 'blue dimer' water oxidation catalyst, cis,cis- [(bpy){sub 2}(H{sub 2}O)Ru{sup III}ORu{sup III}(OH{sub 2})(bpy){sub 2}]{sup 4+} (bpy is 2,2-bipyridine). Two computational approaches were compared: simulations without the core-hole and by modeling of the core-hole within the Z+1 approximation. Good agreement between calculated and experimental XANES spectra is achieved without including the core-hole. Simulations with algorithms beyond the Z+1 approximation were only possible in a framework of the scalar relativistic treatment. Time-dependent DFT (TD-DFT) was used to compute the Ru L-edge spectrum for [Ru(NH{sub 3}){sub 6}]{sup 3+} model compound. Three different core-hole treatments were compared in a real-space full multiple scattering XANES modeling within the Green function formalism (implemented in the FEFF9.5 package) for the [Ru(Mebimpy)(bpm)(H{sub 2}O)]{sup 2+} complex. The latter approaches worked well in cases where spin-orbit treatment of relativistic effects is not required.

Alperovich, Igor; Moonshiram, Dooshaye; Soldatov, Alexander; Pushkar, Yulia (SFU-Russia); (Purdue)

2012-10-09T23:59:59.000Z

32

Ligand Discrimination in Myoglobin from Linear-Scaling DFT+U  

E-Print Network (OSTI)

Myoglobin modulates the binding of diatomic molecules to its heme group via hydrogen-bonding and steric interactions with neighboring residues, and is an important benchmark for computational studies of biomolecules. We have performed calculations on the heme binding site and a significant proportion of the protein environment (more than 1000 atoms) using linear-scaling density functional theory and the DFT+U method to correct for self-interaction errors associated with localized 3d states. We confirm both the hydrogen-bonding nature of the discrimination effect (3.6 kcal/mol) and assumptions that the relative strain energy stored in the protein is low (less than 1 kcal/mol). Our calculations significantly widen the scope for tackling problems in drug design and enzymology, especially in cases where electron localization, allostery or long-ranged polarization influence ligand binding and reaction.

Cole, Daniel J; Payne, Mike C

2013-01-01T23:59:59.000Z

33

A new DFT method for atoms and molecules in Cartesian grid  

E-Print Network (OSTI)

Electronic structure calculation of atoms and molecules, in the past few decades has largely been dominated by density functional methods. This is primarily due to the fact that this can account for electron correlation effects in a rigorous, tractable manner keeping the computational cost at a manageable level. With recent advances in methodological development, algorithmic progress as well as computer technology, larger physical, chemical and biological systems are amenable to quantum mechanical calculations than ever before. Here we report the development of a new method for accurate reliable description of atoms, molecules within the Hohenberg-Kohn-Sham density functional theory (DFT). In a Cartesian grid, atom-centered localized basis set, electron density, molecular orbitals, two-body potentials are directly built on the grid. We employ a Fourier convolution method for classical Coulomb potentials by making an Ewald-type decomposition technique in terms of short- and long-range interactions. One-body ma...

Roy, Amlan K

2013-01-01T23:59:59.000Z

34

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

E-Print Network (OSTI)

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

Lu, Aiyan

2007-01-01T23:59:59.000Z

35

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

Science Conference Proceedings (OSTI)

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

Ramy Nashed; Yehea Ismail; Nageh K. Allam

2013-01-01T23:59:59.000Z

36

On the Structure and Geometry of Biomolecular Binding Motifs (Hydrogen-Bonding, Stacking, X-H· · ·?): WFT and DFT Calculations  

DOE Green Energy (OSTI)

The strengths of noncovalent interactions are generally very sensitive to a number of geometric parameters. Among the most important of these parameters is the separation between the interacting moieties (in the case of an intermolecular interaction, this would be the intermolecular separation). Most works seeking to characterize the properties of intermolecular interactions are mainly concerned with binding energies obtained at the potential energy minimum (as determined at some particular level of theory). In this work, in order to extend our understanding of these types of noncovalent interactions, we investigate the distance dependence of several types of intermolecular interactions, these are hydrogen bonds, stacking interactions, dispersion interactions, and X-H· · ·? interactions. There are several methods that have traditionally been used to treat noncovalent interactions as well as many new methods that have emerged within the past three or four years. Here we obtain reference data using estimated CCSD(T) values at the complete basis set limit (using the CBS(T) method); potential energy curves are also produced using several other methods thought to be accurate for intermolecular interactions, these are MP2/ccpVTZ, MP2/aug-cc-pVDZ,MP2/6-31G*(0.25), SCS(MI)-MP2/cc-pVTZ, estimated MP2.5/CBS, DFT-SAPT/ aug-cc-pVTZ, DFT/M06-2X/6-311+G(2df,2p), and DFT-D/TPSS/6-311++G(3df,3pd). The basis set superposition error is systematically considered throughout the study. It is found that the MP2.5 and DFTSAPT methods, which are both quite computationally intensive, produce potential energy curves that are in very good agreement to those of the reference method. Among the MP2 techniques, which can be said to be of medium computational expense, the best results are obtained with MP2/cc-pVTZ and SCS(MI)-MP2/cc-pVTZ. DFT-D/TPSS/6-311++G(3df,3pd) is the DFT-based method that can be said to give the most well-balanced description of intermolecular interactions.

Riley, Kevin E.; Pitonak, Michal; Cerny, Jiri; Hobza, Pavel

2009-12-09T23:59:59.000Z

37

The Spacetime of Double Field Theory: Review, Remarks, and Outlook  

E-Print Network (OSTI)

We review double field theory (DFT) with emphasis on the doubled spacetime and its generalized coordinate transformations, which unify diffeomorphisms and b-field gauge transformations. We illustrate how the composition of generalized coordinate transformations fails to associate. Moreover, in dimensional reduction, the O(d,d) T-duality transformations of fields can be obtained as generalized diffeomorphisms. Restricted to a half-dimensional subspace, DFT includes `generalized geometry', but is more general in that local patches of the doubled space may be glued together with generalized coordinate transformations. Indeed, we show that for certain T-fold backgrounds with non-geometric fluxes, there are generalized coordinate transformations that induce, as gauge symmetries of DFT, the requisite O(d,d;Z) monodromy transformations. Finally we review recent results on the \\alpha' extension of DFT which, reduced to the half-dimensional subspace, yields intriguing modifications of the basic structures of generalized geometry.

Olaf Hohm; Dieter Lust; Barton Zwiebach

2013-09-11T23:59:59.000Z

38

Monte Carlo Methods and Partial Differential Equations ...  

Science Conference Proceedings (OSTI)

... Up, Monte Carlo Methods and Partial Differential Equations: Algorithms and Implications for High-Performance Computing. ...

2013-08-16T23:59:59.000Z

39

Quantitative Vapor-phase IR Intensities and DFT Computations to Predict Absolute IR Spectra based on Molecular Structure: I. Alkanes  

SciTech Connect

Recently recorded quantitative IR spectra of a variety of gas-phase alkanes are shown to have integrated intensities in both the C-H stretching and C-H bending regions that depend linearly on the molecular size, i.e. the number of C-H bonds. This result is well predicted from CH4 to C15H32 by DFT computations of IR spectra at the B3LYP/6-31+G(d,p) level of DFT theory. A simple model predicting the absolute IR band intensities of alkanes based only on structural formula is proposed: For the C-H stretching band near 2930 cm-1 this is given by (in km/mol): CH¬_str = (34±3)*CH – (41±60) where CH is number of C-H bonds in the alkane. The linearity is explained in terms of coordinated motion of methylene groups rather than the summed intensities of autonomous -CH2- units. The effect of alkyl chain length on the intensity of a C-H bending mode is explored and interpreted in terms of conformer distribution. The relative intensity contribution of a methyl mode compared to the total C-H stretch intensity is shown to be linear in the number of terminal methyl groups in the alkane, and can be used to predict quantitative spectra a priori based on structure alone.

Williams, Stephen D.; Johnson, Timothy J.; Sharpe, Steven W.; Yavelak, Veronica; Oats, R. P.; Brauer, Carolyn S.

2013-11-13T23:59:59.000Z

40

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),

Note: This page contains sample records for the topic "theory dft monte" from the National Library of EnergyBeta (NLEBeta).
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they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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41

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

Science Conference Proceedings (OSTI)

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

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

2012-04-28T23:59:59.000Z

42

Geometrical Characterization of Adenine And Guanine on Cu(110) By NEXAFS, XPS, And DFT Calculation  

Science Conference Proceedings (OSTI)

Adsorption of purine DNA bases (guanine and adenine) on Cu(1 1 0) was studied by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine-structure spectroscopy (NEXAFS), and density-functional theory (DFT) calculation. At coverages near 0.2 monolayers, Angular-resolved NEXAFS analysis revealed that adenine adsorbates lie almost flat and that guanine adsorbates are tilted up on the surface with the purine ring parallel to the atom rows of Cu(1 1 0). Referring to the previous studies on pyrimidine DNA bases [M. Furukawa, H. Fujisawa, S. Katano, H. Ogasawara, Y. Kim, T. Komeda, A. Nilsson, M. Kawai, Surf. Sci. 532-535 (2003) 261], the isomerization of DNA bases on Cu(1 1 0) was found to play an important role in the adsorption geometry. Guanine, thymine and cytosine adsorption have an amine-type nitrogen next to a carbonyl group, which is dehydrogenated into imine nitrogen on Cu(1 1 0). These bases are bonded by the inherent portion of - NH-CO - altered by conversion into enolic form and dehydrogenation. Adenine contains no CO group and is bonded to Cu(1 1 0) by participation of the inherent amine parts, resulting in nearly flatly-lying position.

Furukawa, M.; Yamada, T.; /Wako, RIKEN; Katano, S.; /tohoku U.; Kawai, M.; /Wako, RIKEN /Tokyo U.; Ogasawara, H.; /SLAC, SSRL; Nilsson, A.; /SLAC, SSRL /Stockholm U.

2009-04-30T23:59:59.000Z

43

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

E-Print Network (OSTI)

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

Hautier, Geoffroy

44

Monte Carlo Methods in Chemistry  

Science Conference Proceedings (OSTI)

Monte Carlo methods fulfil an important dual role. At a specific level, they provide a general-purpose numerical approach to problems in a wide range of topics. Using such methods, we can explore the characteristics of specific systems without introducing ...

Jim Doll; David L. Freeman

1994-03-01T23:59:59.000Z

45

Monte Carlo: in the beginning and some great expectations  

SciTech Connect

The central theme will be on the historical setting and origins of the Monte Carlo Method. The scene was post-war Los Alamos Scientific Laboratory. There was an inevitability about the Monte Carlo Event: the ENIAC had recently enjoyed its meteoric rise (on a classified Los Alamos problem); Stan Ulam had returned to Los Alamos; John von Neumann was a frequent visitor. Techniques, algorithms, and applications developed rapidly at Los Alamos. Soon, the fascination of the Method reached wider horizons. The first paper was submitted for publication in the spring of 1949. In the summer of 1949, the first open conference was held at the University of California at Los Angeles. Of some interst perhaps is an account of Fermi's earlier, independent application in neutron moderation studies while at the University of Rome. The quantum leap expected with the advent of massively parallel processors will provide stimuli for very ambitious applications of the Monte Carlo Method in disciplines ranging from field theories to cosmology, including more realistic models in the neurosciences. A structure of multi-instruction sets for parallel processing is ideally suited for the Monte Carlo approach. One may even hope for a modest hardening of the soft sciences.

Metropolis, N.

1985-01-01T23:59:59.000Z

46

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

Science Conference Proceedings (OSTI)

Plane wave pseudopotential (PWP) density functional theory (DFT) calculation is the most widely used method for material simulations, but its absolute speed stagnated due to the inability to use large scale CPU based computers. By a drastic redesign ... Keywords: Density functional theory, Electronic structure, First-principles, GPU, Molecular dynamics, Plane wave pseudopotential

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

2013-10-01T23:59:59.000Z

47

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

48

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"

49

Quantum Monte Carlo with Coupled-Cluster wave functions  

E-Print Network (OSTI)

We introduce a novel many body method which combines two powerful many body techniques, viz., quantum Monte Carlo and coupled cluster theory. Coupled cluster wave functions are introduced as importance functions in a Monte Carlo method designed for the configuration interaction framework to provide rigorous upper bounds to the ground state energy. We benchmark our method on the homogeneous electron gas in momentum space. The importance function used is the coupled cluster doubles wave function. We show that the computational resources required in our method scale polynomially with system size. Our energy upper bounds are in very good agreement with previous calculations of similar accuracy, and they can be systematically improved by including higher order excitations in the coupled cluster wave function.

Roggero, Alessandro; Pederiva, Francesco

2013-01-01T23:59:59.000Z

50

The dynamics of quantum criticality: Quantum Monte Carlo and holography  

E-Print Network (OSTI)

Understanding the real time dynamics of systems near quantum critical points at non-zero temperatures constitutes an important yet challenging problem, especially in two spatial dimensions where interactions are strong. We present detailed quantum Monte Carlo results for two separate realizations of the superfluid-insulator transition of bosons on a lattice: their low-frequency conductivities are found to have the same universal dependence on imaginary frequency and temperature. We then use the structure of the real time dynamics of conformal field theories described by the holographic gauge/gravity duality to make progress on the difficult problem of analytically continuing the Monte Carlo data to real time. Our method yields quantitative and experimentally testable results on the frequency-dependent conductivity at the quantum critical point, and on the spectrum of quasinormal modes in the vicinity of the superfluid-insulator quantum phase transition. Extensions to other observables and universality classes are discussed.

William Witczak-Krempa; Erik Sorensen; Subir Sachdev

2013-09-11T23:59:59.000Z

51

Quantum Monte Carlo with Coupled-Cluster wave functions  

E-Print Network (OSTI)

We introduce a novel many body method which combines two powerful many body techniques, viz., quantum Monte Carlo and coupled cluster theory. Coupled cluster wave functions are introduced as importance functions in a Monte Carlo method designed for the configuration interaction framework to provide rigorous upper bounds to the ground state energy. We benchmark our method on the homogeneous electron gas in momentum space. The importance function used is the coupled cluster doubles wave function. We show that the computational resources required in our method scale polynomially with system size. Our energy upper bounds are in very good agreement with previous calculations of similar accuracy, and they can be systematically improved by including higher order excitations in the coupled cluster wave function.

Alessandro Roggero; Abhishek Mukherjee; Francesco Pederiva

2013-04-04T23:59:59.000Z

52

Duality Symmetric String and M-Theory  

E-Print Network (OSTI)

We review recent developments in duality symmetric string theory. We begin with the world sheet doubled formalism which describes strings in an extended space time with extra coordinates conjugate to winding modes. This formalism is T-duality symmetric and can accommodate non-geometric T-fold backgrounds which are beyond the scope of Riemannian geometry. Vanishing of the conformal anomaly of this theory can be interpreted as a set of spacetime equations for the background fields. These equations follow from an action principle that has been dubbed Double Field Theory (DFT). We review the aspects of generalised geometry relevant for DFT. We outline recent extensions of DFT and explain how, by relaxing the so-called strong constraint with a Scherk Schwarz ansatz, one can obtain backgrounds that simultaneously depend on both the regular and T-dual coordinates. This provides a purely geometric higher dimensional origin to gauged supergravities that arise from non-geometric compactification. We then turn to M-theory and describe recent progress in formulating an E_{n(n)} U-duality covariant description of the dynamics. We describe how spacetime may be extended to accommodate coordinates conjugate to brane wrapping modes and the construction of generalised metrics in this extend space that unite the bosonic fields of supergravity into a single object. We review the action principles for these theories and their novel gauge symmetries. We also describe how a Scherk Schwarz reduction can be applied in the M-theory context and the resulting relationship to the embedding tensor formulation of maximal gauged supergravities.

David S. Berman; Daniel C. Thompson

2013-06-11T23:59:59.000Z

53

The path forward: Monte Carlo Convergence discussion  

SciTech Connect

This is a summary of 'the path forward' discussion session of the NuInt09 workshop which focused on Monte Carlo event generators. The main questions raised as part of this discussion are: how to make Monte Carlo generators more reliable and how important it is to work on a universal Monte Carlo generator of events? In this contribution, several experts in the field summarize their views, as presented at the workshop.

Andreopoulos, Costas [Rutherford Appleton Laboratory, STFC Oxfordshire OX11 0QX (United Kingdom); Gallagher, Hugh [Tufts University, Medford, Massachusetts (United States); Hayato, Yoshinari [Kamioka Observatory, ICRR, University of Tokyo Higashi-Mozumi 456, Kamioka-cho, Hida-city Gifu 506-1205 (Japan); Sobczyk, Jan T. [Institute of Theoretical Physics, Wroclaw, University Poland (Poland); Walter, Chris [Department of Physics, Duke University, Durham, NC 27708 (United States); Zeller, Sam [Los Alamos National Laboratory, Los Alamos, NM (United States)

2009-11-25T23:59:59.000Z

54

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

55

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

DOE Green Energy (OSTI)

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

56

Optimal generalized truncated sequential Monte Carlo test  

Science Conference Proceedings (OSTI)

When it is not possible to obtain the analytical null distribution of a test statistic U, Monte Carlo hypothesis tests can be used to perform the test. Monte Carlo tests are commonly used in a wide variety of applications, including spatial statistics, ... Keywords: 62L05, 62L15, 65C05, Execution time, Power loss, Resampling risk, p-value density

Ivair R. Silva, Renato M. Assunção

2013-10-01T23:59:59.000Z

57

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

58

Data Decomposition of Monte Carlo Particle Transport Simulations...  

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

Data Decomposition of Monte Carlo Particle Transport Simulations via Tally Servers Title Data Decomposition of Monte Carlo Particle Transport Simulations via Tally Servers...

59

Structure and energetics of solvated ferrous and ferric ions: Car-Parrinello molecular dynamics in the DFT+U formalism  

E-Print Network (OSTI)

We implemented a rotationally-invariant Hubbard U extension to density-functional theory in the Car-Parrinello molecular dynamics framework, with the goal of bringing the accuracy of the DFT+U approach to finite-temperature simulations, especially for liquids or solids containing transition-metal ions. First, we studied the effects on the Hubbard U on the static equilibrium structure of the hexa-aqua ferrous and ferric ions, and the inner-sphere reorganization energy for the electron-transfer reaction between aqueous ferrous and ferric ions. It is found that the reorganization energy is increased, mostly as a result of the Fe-O distance elongation in the hexa-aqua ferrous ion. Second, we performed a first-principles molecular dynamics study of the solvation structure of the two aqueous ferrous and ferric ions. The Hubbard term is found to change the Fe-O radial distribution function for the ferrous ion, while having a negligible effect on the aqueous ferric ion. Moreover, the frequencies of vibrations between Fe and oxygen atoms in the first-solvation shell are shown to be unaffected by the Hubbard corrections for both ferrous and ferric ions.

P. H. -L. Sit; Matteo Cococcioni; Nicola Marzari

2007-01-12T23:59:59.000Z

60

General purpose dynamic Monte Carlo with continuous energy for transient analysis  

SciTech Connect

For safety assessments transient analysis is an important tool. It can predict maximum temperatures during regular reactor operation or during an accident scenario. Despite the fact that this kind of analysis is very important, the state of the art still uses rather crude methods, like diffusion theory and point-kinetics. For reference calculations it is preferable to use the Monte Carlo method. In this paper the dynamic Monte Carlo method is implemented in the general purpose Monte Carlo code Tripoli4. Also, the method is extended for use with continuous energy. The first results of Dynamic Tripoli demonstrate that this kind of calculation is indeed accurate and the results are achieved in a reasonable amount of time. With the method implemented in Tripoli it is now possible to do an exact transient calculation in arbitrary geometry. (authors)

Sjenitzer, B. L.; Hoogenboom, J. E. [Delft Univ. of Technology, Dept. of Radiation, Radionuclide and Reactors, Mekelweg 15, 2629JB Delft (Netherlands)

2012-07-01T23:59:59.000Z

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.


61

Exponential convergence with adaptive Monte Carlo  

Science Conference Proceedings (OSTI)

For over a decade, it has been known that exponential convergence on discrete transport problems was possible using adaptive Monte Carlo techniques. Now, exponential convergence has been empirically demonstrated on a spatially continuous problem.

Booth, T.E.

1997-11-01T23:59:59.000Z

62

Canudos/Belo Monte: imagens contando história.  

E-Print Network (OSTI)

??O presente exercício objetiva construir uma leitura da Guerra de Canudos/Belo Monte tendo como documentos centrais as fotos de Flávio de Barros. Justifica-se tal trabalho… (more)

Sérgio Armando Diniz Guerra

2005-01-01T23:59:59.000Z

63

Monte Carlo simulation in financial engineering  

Science Conference Proceedings (OSTI)

This paper reviews the use of Monte Carlo simulation in the field of financial engineering. It focuses on several interesting topics and introduces their recent development, including path generation, pricing American-style derivatives, evaluating Greeks ...

Nan Chen; L. Jeff Hong

2007-12-01T23:59:59.000Z

64

Monte Carlo simulation in systems biology  

E-Print Network (OSTI)

2 The history of Monte Carlo Sampling in Systems Biology 1.1simulation tools: the systems biology workbench and biospiceCellular and Molecular Biology. ASM Press, Washington

Schellenberger, Jan

2010-01-01T23:59:59.000Z

65

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

DOE Green Energy (OSTI)

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

66

Correlated wavefunction quantum Monte Carlo approach to solids  

DOE Green Energy (OSTI)

A method for calculating the electronic and structural properties of solids using correlated wavefunctions together with quantum Monte Carlo techniques is described. The approach retains the exact Coulomb interaction between the electrons and employs a many-electron wavefunction of the Jastrow-Slater form. Several examples are given to illustrate the utility of the method. Topics discussed include the cohesive properties of bulk semiconductors, the magnetic-field- induced Wigner crystal in two dimensions, and the magnetic structure of bcc hydrogen. Landau level mixing is shown to be important in determining the transition between the fractional quantum Hall liquid and the Wigner crystal. Information on electron correlations such as the pair correlation functions which are not accessible to one- electron theories is also obtained. 24 refs, 5 figs, 1 tab.

Louie, S.G.

1992-10-01T23:59:59.000Z

67

Quantum Monte Carlo Endstation for Petascale Computing  

Science Conference Proceedings (OSTI)

The major achievements enabled by QMC Endstation grant include * Performance improvement on clusters of x86 multi-core systems, especially on Cray XT systems * New and improved methods for the wavefunction optimizations * New forms of trial wavefunctions * Implementation of the full application on NVIDIA GPUs using CUDA The scaling studies of QMCPACK on large-scale systems show excellent parallel efficiency up to 216K cores on Jaguarpf (Cray XT5). The GPU implementation shows speedups of 10-15x over the CPU implementation on older generation of x86. We have implemented hybrid OpenMP/MPI scheme in QMC to take advantage of multi-core shared memory processors of petascale systems. Our hybrid scheme has several advantages over the standard MPI-only scheme. * Memory optimized: large read-only data to store one-body orbitals and other shared properties to represent the trial wave function and many-body Hamiltonian can be shared among threads, which reduces the memory footprint of a large-scale problem. * Cache optimized: the data associated with an active Walker are in cache during the compute-intensive drift-diffusion process and the operations on an Walker are optimized for cache reuse. Thread-local objects are used to ensure the data affinity to a thread. * Load balanced: Walkers in an ensemble are evenly distributed among threads and MPI tasks. The two-level parallelism reduces the population imbalance among MPI tasks and reduces the number of point-to-point communications of large messages (serialized objects) for the Walker exchange. * Communication optimized: the communication overhead, especially for the collective operations necessary to determine ET and measure the properties of an ensemble, is significantly lowered by using less MPI tasks. The multiple forms of parallelism afforded by QMC algorithms make them ideal candidates for acceleration in the many-core paradigm. We presented the results of our effort to port the QMCPACK simulation code to the NVIDIA CUDA GPU platform. We restructured the CPU algorithms to express additional parallelism, minimize GPU-CPU communication, and efficiently utilize the GPU memory hierarchy. Using mixed precision on GT200 GPUs and MPI for intercommunication and load balancing, we observe typical full-application speedups of approximately 10x to 15x relative to quad-core Xeon CPUs alone, while reproducing the double-precision CPU results within statistical error. We developed an all-electron quantum Monte Carlo (QMC) method for solids that does not rely on pseudopotentials, and used it to construct a primary ultra-high-pressure calibration based on the equation of state of cubic boron nitride. We computed the static contribution to the free energy with the QMC method and obtained the phonon contribution from density functional theory, yielding a high-accuracy calibration up to 900 GPa usable directly in experiment. We computed the anharmonic Raman frequency shift with QMC simulations as a function of pressure and temperature, allowing optical pressure calibration. In contrast to present experimental approaches, small systematic errors in the theoretical EOS do not increase with pressure, and no extrapolation is needed. This all-electron method is applicable to first-row solids, providing a new reference for ab initio calculations of solids and benchmarks for pseudopotential accuracy. We compared experimental and theoretical results on the momentum distribution and the quasiparticle renormalization factor in sodium. From an x-ray Compton-profile measurement of the valence-electron momentum density, we derived its discontinuity at the Fermi wavevector finding an accurate measure of the renormalization factor that we compared with quantum-Monte-Carlo and G0W0 calculations performed both on crystalline sodium and on the homogeneous electron gas. Our calculated results are in good agreement with the experiment. We have been studying the heat of formation for various Kubas complexes of molecular hydrogen on Ti(1,2)ethylene-nH2 using Diffusion Monte Carlo. This work has been started and is o

David Ceperley

2011-03-02T23:59:59.000Z

68

The Rational Hybrid Monte Carlo Algorithm  

E-Print Network (OSTI)

The past few years have seen considerable progress in algorithmic development for the generation of gauge fields including the effects of dynamical fermions. The Rational Hybrid Monte Carlo (RHMC) algorithm, where Hybrid Monte Carlo is performed using a rational approximation in place the usual inverse quark matrix kernel is one of these developments. This algorithm has been found to be extremely beneficial in many areas of lattice QCD (chiral fermions, finite temperature, Wilson fermions etc.). We review the algorithm and some of these benefits, and we compare against other recent algorithm developements. We conclude with an update of the Berlin wall plot comparing costs of all popular fermion formulations.

M. A. Clark

2006-10-06T23:59:59.000Z

69

First-principles Investigation of Mg-Rare Earth Precipitates and ...  

Science Conference Proceedings (OSTI)

We investigate the coherency strain energy of Mg-?'' binary systems using first ... Using density functional theory (DFT), we explore the thermodynamic stability of ... Kinetic Monte Carlo Study of Fission Gas and Grain Growth in Nuclear Fuels.

70

Electroweak Theory  

Science Conference Proceedings (OSTI)

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

E. A. Paschos

2010-06-01T23:59:59.000Z

71

Relevance of accurate Monte Carlo modeling in nuclear medical imaging  

Science Conference Proceedings (OSTI)

Monte Carlo techniques have become popular in different areas of medical physics with advantage of powerful computing systems. In particular

Habib Zaidi

1999-01-01T23:59:59.000Z

72

Condensed history Monte Carlo methods for photon transport problems  

Science Conference Proceedings (OSTI)

We study methods for accelerating Monte Carlo simulations that retain most of the accuracy of conventional Monte Carlo algorithms. These methods - called Condensed History (CH) methods - have been very successfully used to model the transport of ionizing ... Keywords: Condensed history models, Monte Carlo methods, Radiative transport equation

Katherine Bhan; Jerome Spanier

2007-08-01T23:59:59.000Z

73

QWalk: A quantum Monte Carlo program for electronic structure  

Science Conference Proceedings (OSTI)

We describe QWalk, a new computational package capable of performing quantum Monte Carlo electronic structure calculations for molecules and solids with many electrons. We describe the structure of the program and its implementation of quantum Monte ... Keywords: Monte Carlo, Quantum mechanics, Stochastic methods

Lucas K. Wagner; Michal Bajdich; Lubos Mitas

2009-05-01T23:59:59.000Z

74

Solving Systems of Linear Equations with Relaxed Monte Carlo Method  

Science Conference Proceedings (OSTI)

The problem of solving systems of linear algebraic equations by parallel Monte Carlo numerical methods is considered. A parallel Monte Carlo method with relaxation is presented. This is a report of a research in progress, showing the effectiveness of ... Keywords: Monte Carlo method, linear solver, parallel algorithms, systems of linear algebraic equations

Chih Jeng Kenneth Tan

2002-05-01T23:59:59.000Z

75

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.

Joaquín E. Drut; Timo A. Lähde

2009-01-06T23:59:59.000Z

76

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"

77

Monte Carlo Simulation for Particle Detectors  

E-Print Network (OSTI)

Monte Carlo simulation is an essential component of experimental particle physics in all the phases of its life-cycle: the investigation of the physics reach of detector concepts, the design of facilities and detectors, the development and optimization of data reconstruction software, the data analysis for the production of physics results. This note briefly outlines some research topics related to Monte Carlo simulation, that are relevant to future experimental perspectives in particle physics. The focus is on physics aspects: conceptual progress beyond current particle transport schemes, the incorporation of materials science knowledge relevant to novel detection technologies, functionality to model radiation damage, the capability for multi-scale simulation, quantitative validation and uncertainty quantification to determine the predictive power of simulation. The R&D on simulation for future detectors would profit from cooperation within various components of the particle physics community, and synerg...

Pia, Maria Grazia

2012-01-01T23:59:59.000Z

78

Status of Monte Carlo at Los Alamos  

SciTech Connect

At Los Alamos the early work of Fermi, von Neumann, and Ulam has been developed and supplemented by many followers, notably Cashwell and Everett, and the main product today is the continuous-energy, general-purpose, generalized-geometry, time-dependent, coupled neutron-photon transport code called MCNP. The Los Alamos Monte Carlo research and development effort is concentrated in Group X-6. MCNP treats an arbitrary three-dimensional configuration of arbitrary materials in geometric cells bounded by first- and second-degree surfaces and some fourth-degree surfaces (elliptical tori). Monte Carlo has evolved into perhaps the main method for radiation transport calculations at Los Alamos. MCNP is used in every technical division at the Laboratory by over 130 users about 600 times a month accounting for nearly 200 hours of CDC-7600 time.

Thompson, W.L.; Cashwell, E.D.

1980-01-01T23:59:59.000Z

79

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

E-Print Network (OSTI)

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

Diebold, Ulrike

80

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

E-Print Network (OSTI)

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

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

2013-01-01T23:59:59.000Z

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81

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

82

Fission Matrix Capability for MCNP Monte Carlo  

Science Conference Proceedings (OSTI)

In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, k{sub eff}). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a spatially low-order kernel, the fundamental eigenvector of which should converge faster than that of continuous kernel. We can then redistribute the fission bank to match the fundamental fission matrix eigenvector, effectively eliminating all higher modes. For all computations here biasing is not used, with the intention of comparing the unaltered, conventional Monte Carlo process with the fission matrix results. The source convergence of standard Monte Carlo criticality calculations are, to some extent, always subject to the characteristics of the problem. This method seeks to partially eliminate this problem-dependence by directly calculating the spatial coupling. The primary cost of this, which has prevented widespread use since its inception [2,3,4], is the extra storage required. To account for the coupling of all N spatial regions to every other region requires storing N{sup 2} values. For realistic problems, where a fine resolution is required for the suppression of discretization error, the storage becomes inordinate. Two factors lead to a renewed interest here: the larger memory available on modern computers and the development of a better storage scheme based on physical intuition. When the distance between source and fission events is short compared with the size of the entire system, saving memory by accounting for only local coupling introduces little extra error. We can gain other information from directly tallying the fission kernel: higher eigenmodes and eigenvalues. Conventional Monte Carlo cannot calculate this data - here we have a way to get new information for multiplying systems. In Ref. [5], higher mode eigenfunctions are analyzed for a three-region 1-dimensional problem and 2-dimensional homogenous problem. We analyze higher modes for more realistic problems. There is also the question of practical use of this information; here we examine a way of using eigenmode information to address the negative confidence interval bias due to inter-cycle correlation. We apply this method mainly to four problems: 2D pressurized water reactor (PWR) [6],

Carney, Sean E. [Los Alamos National Laboratory; Brown, Forrest B. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory

2012-09-05T23:59:59.000Z

83

Fission Matrix Capability for MCNP Monte Carlo  

SciTech Connect

In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, k{sub eff}). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a spatially low-order kernel, the fundamental eigenvector of which should converge faster than that of continuous kernel. We can then redistribute the fission bank to match the fundamental fission matrix eigenvector, effectively eliminating all higher modes. For all computations here biasing is not used, with the intention of comparing the unaltered, conventional Monte Carlo process with the fission matrix results. The source convergence of standard Monte Carlo criticality calculations are, to some extent, always subject to the characteristics of the problem. This method seeks to partially eliminate this problem-dependence by directly calculating the spatial coupling. The primary cost of this, which has prevented widespread use since its inception [2,3,4], is the extra storage required. To account for the coupling of all N spatial regions to every other region requires storing N{sup 2} values. For realistic problems, where a fine resolution is required for the suppression of discretization error, the storage becomes inordinate. Two factors lead to a renewed interest here: the larger memory available on modern computers and the development of a better storage scheme based on physical intuition. When the distance between source and fission events is short compared with the size of the entire system, saving memory by accounting for only local coupling introduces little extra error. We can gain other information from directly tallying the fission kernel: higher eigenmodes and eigenvalues. Conventional Monte Carlo cannot calculate this data - here we have a way to get new information for multiplying systems. In Ref. [5], higher mode eigenfunctions are analyzed for a three-region 1-dimensional problem and 2-dimensional homogenous problem. We analyze higher modes for more realistic problems. There is also the question of practical use of this information; here we examine a way of using eigenmode information to address the negative confidence interval bias due to inter-cycle correlation. We apply this method mainly to four problems: 2D pressurized water reactor (PWR) [6],

Carney, Sean E. [Los Alamos National Laboratory; Brown, Forrest B. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory

2012-09-05T23:59:59.000Z

84

Quantum Monte Carlo for vibrating molecules  

SciTech Connect

Quantum Monte Carlo (QMC) has successfully computed the total electronic energies of atoms and molecules. The main goal of this work is to use correlation function quantum Monte Carlo (CFQMC) to compute the vibrational state energies of molecules given a potential energy surface (PES). In CFQMC, an ensemble of random walkers simulate the diffusion and branching processes of the imaginary-time time dependent Schroedinger equation in order to evaluate the matrix elements. The program QMCVIB was written to perform multi-state VMC and CFQMC calculations and employed for several calculations of the H{sub 2}O and C{sub 3} vibrational states, using 7 PES`s, 3 trial wavefunction forms, two methods of non-linear basis function parameter optimization, and on both serial and parallel computers. In order to construct accurate trial wavefunctions different wavefunctions forms were required for H{sub 2}O and C{sub 3}. In order to construct accurate trial wavefunctions for C{sub 3}, the non-linear parameters were optimized with respect to the sum of the energies of several low-lying vibrational states. In order to stabilize the statistical error estimates for C{sub 3} the Monte Carlo data was collected into blocks. Accurate vibrational state energies were computed using both serial and parallel QMCVIB programs. Comparison of vibrational state energies computed from the three C{sub 3} PES`s suggested that a non-linear equilibrium geometry PES is the most accurate and that discrete potential representations may be used to conveniently determine vibrational state energies.

Brown, W.R. [Univ. of California, Berkeley, CA (United States). Chemistry Dept.]|[Lawrence Berkeley National Lab., CA (United States). Chemical Sciences Div.

1996-08-01T23:59:59.000Z

85

Curvature and Frontier Orbital Energies in Density Functional Theory  

SciTech Connect

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

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

2012-12-20T23:59:59.000Z

86

Quantum Field Theory and Representation Theory  

E-Print Network (OSTI)

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

Woit, Peter

87

Discrete diffusion Monte Carlo for frequency-dependent radiative transfer  

SciTech Connect

Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Implicit Monte Carlo radiative-transfer simulations. In this paper, we develop an extension of DDMC for frequency-dependent radiative transfer. We base our new DDMC method on a frequency-integrated diffusion equation for frequencies below a specified threshold. Above this threshold we employ standard Monte Carlo. With a frequency-dependent test problem, we confirm the increased efficiency of our new DDMC technique.

Densmore, Jeffrey D [Los Alamos National Laboratory; Kelly, Thompson G [Los Alamos National Laboratory; Urbatish, Todd J [Los Alamos National Laboratory

2010-11-17T23:59:59.000Z

88

Exascale Monte Carlo R&D  

Science Conference Proceedings (OSTI)

Overview of this presentation is (1) Exascale computing - different technologies, getting there; (2) high-performance proof-of-concept MCMini - features and results; and (3) OpenCL toolkit - Oatmeal (OpenCL Automatic Memory Allocation Library) - purpose and features. Despite driver issues, OpenCL seems like a good, hardware agnostic tool. MCMini demonstrates the possibility for GPGPU-based Monte Carlo methods - it shows great scaling for HPC application and algorithmic equivalence. Oatmeal provides a flexible framework to aid in the development of scientific OpenCL codes.

Marcus, Ryan C. [Los Alamos National Laboratory

2012-07-24T23:59:59.000Z

89

Monte Carlo simulations on Graphics Processing Units  

E-Print Network (OSTI)

Implementation of basic local Monte-Carlo algorithms on ATI Graphics Processing Units (GPU) is investigated. The Ising model and pure SU(2) gluodynamics simulations are realized with the Compute Abstraction Layer (CAL) of ATI Stream environment using the Metropolis and the heat-bath algorithms, respectively. We present an analysis of both CAL programming model and the efficiency of the corresponding simulation algorithms on GPU. In particular, the significant performance speed-up of these algorithms in comparison with serial execution is observed.

Vadim Demchik; Alexei Strelchenko

2009-03-17T23:59:59.000Z

90

Numerical study of error propagation in Monte Carlo depletion simulations.  

E-Print Network (OSTI)

??Improving computer technology and the desire to more accurately model the heterogeneity of the nuclear reactor environment have made the use of Monte Carlo depletion… (more)

Wyant, Timothy Joseph

2012-01-01T23:59:59.000Z

91

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 The Boltzmann transport equation provides high fidelity simulation of a diverse range of kinetic systems....

92

A Kinetic Monte Carlo Model for Material Aging: Simulations of ...  

Science Conference Proceedings (OSTI)

In this paper, we develop a kinetic Monte Carlo framework aiming at ... A Controlled Stress Energy Minimization Method for Coarse-grained Atomistic Simulation.

93

Visualizing Quantum Monte Carlo Study of Photoprotection via...  

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

Photoprotection via Carotenoids in Photosynthetic Centers Quantum Monte Carlo Study of Photoprotection via Carotenoids in Photosynthetic Centers photosynthesisimage30y2004.jpg The...

94

A comparison of the Monte Carlo and the flux gradient method for atmospheric diffusion  

DOE Green Energy (OSTI)

In order to model the dispersal of atmospheric pollutants in the planetary boundary layer, various methods of parameterizing turbulent diffusion have been employed. The purpose of this paper is to use a three-dimensional particle-in-cell transport and diffusion model to compare the Markov chain (Monte Carlo) method of statistical particle diffusion with the deterministic flux gradient (K-theory) method. The two methods are heavily used in the study of atmospheric diffusion under complex conditions, with the Monte Carlo method gaining in popularity partly because of its more direct application of turbulence parameters. The basis of comparison is a data set from night-time drainage flow tracer experiments performed by the US Department of Energy Atmospheric Studies in Complex Terrain (ASCOT) program at the Geysers geothermal region in northern California. The Atmospheric Diffusion Particle-In-Cell (ADPIC) model used is the main model in the Lawrence Livermore National Laboratory emergency response program: Atmospheric Release Advisory Capability (ARAC). As a particle model, it can simulate diffusion in both the flux gradient and Monte Carlo modes. 9 refs., 6 figs.

Lange, R.

1990-05-01T23:59:59.000Z

95

Quantum Monte-Carlo method applied to Non-Markovian barrier transmission  

E-Print Network (OSTI)

In nuclear fusion and fission, fluctuation and dissipation arise due to the coupling of collective degrees of freedom with internal excitations. Close to the barrier, both quantum, statistical and non-Markovian effects are expected to be important. In this work, a new approach based on quantum Monte-Carlo addressing this problem is presented. The exact dynamics of a system coupled to an environment is replaced by a set of stochastic evolutions of the system density. The quantum Monte-Carlo method is applied to systems with quadratic potentials. In all range of temperature and coupling, the stochastic method matches the exact evolution showing that non-Markovian effects can be simulated accurately. A comparison with other theories like Nakajima-Zwanzig or Time-ConvolutionLess ones shows that only the latter can be competitive if the expansion in terms of coupling constant is made at least to fourth order. A systematic study of the inverted parabola case is made at different temperatures and coupling constants. The asymptotic passing probability is estimated in different approaches including the Markovian limit. Large differences with the exact result are seen in the latter case or when only second order in the coupling strength is considered as it is generally assumed in nuclear transport models. On opposite, if fourth order in the coupling or quantum Monte-Carlo method is used, a perfect agreement is obtained.

G. Hupin; D. Lacroix

2010-01-05T23:59:59.000Z

96

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

97

Quantum Monte Carlo for atoms and molecules  

DOE Green Energy (OSTI)

The diffusion quantum Monte Carlo with fixed nodes (QMC) approach has been employed in studying energy-eigenstates for 1--4 electron systems. Previous work employing the diffusion QMC technique yielded energies of high quality for H{sub 2}, LiH, Li{sub 2}, and H{sub 2}O. Here, the range of calculations with this new approach has been extended to include additional first-row atoms and molecules. In addition, improvements in the previously computed fixed-node energies of LiH, Li{sub 2}, and H{sub 2}O have been obtained using more accurate trial functions. All computations were performed within, but are not limited to, the Born-Oppenheimer approximation. In our computations, the effects of variation of Monte Carlo parameters on the QMC solution of the Schroedinger equation were studied extensively. These parameters include the time step, renormalization time and nodal structure. These studies have been very useful in determining which choices of such parameters will yield accurate QMC energies most efficiently. Generally, very accurate energies (90--100% of the correlation energy is obtained) have been computed with single-determinant trail functions multiplied by simple correlation functions. Improvements in accuracy should be readily obtained using more complex trial functions.

Barnett, R.N.

1989-11-01T23:59:59.000Z

98

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":""}]}

99

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

100

Quantum Monte Carlo Endstation for Petascale Computing  

SciTech Connect

NCSU research group has been focused on accomplising the key goals of this initiative: establishing new generation of quantum Monte Carlo (QMC) computational tools as a part of Endstation petaflop initiative for use at the DOE ORNL computational facilities and for use by computational electronic structure community at large; carrying out high accuracy quantum Monte Carlo demonstration projects in application of these tools to the forefront electronic structure problems in molecular and solid systems; expanding the impact of QMC methods and approaches; explaining and enhancing the impact of these advanced computational approaches. In particular, we have developed quantum Monte Carlo code (QWalk, www.qwalk.org) which was significantly expanded and optimized using funds from this support and at present became an actively used tool in the petascale regime by ORNL researchers and beyond. These developments have been built upon efforts undertaken by the PI's group and collaborators over the period of the last decade. The code was optimized and tested extensively on a number of parallel architectures including petaflop ORNL Jaguar machine. We have developed and redesigned a number of code modules such as evaluation of wave functions and orbitals, calculations of pfaffians and introduction of backflow coordinates together with overall organization of the code and random walker distribution over multicore architectures. We have addressed several bottlenecks such as load balancing and verified efficiency and accuracy of the calculations with the other groups of the Endstation team. The QWalk package contains about 50,000 lines of high quality object-oriented C++ and includes also interfaces to data files from other conventional electronic structure codes such as Gamess, Gaussian, Crystal and others. This grant supported PI for one month during summers, a full-time postdoc and partially three graduate students over the period of the grant duration, it has resulted in 13 published papers, 15 invited talks and lectures nationally and internationally. My former graduate student and postdoc Dr. Michal Bajdich, who was supported byt this grant, is currently a postdoc with ORNL in the group of Dr. F. Reboredo and Dr. P. Kent and is using the developed tools in a number of DOE projects. The QWalk package has become a truly important research tool used by the electronic structure community and has attracted several new developers in other research groups. Our tools use several types of correlated wavefunction approaches, variational, diffusion and reptation methods, large-scale optimization methods for wavefunctions and enables to calculate energy differences such as cohesion, electronic gaps, but also densities and other properties, using multiple runs one can obtain equations of state for given structures and beyond. Our codes use efficient numerical and Monte Carlo strategies (high accuracy numerical orbitals, multi-reference wave functions, highly accurate correlation factors, pairing orbitals, force biased and correlated sampling Monte Carlo), are robustly parallelized and enable to run on tens of thousands cores very efficiently. Our demonstration applications were focused on the challenging research problems in several fields of materials science such as transition metal solids. We note that our study of FeO solid was the first QMC calculation of transition metal oxides at high pressures.

Lubos Mitas

2011-01-26T23:59:59.000Z

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.


101

Efficient, automated Monte Carlo methods for radiation transport  

Science Conference Proceedings (OSTI)

Monte Carlo simulations provide an indispensible model for solving radiative transport problems, but their slow convergence inhibits their use as an everyday computational tool. In this paper, we present two new ideas for accelerating the convergence ... Keywords: Computational efficiency, Geometrically convergent Monte Carlo algorithms, Transport equation

Rong Kong; Martin Ambrose; Jerome Spanier

2008-11-01T23:59:59.000Z

102

Adjoint electron-photon transport Monte Carlo calculations with ITS  

Science Conference Proceedings (OSTI)

A general adjoint coupled electron-photon Monte Carlo code for solving the Boltzmann-Fokker-Planck equation has recently been created. It is a modified version of ITS 3.0, a coupled electronphoton Monte Carlo code that has world-wide distribution. The applicability of the new code to radiation-interaction problems of the type found in space environments is demonstrated.

Lorence, L.J.; Kensek, R.P.; Halbleib, J.A. [Sandia National Labs., Albuquerque, NM (United States); Morel, J.E. [Los Alamos National Lab., NM (United States)

1995-02-01T23:59:59.000Z

103

Bold diagrammatic Monte Carlo for the resonant Fermi gas  

E-Print Network (OSTI)

We provide a comprehensive description of the Bold Diagrammatic Monte Carlo algorithm for the normal resonant Fermi gas that was briefly reported and used in [Nature Phys. 8, 366 (2012)] and [arXiv:1303.6245]. Details are given on all key aspects of the scheme: diagrammatic framework, Monte Carlo moves, ultraviolet asymptotics, and resummation techniques.

Van Houcke, K; Prokof'ev, N; Svistunov, B

2013-01-01T23:59:59.000Z

104

Quantum Monte Carlo simulations of solids W. M. C. Foulkes  

E-Print Network (OSTI)

Quantum Monte Carlo simulations of solids W. M. C. Foulkes CMTH Group, Department of Physics and fixed-node diffusion quantum Monte Carlo methods and how they may be used to calculate the properties of quantum many-body effects and serve as benchmarks against which other techniques may be compared

Wu, Zhigang

105

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

106

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

107

Monte Carlo calculations of channeling radiation  

Science Conference Proceedings (OSTI)

Results of classical Monte Carlo calculations are presented for the radiation produced by ultra-relativistic positrons incident in a direction parallel to the (110) plane of Si in the energy range 30 to 100 MeV. The results all show the characteristic CR(channeling radiation) peak in the energy range 20 keV to 100 keV. Plots of the centroid energies, widths, and total yields of the CR peaks as a function of energy show the power law dependences of ..gamma../sup 1/ /sup 5/, ..gamma../sup 1/ /sup 7/, and ..gamma../sup 2/ /sup 5/ respectively. Except for the centroid energies and power-law dependence is only approximate. Agreement with experimental data is good for the centroid energies and only rough for the widths. Adequate experimental data for verifying the yield dependence on ..gamma.. does not yet exist.

Bloom, S.D.; Berman, B.L.; Hamilton, D.C.; Alguard, M.J.; Barrett, J.H.; Datz, S.; Pantell, R.H.; Swent, R.H.

1981-01-01T23:59:59.000Z

108

Hybrid algorithms in quantum Monte Carlo  

SciTech Connect

With advances in algorithms and growing computing powers, quantum Monte Carlo (QMC) methods have become a leading contender for high accuracy calculations for the electronic structure of realistic systems. The performance gain on recent HPC systems is largely driven by increasing parallelism: the number of compute cores of a SMP and the number of SMPs have been going up, as the Top500 list attests. However, the available memory as well as the communication and memory bandwidth per element has not kept pace with the increasing parallelism. This severely limits the applicability of QMC and the problem size it can handle. OpenMP/MPI hybrid programming provides applications with simple but effective solutions to overcome efficiency and scalability bottlenecks on large-scale clusters based on multi/many-core SMPs. We discuss the design and implementation of hybrid methods in QMCPACK and analyze its performance on current HPC platforms characterized by various memory and communication hierarchies.

Esler, Kenneth P [ORNL; Mcminis, Jeremy [University of Illinois, Urbana-Champaign; Morales, Miguel A [Lawrence Livermore National Laboratory (LLNL); Clark, Bryan K. [Princeton University; Shulenburger, Luke [Sandia National Laboratory (SNL); Ceperley, David M [ORNL

2012-01-01T23:59:59.000Z

109

Quantum Ice : a quantum Monte Carlo study  

E-Print Network (OSTI)

Ice states, in which frustrated interactions lead to a macroscopic ground-state degeneracy, occur in water ice, in problems of frustrated charge order on the pyrochlore lattice, and in the family of rare-earth magnets collectively known as spin ice. Of particular interest at the moment are "quantum spin ice" materials, where large quantum fluctuations may permit tunnelling between a macroscopic number of different classical ground states. Here we use zero-temperature quantum Monte Carlo simulations to show how such tunnelling can lift the degeneracy of a spin or charge ice, stabilising a unique "quantum ice" ground state --- a quantum liquid with excitations described by the Maxwell action of 3+1-dimensional quantum electrodynamics. We further identify a competing ordered "squiggle" state, and show how both squiggle and quantum ice states might be distinguished in neutron scattering experiments on a spin ice material.

Nic Shannon; Olga Sikora; Frank Pollmann; Karlo Penc; Peter Fulde

2011-05-20T23:59:59.000Z

110

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

111

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.

112

Quantification of stochastic uncertainty propagation for Monte Carlo depletion methods in reactor analysis.  

E-Print Network (OSTI)

??The Monte Carlo method provides powerful geometric modeling capabilities for large problem domains in 3-D; therefore, the Monte Carlo method is becoming popular for 3-D… (more)

Newell, Quentin Thomas

2011-01-01T23:59:59.000Z

113

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

E-Print Network (OSTI)

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

Cazorla, Claudio

2012-01-01T23:59:59.000Z

114

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

115

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

DOE Green Energy (OSTI)

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

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

2009-03-26T23:59:59.000Z

116

Iterative acceleration methods for Monte Carlo and deterministic criticality calculations  

Science Conference Proceedings (OSTI)

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

117

Hydrogen Adsorption, Absorption and Diffusion on and in Transition Metal Surfaces: A DFT Study  

Science Conference Proceedings (OSTI)

Periodic, self-consistent DFT-GGA(PW91) calculations are used to study the interaction of hydrogen with different facets of seventeen transition metals—the (100) and (111) facets of face-centered cubic (fcc) metals, the (0001) facet of hexagonal-close packed (hcp) metals, and the (100) and (110) facets of body-centered cubic (bcc) metals. Calculated geometries and binding energies for surface and subsurface hydrogen are reported and are, in general, in good agreement with both previous modeling studies and experimental data. There are significant differences between the binding on the close-packed and more open (100) facets of the same metal. Geometries of subsurface hydrogen on different facets of the same metal are generally similar; however, binding energies of hydrogen in the subsurface of the different facets studied showed significant variation. Formation of surface hydrogen is exothermic with respect to gas-phase H? on all metals studied with the exception of Ag and Au. For each metal studied, hydrogen in its preferred subsurface state is always less stable than its preferred surface state. The magnitude of the activation energy for hydrogen diffusion from the surface layer into the first subsurface layer is dominated by the difference in the thermodynamic stability of these two states. Diffusion from the first subsurface layer to one layer further into the bulk does not generally have a large thermodynamic barrier but still has a moderate kinetic barrier. Despite the proximity to the metal surface, the activation energy for hydrogen diffusion from the first to the second subsurface layer is generally similar to experimentally-determined activation energies for bulk diffusion found in the literature. There are also some significant differences in the activation energy for hydrogen diffusion into the bulk through different facets of the same metal.

Ferrin, Peter A.; Kandoi, Shampa; Nilekar, Anand U.; Mavrikakis, Manos

2012-01-04T23:59:59.000Z

118

Theory and Software  

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

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

119

Molecular mean field theory for liquid water  

E-Print Network (OSTI)

Attractive bonding interactions between molecules typically have inherent conservation laws which influence the statistical properties of such systems in terms of corresponding sum rules. We considered lattice water as an example and enunciated the consequences of the sum rule through a general computational procedure called "Molecular mean field" theory. Fluctuations about mean field are computed and many of the liquid properties have been deduced and compared with Monte Carlo simulation, molecular dynamics and experimental results. Large correlation lengths are seen to be a consequence of the sum rule in liquid phase. Long range Coulomb interactions are shown to have minor effects on our results.

Jampa Maruthi Pradeep Kanth; Ramesh Anishetty

2010-04-09T23:59:59.000Z

120

Kinetic Monte Carlo simulations of nanocrystalline film deposition  

E-Print Network (OSTI)

A full diffusion kinetic Monte Carlo algorithm is used to model nanocrystalline film deposition, and study the mechanisms of grain nucleation and microstructure formation in such films. The major finding of this work is ...

Ruan, Shiyun

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

Independent Pixel and Monte Carlo Estimates of Stratocumulus Albedo  

Science Conference Proceedings (OSTI)

Monte Carlo radiative transfer methods are employed here to estimate the plane-parallel albedo bias for marine stratocumulus clouds. This is the bias in estimates of the mesoscale-average albedo, which arises from the assumption that cloud liquid ...

Robert F. Cahalan; William Ridgway; Warren J. Wiscombe; Steven Gollmer; Harshvardhan

1994-12-01T23:59:59.000Z

122

Parallel Fission Bank Algorithms in Monte Carlo Criticality Calculations  

E-Print Network (OSTI)

In this work we describe a new method for parallelizing the source iterations in a Monte Carlo criticality calculation. Instead of having one global fission bank that needs to be synchronized, as is traditionally done, our ...

Romano, Paul Kollath

123

Low Dose Radiation Research Program: Monte Carlo Track Structure...  

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

Monte Carlo Track Structure Simulations for Low-LET Selected Cell Radiation Studies Walt Wilson Washington State University Tri-Cities Why This Project There are many types of...

124

Bayesian inverse problems with Monte Carlo forward models  

E-Print Network (OSTI)

The full application of Bayesian inference to inverse problems requires exploration of a posterior distribution that typically does not possess a standard form. In this context, Markov chain Monte Carlo (MCMC) methods are ...

Bal, Guillaume

125

Enhancements in Continuous-Energy Monte Carlo Capabilities in SCALE  

SciTech Connect

Monte Carlo tools in SCALE are commonly used in criticality safety calculations as well as sensitivity and uncertainty analysis, depletion, and criticality alarm system analyses. Recent improvements in the continuous-energy data generated by the AMPX code system and significant advancements in the continuous-energy treatment in the KENO Monte Carlo eigenvalue codes facilitate the use of SCALE Monte Carlo codes to model geometrically complex systems with enhanced solution fidelity. The addition of continuous-energy treatment to the SCALE Monaco code, which can be used with automatic variance reduction in the hybrid MAVRIC sequence, provides significant enhancements, especially for criticality alarm system modeling. This paper describes some of the advancements in continuous-energy Monte Carlo codes within the SCALE code system.

Bekar, Kursat B [ORNL; Celik, Cihangir [ORNL; Wiarda, Dorothea [ORNL; Peplow, Douglas E. [ORNL; Rearden, Bradley T [ORNL; Dunn, Michael E [ORNL

2013-01-01T23:59:59.000Z

126

Microsoft PowerPoint - 13-02 Monts.pptx  

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

tankAt-tank Characterization for Closure of Hanford Tanks Ping-Rey Jang, Zhiling Long, O. Perry Norton, Walter P. Okhuysen, and David L. Monts Institute for Clean Energy...

127

A hybrid transport-diffusion method for Monte Carlo radiative-transfer simulations  

Science Conference Proceedings (OSTI)

Discrete Diffusion Monte Carlo (DDMC) is a technique for increasing the efficiency of Monte Carlo particle-transport simulations in diffusive media. If standard Monte Carlo is used in such media, particle histories will consist of many small steps, resulting ... Keywords: Hybrid transport-diffusion, Monte Carlo, Radiative transfer

Jeffery D. Densmore; Todd J. Urbatsch; Thomas M. Evans; Michael W. Buksas

2007-03-01T23:59:59.000Z

128

High-Performance Quasi-Monte Carlo Financial Simulation: FPGA vs. GPP vs. GPU  

Science Conference Proceedings (OSTI)

Quasi-Monte Carlo simulation is a special Monte Carlo simulation method that uses quasi-random or low-discrepancy numbers as random sample sets. In many applications, this method has proved advantageous compared to the traditional Monte Carlo simulation ... Keywords: CPU, FPGA, GPU, Maxwell, Quasi-Monte Carlo simulations, option pricing

Xiang Tian; Khaled Benkrid

2010-11-01T23:59:59.000Z

129

Quiet direct simulation Monte-Carlo with random timesteps  

Science Conference Proceedings (OSTI)

Use of a high-order deterministic sampling technique in direct simulation Monte-Carlo (DSMC) simulations eliminates statistical noise and improves computational performance by orders of magnitude. In this paper it is also shown that if a random timestep ... Keywords: 02.50.Ey, 02.70.Tt, 47.11.+j, 52.65.-y, Direct simulation Monte-Carlo, Particle-in-cell methods, Stochastic processess

William Peter

2007-01-01T23:59:59.000Z

130

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

131

RBU: A COMBINED MONTE CARLO REACTOR-BURNUP PROGRAM FOR THE IBM 709  

SciTech Connect

RBU is a digital computer program for the detailed calculation of the neutron, reactivity, and isotopic history of a reactor in which relatively exact models of the geometry and physical processes are included to permit reliable pre dictions of fuel costs and reactor performance. The program uses the Monte Carlo method to obtain the fine structure of the neutron flux in three space dimensions and energy. Using this fine structure, cross sections are averaged over space and energy to obtain the neutronic properties for equivalent homogeneous one- dimensional regions of space and ranges of energy. These are used in diffusion calculations to obtain the macroscopic flux distribution throughout the reactor. The consumption and production of isotopes is computed for a time step by the solution of sets of partial differential equations involving both the macroscopic and microscopic fluxes. With the new concentrations, diffusion calculations are performed again to obtain macroscopic fluxes for the next time step. At variable intervals, Monte Carlo calculations are again performed to determine the changes in microscopic flux distributions. The cycle is repeated until conditions on the reactivity or other properties dictate the end of the calculation. Programmed control rod manipulation may be included in the calculation. The Monte Carlo, diffusion, or burnup portions of the program may be used separately. The unresolved resonance range is treated by random selection of resonance parameters from appropriate distributions using the Doppler broadened single level Breit- Wigner formula. Resolved resonances are treated similarly with the exception that specific values of the resonance parameters are used. The effects of molecular binding and thermal motion of the nuclei on near-thermal scattering are treated by a simple model capable of incorporating the pertinent physical theory and data. (auth)

Leshan, E.J.; Burr, J.R.; Temme, M.; Thompson, G.T.; Triplett, J.R.

1959-09-30T23:59:59.000Z

132

Entanglement in GaAs and CdSe quantum dots: Exact calculations and DFT approximations  

Science Conference Proceedings (OSTI)

We consider two electrons confined in spherical GaAs and CdSe quantum dots and calculate their ground-state spatial entanglement exactly within a parabolic confinement model. We propose a perturbative scheme to approximate the above entanglement within ... Keywords: Density-functional theory, Entanglement, Quantum dots, Quantum information, Semiconductors

J. P. Coe; A. Sudbery; I. D'Amico

2009-03-01T23:59:59.000Z

133

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

134

Frozen-orbital and downfolding calculations with auxiliary-field quantum Monte Carlo  

E-Print Network (OSTI)

We describe the implementation of the frozen-orbital and downfolding approximations in the auxiliary-field quantum Monte Carlo (AFQMC) method. These approaches can provide significant computational savings compared to fully correlating all the electrons. While the many-body wave function is never explicit in AFQMC, its random walkers are Slater determinants, whose orbitals may be expressed in terms of any one-particle orbital basis. It is therefore straightforward to partition the full N-particle Hilbert space into active and inactive parts to implement the frozen-orbital method. In the frozen-core approximation, for example, the core electrons can be eliminated in the correlated part of the calculations, greatly increasing the computational efficiency, especially for heavy atoms. Scalar relativistic effects are easily included using the Douglas-Kroll-Hess theory. Using this method, we obtain a way to effectively eliminate the error due to single-projector, norm-conserving pseudopotentials in AFQMC. We also i...

Purwanto, Wirawan; Krakauer, Henry

2013-01-01T23:59:59.000Z

135

Extrapolating Monte Carlo simulations to infinite volume: Finite-size scaling at {xi}/{ital L}{much_gt}1  

SciTech Connect

We present a simple and powerful method for extrapolating finite-volume Monte Carlo data to infinite volume, based on finite-size-scaling theory. We discuss carefully its systematic and statistical errors, and we illustrate it using three examples: the two-dimensional three-state Potts antiferromagnet on the square lattice, and the two-dimensional {ital O}(3) and {ital O}({infinity}) {sigma} models. In favorable cases it is possible to obtain reliable extrapolations (errors of a few percent) even when the correlation length is 1000 times larger than the lattice.

Caracciolo, S. [Dipartimento di Fisica, Universita di Lecce and INFN-Sezione di Lecce, I-73100 Lecce (Italy)] [Dipartimento di Fisica, Universita di Lecce and INFN-Sezione di Lecce, I-73100 Lecce (Italy); Edwards, R.G. [Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306 (United States)] [Supercomputer Computations Research Institute, Florida State University, Tallahassee, Florida 32306 (United States); Ferreira, S.J. [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Minas Gerais, Caixa Postal 702, Belo Horizonte, Minas Gerais 30161 (Brazil)] [Departamento de Fisica, Instituto de Ciencias Exatas, Universidade Federal de Minas Gerais, Caixa Postal 702, Belo Horizonte, Minas Gerais 30161 (Brazil); Pelissetto, A.; Sokal, A.D. [Department of Physics, New York University, 4 Washington Place, New York, New York 10003 (United States)] [Department of Physics, New York University, 4 Washington Place, New York, New York 10003 (United States)

1995-04-10T23:59:59.000Z

136

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

E-Print Network (OSTI)

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

Brown, Noam

2013-01-01T23:59:59.000Z

137

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

138

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.

139

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

140

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":""}]}

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141

Monte Carlo Simulations for Mine Detection  

DOE Green Energy (OSTI)

During January, 1998, collaboration between LLNL, UCI and Exdet, Ltd. arranged for the testing and evaluation of a Russian developed antitank mine detection system at the Buried Objects Detection Facility (BODF) located at the Nevada Test Site. BODF is a secured 30-acre facility with approximately 300 live antitank mines that were buried in 1993 and 1994. The burial depths range from a few cm to 15 cm and the various metal- and plastic-case antitank mines each contain 6-12 kg of high explosive. Contractors who have tested their mine detection equipment at BODF include: SAIC, SRI, ERIM, MIT/Lincoln Laboratory and Loral Defense Systems. In addition LLNL researchers have used BODF to test antitank mine detection systems based on: dual-band infrared imaging, hyper-spectral imaging, synthetic aperture impulse radar and micro-impulse radar. In a blind test the Russian operated system obtained the highest score of any technology tested to date at BODF. The system is based on combining information from two separate sensors; one to detect anomalous concentrations of hydrogen and the other to detect if such anomalies also have the correct nitrogen to carbon ratio for high explosives. The detection sensitivity is set by the geometry and type of neutron moderator and filters surrounding the neutron source and detectors. Detection of hydrogen anomalies is a rapid process based on neutron scattering. The handheld instrument on the end of a wand could scan a large area at a rate of 4-5 square meters per minute. Once the hydrogen anomalies were located a second sensor was used to measure the thermal neutron excited gamma-ray spectrum at each hydrogen anomaly to determine whether that location in addition contained high concentrations of nitrogen. The second process was slower, taking up to 5 minutes for each location. The information from both sensors were then examined by the operator and a declaration was made as to whether or not the anomaly was a buried antitank mine. Although the system worked extremely well on all classes of anti-tank mines, the Russian hardware components were inferior to those that are commercially available in the United States, i.e. the NaI(Tl) crystals had significantly higher background levels and poorer resolution than their U.S. counterparts, the electronics appeared to be decades old and the photomultiplier tubes were noisy and lacked gain stabilization circuitry. During the evaluation of this technology, the question that came to mind was: could state-of-the-art sensors and electronics and improved software algorithms lead to a neutron based system that could reliably detect much smaller buried mines; namely antipersonnel mines containing 30-40 grams of high explosive? Our goal in this study was to conduct Monte Carlo simulations to gain better understanding of both phases of the mine detection system and to develop an understanding for the system's overall capabilities and limitations. In addition, we examined possible extensions of this technology to see whether or not state-of-the-art improvements could lead to a reliable anti-personnel mine detection system.

Toor, A.; Marchetti, A.A.

2000-03-14T23:59:59.000Z

142

Ferromagnetism in GaN: Gd: A density functional theory study  

SciTech Connect

First principle calculations of the electronic structure and magnetic interaction of GaN:Gd have been performed within the Generalized Gradient Approximation (GGA) of the density functional theory (DFT) with the on-site Coulomb energy U taken into account (also referred to as GGA+U). The ferromagnetic p-d coupling is found to be over two orders of magnitude larger than the s-d exchange coupling. The experimental colossal magnetic moments and room temperature ferromagnetism in GaN:Gd reported recently are explained by the interaction of Gd 4f spins via p-d coupling involving holes introduced by intrinsic defects such as Ga vacancies.

Stevenson, Cynthia; Stevenson, Cynthia

2008-02-04T23:59:59.000Z

143

Density Functional Theory for the Photoionization Dynamics of Uracil  

E-Print Network (OSTI)

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

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

2007-01-01T23:59:59.000Z

144

BNL | CFN: Theory & Computation  

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

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

145

Grand Unified Theory  

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

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

146

String (Faden) Theorie  

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

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

147

Addendum to “Event-chain Monte Carlo algorithms for hard-sphere systems”  

E-Print Network (OSTI)

We extend the event-chain Monte Carlo algorithm from hard-sphere interactions to general potentials. This event-driven Monte Carlo algorithm is nonlocal and rejection free and allows for the breaking of detailed balance. ...

Bernard, Etienne

148

Parallel algorithms for Monte Carlo particle transport simulation on exascale computing architectures  

E-Print Network (OSTI)

Monte Carlo particle transport methods are being considered as a viable option for high-fidelity simulation of nuclear reactors. While Monte Carlo methods offer several potential advantages over deterministic methods, there ...

Romano, Paul K. (Paul Kollath)

2013-01-01T23:59:59.000Z

149

Nested rollout policy adaptation for Monte Carlo tree search  

Science Conference Proceedings (OSTI)

Monte Carlo tree search (MCTS) methods have had recent success in games, planning, and optimization. MCTS uses results from rollouts to guide search; a rollout is a path that descends the tree with a randomized decision at each ply until reaching a leaf. ...

Christopher D. Rosin

2011-07-01T23:59:59.000Z

150

User Manual - Crystal Ball Monte Carlo POD Simulator  

Science Conference Proceedings (OSTI)

This report provides a user manual for a Monte Carlo simulator using Crystal Ball a spreadsheet add-inthat can be used to predict a noise-dependent structural probability of detection (POD) for steam generator tube integrity assessments. The simulator uses plant noise as one of its inputs and provides a plant-specific POD for condition monitoring and operational assessment.

2006-09-18T23:59:59.000Z

151

Monte Carlo study of self-heating in nanoscale devices  

Science Conference Proceedings (OSTI)

Progress in device miniaturization combined with the increase in integrated circuit packing density, as described by Moore's law, have been accompanied by an exponential increase in on-chip heat generation. In this context, there is an increasing demand ... Keywords: Electron transport, Electrothermal modeling, Monte Carlo, Nanoscale semiconductor devices, Nanowire MISFETs, Self-heating, Si/III-V heterostructure FETs, Thermal transport

Toufik Sadi; Robert W. Kelsall; Neil J. Pilgrim; Jean-Luc Thobel; François Dessenne

2012-03-01T23:59:59.000Z

152

Monte Carlo algorithms for evaluating Sobol' sensitivity indices  

Science Conference Proceedings (OSTI)

Sensitivity analysis is a powerful technique used to determine robustness, reliability and efficiency of a model. The main problem in this procedure is the evaluating total sensitivity indices that measure a parameter's main effect and all the interactions ... Keywords: Adaptive Monte Carlo algorithm, Global sensitivity indices, Multidimensional numerical integration, Sensitivity analysis

I. Dimov; R. Georgieva

2010-11-01T23:59:59.000Z

153

Monte-carlo calculations for some problems of quantum mechanics  

Science Conference Proceedings (OSTI)

The Monte-Carlo technique for the calculations of functional integral in two one-dimensional quantum-mechanical problems had been applied. The energies of the bound states in some potential wells were obtained using this method. Also some peculiarities in the calculation of the kinetic energy in the ground state had been studied.

Novoselov, A. A., E-mail: novoselov@goa.bog.msu.ru; Pavlovsky, O. V.; Ulybyshev, M. V. [Moscow State University (Russian Federation)

2012-09-15T23:59:59.000Z

154

Monte Carlo Simulation of Solar Reflectances for Cloudy Atmospheres  

Science Conference Proceedings (OSTI)

Monte Carlo simulations of solar radiative transfer were performed for a well-resolved, large, three-dimensional (3D) domain of boundary layer cloud simulated by a cloud-resolving model. In order to represent 3D distributions of optical ...

H. W. Barker; R. K. Goldstein; D. E. Stevens

2003-08-01T23:59:59.000Z

155

Monte Carlo simulation of neutral beam injection into fusion reactors  

SciTech Connect

Motivations and techniques for the Monte Carlo computer simulation of energetic neutral beam injection for fusion reactors are described. The versatility of this approach allows a significantly more sophisticated treatment of charge transfer collision phenomena and consequent effects on engineering design than available from prior work. Exemplary results for a mirror Fusion Engineering Research Facility (FERF) are discussed. (auth)

Miller, R.L.

1975-09-15T23:59:59.000Z

156

Forecasting Hotel Arrivals and Occupancy Using Monte Carlo Simulation  

E-Print Network (OSTI)

Forecasting Hotel Arrivals and Occupancy Using Monte Carlo Simulation Athanasius Zakhary Faculty University, Giza, Egypt (n.elgayar@fci-cu.edu.eg) #12;Abstract Forecasting hotel arrivals and occupancy simulation approach for the arrivals and occupancy forecasting problem. In this approach we simulate

Atiya, Amir

157

A Monte Carlo electron transport code for the desktop computer  

Science Conference Proceedings (OSTI)

A Monte Carlo electron transport code for the desktop computer is applied to the problem of determining the radiation dose throughout an oblique?surface heterogeneous medium. Absorbed?dose distributions are obtained for 10 MeV electrons incident upon flat?surface and oblique?surface water phantoms

1992-01-01T23:59:59.000Z

158

Transition-Metal Strings Templated on Boron-Doped Carbon Nanotubes: A DFT Investigation  

SciTech Connect

The binding nature, magnetic, and electronic properties of transition-metal (TM) monatomic chains anchored on boron-doped single-walled carbon nanotubes (B-SWCNTs) are studied using density-functional theory. The TM systems studied here include Au, Pt, Ru, Pd, Ag, Co, Ni, Cu, W, and Ti, which are well-known for their technical importance. In conjunction, prototype semiconducting SWCNT(8,0) and metallic SWCNT(6,6) were chosen to model the general features of B-doped SWCNTs. It is found that the TM-strings exhibit well-defined covalent bonds with the boron-doped SWCNTs, in contrast to the pristine SWCNTs. The TMstring/ B-SWCNT composites exhibit high stability and unexpected electronic properties, which are relevant to applications in nanoelectronics, spintronics, nanocatalysis, and sensor devices.

An, Wei; Turner, C. H.

2009-08-27T23:59:59.000Z

159

Experimental and DFT studies of initiation processes for butane isomerization over sulfated-zirconia catalysts  

SciTech Connect

Reaction kinetics studies were conducted of isobutane and n-butane isomerization at 423 K over sulfated-zirconia, with the butane feeds purified of olefins. Dihydrogen evolution was observed during butane isomerization over fresh catalysts, as well as over catalysts selectively poisoned by preadsorbed ammonia. Butane isomerization over sulfated-zirconia can be viewed as a surface chain reaction comprised of initiation, propagation, and termination steps. The primary initiation step in the absence of feed olefins is considered to be the dehydrogenation of butane over sulfated-zirconia, generating butenes which adsorb onto acid sites to form protonated olefinic species associated with the conjugate base form of the acid sites. Quantum-chemical calculations, employing density-functional theory, suggest that the dissociative adsorption of dihydrogen, isobutylene hydrogenation, and dissociative adsorption of isobutane are feasible over the sulfated-zirconia cluster, and these reactions take place over Zr-O sites.

Hong, Z.; Watwe, R.M.; Natal-Santiago, M.A.; Hill, J.M.; Dumesic, J.A. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Chemical Engineering] [Univ. of Wisconsin, Madison, WI (United States). Dept. of Chemical Engineering; Fogash, K.B. [Air Products and Chemicals, Inc., Allentown, PA (United States)] [Air Products and Chemicals, Inc., Allentown, PA (United States); Kim, B. [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering] [State Univ. of New York, Buffalo, NY (United States). Dept. of Chemical Engineering; Masqueda-Jimenez, B.I. [Univ. Autonoma de San Luis Potosi (Mexico). Centro de Investigacion y Estudios de Posgrado] [Univ. Autonoma de San Luis Potosi (Mexico). Centro de Investigacion y Estudios de Posgrado

1998-09-10T23:59:59.000Z

160

1 String field theory  

E-Print Network (OSTI)

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

W. Taylor

2006-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "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

The continuous configurational Boltzmann biased direct Monte Carlo method for free energy properties of polymer chains  

Science Conference Proceedings (OSTI)

We develop here a highly efficient variant of the Monte Carlo method for direct evaluation of the partition function

Jiro Sadanobu; William A. Goddard III

1997-01-01T23:59:59.000Z

162

Analysis of communication costs for domain decomposed Monte Carlo methods in nuclear reactor analysis  

Science Conference Proceedings (OSTI)

A domain decomposed Monte Carlo communication kernel is used to carry out performance tests to establish the feasibility of using Monte Carlo techniques for practical Light Water Reactor (LWR) core analyses. The results of the prototype code are interpreted ... Keywords: Monte Carlo, Neutron transport, Performance modeling, Reactor analysis

A. Siegel; K. Smith; P. Fischer; V. Mahadevan

2012-04-01T23:59:59.000Z

163

Data decomposition of Monte Carlo particle transport simulations via tally servers  

Science Conference Proceedings (OSTI)

An algorithm for decomposing large tally data in Monte Carlo particle transport simulations is developed, analyzed, and implemented in a continuous-energy Monte Carlo code, OpenMC. The algorithm is based on a non-overlapping decomposition of compute ... Keywords: Data decomposition, Exascale, Monte Carlo, Neutron transport, Tally server

Paul K. Romano, Andrew R. Siegel, Benoit Forget, Kord Smith

2013-11-01T23:59:59.000Z

164

Shadow hybrid Monte Carlo: an efficient propagator in phase space of macromolecules  

Science Conference Proceedings (OSTI)

Shadow hybrid Monte Carlo (SHMC) is a new method for sampling the phase space of large molecules, particularly biological molecules. It improves sampling of hybrid Monte Carlo (HMC) by allowing larger time steps and system sizes in the molecular dynamics ... Keywords: conformational sampling, hybrid Monte Carlo, modified Hamiltonian, sampling methods, symplectic integrator

Jesús A. Izaguirre; Scott S. Hampton

2004-11-01T23:59:59.000Z

165

Plasma Kinetic Theory  

Science Conference Proceedings (OSTI)

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

B. Weyssow

166

Theory decision by decomposition  

Science Conference Proceedings (OSTI)

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

Maria Paola Bonacina; Mnacho Echenim

2010-02-01T23:59:59.000Z

167

Model Theory and Quantum  

E-Print Network (OSTI)

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

Mons-Hainaut, Université de

168

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

169

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

170

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

171

Ab initio Monte Carlo investigation of small lithium clusters.  

Science Conference Proceedings (OSTI)

Structural and thermal properties of small lithium clusters are studied using ab initio-based Monte Carlo simulations. The ab initio scheme uses a Hartree-Fock/density functional treatment of the electronic structure combined with a jump-walking Monte Carlo sampling of nuclear configurations. Structural forms of Li{sub 8} and Li{sub 9}{sup +} clusters are obtained and their thermal properties analyzed in terms of probability distributions of the cluster potential energy, average potential energy and configurational heat capacity all considered as a function of the cluster temperature. Details of the gradual evolution with temperature of the structural forms sampled are examined. Temperatures characterizing the onset of structural changes and isomer coexistence are identified for both clusters.

Srinivas, S.

1999-06-16T23:59:59.000Z

172

Monte Carlo Simulations of Neutron Oil well Logging Tools  

E-Print Network (OSTI)

Monte Carlo simulations of simple neutron oil well logging tools into typical geological formations are presented.The simulated tools consist of both 14 MeV pulsed and continuous Am-Be neutron sources with time gated and continuous gamma ray detectors respectively.The geological formation consists of pure limestone with 15% absolute porosity in a wide range of oil saturation.The particle transport was performed with the Monte Carlo N-Particle Transport Code System, MCNP-4B.Several gamma ray spectra were obtained at the detector position that allow to perform composition analysis of the formation.In particular, the ratio C/O was analyzed as an indicator of oil saturation.Further calculations are proposed to simulate actual detector responses in order to contribute to understand the relation between the detector response with the formation composition

Azcurra, M

2002-01-01T23:59:59.000Z

173

MC++: Parallel, portable, Monte Carlo neutron transport in C++  

Science Conference Proceedings (OSTI)

We have developed an implicit Monte Carlo neutron transport code in C++ using the Parallel Object-Oriented Methods and Applications (POOMA) class library. MC++ runs in parallel on and is portable to a wide variety of platforms, including MPPs, clustered SMPs, and individual workstations. It contains appropriate classes and abstractions for particle transport and parallelism. Current capabilities of MC++ are discussed, along with future plans and physics and performance results on many different platforms.

Lee, S.R.; Cummings, J.C. [Los Alamos National Lab., NM (United States); Nolen, S.D. [Texas A& M Univ., College Station, TX (United States). Dept. of Nuclear Engineering

1997-02-01T23:59:59.000Z

174

Towards a Revised Monte Carlo Neutral Particle Surface Interaction Model  

DOE Green Energy (OSTI)

The components of the neutral- and plasma-surface interaction model used in the Monte Carlo neutral transport code DEGAS 2 are reviewed. The idealized surfaces and processes handled by that model are inadequate for accurately simulating neutral transport behavior in present day and future fusion devices. We identify some of the physical processes missing from the model, such as mixed materials and implanted hydrogen, and make some suggestions for improving the model.

D.P. Stotler

2005-06-09T23:59:59.000Z

175

Coupled MHD-Monte Carlo transport model for dense plasmas  

SciTech Connect

A two-dimensional, two fluid model of the MHD equations has been coupled to a Monte Carlo transport model of high energy, non-Maxwellian ions. The MHD part of the model assumes complete ionization and includes a perfect gas law for a scalar pressure, a tensor artificial viscosity, electron and ion thermal conduction, electron-ion coupling, and a radiation loss term. A simple Ohm's Law is used with a B/sub theta/ magnetic field. The MHD equations were solved in Lagrangian coordinates. The conservation equations were differenced explicitly and the diffusion-type equations implicitly using the splitting technique. The Monte Carlo model solves the equation of motion for high energy ions, moving through and suffering small and large angle collisions with the fluid Maxwellian plasma. The source of high energy ions is the thermonuclear reactions of the hydrogen isotopes, or it may be an externally injected beam of neutralized ions. In addition to using the usual Maxwell averaged thermonuclear cross sections for calculating the number of reactions taking place within the Maxwellian plasma, the high energy ions may suffer collisions resulting in a reaction. In the Monte Carlo model all neutrons are assumed to escape, and all energetic ions of Z less than or equal to 2 are followed. (auth)

Chandler, W.P.

1975-06-01T23:59:59.000Z

176

MC generator TAUOLA: Implementation of resonance chiral theory for two and three meson modes. Comparison with experiment  

Science Conference Proceedings (OSTI)

We present a partial upgrade of the Monte Carlo event generator TAUOLA with the two and three hadron decay modes using the theoretical models based on Resonance Chiral Theory. These modes account for 88% of total hadronic width of the tau meson. First results of the model parameters have been obtained using BaBar data for 3{pi} mode.

Shekhovtsova, O.; Nugent, I. M.; Przedzinski, T.; Roig, P.; Was, Z. [IFIC, Universitat de Valencia-CSIC, Apt. Correus 22085, E-46071, Valencia (Spain); RWTH Aachen University, III. Physikalisches Institut B, Aachen (Germany); The Faculty of Physics, Astronomy and Applied Computer Science, Jagellonian University, Reymonta 4, 30-059 Cracow, Poland and CERN PH-TH, CH-1211 Geneva 23 (Switzerland); Grup de Fisica Teorica, Institut de Fisica d'Altes Energies, Universitat Autonoma de Barcelona, E-08193 Bellaterra, Barcelona (Spain); Institute of Nuclear Physics, PAN, Krakow, ul. Radzikowskiego 152, Poland and CERN PH-TH, CH-1211 Geneva 23 (Switzerland)

2012-10-23T23:59:59.000Z

177

Kinetic Lattice Monte Carlo Simulation ofKinetic Lattice Monte Carlo Simulation of Polycrystalline Thin film growthPolycrystalline Thin film growth  

E-Print Network (OSTI)

grain orientations s The first application of this code is to the growth of Mo tips, including chemicalKinetic Lattice Monte Carlo Simulation ofKinetic Lattice Monte Carlo Simulation of Polycrystalline Applications Motorola National Science Foundation National Center for Supercomputer Applications Motorola #12

Adams, James B

178

Minority Influence Theory  

E-Print Network (OSTI)

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

Nemeth, Charlan Jeanne

2010-01-01T23:59:59.000Z

179

Plasma Kinetic Theory  

Science Conference Proceedings (OSTI)

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

B. Weyssow

180

Quantum Physics Theory  

Science Conference Proceedings (OSTI)

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

2010-10-05T23:59:59.000Z

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.


181

Algorithmic information theory  

E-Print Network (OSTI)

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

Grunwald, Peter D

2008-01-01T23:59:59.000Z

182

Free Field Theory as a String Theory?  

E-Print Network (OSTI)

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

Rajesh Gopakumar

2004-09-23T23:59:59.000Z

183

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

SciTech Connect

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

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

2010-01-21T23:59:59.000Z

184

Statistical Properties of Nuclei by the Shell Model Monte Carlo Method  

E-Print Network (OSTI)

We use quantum Monte Carlo methods in the framework of the interacting nuclear shell model to calculate the statistical properties of nuclei at finite temperature and/or excitation energies. With this approach we can carry out realistic calculations in much larger configuration spaces than are possible by conventional methods. A major application of the methods has been the microscopic calculation of nuclear partition functions and level densities, taking into account both correlations and shell effects. Our results for nuclei in the mass region A ~ 50 - 70 are in remarkably good agreement with experimental level densities without any adjustable parameters and are an improvement over empirical formulas. We have recently extended the shell model theory of level statistics to higher temperatures, including continuum effects. We have also constructed simple statistical models to explain the dependence of the microscopically calculated level densities on good quantum numbers such as parity. Thermal signatures of pairing correlations are identified through odd-even effects in the heat capacity.

Y. Alhassid

2006-04-26T23:59:59.000Z

185

An alternative Monte Carlo approach to the thermal radiative transfer problem  

SciTech Connect

The usual Monte Carlo approach to the thermal radiative transfer problem is to view Monte Carlo as a solution technique for the nonlinear thermal radiative transfer equations. The equations contain time derivatives which are approximated by introducing small time steps. An alternative approach avoids time steps by using Monte Carlo to directly sample the time at which the next event occurs. That is, the time is advanced on a natural event-by-event basis rather than by introducing an artificial time step.

Booth, Thomas E., E-mail: teb@lanl.go [Mail Stop A143, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)

2011-02-20T23:59:59.000Z

186

Continuous-Estimator Representation for Monte Carlo Criticality Diagnostics  

Science Conference Proceedings (OSTI)

An alternate means of computing diagnostics for Monte Carlo criticality calculations is proposed. Overlapping spherical regions or estimators are placed covering the fissile material with a minimum center-to-center separation of the 'fission distance', which is defined herein, and a radius that is some multiple thereof. Fission neutron production is recorded based upon a weighted average of proximities to centers for all the spherical estimators. These scores are used to compute the Shannon entropy, and shown to reproduce the value, to within an additive constant, determined from a well-placed mesh by a user. The spherical estimators are also used to assess statistical coverage.

Kiedrowski, Brian C. [Los Alamos National Laboratory; Brown, Forrest B. [Los Alamos National Laboratory

2012-06-18T23:59:59.000Z

187

Bounded limit for the Monte Carlo point-flux-estimator  

Science Conference Proceedings (OSTI)

In a Monte Carlo random walk the kernel K(R,E) is used as an expected value estimator at every collision for the collided flux phi/sub c/ r vector,E) at the detector point. A limiting value for the kernel is derived from a diffusion approximation for the probability current at a radius R/sub 1/ from the detector point. The variance of the collided flux at the detector point is thus bounded using this asymptotic form for K(R,E). The bounded point flux estimator is derived. (WHK)

Grimesey, R.A.

1981-01-01T23:59:59.000Z

188

Process Characterisation with Monte-Carlo Wave-Functions  

E-Print Network (OSTI)

We present a numerically efficient method for the characterisation of a quantum process subject to dissipation and noise. The master equation evolution of a maximally entangled state of the quantum system and a non-evolving ancilla system is simulated by Monte-Carlo wave-functions. We show how each stochastic state vectors provides quantities that are readily combined into an average process \\chi-matrix. Our method significantly reduces the computational complexity in comparison with standard characterisation methods. It also readily provides an upper bound on the trace distance between the ideal and simulated process based on the evolution of only a single wave function of the entangled system.

Jake Gulliksen; D. D. Bhaktavatsala Rao; Klaus Mølmer

2013-09-19T23:59:59.000Z

189

Adaptively Learning an Importance Function Using Transport Constrained Monte Carlo  

Science Conference Proceedings (OSTI)

It is well known that a Monte Carlo estimate can be obtained with zero-variance if an exact importance function for the estimate is known. There are many ways that one might iteratively seek to obtain an ever more exact importance function. This paper describes a method that has obtained ever more exact importance functions that empirically produce an error that is dropping exponentially with computer time. The method described herein constrains the importance function to satisfy the (adjoint) Boltzmann transport equation. This constraint is provided by using the known form of the solution, usually referred to as the Case eigenfunction solution.

Booth, T.E.

1998-06-22T23:59:59.000Z

190

Validation of Phonon Physics in the CDMS Detector Monte Carlo  

SciTech Connect

The SuperCDMS collaboration is a dark matter search effort aimed at detecting the scattering of WIMP dark matter from nuclei in cryogenic germanium targets. The CDMS Detector Monte Carlo (CDMS-DMC) is a simulation tool aimed at achieving a deeper understanding of the performance of the SuperCDMS detectors and aiding the dark matter search analysis. We present results from validation of the phonon physics described in the CDMS-DMC and outline work towards utilizing it in future WIMP search analyses.

McCarthy, K.A.; Leman, S.W.; Anderson, A.J.; /MIT; Brandt, D.; /SLAC; Brink, P.L.; Cabrera, B.; Cherry, M.; /Stanford U.; Do Couto E Silva, E.; /SLAC; Cushman, P.; /Minnesota U.; Doughty, T.; /UC, Berkeley; Figueroa-Feliciano, E.; /MIT; Kim, P.; /SLAC; Mirabolfathi, N.; /UC, Berkeley; Novak, L.; /Stanford U.; Partridge, R.; /SLAC; Pyle, M.; /Stanford U.; Reisetter, A.; /Minnesota U. /St. Olaf Coll.; Resch, R.; /SLAC; Sadoulet, B.; Serfass, B.; Sundqvist, K.M.; /UC, Berkeley /Stanford U.

2012-06-06T23:59:59.000Z

191

Avaliação sócio-econômica e ambiental do complexo hidrelétrico de Belo Monte.  

E-Print Network (OSTI)

??O presente trabalho tem como objetivo tratar da construção do Complexo Hidrelétrico de Belo Monte, trazendo informações sobre aspectos econômicos, de produção e consumo energético.… (more)

Neidja Cristine Silvestre Leitão

2005-01-01T23:59:59.000Z

192

MINT: a Computer Program for Adaptive Monte Carlo Integration and Generation of Unweighted Distributions  

E-Print Network (OSTI)

In this note I illustrate the program MINT, a FORTRAN program for Monte Carlo adaptive integration and generation of unweighted distributions.

Nason, P

2007-01-01T23:59:59.000Z

193

MINT: a Computer Program for Adaptive Monte Carlo Integration and Generation of Unweighted Distributions  

E-Print Network (OSTI)

In this note I illustrate the program MINT, a FORTRAN program for Monte Carlo adaptive integration and generation of unweighted distributions.

P. Nason

2007-09-13T23:59:59.000Z

194

Observations of the formation and maintenance of beach cusps on Del Monte Beach in Monterey, California .  

E-Print Network (OSTI)

??During the period of 5 April 2001 - 16 May 2001, topographic surveys of Del Monte beach in Monterey, California, were performed on a regular… (more)

Miller, Gregory Chad.

2001-01-01T23:59:59.000Z

195

Monte Carlo parameter studies and uncertainty analyses with MCNP5  

SciTech Connect

A software tool called mcnp-pstudy has been developed to automate the setup, execution, and collection of results from a series of MCNPS Monte Carlo calculations. This tool provides a convenient means of performing parameter studies, total uncertainty analyses, parallel job execution on clusters, stochastic geometry modeling, and other types of calculations where a series of MCNPS jobs must be performed with varying problem input specifications. Monte Carlo codes are being used for a wide variety of applications today due to their accurate physical modeling and the speed of today's computers. In most applications for design work, experiment analysis, and benchmark calculations, it is common to run many calculations, not just one, to examine the effects of design tolerances, experimental uncertainties, or variations in modeling features. We have developed a software tool for use with MCNP5 to automate this process. The tool, mcnp-pstudy, is used to automate the operations of preparing a series of MCNP5 input files, running the calculations, and collecting the results. Using this tool, parameter studies, total uncertainty analyses, or repeated (possibly parallel) calculations with MCNP5 can be performed easily. Essentially no extra user setup time is required beyond that of preparing a single MCNP5 input file.

Brown, F. B. (Forrest B.); Sweezy, J. E. (Jeremy E.); Hayes, R. B. (Robert B.)

2004-01-01T23:59:59.000Z

196

Lectures on String Theory  

E-Print Network (OSTI)

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

Tong, David

2009-01-01T23:59:59.000Z

197

Theory Modeling and Simulation  

SciTech Connect

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

Shlachter, Jack [Los Alamos National Laboratory

2012-08-23T23:59:59.000Z

198

Theory and Software Science  

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

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

199

Atomic Theory of Lithium  

Science Conference Proceedings (OSTI)

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

2011-10-06T23:59:59.000Z

200

Introduction to String Theory  

E-Print Network (OSTI)

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

Belhaj, Adil

2008-01-01T23:59:59.000Z

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

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

202

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

E-Print Network (OSTI)

Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive proper...

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

2013-01-01T23:59:59.000Z

203

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

E-Print Network (OSTI)

Density-functional theory (DFT) has been widely used to study water and ice for at least 20 years. However, the reliability of different DFT exchange-correlation (xc) functionals for water remains a matter of considerable debate. This is particularly true in light of the recent development of DFT based methods that account for van der Waals (vdW) dispersion forces. Here, we report a detailed study with several xc functionals (semi-local, hybrid, and vdW inclusive approaches) on ice Ih and six proton ordered phases of ice. Consistent with our previous study [Phys. Rev. Lett. 107, 185701 (2011)] which showed that vdW forces become increasingly important at high pressures, we find here that all vdW inclusive methods considered improve the relative energies and transition pressures of the high-pressure ice phases compared to those obtained with semi-local or hybrid xc functionals. However, we also find that significant discrepancies between experiment and the vdW inclusive approaches remain in the cohesive properties of the various phases, causing certain phases to be absent from the phase diagram. Therefore, room for improvement in the description of water at ambient and high pressures remains and we suggest that because of the stern test the high pressure ice phases pose they should be used in future benchmark studies of simulation methods for water.

Biswajit Santra; Ji?í Klimeš; Alexandre Tkatchenko; Dario Alfè; Ben Slater; Angelos Michaelides; Roberto Car; Matthias Scheffler

2013-07-12T23:59:59.000Z

204

DFT repositories and informatics  

Science Conference Proceedings (OSTI)

... includes: Establishing best practices for future and current practitioners,; Developing data-sharing tools and repositories,; ...

2013-07-18T23:59:59.000Z

205

DFT Exercises - TMS  

Science Conference Proceedings (OSTI)

Mar 24, 2008 ... benzene silicon sodium graphite comparison of covalent, ionic, and metallic bonding. Van Hove singularities surface reconstruction on silicon

206

A First-Passage Kinetic Monte Carlo algorithm for complex diffusion-reaction systems  

Science Conference Proceedings (OSTI)

We develop an asynchronous event-driven First-Passage Kinetic Monte Carlo (FPKMC) algorithm for continuous time and space systems involving multiple diffusing and reacting species of spherical particles in two and three dimensions. The FPKMC algorithm ... Keywords: Asynchronous algorithms, Diffusion-reaction, First-passage, Kinetic Monte Carlo

Aleksandar Donev; Vasily V. Bulatov; Tomas Oppelstrup; George H. Gilmer; Babak Sadigh; Malvin H. Kalos

2010-05-01T23:59:59.000Z

207

Sequential Monte Carlo for Bayesian sequentially designed experiments for discrete data  

Science Conference Proceedings (OSTI)

In this paper we present a sequential Monte Carlo algorithm for Bayesian sequential experimental design applied to generalised non-linear models for discrete data. The approach is computationally convenient in that the information of newly observed data ... Keywords: Clinical trials, Generalised linear model, Generalised non-linear model, Sequential Monte Carlo, Sequential design, Target stimulus

Christopher C. Drovandi; James M. Mcgree; Anthony N. Pettitt

2013-01-01T23:59:59.000Z

208

Monte Carlo modeling of spin FETs controlled by spin-orbit interaction  

Science Conference Proceedings (OSTI)

A method for Monte Carlo simulation of 2D spin-polarized electron transport in III-V semiconductor heterojunction (FETs) is presented. In the simulation, the dynamics of the electrons in coordinate and momentum space is treated semiclassically. The density ... Keywords: FET, Monte Carlo, spin orbit, spintronics

Min Shen; Semion Saikin; Ming-C. Cheng; Vladimir Privman

2004-05-01T23:59:59.000Z

209

Asymptotic diffusion limit of the symbolic Monte-Carlo method for the transport equation  

Science Conference Proceedings (OSTI)

We use asymptotic analysis to study the diffusion limit of the Symbolic Implicit Monte-Carlo (SIMC) method for the transport equation. For standard SIMC with piecewise constant basis functions, we demonstrate mathematically that the solution converges ... Keywords: Monte-Carlo method, radiative transfer

J.-F. Clouët; G. Samba

2004-03-01T23:59:59.000Z

210

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

Science Conference Proceedings (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. Fiúza

2010-08-01T23:59:59.000Z

211

Methods for coupling radiation, ion, and electron energies in grey Implicit Monte Carlo  

Science Conference Proceedings (OSTI)

We present three methods for extending the Implicit Monte Carlo (IMC) method to treat the time-evolution of coupled radiation, electron, and ion energies. The first method splits the ion and electron coupling and conduction from the standard IMC radiation-transport ... Keywords: Implicit Monte Carlo, Thermal radiation transport, Three-temperature model

T. M. Evans; J. D. Densmore

2007-08-01T23:59:59.000Z

212

A comparison of generalized hybrid Monte Carlo methods with and without momentum flip  

Science Conference Proceedings (OSTI)

The generalized hybrid Monte Carlo (GHMC) method combines Metropolis corrected constant energy simulations with a partial random refreshment step in the particle momenta. The standard detailed balance condition requires that momenta are negated upon ... Keywords: Langevin dynamics, Molecular dynamics, Monte Carlo methods, Sampling

Elena Akhmatskaya; Nawaf Bou-Rabee; Sebastian Reich

2009-04-01T23:59:59.000Z

213

An efficient, robust, domain-decomposition algorithm for particle Monte Carlo  

Science Conference Proceedings (OSTI)

A previously described algorithm [T.A. Brunner, T.J. Urbatsch, T.M. Evans, N.A. Gentile, Comparison of four parallel algorithms for domain decomposed implicit Monte Carlo, Journal of Computational Physics 212 (2) (2006) 527-539] for doing domain decomposed ... Keywords: Monte Carlo methods, Neutron transport, Parallel computation, Radiative transfer

Thomas A. Brunner; Patrick S. Brantley

2009-06-01T23:59:59.000Z

214

Introduction to string theory and conformal field theory  

Science Conference Proceedings (OSTI)

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

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

2010-05-15T23:59:59.000Z

215

Multi-Determinant Wave-functions in Quantum Monte Carlo  

E-Print Network (OSTI)

Quantum Monte Carlo (QMC) methods have received considerable attention over the last decades due to their great promise for providing a direct solution to the many-body Schrodinger equation in electronic systems. Thanks to their low scaling with number of particles, QMC methods present a compelling competitive alternative for the accurate study of large molecular systems and solid state calculations. In spite of such promise, the method has not permeated the quantum chemistry community broadly, mainly because of the fixed-node error, which can be large and whose control is difficult. In this Perspective, we present a systematic application of large scale multi-determinant expansions in QMC, and report on its impressive performance with first row dimers and the 55 molecules of the G1 test set. We demonstrate the potential of this strategy for systematically reducing the fixed-node error in the wave function and for achieving chemical accuracy in energy predictions. When compared to traditional quantum chemistr...

Morales, M A; Clark, B K; Kim, J; Scuseria, G; 10.1021/ct3003404

2013-01-01T23:59:59.000Z

216

Optimization of Monte Carlo transport simulations in stochastic media  

Science Conference Proceedings (OSTI)

This paper presents an accurate and efficient approach to optimize radiation transport simulations in a stochastic medium of high heterogeneity, like the Very High Temperature Gas-cooled Reactor (VHTR) configurations packed with TRISO fuel particles. Based on a fast nearest neighbor search algorithm, a modified fast Random Sequential Addition (RSA) method is first developed to speed up the generation of the stochastic media systems packed with both mono-sized and poly-sized spheres. A fast neutron tracking method is then developed to optimize the next sphere boundary search in the radiation transport procedure. In order to investigate their accuracy and efficiency, the developed sphere packing and neutron tracking methods are implemented into an in-house continuous energy Monte Carlo code to solve an eigenvalue problem in VHTR unit cells. Comparison with the MCNP benchmark calculations for the same problem indicates that the new methods show considerably higher computational efficiency. (authors)

Liang, C.; Ji, W. [Dept. of Mechanical, Aerospace and Nuclear Engineering, Rensselaer Polytechnic Inst., 110 8th street, Troy, NY (United States)

2012-07-01T23:59:59.000Z

217

Monte Carlo Simulation Tool Installation and Operation Guide  

Science Conference Proceedings (OSTI)

This document provides information on software and procedures for Monte Carlo simulations based on the Geant4 toolkit, the ROOT data analysis software and the CRY cosmic ray library. These tools have been chosen for its application to shield design and activation studies as part of the simulation task for the Majorana Collaboration. This document includes instructions for installation, operation and modification of the simulation code in a high cyber-security computing environment, such as the Pacific Northwest National Laboratory network. It is intended as a living document, and will be periodically updated. It is a starting point for information collection by an experimenter, and is not the definitive source. Users should consult with one of the authors for guidance on how to find the most current information for their needs.

Aguayo Navarrete, Estanislao; Ankney, Austin S.; Berguson, Timothy J.; Kouzes, Richard T.; Orrell, John L.; Troy, Meredith D.; Wiseman, Clinton G.

2013-09-02T23:59:59.000Z

218

The Quantum Energy Density: Improved Efficiency for Quantum Monte Carlo  

E-Print Network (OSTI)

We establish a physically meaningful representation of a quantum energy density for use in Quantum Monte Carlo calculations. The energy density operator, defined in terms of Hamiltonian components and density operators, returns the correct Hamiltonian when integrated over a volume containing a cluster of particles. This property is demonstrated for a helium-neon "gas," showing that atomic energies obtained from the energy density correspond to eigenvalues of isolated systems. The formation energies of defects or interfaces are typically calculated as total energy differences. Using a model of delta-doped silicon (where dopant atoms form a thin plane) we show how interfacial energies can be calculated more efficiently with the energy density, since the region of interest is small. We also demonstrate how the energy density correctly transitions to the bulk limit away from the interface where the correct energy is obtainable from a separate total energy calculation.

Krogel, Jaron T; Kim, Jeongnim; Ceperley, David M

2013-01-01T23:59:59.000Z

219

Bayesian Inference in Monte-Carlo Tree Search  

E-Print Network (OSTI)

Monte-Carlo Tree Search (MCTS) methods are drawing great interest after yielding breakthrough results in computer Go. This paper proposes a Bayesian approach to MCTS that is inspired by distributionfree approaches such as UCT [13], yet significantly differs in important respects. The Bayesian framework allows potentially much more accurate (Bayes-optimal) estimation of node values and node uncertainties from a limited number of simulation trials. We further propose propagating inference in the tree via fast analytic Gaussian approximation methods: this can make the overhead of Bayesian inference manageable in domains such as Go, while preserving high accuracy of expected-value estimates. We find substantial empirical outperformance of UCT in an idealized bandit-tree test environment, where we can obtain valuable insights by comparing with known ground truth. Additionally we rigorously prove on-policy and off-policy convergence of the proposed methods.

Tesauro, Gerald; Segal, Richard

2012-01-01T23:59:59.000Z

220

Weak and Strong Coupling Theories for Polarizable Colloids and Nano-Particles  

E-Print Network (OSTI)

A theory is presented which allows us to accurately calculate the density profile of monovalent and multivalent counterions in suspensions of polarizable colloids or nano-particles. In the case of monovalent ions, we derive a weak-coupling theory that explicitly accounts for the ion-image interaction, leading to a modified Poisson-Boltzmann equation. For suspensions with multivalent counterions, a strong-coupling theory is used to calculate the density profile near the colloidal surface and a Poisson-Boltzmann equation with a renormalized boundary condition to account for the counterion distribution in the far-field. All the results are compared with the Monte Carlo simulations, showing an excellent agreement between the theory and the simulations.

Amin Bakhshandeh; Alexandre Pereira dos Santos; Yan Levin

2011-09-21T23:59:59.000Z

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.


221

Dirac Kirchhoff diffraction theory  

E-Print Network (OSTI)

Kirchhoff's scalar diffraction theory is applied throughout photon and electron optics. It is based on the stationary electromagnetic or Schr\\"odinger wave equation, and is useful in describing interference phenomena for both light and matter waves. Here, Kirchhoff's diffraction theory is derived from the relativistic Dirac equation, thus reformulated to work on Dirac spinors. The parallels with the "classic" scalar theory are highlighted, and a basic interpretation of the result obtained for the Fraunhofer diffraction limit is given. The goal of this paper is to emphasize the similarity between the two equations on the most fundamental level.

Ruben Van Boxem; Bart Partoens; Jo Verbeeck

2013-03-05T23:59:59.000Z

222

Dirac Kirchhoff diffraction theory  

E-Print Network (OSTI)

Kirchhoff's scalar diffraction theory is applied throughout photon and electron optics. It is based on the stationary electromagnetic or Schr\\"odinger wave equation, and is useful in describing interference phenomena for both light and matter waves. Here, Kirchhoff's diffraction theory is derived from the relativistic Dirac equation, thus reformulated to work on Dirac spinors. The parallels with the "classic" scalar theory are highlighted, and a basic interpretation of the result obtained for the Fraunhofer diffraction limit is given. The goal of this paper is to emphasize the similarity between the two equations on the most fundamental level.

Van Boxem, Ruben; Verbeeck, Jo

2013-01-01T23:59:59.000Z

223

Monte Carlo Study of Strongly-Interacting Degenerate Fermions: a Model for Voltage-Biased Bilayer Graphene  

E-Print Network (OSTI)

We formulate a model of N_f=4 flavors of relativistic fermion in 2+1d in the presence of a chemical potential mu coupled to two flavor doublets with opposite sign, akin to isopsin chemical potential in QCD. This is argued to be an effective theory for low energy electronic excitations in bilayer graphene, in which an applied voltage between the layers ensures equal populations of particles on one layer and holes on the other. The model is then reformulated on a spacetime lattice using staggered fermions, and in the absence of a sign problem, simulated using an orthodox hybrid Monte Carlo algorithm. With the coupling strength chosen to be close to a quantum critical point believed to exist for N_ftheory, while the conventional chiral condensate is strongly suppressed. The corresponding ground state is speculated to be a strongly-correlated degenerate fermion system, with a remnant Fermi surface distorted by a superfluid excitonic condensate. The model thus shows qualitatively different behaviour to any model with mu=/=0 previously studied by lattice simulation.

Wes Armour; Simon Hands; Costas Strouthos

2013-02-01T23:59:59.000Z

224

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.

225

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

226

Warped Conformal Field Theory  

E-Print Network (OSTI)

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

Detournay, Stephane; Hofman, Diego M

2012-01-01T23:59:59.000Z

227

Warped Conformal Field Theory  

E-Print Network (OSTI)

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

Stephane Detournay; Thomas Hartman; Diego M. Hofman

2012-10-01T23:59:59.000Z

228

Argonne Physics Division - Theory Group  

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

23rd Annual Midwest Theory Get-Together 2010 Theory Group Theoretical research in Argonne's Physics Division addresses a broad range of problems involving the stucture and dynamics...

229

Argonne Physics Division - Theory Group  

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

Argonne Theory Group: Postdoctoral Position The Theory Group in the Physics Division at Argonne National Laboratory is seeking exceptional candidates for a postdoctoral position...

230

The Particle Adventure | Unsolved Mysteries | String theory  

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

String theory String theory Modern physics has good theories for quantum mechanics, relativity, and gravity. But these theories do not quite work with each other. There are...

231

Quantum Monte Carlo for electronic structure: Recent developments and applications  

DOE Green Energy (OSTI)

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

232

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Use of Composting · Composting has ­ British Columbia 2009 #12;Disposal: Science and Theory · Initial farm linked to NY LBM · Two additional and pile procedure Delmarva 2004 #12;Disposal: Science and Theory Delmarva 2004 · Composting used

Benson, Eric R.

233

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Foam Used in Actual Outbreak · Water #12;Disposal: Science and Theory Water Based Foam Culling Demo · First large scale comparison · Two:46 (m:s) #12;Disposal: Science and Theory WV H5N2 AIV 2007 · AIV positive turkeys ­ 25,000 turkey farm

Benson, Eric R.

234

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · El compostaje se ha usado como Virginia (2007) ­ British Columbia (2009) Uso del compostaje #12;Disposal: Science and Theory · Primera apilamiento Delmarva (2004) #12;Disposal: Science and Theory · El compostaje se usó para proteger una densa

Benson, Eric R.

235

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Previous Research · Composting, et.al. 2005; Bendfeldt et al., 2006; DeRouchey et al., 2005) #12;Disposal: Science and Theory: Science and Theory Scientific Validation of Composting · Experiment 1 Impact of foam on composting

Benson, Eric R.

236

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Poultry Farm Daily Disposal Methods 0;Disposal: Science and Theory First Composter in Delaware · Delmarva was of the first daily composting · 120 in USA over next 10 years #12;Disposal: Science and Theory Composting Procedure · Mixture ­ 1 ½ to 2

Benson, Eric R.

237

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Brief History of Foam 2004 ­ Bud and foam 2009 ­ No advantage for gas #12;Disposal: Science and Theory What is foam? · What is fire fighting system. #12;Disposal: Science and Theory Foam Composition · Foam can include ­ Mixture of surfactants

Benson, Eric R.

238

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Compostaje de aves de corralRouchey et al., 2005) Investigación previa #12;Disposal: Science and Theory · Se ha evaluado y documentado el, bovino Investigación previa #12;Disposal: Science and Theory · Experimento nro. 1 Impacto de la espuma en

Benson, Eric R.

239

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Se ubica el carretón con el enfriamiento Ventiladores de túnel de viento #12;Disposal: Science and Theory · Se estaciona el remolque en uno: Science and Theory · Se usa un equipo de dos personas para hacer funcionar el sistema: ­ Operario del

Benson, Eric R.

240

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Opciones para la eliminación · ¿Qué compostaje durante brotes de enfermedades Lista de contenido #12;Disposal: Science and Theory "Ante un brote brotes de IIAP #12;Disposal: Science and Theory · En 2004, se despoblaron 100 millones de aves en todo el

Benson, Eric R.

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

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Las recomendaciones de campo se la espuma #12;Disposal: Science and Theory · Múltiples especies de aves pueden despoblarse con espuma cesación #12;Disposal: Science and Theory · Dentro de una especie, pueden existir variaciones ­ Los ánades

Benson, Eric R.

242

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Summary · Foam is currently a viable ­ Foam application directly to cage #12;Disposal: Science and Theory Legal Status of Foam · Procedure depopulation, culling, and euthanasia #12;Disposal: Science and Theory Acknowledgements · USDA AICAP2 · USDA

Benson, Eric R.

243

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Mass Emergency Composting · Basic ­ Create carcass and litter windrow #12;Disposal: Science and Theory Mass Emergency Composting · Basic cover ­ Clean and disinfect house ­ Sample for virus again #12;Disposal: Science and Theory Mass

Benson, Eric R.

244

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Gassing is a preferred #12;Disposal: Science and Theory Carbon Dioxide Gassing · Carbon dioxide (CO2) one of the standard sensitivity time #12;Disposal: Science and Theory · Argon-CO2 gas depopulation evaluated under laboratory

Benson, Eric R.

245

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · El compostaje se define como la: Science and Theory · Compostaje óptimo ­ Relación carbono/nitrógeno (C:N): 20:1 a 35:1 ­ Contenido de Compostaje #12;Disposal: Science and Theory · Se ha utilizado satisfactoriamente una variedad de materiales

Benson, Eric R.

246

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Foam Generator Setup · Drop off foam generator cart at one end of house #12;Disposal: Science and Theory Foam Generator Setup · Trailer parked generator attached to hose #12;Disposal: Science and Theory Foam Generation Begins · Team of two to operate

Benson, Eric R.

247

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Foaming Options · Compressed Air Foam Systems (CAFS) · Foam Blower · Foam Generator · Nozzle Systems #12;Disposal: Science and Theory Compressed ­ Industry owned response team #12;Disposal: Science and Theory Commercial CAFS for Poultry · Poultry

Benson, Eric R.

248

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory 0 20 40 60 80 100 Compostaje #12;Disposal: Science and Theory · Delmarva fue de las primeras granjas en realizar el compostaje de en EE.UU. en los próximos 10 años. Pionera en compostaje en Delaware #12;Disposal: Science and Theory

Benson, Eric R.

249

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Procedimiento básico ­ Desarrollar una pila de carcasas y lecho. Compostaje masivo de emergencia #12;Disposal: Science and Theory de emergencia #12;Disposal: Science and Theory · Desarrollar planes antes de que ocurra una

Benson, Eric R.

250

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Composting · Composting is defined drop #12;Disposal: Science and Theory Composting · Optimal composting ­ Carbon to nitrogen ratio (C;Disposal: Science and Theory Compost Composition · A variety of supplemental carbon materials have been

Benson, Eric R.

251

Matrix Product States for Lattice Field Theories  

E-Print Network (OSTI)

The term Tensor Network States (TNS) refers to a number of families of states that represent different ans\\"atze for the efficient description of the state of a quantum many-body system. Matrix Product States (MPS) are one particular case of TNS, and have become the most precise tool for the numerical study of one dimensional quantum many-body systems, as the basis of the Density Matrix Renormalization Group method. Lattice Gauge Theories (LGT), in their Hamiltonian version, offer a challenging scenario for these techniques. While the dimensions and sizes of the systems amenable to TNS studies are still far from those achievable by 4-dimensional LGT tools, Tensor Networks can be readily used for problems which more standard techniques, such as Markov chain Monte Carlo simulations, cannot easily tackle. Examples of such problems are the presence of a chemical potential or out-of-equilibrium dynamics. We have explored the performance of Matrix Product States in the case of the Schwinger model, as a widely used ...

Bañuls, Mari Carmen; Cirac, J Ignacio; Jansen, Karl; Saito, Hana

2013-01-01T23:59:59.000Z

252

Monte Carlo simulations for generic granite repository studies  

SciTech Connect

In a collaborative study between Los Alamos National Laboratory (LANL) and Sandia National Laboratories (SNL) for the DOE-NE Office of Fuel Cycle Technologies Used Fuel Disposition (UFD) Campaign project, we have conducted preliminary system-level analyses to support the development of a long-term strategy for geologic disposal of high-level radioactive waste. A general modeling framework consisting of a near- and a far-field submodel for a granite GDSE was developed. A representative far-field transport model for a generic granite repository was merged with an integrated systems (GoldSim) near-field model. Integrated Monte Carlo model runs with the combined near- and farfield transport models were performed, and the parameter sensitivities were evaluated for the combined system. In addition, a sub-set of radionuclides that are potentially important to repository performance were identified and evaluated for a series of model runs. The analyses were conducted with different waste inventory scenarios. Analyses were also conducted for different repository radionuelide release scenarios. While the results to date are for a generic granite repository, the work establishes the method to be used in the future to provide guidance on the development of strategy for long-term disposal of high-level radioactive waste in a granite repository.

Chu, Shaoping [Los Alamos National Laboratory; Lee, Joon H [SNL; Wang, Yifeng [SNL

2010-12-08T23:59:59.000Z

253

Non-analog Monte Carlo estimators for radiation momentum deposition  

SciTech Connect

The standard method for calculating radiation momentum deposition in Monte Carlo simulations is the analog estimator, which tallies the change in a particle's momentum at each interaction with the matter. Unfortunately, the analog estimator can suffer from large amounts of statistical error. In this paper, we present three new non-analog techniques for estimating momentum deposition. Specifically, we use absorption, collision, and track-length estimators to evaluate a simple integral expression for momentum deposition that does not contain terms that can cause large amounts of statistical error in the analog scheme. We compare our new non-analog estimators to the analog estimator with a set of test problems that encompass a wide range of material properties and both isotropic and anisotropic scattering. In nearly all cases, the new non-analog estimators outperform the analog estimator. The track-length estimator consistently yields the highest performance gains, improving upon the analog-estimator figure of merit by factors of up to two orders of magnitude.

Densmore, Jeffery D [Los Alamos National Laboratory; Hykes, Joshua M [Los Alamos National Laboratory

2008-01-01T23:59:59.000Z

254

Reduced Variance for Material Sources in Implicit Monte Carlo  

SciTech Connect

Implicit Monte Carlo (IMC), a time-implicit method due to Fleck and Cummings, is used for simulating supernovae and inertial confinement fusion (ICF) systems where x-rays tightly and nonlinearly interact with hot material. The IMC algorithm represents absorption and emission within a timestep as an effective scatter. Similarly, the IMC time-implicitness splits off a portion of a material source directly into the radiation field. We have found that some of our variance reduction and particle management schemes will allow large variances in the presence of small, but important, material sources, as in the case of ICF hot electron preheat sources. We propose a modification of our implementation of the IMC method in the Jayenne IMC Project. Instead of battling the sampling issues associated with a small source, we bypass the IMC implicitness altogether and simply deterministically update the material state with the material source if the temperature of the spatial cell is below a user-specified cutoff. We describe the modified method and present results on a test problem that show the elimination of variance for small sources.

Urbatsch, Todd J. [Los Alamos National Laboratory

2012-06-25T23:59:59.000Z

255

Monte Carlo Simulations of Cosmic Rays Hadronic Interactions  

Science Conference Proceedings (OSTI)

This document describes the construction and results of the MaCoR software tool, developed to model the hadronic interactions of cosmic rays with different geometries of materials. The ubiquity of cosmic radiation in the environment results in the activation of stable isotopes, referred to as cosmogenic activities. The objective is to use this application in conjunction with a model of the MAJORANA DEMONSTRATOR components, from extraction to deployment, to evaluate cosmogenic activation of such components before and after deployment. The cosmic ray showers include several types of particles with a wide range of energy (MeV to GeV). It is infeasible to compute an exact result with a deterministic algorithm for this problem; Monte Carlo simulations are a more suitable approach to model cosmic ray hadronic interactions. In order to validate the results generated by the application, a test comparing experimental muon flux measurements and those predicted by the application is presented. The experimental and simulated results have a deviation of 3%.

Aguayo Navarrete, Estanislao; Orrell, John L.; Kouzes, Richard T.

2011-04-01T23:59:59.000Z

256

Numerical study of error propagation in Monte Carlo depletion simulations  

Science Conference Proceedings (OSTI)

Improving computer technology and the desire to more accurately model the heterogeneity of the nuclear reactor environment have made the use of Monte Carlo depletion codes more attractive in recent years, and feasible (if not practical) even for 3-D depletion simulation. However, in this case statistical uncertainty is combined with error propagating through the calculation from previous steps. In an effort to understand this error propagation, a numerical study was undertaken to model and track individual fuel pins in four 17 x 17 PWR fuel assemblies. By changing the code's initial random number seed, the data produced by a series of 19 replica runs was used to investigate the true and apparent variance in k{sub eff}, pin powers, and number densities of several isotopes. While this study does not intend to develop a predictive model for error propagation, it is hoped that its results can help to identify some common regularities in the behavior of uncertainty in several key parameters. (authors)

Wyant, T.; Petrovic, B. [Nuclear and Radiological Engineering, Georgia Inst. of Technology, 770 State Street, Atlanta, GA 30332-0745 (United States)

2012-07-01T23:59:59.000Z

257

Mountain Waves over Mont Blanc: Influence of a Stagnant Boundary Layer  

Science Conference Proceedings (OSTI)

A stationary mountain wave, embedded in southwesterly flow over Mont Blanc in the Alps, was observed simultaneously by three research aircraft and three types of remote sensing: GPS dropsondes, airborne light detecting and ranging (lidar), and ...

Ronald B. Smith; Steven Skubis; James D. Doyle; Adrian S. Broad; Christoph Kiemle; Hans Volkert

2002-07-01T23:59:59.000Z

258

MERADGEN: Monte Carlo generator for the simulation of radiative events in polarized Moller scattering  

SciTech Connect

The Monte Carlo generator MERADGEN for the simulation of QED radiative events in polarized Moller scattering has been developed. Analytical integration wherever it is possible provides rather fast generation. Some numerical tests and histograms are presented.

Andrei Afanasev; Eugene Chudakov; Alexander Ilyichev; Vladimir Zykunov

2006-04-04T23:59:59.000Z

259

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

260

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

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.


261

Remote Sounding of High Clouds. III: Monte Carlo Calculations of Multiple-Scattered Lidar Returns  

Science Conference Proceedings (OSTI)

Monte Carlo calculations of multiple-scattered contributions to the total energy received in a lidar beam have been made for a representative cirrus ice-cloud scattering phase function. The phase function is varied arbitrarily near the back ...

C. M. R. Platt

1981-01-01T23:59:59.000Z

262

Nonlinear Parameter Estimation: Comparison of an Ensemble Kalman Smoother with a Markov Chain Monte Carlo Algorithm  

Science Conference Proceedings (OSTI)

This paper explores the temporal evolution of cloud microphysical parameter uncertainty using an idealized 1D model of deep convection. Model parameter uncertainty is quantified using a Markov chain Monte Carlo (MCMC) algorithm. A new form of the ...

Derek J. Posselt; Craig H. Bishop

2012-06-01T23:59:59.000Z

263

Time-domain non-Monte Carlo noise simulation for nonlinear dynamic circuits with arbitrary excitations  

Science Conference Proceedings (OSTI)

A new, time-domain, non-Monte Carlo method for computer simulation of electrical noise in nonlinear dynamic circuits with arbitrary excitations is presented. This time-domain noise simulation ...

Alper Demir; Edward W. Y. Liu; Alberto L. Sangiovanni-Vincentelli

1994-11-01T23:59:59.000Z

264

Clustering and Short-Range Orer in Fe-Cr Alloys: A Monte Carlo Study  

Science Conference Proceedings (OSTI)

May 1, 2007 ... Clustering and Short-Range Orer in Fe-Cr Alloys: A Monte Carlo Study by Mikhail Lavrentiev, Duc Nguyen-Manh, Sergei Dudarev, Ralf Drautz, ...

265

Estimation of Wind Speed Distribution Using Markov Chain Monte Carlo Techniques  

Science Conference Proceedings (OSTI)

The Weibull distribution is the most commonly used statistical distribution for describing wind speed data. Maximum likelihood has traditionally been the main method of estimation for Weibull parameters. In this paper, Markov chain Monte Carlo ...

Wan-Kai Pang; Jonathan J. Forster; Marvin D. Troutt

2001-08-01T23:59:59.000Z

266

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

267

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.

268

Near quantitative agreement of model free DFT- MD predictions with XAFS observations of the hydration structure of highly charged transition metal ions  

Science Conference Proceedings (OSTI)

DFT-MD simulations (PBE96 and PBE0) with MD-XAFS scattering calculations (FEFF9) show near quantitative agreement with new and existing XAFS measurements for a comprehensive series of transition metal ions which interact with their hydration shells via complex mechanisms (high spin, covalency, charge transfer, etc.). This work was supported by the U.S. Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Pacific Northwest National Laboratory (PNNL) is operated for the U.S. DOE by Battelle. A portion of the research was performed using EMSL, a national scientific user facility sponsored by the U.S. DOE's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.

Fulton, John L.; Bylaska, Eric J.; Bogatko, Stuart A.; Balasubramanian, Mahalingam; Cauet, Emilie L.; Schenter, Gregory K.; Weare, John H.

2012-09-20T23:59:59.000Z

269

Mathematical Quantum Field Theory and Renormalization Theory  

E-Print Network (OSTI)

This volume of Math-for-Industry Lecture Note Series is dedicated to Professor Izumi Ojima and Professor Kei-ichi Ito on the occasion of their sixtieth birthdays. Professor Izumi Ojima and Professor Kei-ichi Ito have organized a lot of interesting and advanced conferences, e.g., RIMS conference, on quantum field theory and related topics, and they have encouraged not only young but also senior scientists. We would like to express our hearty gratitude to Professor Izumi Ojima and Professor Kei-ichi Ito for their continuous encouragement to us, stimulating our works, innumerable, unbounded helpful comments to our scientific researches. This lecture note is collecting several research papers and survey articles contributed by invited speakers of the international conference

Renormalization

2009-01-01T23:59:59.000Z

270

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

271

A NEW MONTE CARLO METHOD FOR TIME-DEPENDENT NEUTRINO RADIATION TRANSPORT  

Science Conference Proceedings (OSTI)

Monte Carlo approaches to radiation transport have several attractive properties such as simplicity of implementation, high accuracy, and good parallel scaling. Moreover, Monte Carlo methods can handle complicated geometries and are relatively easy to extend to multiple spatial dimensions, which makes them potentially interesting in modeling complex multi-dimensional astrophysical phenomena such as core-collapse supernovae. The aim of this paper is to explore Monte Carlo methods for modeling neutrino transport in core-collapse supernovae. We generalize the Implicit Monte Carlo photon transport scheme of Fleck and Cummings and gray discrete-diffusion scheme of Densmore et al. to energy-, time-, and velocity-dependent neutrino transport. Using our 1D spherically-symmetric implementation, we show that, similar to the photon transport case, the implicit scheme enables significantly larger timesteps compared with explicit time discretization, without sacrificing accuracy, while the discrete-diffusion method leads to significant speed-ups at high optical depth. Our results suggest that a combination of spectral, velocity-dependent, Implicit Monte Carlo and discrete-diffusion Monte Carlo methods represents a robust approach for use in neutrino transport calculations in core-collapse supernovae. Our velocity-dependent scheme can easily be adapted to photon transport.

Abdikamalov, Ernazar; Ott, Christian D.; O'Connor, Evan [TAPIR, California Institute of Technology, MC 350-17, 1200 E California Blvd., Pasadena, CA 91125 (United States); Burrows, Adam; Dolence, Joshua C. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States); Loeffler, Frank; Schnetter, Erik, E-mail: abdik@tapir.caltech.edu [Center for Computation and Technology, Louisiana State University, 216 Johnston Hall, Baton Rouge, LA 70803 (United States)

2012-08-20T23:59:59.000Z

272

Novel Hybrid Monte Carlo/Deterministic Technique for Shutdown Dose Rate Analyses of Fusion Energy Systems  

SciTech Connect

The rigorous 2-step (R2S) method uses three-dimensional Monte Carlo transport simulations to calculate the shutdown dose rate (SDDR) in fusion reactors. Accurate full-scale R2S calculations are impractical in fusion reactors because they require calculating space- and energy-dependent neutron fluxes everywhere inside the reactor. The use of global Monte Carlo variance reduction techniques was suggested for accelerating the neutron transport calculation of the R2S method. The prohibitive computational costs of these approaches, which increase with the problem size and amount of shielding materials, inhibit their use in the accurate full-scale neutronics analyses of fusion reactors. This paper describes a novel hybrid Monte Carlo/deterministic technique that uses the Consistent Adjoint Driven Importance Sampling (CADIS) methodology but focuses on multi-step shielding calculations. The Multi-Step CADIS (MS-CADIS) method speeds up the Monte Carlo neutron calculation of the R2S method using an importance function that represents the importance of the neutrons to the final SDDR. Using a simplified example, preliminarily results showed that the use of MS-CADIS enhanced the efficiency of the neutron Monte Carlo simulation of an SDDR calculation by a factor of 550 compared to standard global variance reduction techniques, and that the increase over analog Monte Carlo is higher than 10,000.

Ibrahim, Ahmad M [ORNL; Peplow, Douglas E. [ORNL; Peterson, Joshua L [ORNL; Grove, Robert E [ORNL

2013-01-01T23:59:59.000Z

273

A new class of accelerated kinetic Monte Carlo algorithms  

Science Conference Proceedings (OSTI)

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

274

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

SciTech Connect

Spin and orbital and electron correlations are known to be important when treating the high-temperature {delta} phase of plutonium within the framework of density-functional theory (DFT). One of the more successful attempts to model {delta}-Pu within this approach has included condensed-matter generalizations of Hund's three rules for atoms, i.e., spin polarization, orbital polarization, and spin-orbit coupling. Here they perform a quantitative analysis of these interactions relative rank for the bonding and electronic structure in {delta}-Pu within the DFT model. The result is somewhat surprising in that spin-orbit coupling and orbital polarization are far more important than spin polarization for a realistic description of {delta}-Pu. They show that these orbital correlations on their own, without any formation of magnetic spin moments, can account for the low atomic density of the {delta} phase with a reasonable equation-of-state. In addition, this unambiguously non-magnetic (NM) treatment produces a one-electron spectra with resonances close to the Fermi level consistent with experimental valence band photoemission spectra.

Soderlind, P; Wolfer, W

2007-07-27T23:59:59.000Z

275

Quantum Game Theory  

E-Print Network (OSTI)

Quantum game theory is the study of strategic behavior by agents with access to quantum technology. Broadly speaking, this technology can be employed in either of two ways: As part of a randomization device or as part of a communications protocol. We survey some of the main ideas from both branches of the subject.

Landsburg, Steven E

2011-01-01T23:59:59.000Z

276

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

277

The smooth cut-off Hierarchical Reference Theory of fluids  

E-Print Network (OSTI)

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

Alberto Parola; Davide Pini; Luciano Reatto

2009-01-14T23:59:59.000Z

278

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory · Field recommendations based of activity ­ Corticosterone ­ EEG, ECG and motion studies · Large scale testing ­ Field scale units Science of Foam #12;Disposal: Science and Theory Cessation Time · Multiple bird species can be depopulated

Benson, Eric R.

279

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Opciones para la producción de espuma espuma · Sistemas de boquilla #12;Disposal: Science and Theory Requisitos estimados: · Tiempo: 2 a 3 compactas ­ Equipo de respuesta propio de la industria Espuma de aire comprimido #12;Disposal: Science

Benson, Eric R.

280

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory 2004 ­ Participación de Bud Malone y la espuma 2009 ­ Ninguna ventaja para el gas Breve historia de la espuma #12;Disposal: Science sistema de boquilla ¿Qué es la espuma? #12;Disposal: Science and Theory · La espuma puede incluir: ­ Una

Benson, Eric R.

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

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Table of Contents · Why Depopulate? · Depopulation Methods · Basics of Foam · Types of Foam Equipment · Science Behind Foam · Implementing Foam Depopulation · Use of Foam in the Field · Conclusions #12;Disposal: Science and Theory "When HPAI outbreaks

Benson, Eric R.

282

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

283

Salinas : theory manual.  

Science Conference Proceedings (OSTI)

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

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

2011-11-01T23:59:59.000Z

284

Theory and Modeling of Weakly Bound/Physisorbed Materials  

E-Print Network (OSTI)

by physisorption: ­ CNT, fullerenes, carbon aerogels ­ Doping, Decorating, Charging · Accuracy of Methods: DFT, QMC CNT may have increased absorption3 · Carbon aerogels4 have exhibited 5 wt% for high surface areas, ~1

285

OPTIMIZATION OF THE HYSPEC DESIGN USING MONTE CARLO SIMULATIONS.  

DOE Green Energy (OSTI)

HYSPEC is a direct geometry spectrometer to be installed at the SNS [1] on beamline 14B where it will view a cryogenic coupled hydrogen moderator, The ''hybrid'' design combines time-of-flight spectroscopy with focusing Bragg optics to provide a high monochromatic flux on small single crystal samples, with a very low background at an extended detector bank. The instrument is optimized for an incident energy range of 3-90meV. It will have a medium energy resolution (2-10%) and will provide a flux on sample of the order of 10{sup 6}-10{sup 7} neutrons/s-cm{sup 2}. The spectrometer will be located in a satellite building outside the SNS experimental hall at the end of a 35m curved supermirror guide. A straight-slotted Fermi chopper will be used to monochromate the neutron beam and to determine the burst width. The 15cm high, 4cm wide beam will be focused onto a 2cm by 2cm area at the sample position using Bragg reflection from one of two crystal arrays. For unpolarized neutron studies these will be Highly Oriented Pyrolitic graphite crystals while for polarized neutron studies these will be replaced with Heusler alloy crystals. These focusing crystal arrays will be placed in a drum shield similar to those used for triple axis spectrometers. Hyspec will have a movable detector bank housing 160 position sensitive detectors. This detector bank will pivot about the sample axis. It will have a radius of 4.5m, a horizontal range of 60{sup o}, and a vertical range of {+-} 7.5{sup o}. In order to reduce background at the detector bank both a curved guide and a T0 chopper will be used. A bank of 20 supermirror bender polarization analyzers [2] will be used to spatially separate the polarized neutrons in the scattered beam so that both scattered neutron spin states can be measured simultaneously. The results of Monte Carlo simulations performed to optimize the instrument design will be discussed.

GHOSH, V.J.; HAGEN, M.E.; LEONHARDT, W.J.; ZALIZNYAK, I.; SHAPIRO, S.M.; PASSELL, L.

2005-04-25T23:59:59.000Z

286

LA COLONISATION DE L'AMAZONIE FACE AU DEVELOPPEMENT DURABLE : L'EXEMPLE DU BARRAGE DE BELO MONTE  

E-Print Network (OSTI)

LA COLONISATION DE L'AMAZONIE FACE AU DEVELOPPEMENT DURABLE : L'EXEMPLE DU BARRAGE DE BELO MONTE projets phare du programme Avança Brasil, le barrage de Belo Monte, barrage que nous replaçons dans l on the detailed study of one of the most important projcet of the Avança Brazil Program, the Belo Monte dam, we

Paris-Sud XI, Université de

287

Monte Carlo simulation of radiation heat transfer in arrays of fixed discrete surfaces using cell-to-cell photon transport  

DOE Green Energy (OSTI)

Radiation heat transfer in an array of fixed discrete surfaces is an important problem that is particularly difficult to analyze because of the nonhomogeneous and anisotropic optical properties involved. This article presents an efficient Monte Carlo method for evaluating radiation heat transfer in arrays of fixed discrete surfaces. This Monte Carlo model has been optimized to take advantage of the regular arrangement of surfaces often encountered in these arrays. Monte Carlo model predictions have been compared with analytical and experimental results.

Drost, M.K. (Pacific Northwest Lab., Richland, WA (United States)); Welty, J.R. (Oregon State Univ., Corvallis, OR (United States))

1992-08-01T23:59:59.000Z

288

NUCLEAR THEORY WHITE PAPER 1995  

E-Print Network (OSTI)

We review the accomplishments of nuclear theory during the past five years and identify the future challenges and research opportunities. [Final, substantially revised version of the nuclear theory white paper

G. Bertsch; B. Mueller; J. Negele; J. Friar; V. Pandharipande

1995-02-15T23:59:59.000Z

289

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

DOE Green Energy (OSTI)

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

290

Kinetic Theory of Plasma Waves  

Science Conference Proceedings (OSTI)

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

D. Van Eester; E. Lerche

291

Renormalized weak plasma turbulence theory  

SciTech Connect

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

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

1979-02-01T23:59:59.000Z

292

Use of the linear variate method of Monte Carlo for estimating uncertainty in thermal-hydraulic codes  

SciTech Connect

Thermal-hydraulic computer codes represent non-linear functions that may contain discontinuities. Monte Carlo methods are an effective means of accurately evaluating the effect of uncertainty on a nonlinear function with discontinuities, but the computational requirements of standard Monte Carlo methods may be prohibitive. The linear variate Monte Carlo method is a means of reducing the computational requirements. The linear variate method combines the linear response surface method with Monte Carlo analysis to obtain an efficient and accurate method of nonlinear uncertainty analysis. The method is applied to the power limit analysis for the Savannah River Site reactors. 7 refs., 2 figs., 3 tabs.

Kubic, W.L. Jr.; White, A.M. (Los Alamos National Lab., NM (USA); Westinghouse Savannah River Co., Aiken, SC (USA))

1989-01-01T23:59:59.000Z

293

Gauge theory and group representations  

SciTech Connect

The mathematical foundations of gauge theories based on indecomposable representations of space-time symmetry groups are investigated. In particular, twistors and singletons are given a uniform treatment as gauge theories of this type. This is a step toward geometrically unifying all representation based gauge theories. In addition, some implications with respect to the geometric construction of group representations are noted.

Nakashima, M.M.

1988-01-01T23:59:59.000Z

294

Quantum Field Theory Frank Wilczeky  

E-Print Network (OSTI)

Quantum Field Theory Frank Wilczeky Institute for Advanced Study, School of Natural Science, Olden Lane, Princeton, NJ 08540 I discuss the general principles underlying quantum eld theory, and attempt achieved and prospective. Possible limitations of quantum eld theory are viewed in the light of its history

Wilczek, Frank

295

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

296

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

297

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

298

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

299

Revised methods for few-group cross sections generation in the Serpent Monte Carlo code  

Science Conference Proceedings (OSTI)

This paper presents new calculation methods, recently implemented in the Serpent Monte Carlo code, and related to the production of homogenized few-group constants for deterministic 3D core analysis. The new methods fall under three topics: 1) Improved treatment of neutron-multiplying scattering reactions, 2) Group constant generation in reflectors and other non-fissile regions and 3) Homogenization in leakage-corrected criticality spectrum. The methodology is demonstrated by a numerical example, comparing a deterministic nodal diffusion calculation using Serpent-generated cross sections to a reference full-core Monte Carlo simulation. It is concluded that the new methodology improves the results of the deterministic calculation, and paves the way for Monte Carlo based group constant generation. (authors)

Fridman, E. [Reactor Safety Div., Helmholz-Zentrum Dresden-Rossendorf, POB 51 01 19, Dresden, 01314 (Germany); Leppaenen, J. [VTT Technical Research Centre of Finland, POB 1000, FI-02044 VTT (Finland)

2012-07-01T23:59:59.000Z

300

Crossing the mesoscale no-mans land via parallel kinetic Monte Carlo.  

Science Conference Proceedings (OSTI)

The kinetic Monte Carlo method and its variants are powerful tools for modeling materials at the mesoscale, meaning at length and time scales in between the atomic and continuum. We have completed a 3 year LDRD project with the goal of developing a parallel kinetic Monte Carlo capability and applying it to materials modeling problems of interest to Sandia. In this report we give an overview of the methods and algorithms developed, and describe our new open-source code called SPPARKS, for Stochastic Parallel PARticle Kinetic Simulator. We also highlight the development of several Monte Carlo models in SPPARKS for specific materials modeling applications, including grain growth, bubble formation, diffusion in nanoporous materials, defect formation in erbium hydrides, and surface growth and evolution.

Garcia Cardona, Cristina (San Diego State University); Webb, Edmund Blackburn, III; Wagner, Gregory John; Tikare, Veena; Holm, Elizabeth Ann; Plimpton, Steven James; Thompson, Aidan Patrick; Slepoy, Alexander (U. S. Department of Energy, NNSA); Zhou, Xiao Wang; Battaile, Corbett Chandler; Chandross, Michael Evan

2009-10-01T23:59:59.000Z

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

Crossing the mesoscale no-mans land via parallel kinetic Monte Carlo.  

SciTech Connect

The kinetic Monte Carlo method and its variants are powerful tools for modeling materials at the mesoscale, meaning at length and time scales in between the atomic and continuum. We have completed a 3 year LDRD project with the goal of developing a parallel kinetic Monte Carlo capability and applying it to materials modeling problems of interest to Sandia. In this report we give an overview of the methods and algorithms developed, and describe our new open-source code called SPPARKS, for Stochastic Parallel PARticle Kinetic Simulator. We also highlight the development of several Monte Carlo models in SPPARKS for specific materials modeling applications, including grain growth, bubble formation, diffusion in nanoporous materials, defect formation in erbium hydrides, and surface growth and evolution.

Garcia Cardona, Cristina (San Diego State University); Webb, Edmund Blackburn, III; Wagner, Gregory John; Tikare, Veena; Holm, Elizabeth Ann; Plimpton, Steven James; Thompson, Aidan Patrick; Slepoy, Alexander (U. S. Department of Energy, NNSA); Zhou, Xiao Wang; Battaile, Corbett Chandler; Chandross, Michael Evan

2009-10-01T23:59:59.000Z

302

DUSEL Theory White Paper  

E-Print Network (OSTI)

The NSF has chosen the site for the Deep Underground Science and Engineering Laboratory (DUSEL) to be in Lead, South Dakota. In fact, the state of South Dakota has already stepped up to the plate and contributed its own funding for the proposed lab, see http://www.sanfordlaboratoryathomestake.org/index.html. The final decision by NSF for funding the Initial Suite of Experiments for DUSEL will be made early in 2009. At that time the NSF Science Board must make a decision. Of order 200 experimentalists have already expressed an interest in performing experiments at DUSEL. In order to assess the interest of the theoretical community, the Center for Cosmology and Astro-Particle Physics (CCAPP) at The Ohio State University (OSU) organized a 3-day DUSEL Theory Workshop in Columbus, Ohio from April 4 - 6, 2008. The workshop focused on the scientific case for six proposed experiments for DUSEL: long baseline neutrino oscillations, proton decay, dark matter, astrophysical neutrinos, neutrinoless double beta decay and N-Nbar oscillations. The outcome of this workshop is the DUSEL Theory White paper addressing the scientific case at a level which may be useful in the decision making process for policy makers at the NSF and in the U.S. Congress. In order to assess the physics interest in the DUSEL project we have posted the DUSEL Theory White paper on the following CCAPP link http://ccapp.osu.edu/whitepaper.html . Please read the white paper and, if you are interested, use the link to show your support by co-signing the white paper.

S. Raby; T. Walker; K. S. Babu; H. Baer; A. B. Balantekin; V. Barger; Z. Berezhiani; A. de Gouvea; R. Dermisek; A. Dolgov; P. Fileviez Perez; G. Gabadadze; A. Gal; P. Gondolo; W. Haxton; Y. Kamyshkov; B. Kayser; E. Kearns; B. Kopeliovich; K. Lande; D. Marfatia; R. N. Mohapatra; P. Nath; Y. Nomura; K. A. Olive; J. Pati; S. Profumo; R. Shrock; Z. Tavartkiladze; K. Whisnant; L. Wolfenstein

2008-10-24T23:59:59.000Z

303

ROHF Theory Made Simple  

E-Print Network (OSTI)

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

Tsuchimochi, Takashi

2010-01-01T23:59:59.000Z

304

Theory of amorphous ices  

E-Print Network (OSTI)

We use large-deviation theory to study nonequilibrium transitions between amorphous solids and liquid in an atomistic model of supercooled water. Along with nonequilibrium transitions between the ergodic liquid and two distinct amorphous solids, we establish coexistence between the two amorphous solids, a finding that is consistent with experiment. The phase diagram we predict includes a nonequilibrium triple point where the two amorphous phases and the liquid coexist. While the amorphous solids are long-lived and slowly-aging glasses, their melting leads quickly to the formation of ice. This irreversible behavior is demonstrated in our theoretical treatment and compared with experiment.

David T Limmer; David Chandler

2013-06-20T23:59:59.000Z

305

FREYA-a new Monte Carlo code for improved modeling of fission chains  

Science Conference Proceedings (OSTI)

A new simulation capability for modeling of individual fission events and chains and the transport of fission products in materials is presented. FREYA ( Fission Yield Event Yield Algorithm ) is a Monte Carlo code for generating fission events providing correlated kinematic information for prompt neutrons, gammas, and fragments. As a standalone code, FREYA calculates quantities such as multiplicity-energy, angular, and gamma-neutron energy sharing correlations. To study materials with multiplication, shielding effects, and detectors, we have integrated FREYA into the general purpose Monte Carlo code MCNP. This new tool will allow more accurate modeling of detector responses including correlations and the development of SNM detectors with increased sensitivity.

Hagmann, C A; Randrup, J; Vogt, R L

2012-06-12T23:59:59.000Z

306

Calculating kinetics parameters and reactivity changes with continuous-energy Monte Carlo  

SciTech Connect

The iterated fission probability interpretation of the adjoint flux forms the basis for a method to perform adjoint weighting of tally scores in continuous-energy Monte Carlo k-eigenvalue calculations. Applying this approach, adjoint-weighted tallies are developed for two applications: calculating point reactor kinetics parameters and estimating changes in reactivity from perturbations. Calculations are performed in the widely-used production code, MCNP, and the results of both applications are compared with discrete ordinates calculations, experimental measurements, and other Monte Carlo calculations.

Kiedrowski, Brian C [Los Alamos National Laboratory; Brown, Forrest B [Los Alamos National Laboratory; Wilson, Paul [UNIV. WISCONSIN

2009-01-01T23:59:59.000Z

307

Monte Carlo simulation of the Massachusetts Institute of Technology Research Reactor  

SciTech Connect

The three-dimensional continuous-energy MCNP Monte Carlo code is used to develop a versatile and accurate reactor physics model of the Massachusetts Institute of Technology Research Reactor 2 (MITR-2). The validation of the model against existing experimental data is presented. Core multiplication factors as well as fast neutron in-core flux measurements were used in the validation process. The agreement between the MCNP predictions and the experimentally determined values is very good, which indicates that the Monte Carlo model is correctly simulating the MITR-2.

Redmond, E.L. II; Yanch, J.C.; Harling, O.K. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Nuclear Engineering Dept.)

1994-04-01T23:59:59.000Z

308

Penalized Splines for Smooth Representation of High-dimensional Monte Carlo Datasets  

E-Print Network (OSTI)

Detector response to a high-energy physics process is often estimated by Monte Carlo simulation. For purposes of data analysis, the results of this simulation are typically stored in large multi-dimensional histograms, which can quickly become both too large to easily store and manipulate and numerically problematic due to unfilled bins or interpolation artifacts. We describe here an application of the penalized spline technique to efficiently compute B-spline representations of such tables and discuss aspects of the resulting B-spline fits that simplify many common tasks in handling tabulated Monte Carlo data in high-energy physics analysis, in particular their use in maximum-likelihood fitting.

Whitehorn, Nathan; Lafebre, Sven

2013-01-01T23:59:59.000Z

309

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

310

A DFT+U study of structure and reducibility of CenO2n-x (n?4, 0?x?n) nanoclusters  

Science Conference Proceedings (OSTI)

Equilibrium structures, stability and reducibility of Ce{sub n}O{sub 2n-x} (n=1,4, x=0{approx}4) nanoclusters have been studied using first principles DFT+U method. The planar rhombus Ce{sub 2}O{sub 2} structure is found to be the building block for the most stable Ce{sub n}O{sub 2n-x} clusters. The normalized binding energy of the cluster decreases linearly with increasing cluster size. The most stable stoichiometric Ce{sub n}O{sub 2n-x} clusters are electronically in closed-shell configuration (singlet), while the non-stoichiometric Ce{sub n}O{sub 2n-x} clusters are in a high spin state (triplet or quintet). The reduction energy, i.e., the energy required to remove an oxygen atom from a cluster, increases with the size and the extent of reduction. On the other hand, per electron based reduction energy for the cluster to reach the same formal oxidation state is independent of the cluster size.

Mei, Donghai; Ge, Qingfeng

2012-05-01T23:59:59.000Z

311

A sampling-based computational strategy for the representation of epistemic uncertainty in model predictions with evidence theory.  

Science Conference Proceedings (OSTI)

Evidence theory provides an alternative to probability theory for the representation of epistemic uncertainty in model predictions that derives from epistemic uncertainty in model inputs, where the descriptor epistemic is used to indicate uncertainty that derives from a lack of knowledge with respect to the appropriate values to use for various inputs to the model. The potential benefit, and hence appeal, of evidence theory is that it allows a less restrictive specification of uncertainty than is possible within the axiomatic structure on which probability theory is based. Unfortunately, the propagation of an evidence theory representation for uncertainty through a model is more computationally demanding than the propagation of a probabilistic representation for uncertainty, with this difficulty constituting a serious obstacle to the use of evidence theory in the representation of uncertainty in predictions obtained from computationally intensive models. This presentation describes and illustrates a sampling-based computational strategy for the representation of epistemic uncertainty in model predictions with evidence theory. Preliminary trials indicate that the presented strategy can be used to propagate uncertainty representations based on evidence theory in analysis situations where naive sampling-based (i.e., unsophisticated Monte Carlo) procedures are impracticable due to computational cost.

Johnson, J. D. (Prostat, Mesa, AZ); Oberkampf, William Louis; Helton, Jon Craig (Arizona State University, Tempe, AZ); Storlie, Curtis B. (North Carolina State University, Raleigh, NC)

2006-10-01T23:59:59.000Z

312

A New Lorentz Violating Nonlocal Field Theory From String-Theory  

E-Print Network (OSTI)

29] J. Polchinski, “String theory. Vol. 2: SuperstringNonlocal Field Theory From String-Theory Ori J. GanorNonlocal Field Theory From String-Theory Ori J. Ganor ?

Ganor, Ori J.

2009-01-01T23:59:59.000Z

313

Duality in quantum field theory (and string theory)  

Science Conference Proceedings (OSTI)

These lectures give an introduction to duality in Quantum Field Theory. We discuss the phases of gauge theories and the implications of the electric-magnetic duality transformation to describe the mechanism of confinement. We review the exact results of N=1 supersymmetric QCD and the Seiberg-Witten solution of N=2 super Yang-Mills. Some of its extensions to String Theory are also briefly discussed.

Luis Álvarez-Gaumé; Frederic Zamora

1998-01-01T23:59:59.000Z

314

New Results in Topological Field Theory and Abelian Gauge Theory  

E-Print Network (OSTI)

These are the lecture notes of a set of lectures delivered at the 1995 Trieste summer school in June. I review some recent work on duality in four dimensional Maxwell theory on arbitrary four manifolds, as well as a new set of topological invariants known as the Seiberg-Witten invariants. Much of the necessary background material is given, including a crash course in topological field theory, cohomology of manifolds, topological gauge theory and the rudiments of four manifold theory. My main hope is to wet the readers appetite, so that he or she will wish to read the original works and perhaps to enter this field.

George Thompson

1995-11-06T23:59:59.000Z

315

DUSEL Theory White Paper  

SciTech Connect

The scientific case for a Deep Underground Science and Engineering Laboratory [DUSEL] located at the Homestake mine in Lead, South Dakota is exceptional. The site of this future laboratory already claims a discovery for the detection of solar neutrinos, leading to a Nobel Prize for Ray Davis. Moreover this work provided the first step to our present understanding of solar neutrino oscillations and a chink in the armor of the Standard Model of particle physics. We now know, from several experiments located in deep underground experimental laboratories around the world, that neutrinos have mass and even more importantly this mass appears to fit into the framework of theories which unify all the known forces of nature, i.e. the strong, weak, electromagnetic and gravitational. Similarly, DUSEL can forge forward in the discovery of new realms of nature, housing six fundamental experiments that will test the frontiers of our knowledge: (1) Searching for nucleon decay (the decay of protons and neutrons predicted by grand unified theories of nature); (2) Searching for neutrino oscillations and CP violation by detecting neutrinos produced at a neutrino source (possibly located at Brookhaven National Laboratory and/or Fermi National Laboratory); (3) Searching for astrophysical neutrinos originating from the sun, from cosmic rays hitting the upper atmosphere or from other astrophysical sources, such a supernovae; (4) Searching for dark matter particles (the type of matter which does not interact electromagnetically, yet provides 24% of the mass of the Universe); (5) Looking for the rare process known as neutrino-less double beta decay which is predicted by most theories of neutrino mass and allows two neutrons in a nucleus to spontaneously change into two protons and two electrons; and (6) Searching for the rare process of neutron- anti-neutron oscillations, which would establish violation of baryon number symmetry. A large megaton water Cherenkov detector for neutrinos and nucleon decay, located in DUSEL and roughly 20 times the size of current detectors, can perform the first three of these experiments. The last 3 can utilize the unique environment afforded by DUSEL to perform the most sensitive tests to date. Any one of these experiments can greatly increase our knowledge of nature. The Deep Underground Science and Engineering Laboratory (DUSEL), with a Large Megaton Size Detector, is desperately needed to address a set of fundamental issues in particle and astrophysics.

Raby, S.; /Ohio State U.; Walker, T.; /Ohio State U. /Ohio State U., Dept. Astron. /Ohio State U., CCAPP; Babu, K.S.; /Oklahoma State U.; Baer, H.; /Florida State U.; Balantekin, A.B.; Barger, V.; /Wisconsin U., Madison; Berezhiani, Z.; /Gran Sasso; de Gouvea, A.; /Northwestern U.; Dermisek, R.; /Princeton U.; Dolgov, A.; /Moscow, ITEP /Ferrara U.; Fileviez Perez, P.; /Wisconsin U., Madison; Gabadadze, G.; /New York U.; Gal, A.; /Hebrew U.; Gondolo, P.; /Utah U.; Haxton, W.; /Washington U., Seattle; Kamyshkov, Y.; /Tennessee U.; Kayser, B.; /Fermilab; Kearns, E.; /Boston U.; Kopeliovich, B.; /Santa Maria U., Valparaiso; Lande, K.; /Pennsylvania U.; Marfatia, D.; /Kansas U. /Maryland U. /Northeastern U. /UC, Berkeley /LBL, Berkeley /Minnesota U. /SLAC /UC, Santa Cruz /SUNY, Stony Brook /Oklahoma State U. /Iowa State U. /Carnegie Mellon U.

2011-11-14T23:59:59.000Z

316

Volume dependence in 2+1 Yang-Mills theory  

E-Print Network (OSTI)

We present the results of an analysis of a 2+1 dimensional pure SU(N) Yang-Mills theory formulated on a 2-dimensional spatial torus with non-trivial magnetic flux. We focus on investigating the dependence of the electric-flux spectrum, extracted from Polyakov loop correlators, with the spatial size l, the number of colours N, and the magnetic flux m. The size of the torus acts a parameter that allows to control the onset of non-perturbative effects. In the small volume regime, where perturbation theory holds, we derive the one-loop self-energy correction to the single-gluon spectrum, for arbitrary N and m. We discuss the transition from small to large volumes that has been investigated by means of Monte-Carlo simulations. We argue that the energy of electric flux e, for the lowest gluon momentum, depends solely on e/N and on the dimensionless variable x=lambda N l, with lambda the 't Hooft coupling. The variable x can be interpreted as the dimensionless 't Hooft coupling for an effective box size given by Nl. This implies a version of reduction that allows to trade l by N without modifying the electric-flux energy.

Margarita Garcia Perez; Antonio Gonzalez-Arroyo; Masanori Okawa

2012-11-05T23:59:59.000Z

317

Theory Seminar Schedule  

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

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

318

Invariants from classical field theory  

Science Conference Proceedings (OSTI)

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

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

2008-06-15T23:59:59.000Z

319

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

Science Conference Proceedings (OSTI)

An Engle---Granger 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 Engle---Granger two-step method leads to biased ... Keywords: Asymmetry, Gasoline, Modeling, Oil prices

Afshin Honarvar

2010-10-01T23:59:59.000Z

320

Benchmark calculation of no-core Monte Carlo shell model in light nuclei  

E-Print Network (OSTI)

The Monte Carlo shell model is firstly applied to the calculation of the no-core shell model in light nuclei. The results are compared with those of the full configuration interaction. The agreements between them are within a few % at most.

T. Abe; P. Maris; T. Otsuka; N. Shimizu; Y. Utsuno; J. P. Vary

2011-07-09T23:59:59.000Z

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

GPU-Based Monte-Carlo Volume Raycasting Christof Rezk Salama  

E-Print Network (OSTI)

- ducing convincing images, yet flexible enough for digital productions in practice. 1 Introduction Volume can be found in the book by Engel et al. [1]. The first solely GPU-based implementations of volumeGPU-Based Monte-Carlo Volume Raycasting Christof Rezk Salama Computer Graphics Group, University

Blanz, Volker

322

State space exploration using feedback constraint generation and Monte-Carlo sampling  

Science Conference Proceedings (OSTI)

The systematic exploration of the space of all the behaviours of a software system forms the basis of numerous approaches to verification. However, existing approaches face many challenges with scalability and precision. We propose a framework for validating ... Keywords: model-checking, monte-carlo, statistical sampling, verification

Sriram Sankaranarayanan; Richard M. Chang; Guofei Jiang; Franjo Ivan?i?

2007-09-01T23:59:59.000Z

323

A Monte Carlo model for seeded atomic flows in the transition regime  

Science Conference Proceedings (OSTI)

A simple model for the numerical determination of separation effects in seeded atomic gas flows is presented. The model is based on the known possibility to provide a statistically convergent estimate of the exact solution for a linear transport equation ... Keywords: Compressible flows, Monte Carlo simulation, Multi-component flows, Numerical methods, Rarefied flows

S. Longo; P. Diomede

2009-06-01T23:59:59.000Z

324

Benchmark calculation of no-core Monte Carlo shell model in light nuclei  

E-Print Network (OSTI)

The Monte Carlo shell model is firstly applied to the calculation of the no-core shell model in light nuclei. The results are compared with those of the full configuration interaction. The agreements between them are within a few % at most.

Abe, T; Otsuka, T; Shimizu, N; Utsuno, Y; Vary, J P; 10.1063/1.3584062

2011-01-01T23:59:59.000Z

325

Benchmark calculation of no-core Monte Carlo shell model in light nuclei  

SciTech Connect

The Monte Carlo shell model is firstly applied to the calculation of the no-core shell model in light nuclei. The results are compared with those of the full configuration interaction. The agreements between them are within a few % at most.

Abe, T.; Shimizu, N. [Department of Physics, the University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Maris, P.; Vary, J. P. [Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States); Otsuka, T. [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); CNS, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); NSCL, Michigan State University, East Lansing, Michigan 48824 (United States); Utsuno, Y. [ASRC, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan)

2011-05-06T23:59:59.000Z

326

Dose verification with Monte Carlo technique for prostate brachytherapy implants with {sup 125}I sources  

SciTech Connect

The Monte Carlo technique has been implemented to generate the dose distributions in a model prostate patient, implanted with iodine-125 ({sup 125}I) brachytherapy sources. The results of these calculations are also compared with the dose distributions calculated by a commercially available treatment planning system. The comparison shows that with the source strength suggested by the Monte Carlo technique, the current clinical planning system is found to provide 100% coverage of the prostate with the prescription dose for the same implant pattern. However, the dose-volume histogram of this investigation shows that the VariSeedTM treatment planning system has a 29% and 136% larger dose coverage for the 150% and 200% isodose lines, respectively, than the Monte Carlo simulation. These differences are attributed to the oversimplification of the current planning system using the point source approximation, and also to the interseed effects from multisources that are neglected in the conventional planning systems. The results of this study provide evidence that supports the use of the Monte Carlo technique in treatment planning systems to provide accurate dose calculations in brachytherapy implants.

Zhang Hualin [Department of Radiation Medicine, University of Kentucky Medical Center, Lexington, KY (United States)]. E-mail: hualinzhang@yahoo.com; Baker, Curtis [Department of Radiation Medicine, University of Kentucky Medical Center, Lexington, KY (United States); McKinsey, Rachel [Department of Radiation Medicine, University of Kentucky Medical Center, Lexington, KY (United States); Meigooni, Ali [Department of Radiation Medicine, University of Kentucky Medical Center, Lexington, KY (United States)

2005-06-30T23:59:59.000Z

327

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

328

Evaluating Simulation Heuristics in Monte?Carlo Tree Search and its Application to a Production Scheduling  

Science Conference Proceedings (OSTI)

This paper reports simulation heuristics of Monte?Carlo Tree Search (MCTS) and shows an application example. MCTS introduced by Coulom is a best?first search where pseudorandom simulations guide the solution of problem. Recent improvements on MCTS have produced strong computer Go program

Shimpei Matsumoto; Kosuke Kato; Noriaki Hirosue; Hiroaki Ishii

2010-01-01T23:59:59.000Z

329

Monte Carlo simulation of solar radiation in maize canopies and its visualization  

Science Conference Proceedings (OSTI)

The spatial distribution of solar radiation casts important influences on eco-physiological functions of plant canopies. A simulation model of the three-dimensional of direct and indirect solar radiation in real maize canopies is developed from measured ... Keywords: Monte Carlo algorithm, plant canopy, radiosity, ray tracing, three-dimensional distribution

Zhang Yuan; Lao Cai-lian; Lee Bao-Guo; Chen Yan; Guo Yan; Wang Xi-ping; Ma Yun-tao; Zhao Ming

2007-04-01T23:59:59.000Z

330

Generation reliability assessment in power markets using Monte Carlo simulation and soft computing  

Science Conference Proceedings (OSTI)

Deregulation policy has caused some changes in the concepts of power systems reliability assessment and enhancement. In the present research, generation reliability is considered, and a method for its assessment is proposed using intelligent systems. ... Keywords: Generation reliability, Intelligent systems, Monte Carlo simulation, Power pool market

H. Haroonabadi; M. -R. Haghifam

2011-12-01T23:59:59.000Z

331

Is the Standard Monte Carlo Power Iteration Approach the Wrong Approach? Part 2  

Science Conference Proceedings (OSTI)

The recent work 'Is the Standard Monte Carlo Power Iteration Approach the Wrong Approach?' speculated that the second eigenfunction could be built using essentially the same 'building brick' approach that obtained the first eigenfunction in LA-UR-12-21928. This note shows that the speculation was at least partially correct, but not complete.

Booth, Thomas E. [Los Alamos National Laboratory

2012-07-11T23:59:59.000Z

332

A Monte Carlo Assessment of Uncertainties in Heavy Precipitation Frequency Variations  

Science Conference Proceedings (OSTI)

A Monte Carlo analysis was used to assess the effects of missing data and limited station density on the uncertainties in the temporal variations of U.S. heavy precipitation event frequencies observed for 1895–2004 using data from the U.S. ...

Kenneth E. Kunkel; Thomas R. Karl; David R. Easterling

2007-10-01T23:59:59.000Z

333

Monte Carlo simulation-based algorithms for estimating the reliability of mobile agent-based systems  

Science Conference Proceedings (OSTI)

In this paper, we propose two algorithms for estimating the task route reliability of mobile agent-based systems (MABS), which are based on the conditions of the underlying computer network. In addition, we propose a third algorithm for generating a ... Keywords: Algorithms, Mobile agents, Monte Carlo simulation, Random walk, Reliability

Mosaab Daoud; Qusay H. Mahmoud

2008-01-01T23:59:59.000Z

334

Monte Carlo Study of the Scattering Error of a Quartz Reflective Absorption Tube  

Science Conference Proceedings (OSTI)

A Monte Carlo model was used to study the scattering error of an absorption meter with a divergent light beam and a limited acceptance angle of the receiver. Reflections at both ends of the tube were taken into account. Calculations of the effect ...

Jacek Piskozub; Piotr J. Flatau; J. V. Ronald Zaneveld

2001-03-01T23:59:59.000Z

335

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

336

A Mersenne Twister Hardware Implementation for the Monte Carlo Localization Algorithm  

Science Conference Proceedings (OSTI)

Mobile robot localization is the problem of estimating a robot position based on sensor data and a map of the environment. One of the most used methods to address this problem is based on the Monte Carlo Localization (MCL) algorithm, which is a sample ... Keywords: Embedded mobile robotics, FPGA, Mersenne twister, Particle filter

Vanderlei Bonato; Bruno F. Mazzotti; Marcio Merino Fernandes; Eduardo Marques

2013-01-01T23:59:59.000Z

337

Fermilab | Science at Fermilab | Theory  

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

Theory Theorist Rakhi Mahbubani Theorist Rakhi Mahbubani Theoretical physics at Fermilab Fermilab is a laboratory where advances in particle physics, astrophysics and cosmology...

338

Argonne Physics Division - Theory Group  

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

Administration Secretary: Debbie Morrison EMail: morrison@anl.gov Phone: 630252-4100 Fax: 630252-3903 Address: Theory Group Physics Division, Building 203 Argonne National...

339

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

Science Conference Proceedings (OSTI)

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

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

2010-11-19T23:59:59.000Z

340

Disposal: Science and Theory Disposal: Science and Theory  

E-Print Network (OSTI)

Disposal: Science and Theory #12;Disposal: Science and Theory Table of Contents · Disposal options emergency mortality composting procedure · Use of composting during outbreaks #12;Disposal: Science and disinfection of farms and surveillance around affected flocks. " USDA APHIS VS EMD, 2007 #12;Disposal: Science

Benson, Eric R.

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

Granular Rough Theory: A representation semantics oriented theory of roughness  

Science Conference Proceedings (OSTI)

The present work is an archival paper for a series of contributions proposed in last few years on building a theory of roughness over pure mereological relations among information granules. There are five major efforts taken in the present paper: (1) ... Keywords: Granular Representation Calculus, Granular Rough Theory, Granular-Rough Computational Web Intelligence

Bo Chen; Ming Sun; Mingtian Zhou

2009-03-01T23:59:59.000Z

342

Acceleration of Monte Carlo Criticality Calculations Using Deterministic-Based Starting Sources  

SciTech Connect

A new automatic approach that uses approximate deterministic solutions for providing the starting fission source for Monte Carlo eigenvalue calculations was evaluated in this analysis. By accelerating the Monte Carlo source convergence and decreasing the number of cycles that has to be skipped before the tallies estimation, this approach was found to increase the efficiency of the overall simulation, even with the inclusion of the extra computational time required by the deterministic calculation. This approach was also found to increase the reliability of the Monte Carlo criticality calculations of loosely coupled systems because the use of the better starting source reduces the likelihood of producing an undersampled k{sub eff} due to the inadequate source convergence. The efficiency improvement was demonstrated using two of the standard test problems devised by the OECD/NEA Expert Group on Source Convergence in Criticality-Safety Analysis to measure the source convergence in Monte Carlo criticality calculations. For a fixed uncertainty objective, this approach increased the efficiency of the overall simulation by factors between 1.2 and 3 depending on the difficulty of the source convergence in these problems. The reliability improvement was demonstrated in a modified version of the 'k{sub eff} of the world' problem that was specifically designed to demonstrate the limitations of the current Monte Carlo power iteration techniques. For this problem, the probability of obtaining a clearly undersampled k{sub eff} decreased from 5% with a uniform starting source to zero with a deterministic starting source when batch sizes with more than 15,000 neutron/cycle were used.

Ibrahim, A. [University of Wisconsin; Peplow, Douglas E. [ORNL; Wagner, John C [ORNL; Mosher, Scott W [ORNL; Evans, Thomas M [ORNL

2012-01-01T23:59:59.000Z

343

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

E-Print Network (OSTI)

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

Jeng-Da Chai; Po-Ta Chen

2012-11-03T23:59:59.000Z

344

Symmetries and exponential error reduction in YM theories on the lattice: theoretical aspects and simulation results  

E-Print Network (OSTI)

The path integral of a quantum system with an exact symmetry can be written as a sum of functional integrals each giving the contribution from quantum states with definite symmetry properties. We propose a strategy to compute each of them, normalized to the one with vacuum quantum numbers, by a Monte Carlo procedure whose cost increases power-like with the time extent of the lattice. This is achieved thanks to a multi-level integration scheme, inspired by the transfer matrix formalism, which exploits the symmetry and the locality in time of the underlying statistical system. As a result the cost of computing the lowest energy level in a given channel, its multiplicity and its matrix elements is exponentially reduced with respect to the standard path-integral Monte Carlo. We briefly illustrate the approach in the simple case of the one-dimensional harmonic oscillator and discuss in some detail its extension to the four-dimensional Yang Mills theories. We report on our recent new results in the SU(3) Yang--Mills theory on the relative contribution to the partition function of the parity-odd states.

Michele Della Morte; Leonardo Giusti

2009-10-13T23:59:59.000Z

345

Geometrical Methods in Gauge Theory  

E-Print Network (OSTI)

In this work we explore the geometrical interpretation of gauge theories through the formalism of fiber bundles. Moreover, we conduct an investigation in the topology of fiber bundles, providing a proof of the Classification Theorem. In the last chapter we present some applications, such as electromagnetism and generalized Kaluza-Klein Theory.

Henrique de A. Gomes

2006-10-25T23:59:59.000Z

346

A Simple Theory for Waterspouts  

Science Conference Proceedings (OSTI)

It is shown that the simple thermodynamic theory for dust devils, proposed by Rennó et al., also applies to waterspouts. The theory is based on the thermodynamics of heat engines and predicts the central pressure and the wind speed of these ...

Nilton O. Rennó; Howard B. Bluestein

2001-04-01T23:59:59.000Z

347

Theory of market fluctuations  

E-Print Network (OSTI)

We propose coalescent mechanism of firms growing, driving by the supply and redistribution of external resources. We show, that it leads to Zipf distribution of firms over their sizes, which turns to stretched exponent because of size-dependent effects. We also present new approach to describe fluctuations in the market, based on separation of hot (short-time) and cold (long-time) degrees of freedoms. It predicts observable tent-like distribution of firm grow rates with the same exponent of the power tail for different time scales. The theory explains observable grow and decrease asymmetry of the distribution, and its dependence on firm size. We also calculate the uni- and bivariate probability distributions of price fluctuations in financial market. The model takes into account feedback between price expectations and the real price, and explains first time all the set of empirical data for all groups of stocks: "compass rose" and "market mill" patterns, conditional distribution, "D-smile", z-shaped response,...

Panyukov, S V

2008-01-01T23:59:59.000Z

348

Duality Invariance: From M-theory to Double Field Theory  

E-Print Network (OSTI)

We show how the duality invariant approach to M-theory formulated by Berman and Perry relates to the double field theory proposed by Hull and Zwiebach. In doing so we provide suggestions as to how Ramond fields can be incorporated into the double field theory. We find that the standard dimensional reduction procedure has a duality invariant (doubled) analogue in which the gauge fields of the doubled Kaluza-Klein ansatz encode the Ramond potentials. We identify the internal gauge index of these gauge fields with a spinorial index of O(d,d).

Daniel C. Thompson

2011-06-20T23:59:59.000Z

349

Some nonrenormalizable theories are well-behaved  

E-Print Network (OSTI)

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

Kevin Cahill

2013-03-17T23:59:59.000Z

350

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

E-Print Network (OSTI)

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

Blanchard, P

1975-01-01T23:59:59.000Z

351

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

352

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,

353

The energy injection and losses in the Monte Carlo simulations of a diffusive shock  

E-Print Network (OSTI)

Although diffusive shock acceleration (DSA) could be simulated by some well-established models, the assumption of the injection rate from the thermal particles to the superthermal population is still a contentious problem. But in the self-consistent Monte Carlo simulations, because of the prescribed scattering law instead of the assumption of the injected function, hence particle injection rate is intrinsically defined by the prescribed scattering law. We expect to examine the correlation of the energy injection with the prescribed multiple scattering angular distributions. According to the Rankine-Hugoniot conditions, the energy injection and the losses in the simulation system can directly decide the shock energy spectrum slope. By the simulations performed with multiple scattering law in the dynamical Monte Carlo model, the energy injection and energy loss functions are obtained. As results, the case applying anisotropic scattering law produce a small energy injection and large energy losses leading to a s...

Wang, Xin

2011-01-01T23:59:59.000Z

354

Using high performance computing and Monte Carlo simulation for pricing american options  

E-Print Network (OSTI)

High performance computing (HPC) is a very attractive and relatively new area of research, which gives promising results in many applications. In this paper HPC is used for pricing of American options. Although the American options are very significant in computational finance; their valuation is very challenging, especially when the Monte Carlo simulation techniques are used. For getting the most accurate price for these types of options we use Quasi Monte Carlo simulation, which gives the best convergence. Furthermore, this algorithm is implemented on both GPU and CPU. Additionally, the CUDA architecture is used for harnessing the power and the capability of the GPU for executing the algorithm in parallel which is later compared with the serial implementation on the CPU. In conclusion this paper gives the reasons and the advantages of applying HPC in computational finance.

Cvetanoska, Verche

2012-01-01T23:59:59.000Z

355

Under-Prediction of Localized Tally Uncertainties in Monte Carlo Eigenvalue Calculations  

SciTech Connect

Modeling and simulation using Monte Carlo methods is widely used in nuclear reactor criticality benchmarking applications. However, obtaining good statistics not only takes a large amount of computational time, but it has been shown that localized tally uncertainties may be under-predicted by a factor of five or more in select cases. The primary components of this under-prediction include poor sampling due to improper source convergence and cycle-to-cycle correlations in the fission source. Additional components relate to the flux shape and the size of the tally cells. These issues must be understood and dealt with in order to support the practical use of modern Monte Carlo software packages.

Mervin, Mervin Brenden [University of Tennessee, Knoxville (UTK); Mosher, Scott W [ORNL; Wagner, John C [ORNL; Maldonado, G. Ivan [University of Tennessee, Knoxville (UTK)

2011-01-01T23:59:59.000Z

356

Empirical Analysis of Stochastic Volatility Model by Hybrid Monte Carlo Algorithm  

E-Print Network (OSTI)

The stochastic volatility model is one of volatility models which infer latent volatility of asset returns. The Bayesian inference of the stochastic volatility (SV) model is performed by the hybrid Monte Carlo (HMC) algorithm which is superior to other Markov Chain Monte Carlo methods in sampling volatility variables. We perform the HMC simulations of the SV model for two liquid stock returns traded on the Tokyo Stock Exchange and measure the volatilities of those stock returns. Then we calculate the accuracy of the volatility measurement using the realized volatility as a proxy of the true volatility and compare the SV model with the GARCH model which is one of other volatility models. Using the accuracy calculated with the realized volatility we find that empirically the SV model performs better than the GARCH model.

Takaishi, Tetsuya

2013-01-01T23:59:59.000Z

357

Comments on the use of the Monte Carlo method for criticality calculations  

SciTech Connect

As evidenced by recent papers given at Nuclear Criticality Safety Division meetings, the use of the Monte Carlo method has become a very popular computational tool. The ease of use has undoubtably been a primary reason for this popularity. This ease of use, however, may lead to a false sense of security when using the method. Guidance on the effective use of the method and some suggestions on how to avoid some of the pitfalls that can occur are presented. (TFD)

Whitesides, G.E.

1975-01-01T23:59:59.000Z

358

Radiative equilibrium in Monte Carlo radiative transfer using frequency distribution adjustment  

E-Print Network (OSTI)

The Monte Carlo method is a powerful tool for performing radiative equilibrium calculations, even in complex geometries. The main drawback of the standard Monte Carlo radiative equilibrium methods is that they require iteration, which makes them numerically very demanding. Bjorkman & Wood recently proposed a frequency distribution adjustment scheme, which allows radiative equilibrium Monte Carlo calculations to be performed without iteration, by choosing the frequency of each re-emitted photon such that it corrects for the incorrect spectrum of the previously re-emitted photons. Although the method appears to yield correct results, we argue that its theoretical basis is not completely transparent, and that it is not completely clear whether this technique is an exact rigorous method, or whether it is just a good and convenient approximation. We critically study the general problem of how an already sampled distribution can be adjusted to a new distribution by adding data points sampled from an adjustment distribution. We show that this adjustment is not always possible, and that it depends on the shape of the original and desired distributions, as well as on the relative number of data points that can be added. Applying this theorem to radiative equilibrium Monte Carlo calculations, we provide a firm theoretical basis for the frequency distribution adjustment method of Bjorkman & Wood, and we demonstrate that this method provides the correct frequency distribution through the additional requirement of radiative equilibrium. We discuss the advantages and limitations of this approach, and show that it can easily be combined with the presence of additional heating sources and the concept of photon weighting. However, the method may fail if small dust grains are included... (abridged)

Maarten Baes; Dimitris Stamatellos; Jonathan I. Davies; Anthony P. Whitworth; Sabina Sabatini; Sarah Roberts; Suzanne M. Linder; Rhodri Evans

2005-04-01T23:59:59.000Z

359

Validation of a Monte Carlo Based Depletion Methodology Using HFIR Post-Irradiation Measurements  

Science Conference Proceedings (OSTI)

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

360

Calculation of shielding door thicknesses for radiation therapy facilities using the ITS Monte Carlo program  

SciTech Connect

Shielding calculations for door thicknesses for megavoltage radiotherapy facilities with mazes are generally straightforward. To simplify the calculations, the standard formalism adopts several approximations relating to the average beam path, scattering coefficients, and the mean energy of the spectrum of scattered radiation. To test the accuracy of these calculations, the Monte Carlo program, ITS, was applied to this problem by determining the dose and energy spectrum of the radiation at the door for 4- and 10-MV bremsstrahlung beams incident on a phantom at isocenter. This was performed for mazes, one termed 'standard' and the other a shorter maze where the primary beam is incident on the wall adjacent to the door. The peak of the photon-energy spectrum at the door was found to be the same for both types of maze, independent of primary beam energy, and also, in the case of the conventional maze, of the primary beam orientation. The spectrum was harder for the short maze and for 10 MV vs. 4 MV. The thickness of the lead door for a short maze configuration was 1.5 cm for 10 MV and 1.2 cm for 4 MV vs. approximately less than 1 mm for a conventional maze. For the conventional maze, the Monte Carlo calculation predicts the dose at the door to be lower than given by NCRP 49 and NCRP 51 by about a factor of 2 at 4 MV but to be the same at 10 MV. For the short maze, the Monte Carlo predicts the dose to be a factor of 3 lower for 4 MV and about a factor of 1.5 lower for 10 MV. Experimental results support the Monte Carlo findings for the short maze.

Biggs, P.J. (Department of Radiation Oncology, Massachusetts General Hospital, Harvard Medical School, Boston (United States))

1991-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "theory dft monte" from the National Library of EnergyBeta (NLEBeta).
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361

A Reevaluation of Two Dispersion Theories  

Science Conference Proceedings (OSTI)

Three of the atmospheric datasets that were originally used to verity statistical dispersion theory are reevaluated. These datasets are described as well by transilient turbulence theory as by statistical theory over the range of time periods of ...

Roland Stull

1988-07-01T23:59:59.000Z

362

Argonne CNM: Theory and Modeling Research  

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

Theory and Modeling Group Leader: Stephen Gray An exciting aspect of nanoscience is the close interplay between theory and experiment. In the Theory and Modeling Group, we focus on...

363

Unstable Baroclinic Waves beyond Quasigeostrophic Theory  

Science Conference Proceedings (OSTI)

Quasigeostrophic theory is an approximation of the primitive equations in which the dynamics of geostrophically balanced motions are described by the advection of potential vorticity. Quasigeostrophic theory also represents a leading-order theory ...

Richard Rotunno; David J. Muraki; Chris Snyder

2000-10-01T23:59:59.000Z

364

THE SOGGY SADDLE THEORY OF FISSION  

E-Print Network (OSTI)

SOGGY SADDLE THEORY OF FISSION L.G. Moretto and G. GuarinoMIWW The soggy saddle theory of fission L.6. Moretto and G.transition state theory of fission is generalized to allow

Moretto, L.G.

2010-01-01T23:59:59.000Z

365

String field theory and tachyon condensation  

E-Print Network (OSTI)

In this thesis I discuss various aspects of Witten's cubic string field theory. After a brief review of the basics of string field theory we begin by showing how string field theory can be used to check certain conjectures ...

Ellwood, Ian Thomas, 1977-

2004-01-01T23:59:59.000Z

366

Quantum proof systems and entanglement theory  

E-Print Network (OSTI)

Quantum complexity theory is important from the point of view of not only theory of computation but also quantum information theory. In particular, quantum multi-prover interactive proof systems are defined based on ...

Abolfathe Beikidezfuli, Salman

2009-01-01T23:59:59.000Z

367

Analytic progress in open string field theory  

E-Print Network (OSTI)

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

Kiermaier, Michael Stefan

2009-01-01T23:59:59.000Z

368

Monte Carlo Simulation of Daily Regional Sulfur Distribution: Comparison with SURE Sulfate Data and Visual Range Observations during August 1977  

Science Conference Proceedings (OSTI)

The daily distribution of sulfate concentration over the eastern United States during August 1977 is simulated by a Monte Carlo model using quantized emissions, positioned in accordance with the 1973 EPA SO2 emission inventory. Horizontal ...

D. E. Patterson; R. B. Husar; W. E. Wilson; L. F. Smith

1981-04-01T23:59:59.000Z

369

Bayesian Inference and Markov Chain Monte Carlo Sampling to Reconstruct a Contaminant Source on a Continental Scale  

Science Conference Proceedings (OSTI)

A methodology combining Bayesian inference with Markov chain Monte Carlo (MCMC) sampling is applied to a real accidental radioactive release that occurred on a continental scale at the end of May 1998 near Algeciras, Spain. The source parameters (...

Luca Delle Monache; Julie K. Lundquist; Branko Kosovi?; Gardar Johannesson; Kathleen M. Dyer; Roger D. Aines; Fotini K. Chow; Rich D. Belles; William G. Hanley; Shawn C. Larsen; Gwen A. Loosmore; John J. Nitao; Gayle A. Sugiyama; Philip J. Vogt

2008-10-01T23:59:59.000Z

370

Dispersion of Particles Released into a Neutral Planetary Boundary Layer Using a Markov Chain–Monte Carlo Model  

Science Conference Proceedings (OSTI)

The dispersion and concentration of particles (fluid elements) that are continuously released into a neutral planetary boundary layer is presented. The velocity fluctuations of the particles are generated using a Markov chain–Monte Carlo (MCMC) ...

R. Avila; S. S. Raza

2005-07-01T23:59:59.000Z

371

Computational Cost and Accuracy in Calculating Three-Dimensional Radiative Transfer: Results for New Implementations of Monte Carlo and SHDOM  

Science Conference Proceedings (OSTI)

This paper examines the tradeoffs between computational cost and accuracy for two new state-of-the-art codes for computing three-dimensional radiative transfer: a community Monte Carlo model and a parallel implementation of the Spherical ...

Robert Pincus; K. Franklin Evans

2009-10-01T23:59:59.000Z

372

Nonequilibrium candidate Monte Carlo: A new tool for efficient equilibrium simulation  

SciTech Connect

Metropolis Monte Carlo simulation is a powerful tool for studying the equilibrium properties of matter. In complex condensed-phase systems, however, it is difficult to design Monte Carlo moves with high acceptance probabilities that also rapidly sample uncorrelated configurations. Here, we introduce a new class of moves based on nonequilibrium dynamics: candidate configurations are generated through a finite-time process in which a system is actively driven out of equilibrium, and accepted with criteria that preserve the equilibrium distribution. The acceptance rule is similar to the Metropolis acceptance probability, but related to the nonequilibrium work rather than the instantaneous energy difference. Our method is applicable to sampling from both a single thermodynamic state or a mixture of thermodynamic states, and allows both coordinates and thermodynamic parameters to be driven in nonequilibrium proposals. While generating finite-time switching trajectories incurs an additional cost, driving some degrees of freedom while allowing others to evolve naturally can lead to large enhancements in acceptance probabilities, greatly reducing structural correlation times. Using nonequilibrium driven processes vastly expands the repertoire of useful Monte Carlo proposals in simulations of dense solvated systems.

Nilmeier, Jerome P.; Crooks, Gavin E.; Minh, David D. L.; Chodera, John D.

2011-11-08T23:59:59.000Z

373

A comparison of generalized hybrid Monte Carlo methods with and without momentum flip  

Science Conference Proceedings (OSTI)

The generalized hybrid Monte Carlo (GHMC) method combines Metropolis corrected constant energy simulations with a partial random refreshment step in the particle momenta. The standard detailed balance condition requires that momenta are negated upon rejection of a molecular dynamics proposal step. The implication is a trajectory reversal upon rejection, which is undesirable when interpreting GHMC as thermostated molecular dynamics. We show that a modified detailed balance condition can be used to implement GHMC without momentum flips. The same modification can be applied to the generalized shadow hybrid Monte Carlo (GSHMC) method. Numerical results indicate that GHMC/GSHMC implementations with momentum flip display a favorable behavior in terms of sampling efficiency, i.e., the traditional GHMC/GSHMC implementations with momentum flip got the advantage of a higher acceptance rate and faster decorrelation of Monte Carlo samples. The difference is more pronounced for GHMC. We also numerically investigate the behavior of the GHMC method as a Langevin-type thermostat. We find that the GHMC method without momentum flip interferes less with the underlying stochastic molecular dynamics in terms of autocorrelation functions and it to be preferred over the GHMC method with momentum flip. The same finding applies to GSHMC.

Akhmatskaya, Elena [Fujitsu Laboratories of Europe Ltd (FLE), Hayes Park Central, Hayes End Road, Hayes UB4 8FE (United Kingdom); Bou-Rabee, Nawaf [Department of Mathematics, Freie Universitaet Berlin, Arnimallee 2-6, 14195 Berlin (Germany); Reich, Sebastian [Universitaet Potsdam, Institut fuer Mathematik, Am Neuen Palais 10, D-14469 Potsdam (Germany)], E-mail: s.reich@ic.ac.uk

2009-04-01T23:59:59.000Z

374

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

375

Combining Total Monte Carlo and Benchmarks for nuclear data uncertainty propagation on an LFRs safety parameters  

E-Print Network (OSTI)

Analyses are carried out to assess the impact of nuclear data uncertainties on keff for the European Lead Cooled Training Reactor (ELECTRA) using the Total Monte Carlo method. A large number of Pu-239 random ENDF-formated libraries generated using the TALYS based system were processed into ACE format with NJOY99.336 code and used as input into the Serpent Monte Carlo neutron transport code to obtain distribution in keff. The keff distribution obtained was compared with the latest major nuclear data libraries - JEFF-3.1.2, ENDF/B-VII.1 and JENDL-4.0. A method is proposed for the selection of benchmarks for specific applications using the Total Monte Carlo approach. Finally, an accept/reject criterion was investigated based on chi square values obtained using the Pu-239 Jezebel criticality benchmark. It was observed that nuclear data uncertainties in keff were reduced considerably from 748 to 443 pcm by applying a more rigid acceptance criteria for accepting random files.

Alhassan, Erwin; Duan, Junfeng; Gustavsson, Cecilia; Koning, Arjan; Pomp, Stephan; Rochman, Dimitri; Österlund, Michael

2013-01-01T23:59:59.000Z

376

A second-quantized red herring in full configuration-interaction Monte Carlo  

E-Print Network (OSTI)

Full configuration-interaction quantum Monte Carlo (FCI-QMC) is a Monte Carlo method that allows for exact solution of the ground state of fermionic Hamiltonians (albeit at exponential cost). FCI-QMC involves stochastic projection to the ground state, working in a basis of second- quantized determinants. While a Fermi sign problem still exists within FCI-QMC, it has been suggested that even without annihilation the sign problem is fundamentally distinct from that of more standard techniques such as diffusion Monte Carlo, as a result of working in determinant space. Furthermore, it is widely believed that this distinction is at least partially responsible for the success of FCI-QMC in mitigating the sign problem. In this paper, we show that second quantization is a red herring; the sign problem of FCI-QMC comes from the conventional instability to a bosonic ground state, and in fact FCI-QMC without annihilation can be equated step-by-step to a first-quantized algorithm where anti-symmetry comes only from initi...

Kolodrubetz, Michael

2012-01-01T23:59:59.000Z

377

Combining Total Monte Carlo and Benchmarks for nuclear data uncertainty propagation on an LFRs safety parameters  

E-Print Network (OSTI)

Analyses are carried out to assess the impact of nuclear data uncertainties on keff for the European Lead Cooled Training Reactor (ELECTRA) using the Total Monte Carlo method. A large number of Pu-239 random ENDF-formated libraries generated using the TALYS based system were processed into ACE format with NJOY99.336 code and used as input into the Serpent Monte Carlo neutron transport code to obtain distribution in keff. The keff distribution obtained was compared with the latest major nuclear data libraries - JEFF-3.1.2, ENDF/B-VII.1 and JENDL-4.0. A method is proposed for the selection of benchmarks for specific applications using the Total Monte Carlo approach. Finally, an accept/reject criterion was investigated based on chi square values obtained using the Pu-239 Jezebel criticality benchmark. It was observed that nuclear data uncertainties in keff were reduced considerably from 748 to 443 pcm by applying a more rigid acceptance criteria for accepting random files.

Erwin Alhassan; Henrik Sjöstrand; Junfeng Duan; Cecilia Gustavsson; Arjan Koning; Stephan Pomp; Dimitri Rochman; Michael Österlund

2013-03-26T23:59:59.000Z

378

Fusion Categories and Homotopy Theory  

E-Print Network (OSTI)

We apply the yoga of classical homotopy theory to classification problems of G-extensions of fusion and braided fusion categories, where G is a finite group. Namely, we reduce such problems to classification (up to homotopy) ...

Etingof, Pavel I.

379

Das Standard Modell als Theorie  

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

as a Theory as a Theory Ungelöste Rätsel Das Standard Modell als Theorie Auch wenn das Standard Modell die im Experiment beobachteten Phänomene sehr gut beschreibt, so ist es dennoch eine unvollständige Theorie. Das Problem liegt darin, dass das Standard Modell nicht erklären kann, warum einige Teilchen gerade diejenigen Eigenschaften haben, die wir beobachten. Zum Beispiel, auch wenn den Physikern die Massen aller Quarks - mit Ausnahme derjenigen des top Quarks - seit Jahren bekannt waren, so war es dennoch nicht möglich die Masse des top Quarks ohne die Hilfe experimenteller Daten genau vorherzusagen. Das ist deshalb so, weil das Standard Modell keine Erklärung dafür geben kann, warum die Liste der Teilchenmassen gerade diese Zahlenwerte aufweist.

380

Social impact theory based optimizer  

Science Conference Proceedings (OSTI)

This paper introduces a novel stochastic and population-based binary optimization method inspired by social psychology. It is called Social Impact Theory based Optimization (SITO). The method has been developed with the use of some simple modifications ...

Martin Macaš; Lenka Lhotská

2007-09-01T23:59:59.000Z

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.


381

STATISTICAL MECHANICS AND FIELD THEORY  

E-Print Network (OSTI)

1. L. 1. Schiff, Quantum Mechanics, third edition (McGraw-two-dimensional quantum mechanics problem vith a potential,Theory Methods to Statistical Mechanics Chapter I The Use of

Samuel, S.A.

2010-01-01T23:59:59.000Z

382

Argonne Physics Division - Theory Group  

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

Theory Seminar Schedule Seminars are usually held in room B-221 of the Physics Building (203) at 3:00 pm. Click on a title to read an abstract, if available (underlined). Aroow...

383

Argonne Physics Division - Theory Group  

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

XXVI Midwest Theory Get-Together, 6 & 7 September 2013. This XXVIth meeting in the series is being organised by Wayne Polyzou, polyzou@uiowa.edu from the University of Iowa, Iowa...

384

Microsoft Word - FEL theory  

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

INTEGRAL EQUATION FOR A HIGH GAIN FEL N. A. Vinokurov * Introduction The theory of a high gain free electron laser (FEL) is now well developed (e.g., see 1). In this paper I...

385

Information Theory and Climate Prediction  

Science Conference Proceedings (OSTI)

This paper introduces the use of information theory in characterizing climate predictability. Specifically, the concepts of entropy and transinformation are employed. Entropy measures the amount of uncertainty in our knowledge of the state of the ...

Lai-Yung Leung; Gerald R. North

1990-01-01T23:59:59.000Z

386

Legendre-Transformable Semigeostrophic Theories  

Science Conference Proceedings (OSTI)

For semigeostrophic (SG) theories derived from the Hamiltonian principles suggested by Salmon it is known that a duality exists between the physical coordinates and geopotential, on the one hand, and isentropic geostrophic momentum coordinates ...

R. J. Purser

1999-08-01T23:59:59.000Z

387

Segmental alternations and metrical theory  

E-Print Network (OSTI)

This dissertation focuses on phonological alternations that are influenced or constrained by word-internal prosody, i.e. prominence and foot structure, and what these alternations can tell us about metrical theory. Detailed ...

Vaysman, Olga

2009-01-01T23:59:59.000Z

388

Chiral Gauge Theory for Graphene  

E-Print Network (OSTI)

We construct a chiral gauge theory to describe fractionalization of fermions in graphene. Thereby we extend a recently proposed model, which relies on vortex formation. Our chiral gauge fields provide dynamics for the vortices and also couple to the fermions.

R. Jackiw; S. -Y. Pi

2007-01-30T23:59:59.000Z

389

Supercritical N = 2 string theory  

E-Print Network (OSTI)

The N=2 string is examined in dimensions above the critical dimension (D=4) in a linear dilaton background. We demonstrate that string states in this background propagate in a single physical time dimension, as opposed to two such dimensions present when the dilaton gradient vanishes in D=4. We also find exact solutions describing dynamical dimensional reduction and transitions from N=2 string theory to bosonic string theory via closed-string tachyon condensation.

Hellerman, Simeon

2007-01-01T23:59:59.000Z

390

Spaces of Quantum Field Theories  

E-Print Network (OSTI)

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

Michael R. Douglas

2010-05-16T23:59:59.000Z

391

Theory and Computation | Center for Functional Nanomaterials  

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

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

392

Theory, Modeling & Simulation | More Science | ORNL  

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

Theory, Modeling and Simulation SHARE Theory, Modeling and Simulation ORNL conducts a broad range of theoretical research in the physical sciences with over 60 staff members and...

393

Theory, Modeling & Simulation | More Science | ORNL  

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

Materials Theory and Simulation SHARE Materials Theory and Simulation ORNL conducts a broad range of theoretical research in the physical sciences with over 60 staff members and...

394

MSD Condensed Matter Theory - Argonne National Laboratories,...  

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

Home Condensed Matter Theory Condensed Matter Theory research interacts with the materials research program at ANL through a mix of individual theoretical studies and...

395

Argonne Physics Division - Theory Group  

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

25 May 2010 Special Day: Tuesday Jonathon Carroll 25 May 2010 Special Day: Tuesday Jonathon Carroll University of Adelaide, Australia jcarroll@physics.adelaide.edu.au QMC as a model of dense matter: from finite nuclei to hybrid stars 13 May 2010 Ivan Brida Argonne brida@anl.gov Monte Carlo calculations of beryllium isotopes and spectroscopic factors in light nuclei 11 May 2010 Special Day: Tuesday Roberto Anglani Argonne anglani@anl.gov Collective modes in the color-flavor-locked phase of quantum chromodynamics 13 April 2010 Special Day: Tuesday Special Time: 2:00PM Special Place: R-150 Toshihiko Kawano Los Alamos National Lab. kawano@lanl.gov Combining the statistical model with nuclear structure data for nuclear decay property study 1 April 2010 Special Time: 3:30PM Diana Nicmorus University of Graz, Austria

396

TOPAS: An innovative proton Monte Carlo platform for research and clinical applications  

Science Conference Proceedings (OSTI)

Purpose: While Monte Carlo particle transport has proven useful in many areas (treatment head design, dose calculation, shielding design, and imaging studies) and has been particularly important for proton therapy (due to the conformal dose distributions and a finite beam range in the patient), the available general purpose Monte Carlo codes in proton therapy have been overly complex for most clinical medical physicists. The learning process has large costs not only in time but also in reliability. To address this issue, we developed an innovative proton Monte Carlo platform and tested the tool in a variety of proton therapy applications. Methods: Our approach was to take one of the already-established general purpose Monte Carlo codes and wrap and extend it to create a specialized user-friendly tool for proton therapy. The resulting tool, TOol for PArticle Simulation (TOPAS), should make Monte Carlo simulation more readily available for research and clinical physicists. TOPAS can model a passive scattering or scanning beam treatment head, model a patient geometry based on computed tomography (CT) images, score dose, fluence, etc., save and restart a phase space, provides advanced graphics, and is fully four-dimensional (4D) to handle variations in beam delivery and patient geometry during treatment. A custom-designed TOPAS parameter control system was placed at the heart of the code to meet requirements for ease of use, reliability, and repeatability without sacrificing flexibility. Results: We built and tested the TOPAS code. We have shown that the TOPAS parameter system provides easy yet flexible control over all key simulation areas such as geometry setup, particle source setup, scoring setup, etc. Through design consistency, we have insured that user experience gained in configuring one component, scorer or filter applies equally well to configuring any other component, scorer or filter. We have incorporated key lessons from safety management, proactively removing possible sources of user error such as line-ordering mistakes. We have modeled proton therapy treatment examples including the UCSF eye treatment head, the MGH stereotactic alignment in radiosurgery treatment head and the MGH gantry treatment heads in passive scattering and scanning modes, and we have demonstrated dose calculation based on patient-specific CT data. Initial validation results show agreement with measured data and demonstrate the capabilities of TOPAS in simulating beam delivery in 3D and 4D. Conclusions: We have demonstrated TOPAS accuracy and usability in a variety of proton therapy setups. As we are preparing to make this tool freely available for researchers in medical physics, we anticipate widespread use of this tool in the growing proton therapy community.

Perl, J.; Shin, J.; Schuemann, J.; Faddegon, B.; Paganetti, H. [SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025 (United States); University of California San Francisco Comprehensive Cancer Center, 1600 Divisadero Street, San Francisco, California 94143-1708 (United States); Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States); University of California San Francisco Comprehensive Cancer Center, 1600 Divisadero Street, San Francisco, California 94143-1708 (United States); Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114 (United States)

2012-11-15T23:59:59.000Z

397

A dose point kernel database using GATE Monte Carlo simulation toolkit for nuclear medicine applications: Comparison with other Monte Carlo codes  

Science Conference Proceedings (OSTI)

Purpose: GATE is a Monte Carlo simulation toolkit based on the Geant4 package, widely used for many medical physics applications, including SPECT and PET image simulation and more recently CT image simulation and patient dosimetry. The purpose of the current study was to calculate dose point kernels (DPKs) using GATE, compare them against reference data, and finally produce a complete dataset of the total DPKs for the most commonly used radionuclides in nuclear medicine. Methods: Patient-specific absorbed dose calculations can be carried out using Monte Carlo simulations. The latest version of GATE extends its applications to Radiotherapy and Dosimetry. Comparison of the proposed method for the generation of DPKs was performed for (a) monoenergetic electron sources, with energies ranging from 10 keV to 10 MeV, (b) beta emitting isotopes, e.g., {sup 177}Lu, {sup 90}Y, and {sup 32}P, and (c) gamma emitting isotopes, e.g., {sup 111}In, {sup 131}I, {sup 125}I, and {sup 99m}Tc. Point isotropic sources were simulated at the center of a sphere phantom, and the absorbed dose was stored in concentric spherical shells around the source. Evaluation was performed with already published studies for different Monte Carlo codes namely MCNP, EGS, FLUKA, ETRAN, GEPTS, and PENELOPE. A complete dataset of total DPKs was generated for water (equivalent to soft tissue), bone, and lung. This dataset takes into account all the major components of radiation interactions for the selected isotopes, including the absorbed dose from emitted electrons, photons, and all secondary particles generated from the electromagnetic interactions. Results: GATE comparison provided reliable results in all cases (monoenergetic electrons, beta emitting isotopes, and photon emitting isotopes). The observed differences between GATE and other codes are less than 10% and comparable to the discrepancies observed among other packages. The produced DPKs are in very good agreement with the already published data, which allowed us to produce a unique DPKs dataset using GATE. The dataset contains the total DPKs for {sup 67}Ga, {sup 68}Ga, {sup 90}Y, {sup 99m}Tc, {sup 111}In, {sup 123}I, {sup 124}I, {sup 125}I, {sup 131}I, {sup 153}Sm, {sup 177}Lu {sup 186}Re, and {sup 188}Re generated in water, bone, and lung. Conclusions: In this study, the authors have checked GATE's reliability for absorbed dose calculation when transporting different kind of particles, which indicates its robustness for dosimetry applications. A novel dataset of DPKs is provided, which can be applied in patient-specific dosimetry using analytical point kernel convolution algorithms.

Papadimitroulas, Panagiotis; Loudos, George; Nikiforidis, George C.; Kagadis, George C. [Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 265 04 (Greece) and Department of Medical Instruments Technology, Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo GR 122 10, Athens (Greece); Department of Medical Instruments Technology, Technological Educational institute of Athens, Ag. Spyridonos Street, Egaleo GR 122 10, Athens (Greece); Department of Medical Physics, School of Medicine, University of Patras, Rion, GR 265 04 (Greece)

2012-08-15T23:59:59.000Z

398

Sheldon Glashow, the Electroweak Theory, and the Grand Unified Theory  

Office of Scientific and Technical Information (OSTI)

Sheldon Glashow and the Electroweak Theory Sheldon Glashow and the Electroweak Theory Resources with Additional Information Sheldon Glashow Courtesy AIP Emilio Segrè Visual Archives, Segrè Collection [Sheldon] 'Glashow shared the 1979 Nobel Prize for physics with Steven Weinberg and Abdus Salam for unifying the theories of weak and electromagnetic forces. The new "electroweak" theory underlies all of particle physics and provides a framework for understanding how the early universe evolved and how the chemical elements were created. ... "Glashow's work has been instrumental in our understanding of how our universe came into being," says Lawrence R. Sulak, chairman of the Boston University physics department. "In the years since winning the prize, Glashow has helped develop the Grand Unified Theory of all particles and all forces. Its predictions led to the construction of massive underground detectors, the refinement of the unification models, the first observation of neutrinos from a supernova, and the recent discovery that neutrinos have mass. Glashow has fueled an ongoing search for rare events and exotic effects that may shed further light on the evolution of the early universe."1

399

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

E-Print Network (OSTI)

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

Cheng, Zhuo; Lo, Cynthia S

2012-01-01T23:59:59.000Z

400

Effects of receptor clustering on ligand dissociation: Theory and simulations  

E-Print Network (OSTI)

Receptor-ligand binding is a critical first step in signal transduction and the duration of the interaction can impact signal generation. In mammalian cells, clustering of receptors may be facilitated by heterogeneous zones of lipids, known as lipid rafts. In vitro experiments show that disruption of rafts significantly alters the dissociation of fibroblast growth factor-2 (FGF-2) from heparan sulfate proteoglycans, co-receptors for FGF-2. In this paper, we develop a continuum stochastic formalism in order to (i) study how rebinding affects the dissociation of ligands from a planar substrate, and (ii) address the question of how receptor clustering influences ligand rebinding. We find that clusters reduce the effective dissociation rate dramatically when the clusters are dense and the overall surface density of receptors is low. The effect is much less pronounced in the case of high receptor density and shows non-monotonic behavior with time. These predictions are verified via lattice Monte Carlo simulations. Comparison with experimental results suggests that the theory does not capture the complete biological system. We speculate that additional co-operative mechanisms might be present in order to increase ligand retention, and present one possible ``internal diffusion'' model.

Manoj Gopalakrishnan; Kimberly Forsten-Williams; Matthew A. Nugent; Uwe C. Tauber

2004-07-08T23:59:59.000Z

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.


401

Thermodynamics of SU(3) Gauge Theory in 2 + 1 Dimensions  

E-Print Network (OSTI)

The pressure, and the energy and entropy densities are determined for the SU(3) gauge theory in $2 + 1$ dimensions from lattice Monte Carlo calculations in the interval $0.6 \\leq T/T_c \\leq 15$. The finite temperature lattices simulated have temporal extent $N_\\tau = 2, 4, 6$ and 8, and spatial volumes $N_S^2$ such that the aspect ratio is $N_S/N_\\tau = 8$. To obtain the thermodynamical quantities, we calculate the averages of the temporal plaquettes $P_\\tau$ and the spatial plaquettes $P_S$ on these lattices. We also need the zero temperature averages of the plaquettes $P_0$, calculated on symmetric lattices with $N_\\tau = N_S$. We discuss in detail the finite size ($N_S$-dependent) effects. These disappear exponentially. For the zero temperature lattices we find that the coefficient of $N_S$ in the exponent is of the order of the glueball mass. On the finite temperature lattices it lies between the two lowest screening masses. For the aspect ratio equal to eight, the systematic errors coming from the finite size effects are much smaller than our statistical errors. We argue that in the continuum limit, at high enough temperature, the pressure can be parametrized by the very simple formula $p=a-bT_c/T$ where $a$ and $b$ are two constants. Using the thermodynamical identities for a large homogeneous system, this parametrization then determines the other thermodynamical variables in the same temperature range.

P. Bialas; L. Daniel; A. Morel; B. Petersson

2008-07-07T23:59:59.000Z

402

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

E-Print Network (OSTI)

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

Hirunsit, Pussana

2010-08-01T23:59:59.000Z

403

Lattice QCD and String Theory  

E-Print Network (OSTI)

Bosonic string formation in gauge theories is reviewed with particular attention to the confining flux in lattice QCD and its string theory description. Recent results on the Casimir energy of the ground state and the string excitation spectrum are analyzed in the Dirichlet string limit of large separation between static sources. The closed string-soliton (torelon) with electric flux winding around a compact dimension and the three-string with a Y-junction created by three static sources are also reviewed. It is shown that string spectra from lattice simulations are consistent with universal predictions of the leading operators from the derivative expansion of a Poincare invariant effective string Lagrangian with reparameterization symmetry. Important characterisitics of the confining flux, like stiffness and the related massive breather modes, are coded in operators with higher derivatives and their determination remains a difficult challenge for lattice gauge theory.

Julius Kuti

2005-11-08T23:59:59.000Z

404

Free Energy of ABJM Theory  

E-Print Network (OSTI)

The free energy of ABJM theory has previously been computed in the strong and weak coupling limits. In this note, we report on results for the computation of the first non-vanishing quantum correction to the free energy, from the field theory side. The correction can be expressed in terms of a thermal mass for the scalar fields. This mass vanishes to 1-loop order, but there is a non-vanishing result to 2-loop order. Hence, the leading correction to the free energy is non-analytic in the 't Hooft coupling constant lambda. The reason is that the infrared divergences necessitate a resummation of ring diagrams and a related reorganization of perturbation theory, in which already the leading correction receives contributions from all orders in lambda. These results suggest that the free energy interpolates smoothly between weak and strong coupling.

Mikael Smedbäck

2011-03-24T23:59:59.000Z

405

Heavy ions and string theory  

E-Print Network (OSTI)

We review a selection of recent developments in the application of ideas of string theory to heavy ion physics. Our topics divide naturally into equilibrium and non-equilibrium phenomena. On the non-equilibrium side, we discuss generalizations of Bjorken flow, numerical simulations of black hole formation in asymptotically anti-de Sitter geometries, equilibration in the dual field theory, and hard probes. On the equilibrium side, we summarize improved holographic QCD, extraction of transport coefficients, inclusion of chemical potentials, and approaches to the phase diagram. We close with some possible directions for future research.

Oliver DeWolfe; Steven S. Gubser; Christopher Rosen; Derek Teaney

2013-04-29T23:59:59.000Z

406

Quantum field theory without divergences  

E-Print Network (OSTI)

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

Altaisky, M V

2010-01-01T23:59:59.000Z

407

Quantum field theory without divergences  

E-Print Network (OSTI)

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

M. V. Altaisky

2010-02-12T23:59:59.000Z

408

Principles of Arrangement Field Theory  

E-Print Network (OSTI)

In this paper I attempt to summarize the fundamental principles which underlie to Arrangement Field Theory. In my intention the exposition would be the most possible intelligible and self-contained. However the exposed concepts are revisited in the light of the new researches, so that they could appear slightly different than in the previous works. Much emphasis is posed here to the power of theory to predict the number of fermionic families (flavours) and space-time dimensions. I also give a quick glance to the entanglement phenomenon and its interpretation as microscopic wormhole.

Diego Marin

2012-07-07T23:59:59.000Z

409

A User's Manual for MASH V1.5 - A Monte Carlo Adjoint Shielding Code System  

Science Conference Proceedings (OSTI)

The Monte Carlo ~djoint ~ielding Code System, MASH, calculates neutron and gamma- ray environments and radiation protection factors for armored military vehicles, structures, trenches, and other shielding configurations by coupling a forward discrete ordinates air- over-ground transport calculation with an adjoint Monte Carlo treatment of the shielding geometry. Efficiency and optimum use of computer time are emphasized. The code system includes the GRTUNCL and DORT codes for air-over-ground transport calculations, the MORSE code with the GIFT5 combinatorial geometry package for adjoint shielding calculations, and several peripheral codes that perform the required data preparations, transformations, and coupling functions. The current version, MASH v 1.5, is the successor to the original MASH v 1.0 code system initially developed at Oak Ridge National Laboratory (ORNL). The discrete ordinates calculation determines the fluence on a coupling surface surrounding the shielding geometry due to an external neutron/gamma-ray source. The Monte Carlo calculation determines the effectiveness of the fluence at that surface in causing a response in a detector within the shielding geometry, i.e., the "dose importance" of the coupling surface fluence. A coupling code folds the fluence together with the dose importance, giving the desired dose response. The coupling code can determine the dose response as a function of the shielding geometry orientation relative to the source, distance from the source, and energy response of the detector. This user's manual includes a short description of each code, the input required to execute the code along with some helpful input data notes, and a representative sample problem.

C. O. Slater; J. M. Barnes; J. O. Johnson; J.D. Drischler

1998-10-01T23:59:59.000Z

410

Calculation of the Gibbs Free Energy of Solvation and Dissociation of HCl in Water via Monte Carlo Simulations and Continuum Solvation Models  

Science Conference Proceedings (OSTI)

The free energy of solvation and dissociation of hydrogen chloride in water is calculated through a combined molecular simulation quantum chemical approach at four temperatures between T = 300 and 450 K. The free energy is first decomposed into the sum of two components: the Gibbs free energy of transfer of molecular HCl from the vapor to the aqueous liquid phase and the standard-state free energy of acid dissociation of HCl in aqueous solution. The former quantity is calculated using Gibbs ensemble Monte Carlo simulations using either Kohn-Sham density functional theory or a molecular mechanics force field to determine the system’s potential energy. The latter free energy contribution is computed using a continuum solvation model utilizing either experimental reference data or micro-solvated clusters. The predicted combined solvation and dissociation free energies agree very well with available experimental data. CJM was supported by the US Department of Energy,Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

McGrath, Matthew; Kuo, I-F W.; Ngouana, Brice F.; Ghogomu, Julius N.; Mundy, Christopher J.; Marenich, Aleksandr; Cramer, Christopher J.; Truhlar, Donald G.; Siepmann, Joern I.

2013-08-28T23:59:59.000Z

411

Sequential Monte Carlo simulation for composite power system reliability analysis with time varying loads  

SciTech Connect

The paper illustrates the development and utilization of an annual chronological load curve for each load bus in a composite generation and transmission system and a sequential Monte Carlo simulation approach for composite system reliability assessment. Antithetic variates as a variance reduction technique has been applied to the simulation model to increase the efficiency of the simulation. An approximate method using a load duration curve of the system load and an enumeration process have been applied to the developed load model and the results are compared in this paper.

Sankarakrishnan, A.; Billinton, R. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada). Power Systems Research Group

1995-08-01T23:59:59.000Z

412

Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs. experimental data  

E-Print Network (OSTI)

We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low energy e+e- colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on tau decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and tau decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed.

Actis, S; Arbuzov, A; Balossini, G; Beltrame, P; Bignamini, C; Bonciani, R; Carloni Calame, C M; Cherepanov, V; Czakon, M; Czyz, H; Denig, A; Eidelman, S; Fedotovich, G V; Ferroglia, A; Gluza, J; Grzeli nska, A; Gunia, M; Hafner, A; Ignatov, F; Jadach, S; Jegerlehner, F; Kalinowski, A; Kluge, W; Korchin, A; Kuhn, J H; Kuraev, E A; Lukin, P; Mastrolia, P; Montagna, G; Muller, S E; Nguyen, F; Nicrosini, O; Nomura, D; Pakhlova, G; Pancheri, G; Passera, M; Penin, A; Piccinini, F; Placzek, W; Przedzinski, T; Remiddi, E; Riemann, T; Rodrigo, G; Roig, P; Shekhovtsova, O; Shen, C P; Sibidanov, A L; Teubner, T; Trentadue, L; Venanzoni, G; van der Bij, J J; Wang, P; Ward, B F L; Was, Z; Worek, M; Yuan, C Z

2010-01-01T23:59:59.000Z

413

First Results From GLAST-LAT Integrated Towers Cosmic Ray Data Taking And Monte Carlo Comparison  

SciTech Connect

GLAST Large Area Telescope (LAT) is a gamma ray telescope instrumented with silicon-strip detector planes and sheets of converter, followed by a calorimeter (CAL) and surrounded by an anticoincidence system (ACD). This instrument is sensitive to gamma rays in the energy range between 20 MeV and 300 GeV. At present, the first towers have been integrated and pre-launch data taking with cosmic ray muons is being performed. The results from the data analysis carried out during LAT integration will be discussed and a comparison with the predictions from the Monte Carlo simulation will be shown.

Brigida, M.; Caliandro, A.; Favuzzi, C.; Fusco, P.; Gargano, F.; Giordano, F.; Giglietto, N.; Loparco, F.; Marangelli, B.; Mazziotta, M.N.; Mirizzi, N.; Raino, S.; Spinelli, P.; /Bari U. /INFN, Bari

2007-02-15T23:59:59.000Z

414

A Hybrid (Monte-Carlo/Deterministic) Approach for Multi-Dimensional Radiation Transport  

E-Print Network (OSTI)

A novel hybrid Monte Carlo transport scheme is demonstrated in a scene with solar illumination, scattering and absorbing 2D atmosphere, a textured reflecting mountain, and a small detector located in the sky (mounted on a satellite or a airplane). It uses a deterministic approximation of an adjoint transport solution to reduce variance, computed quickly by ignoring atmospheric interactions. This allows significant variance and computational cost reductions when the atmospheric scattering and absorption coefficient are small. When combined with an atmospheric photon-redirection scheme, significant variance reduction (equivalently acceleration) is achieved in the presence of atmospheric interactions.

Guillaume Bal; Anthony Davis; Ian Langmore

2011-05-07T23:59:59.000Z

415

Extrapolation method in the Monte Carlo Shell Model and its applications  

SciTech Connect

We demonstrate how the energy-variance extrapolation method works using the sequence of the approximated wave functions obtained by the Monte Carlo Shell Model (MCSM), taking {sup 56}Ni with pf-shell as an example. The extrapolation method is shown to work well even in the case that the MCSM shows slow convergence, such as {sup 72}Ge with f5pg9-shell. The structure of {sup 72}Se is also studied including the discussion of the shape-coexistence phenomenon.

Shimizu, Noritaka; Abe, Takashi [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Utsuno, Yutaka [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Mizusaki, Takahiro [Institute of Natural Sciences, Senshu University, Tokyo, 101-8425 (Japan); Otsuka, Takaharu [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan (United States); Honma, Michio [Center for Mathematical Sciences, Aizu University, Aizu-Wakamatsu, Fukushima 965-8580 (Japan)

2011-05-06T23:59:59.000Z

416

Characterisation of radiation damage in silicon photomultipliers with a Monte Carlo model  

E-Print Network (OSTI)

Measured response functions and low photon yield spectra of silicon photomultipliers (SiPM) were compared to multi-photoelectron pulse-height distributions generated by a Monte Carlo model. Characteristic parameters for SiPM were derived. The devices were irradiated with 14 MeV electrons at the Mainz microtron MAMI. It is shown that the first noticeable damage consists of an increase in the rate of dark pulses and the loss of uniformity in the pixel gains. Higher radiation doses reduced also the photon detection efficiency. The results are especially relevant for applications of SiPM in fibre detectors at high luminosity experiments.

S. Sanchez Majos; P. Achenbach; J. Pochodzalla

2008-05-27T23:59:59.000Z

417

ETRANMS: a one-dimensional Monte Carlo electron/photon transport code for multimaterial targets  

SciTech Connect

ETRANMS is an LLL-modified version of the one-dimensional electron/ photon transport code ETRAN 15 developed at the National bureau of Standards. The major modifications include the use of LLL photon cross sections and the application to multislab, multimaterial targets. The code uses Monte Carlo sampling techniques to calculate electron and photon transport and energy and charge deposition within target material subjected to electron or photon radiation. It has been programmed to be a very rapid running, user-oriented code for use on LLL's CDC 7600 computers. (auth)

Kovar, F.R.

1973-11-30T23:59:59.000Z

418

A 3D Monte Carlo Photoionization Code for Modeling Diffuse Ionized Gas  

E-Print Network (OSTI)

We have developed a three dimensional Monte Carlo photoionization code tailored for the study of Galactic H II regions and the percolation of ionizing photons in diffuse ionized gas. We describe the code, our calculation of photoionization, heating & cooling, and the approximations we have employed for the low density H II regions we wish to study. Our code gives results in agreement with the Lexington H II region benchmarks. We show an example of a 2D shadowed region and point out the very significant effect that diffuse radiation produced by recombinations of helium has on the temperature within the shadow.

Wood, K; Ercolano, B

2004-01-01T23:59:59.000Z

419

Monte Carlo simulation of ferroelectric domain structure: Electrostatic and elastic strain energy contributions  

DOE Green Energy (OSTI)

A lattice-Monte Carlo approach was developed to simulate ferroelectric domain behavior. The model utilizes a Hamiltonian for the total energy that includes electrostatic terms (involving dipole-dipole interactions, local polarization gradients, and applied electric field), and elastic strain energy. The contributions of these energy components to the domain structure and to the overall applied field response of the system were examined. In general, the model exhibited domain structure characteristics consistent with those observed in a tetragonally distorted ferroelectric. Good qualitative agreement between the appearance of simulated electrical hysteresis loops and those characteristic of real ferroelectric materials was found.

POTTER JR.,BARRETT G.; TUTTLE,BRUCE A.; TIKARE,VEENA

2000-04-04T23:59:59.000Z

420

SIM-RIBRAS: A Monte-Carlo simulation package for RIBRAS system  

Science Conference Proceedings (OSTI)

SIM-RIBRAS is a Root-based Monte-Carlo simulation tool designed to help RIBRAS users on experience planning and experimental setup enhancing and caracterization. It is divided into two main programs: CineRIBRAS, aiming beam kinematics, and SolFocus, aiming beam optics. SIM-RIBRAS replaces other methods and programs used in the past, providing more complete and accurate results and requiring much less manual labour. Moreover, the user can easily make modifications in the codes, adequating it for specific requirements of an experiment.

Leistenschneider, E.; Lepine-Szily, A.; Lichtenthaeler, R. [Departamento de Fisica Nuclear, Instituto de Fisica, Universidade de Sao Paulo (Brazil)

2013-05-06T23:59:59.000Z

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.


421

Ground state energy of dilute neutron matter at next-to-leading order in lattice chiral effective field theory  

E-Print Network (OSTI)

We present lattice calculations for the ground state energy of dilute neutron matter at next-to-leading order in chiral effective field theory. This study follows a series of recent papers on low-energy nuclear physics using chiral effective field theory on the lattice. In this work we introduce an improved spin- and isospin-projected leading-order action which allows for a perturbative treatment of corrections at next-to-leading order and smaller estimated errors. Using auxiliary fields and Euclidean-time projection Monte Carlo, we compute the ground state of 8, 12, and 16 neutrons in a periodic cube, covering a density range from 2% to 10% of normal nuclear density.

Evgeny Epelbaum; Hermann Krebs; Dean Lee; Ulf-G. Meißner

2008-12-18T23:59:59.000Z

422

Effective theory for deformed nuclei  

E-Print Network (OSTI)

Techniques from effective field theory are applied to nuclear rotation. This approach exploits the spontaneous breaking of rotational symmetry and the separation of scale between low-energy Nambu-Goldstone rotational modes and high-energy vibrational and nucleonic degrees of freedom. A power counting is established and the Hamiltonian is constructed at next-to-leading order.

Papenbrock, T

2010-01-01T23:59:59.000Z

423

"Chromatic" homotopy theory Haynes Miller  

E-Print Network (OSTI)

of large but finite dimension. Chro- matic homotopy theory is an organizing principle which is highly devel Hq+n(n K) = Hq(K) By functoriality, there are maps [K, L] [K, L] [2 K, 2 L] · · · and these maps

Miller, Haynes

424

Asymptotically Free Gauge Theories. I  

DOE R&D Accomplishments (OSTI)

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

Wilczek, Frank; Gross, David J.

1973-07-00T23:59:59.000Z

425

Quantum Field Theory in Graphene  

E-Print Network (OSTI)

This is a short non-technical introduction to applications of the Quantum Field Theory methods to graphene. We derive the Dirac model from the tight binding model and describe calculations of the polarization operator (conductivity). Later on, we use this quantity to describe the Quantum Hall Effect, light absorption by graphene, the Faraday effect, and the Casimir interaction.

Fialkovsky, I V

2011-01-01T23:59:59.000Z

426

Quantum Field Theory in Graphene  

E-Print Network (OSTI)

This is a short non-technical introduction to applications of the Quantum Field Theory methods to graphene. We derive the Dirac model from the tight binding model and describe calculations of the polarization operator (conductivity). Later on, we use this quantity to describe the Quantum Hall Effect, light absorption by graphene, the Faraday effect, and the Casimir interaction.

I. V. Fialkovsky; D. V. Vassilevich

2011-11-13T23:59:59.000Z

427

Moriond Electroweak 2006: Theory summary  

SciTech Connect

A concise look at the big picture of particle physics, including the status of the Standard Model, neutrinos, supersymmetry, extra dimensions and cosmology. Based upon the theoretical summary presented at the XLIst Rencontres de Moriond on Electroweak Interactions and Unified Theories, La Thuile, 11-18 March 2006.

Lykken, Joseph D.; /Fermilab

2006-07-01T23:59:59.000Z

428

Computers for Lattice Field Theories  

E-Print Network (OSTI)

Parallel computers dedicated to lattice field theories are reviewed with emphasis on the three recent projects, the Teraflops project in the US, the CP-PACS project in Japan and the 0.5-Teraflops project in the US. Some new commercial parallel computers are also discussed. Recent development of semiconductor technologies is briefly surveyed in relation to possible approaches toward Teraflops computers.

Y. Iwasaki

1994-01-26T23:59:59.000Z

429

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

Science Conference Proceedings (OSTI)

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

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

2007-10-28T23:59:59.000Z

430

Theory and modelling of helium enrichment in plasma experiments with pump limiters  

DOE Green Energy (OSTI)

Helium enrichment in the exhaust gas stream flowing from a hydrogen-helium plasma is studied using an analytical theory and Monte Carlo simulations. To provide a sensitive experimental test in a tokamak, an unusual configuration, inverted from traditional designs, is proposed for a pump limiter. The principle can be tested in other plasma devices as well. The theory suggests that for typical plasma edge conditions in a confinement device, namely, n = 10/sup 13/cm/sup -3/ and T/sub i/ = T/sub e/ approx. = 5-30eV, helium enrichment in the neutral gas exhaust stream can be very high, in the range 5 to 7, relative to the helium-hydrogen ratio in the plasma. Such high enrichment factors are achieved by exploiting the difference between the ionization rates of hydrogen and helium and the negligible helium charge exchange rate at these plasma conditions. A limiter arrangement is proposed in which the natural curvature of the toroidal magnetic field is used to isolate, using the plasma itself, the point of plasma neutralization from the location of the gas exhaust. The plasma region then acts to preferentially screen the recycling hydrogen by the processes of ionization and of charge-exchange-induced losses at open boundaries. The theory and analysis suggests that an experiment can provide a sensitive test of modules used to describe the plasma edge and of atomic and surface physics data used in these models.

Prinja, A.K.; Conn, R.W.

1984-01-01T23:59:59.000Z

431

Use of SCALE Continuous-Energy Monte Carlo Tools for Eigenvalue Sensitivity Coefficient Calculations  

Science Conference Proceedings (OSTI)

The TSUNAMI code within the SCALE code system makes use of eigenvalue sensitivity coefficients for an extensive number of criticality safety applications, such as quantifying the data-induced uncertainty in the eigenvalue of critical systems, assessing the neutronic similarity between different critical systems, and guiding nuclear data adjustment studies. The need to model geometrically complex systems with improved fidelity and the desire to extend TSUNAMI analysis to advanced applications has motivated the development of a methodology for calculating sensitivity coefficients in continuous-energy (CE) Monte Carlo applications. The CLUTCH and Iterated Fission Probability (IFP) eigenvalue sensitivity methods were recently implemented in the CE KENO framework to generate the capability for TSUNAMI-3D to perform eigenvalue sensitivity calculations in continuous-energy applications. This work explores the improvements in accuracy that can be gained in eigenvalue and eigenvalue sensitivity calculations through the use of the SCALE CE KENO and CE TSUNAMI continuous-energy Monte Carlo tools as compared to multigroup tools. The CE KENO and CE TSUNAMI tools were used to analyze two difficult models of critical benchmarks, and produced eigenvalue and eigenvalue sensitivity coefficient results that showed a marked improvement in accuracy. The CLUTCH sensitivity method in particular excelled in terms of efficiency and computational memory requirements.

Perfetti, Christopher M [ORNL; Rearden, Bradley T [ORNL

2013-01-01T23:59:59.000Z

432

Quantum Monte Carlo algorithms for electronic structure at the petascale; the endstation project.  

SciTech Connect

Over the past two decades, continuum quantum Monte Carlo (QMC) has proved to be an invaluable tool for predicting of the properties of matter from fundamental principles. By solving the Schrodinger equation through a stochastic projection, it achieves the greatest accuracy and reliability of methods available for physical systems containing more than a few quantum particles. QMC enjoys scaling favorable to quantum chemical methods, with a computational effort which grows with the second or third power of system size. This accuracy and scalability has enabled scientific discovery across a broad spectrum of disciplines. The current methods perform very efficiently at the terascale. The quantum Monte Carlo Endstation project is a collaborative effort among researchers in the field to develop a new generation of algorithms, and their efficient implementations, which will take advantage of the upcoming petaflop architectures. Some aspects of these developments are discussed here. These tools will expand the accuracy, efficiency and range of QMC applicability and enable us to tackle challenges which are currently out of reach. The methods will be applied to several important problems including electronic and structural properties of water, transition metal oxides, nanosystems and ultracold atoms.

Kim, J; Ceperley, D M; Purwanto, W; Walter, E J; Krakauer, H; Zhang, S W; Kent, P.R. C; Hennig, R G; Umrigar, C; Bajdich, M; Kolorenc, J; Mitas, L

2008-10-01T23:59:59.000Z

433

Massively parallel Monte Carlo for many-particle simulations on GPUs  

E-Print Network (OSTI)

Current trends in parallel processors call for the design of efficient massively parallel algorithms for scientific computing. Parallel algorithms for Monte Carlo simulations of thermodynamic ensembles of particles have received little attention because of the inherent serial nature of the statistical sampling. In this paper, we present a massively parallel method that obeys detailed balance and implement it for a system of hard disks on the GPU. We reproduce results of serial high-precision Monte Carlo runs to verify the method. This is a good test case because the hard disk equation of state over the range where the liquid transforms into the solid is particularly sensitive to small deviations away from the balance conditions. On a Tesla K20, our GPU implementation executes over one billion trial moves per second, which is 148 times faster than on a single Intel Xeon E5540 CPU core, enables 27 times better performance per dollar, and cuts energy usage by a factor of 13. With this improved performance we are able to calculate the equation of state for systems of up to one million hard disks. These large system sizes are required in order to probe the nature of the melting transition, which has been debated for the last forty years. In this paper we present the details of our computational method, and discuss the thermodynamics of hard disks separately in a companion paper.

Joshua A. Anderson; Eric Jankowski; Thomas L. Grubb; Michael Engel; Sharon C. Glotzer

2012-11-07T23:59:59.000Z

434

Exploiting symmetries for exponential error reduction in path integral Monte Carlo  

E-Print Network (OSTI)

The path integral of a quantum system with an exact symmetry can be written as a sum of functional integrals each giving the contribution from quantum states with definite symmetry properties. We propose a strategy to compute each of them, normalized to the one with vacuum quantum numbers, by a Monte Carlo procedure whose cost increases power-like with the time extent of the lattice. This is achieved thanks to a multi-level integration scheme, inspired by the transfer matrix formalism, which exploits the symmetry and the locality in time of the underlying statistical system. As a result the cost of computing the lowest energy level in a given channel, its multiplicity and its matrix elements is exponentially reduced with respect to the standard path-integral Monte Carlo. We test the strategy with a one-dimensional harmonic oscillator, by computing the ratio of the parity odd over the parity even functional integrals and the two-point correlation function. The cost of the simulations scales as expected. In par...

Della Morte, Michele

2009-01-01T23:59:59.000Z

435

Electron energy losses near pulsar polar caps: a Monte Carlo approach  

E-Print Network (OSTI)

We use Monte Carlo approach to study the energetics of electrons accelerated in a pulsar polar gap. As energy-loss mechanisms we consider magnetic Compton scattering of thermal X-ray photons and curvature radiation. The results are compared with previous calculations which assumed that changes of electron energy occurred smoothly according to approximations for the average energy loss rate due to the Compton scattering. We confirm a general dependence of efficiency of electron energy losses due to inverse Compton mechanism on the temperature and size of a thermal polar cap and on the pulsar magnetic field. However, we show that trajectories of electrons in energy-altitude space as calculated in the smooth way do not always coincide with averaged Monte Carlo behaviour. In particular, for pulsars with high magnetic field strength ($B_{pc} > 3\\times 10^{12}$ G) and low thermal polar cap temperatures ($T < 5\\times 10^6$ K) final electron Lorentz factors computed with the two methods may differ by a few orders of magnitude. We discuss consequences for particular objects with identified thermal X-ray spectral components like Geminga, Vela, and PSR B1055-52.

J. Dyks; B. Rudak

2000-03-07T23:59:59.000Z

436

Physics and Algorithm Enhancements for a Validated MCNP/X Monte Carlo Simulation Tool, Phase VII  

SciTech Connect

Currently the US lacks an end-to-end (i.e., source-to-detector) radiation transport simulation code with predictive capability for the broad range of DHS nuclear material detection applications. For example, gaps in the physics, along with inadequate analysis algorithms, make it difficult for Monte Carlo simulations to provide a comprehensive evaluation, design, and optimization of proposed interrogation systems. With the development and implementation of several key physics and algorithm enhancements, along with needed improvements in evaluated data and benchmark measurements, the MCNP/X Monte Carlo codes will provide designers, operators, and systems analysts with a validated tool for developing state-of-the-art active and passive detection systems. This project is currently in its seventh year (Phase VII). This presentation will review thirty enhancements that have been implemented in MCNPX over the last 3 years and were included in the 2011 release of version 2.7.0. These improvements include 12 physics enhancements, 4 source enhancements, 8 tally enhancements, and 6 other enhancements. Examples and results will be provided for each of these features. The presentation will also discuss the eight enhancements that will be migrated into MCNP6 over the upcoming year.

McKinney, Gregg W [Los Alamos National Laboratory

2012-07-17T23:59:59.000Z

437

Surface Structures of Cubo-octahedral Pt-Mo Catalyst Nanoparticles from Monte Carlo Simulations  

DOE Green Energy (OSTI)

The surface structures of cubo-octahedral Pt-Mo nanoparticles have been investigated using the Monte Carlo method and modified embedded atom method potentials that we developed for Pt-Mo alloys. The cubo-octahedral Pt-Mo nanoparticles are constructed with disordered fcc configurations, with sizes from 2.5 to 5.0 nm, and with Pt concentrations from 60 to 90 at. percent. The equilibrium Pt-Mo nanoparticle configurations were generated through Monte Carlo simulations allowing both atomic displacements and element exchanges at 600 K. We predict that the Pt atoms weakly segregate to the surfaces of such nanoparticles. The Pt concentrations in the surface are calculated to be 5 to 14 at. percent higher than the Pt concentrations of the nanoparticles. Moreover, the Pt atoms preferentially segregate to the facet sites of the surface, while the Pt and Mo atoms tend to alternate along the edges and vertices of these nanoparticles. We found that decreasing the size or increasing the Pt concentration leads to higher Pt concentrations but fewer Pt-Mo pairs in the Pt-Mo nanoparticle surfaces.

Wang, Guofeng; Van Hove, M.A.; Ross, P.N.; Baskes, M.I.

2005-03-31T23:59:59.000Z

438

An Evaluation of Monte Carlo Simulations of Neutron Multiplicity Measurements of Plutonium Metal  

Science Conference Proceedings (OSTI)

In January 2009, Sandia National Laboratories conducted neutron multiplicity measurements of a polyethylene-reflected plutonium metal sphere. Over the past 3 years, those experiments have been collaboratively analyzed using Monte Carlo simulations conducted by University of Michigan (UM), Los Alamos National Laboratory (LANL), Sandia National Laboratories (SNL), and North Carolina State University (NCSU). Monte Carlo simulations of the experiments consistently overpredict the mean and variance of the measured neutron multiplicity distribution. This paper presents a sensitivity study conducted to evaluate the potential sources of the observed errors. MCNPX-PoliMi simulations of plutonium neutron multiplicity measurements exhibited systematic over-prediction of the neutron multiplicity distribution. The over-prediction tended to increase with increasing multiplication. MCNPX-PoliMi had previously been validated against only very low multiplication benchmarks. We conducted sensitivity studies to try to identify the cause(s) of the simulation errors; we eliminated the potential causes we identified, except for Pu-239 {bar {nu}}. A very small change (-1.1%) in the Pu-239 {bar {nu}} dramatically improved the accuracy of the MCNPX-PoliMi simulation for all 6 measurements. This observation is consistent with the trend observed in the bias exhibited by the MCNPX-PoliMi simulations: a very small error in {bar {nu}} is 'magnified' by increasing multiplication. We applied a scalar adjustment to Pu-239 {bar {nu}} (independent of neutron energy); an adjustment that depends on energy is probably more appropriate.

Mattingly, John [North Carolina State University; Miller, Eric [University of Michigan; Solomon, Clell J. Jr. [Los Alamos National Laboratory; Dennis, Ben [University of Michigan; Meldrum, Amy [University of Michigan; Clarke, Shaun [University of Michigan; Pozzi, Sara [University of Michigan

2012-06-21T23:59:59.000Z

439

Speciation model selection by Monte Carlo analysis of optical absorption spectra: Plutonium(IV) nitrate complexes  

Science Conference Proceedings (OSTI)

Standard modeling approaches can produce the most likely values of the formation constants of metal-ligand complexes if a particular set of species containing the metal ion is known or assumed to exist in solution equilibrium with complexing ligands. Identifying the most likely set of species when more than one set is plausible is a more difficult problem to address quantitatively. A Monte Carlo method of data analysis is described that measures the relative abilities of different speciation models to fit optical spectra of open-shell actinide ions. The best model(s) can be identified from among a larger group of models initially judged to be plausible. The method is demonstrated by analyzing the absorption spectra of aqueous Pu(IV) titrated with nitrate ion at constant 2 molal ionic strength in aqueous perchloric acid. The best speciation model supported by the data is shown to include three Pu(IV) species with nitrate coordination numbers 0, 1, and 2. Formation constants are {beta}{sub 1}=3.2{+-}0.5 and {beta}{sub 2}=11.2{+-}1.2, where the uncertainties are 95% confidence limits estimated by propagating raw data uncertainties using Monte Carlo methods. Principal component analysis independently indicates three Pu(IV) complexes in equilibrium. (c) 2000 Society for Applied Spectroscopy.

Berg, John M. [Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Veirs, D. Kirk [Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Vaughn, Randolph B. [Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Cisneros, Michael R. [Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Smith, Coleman A. [Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2000-06-01T23:59:59.000Z

440

Configuration-interaction Monte Carlo method and its application to the trapped unitary Fermi gas  

E-Print Network (OSTI)

We develop a quantum Monte Carlo method to estimate the ground-state energy of a fermionic many-particle system in the configuration-interaction shell model approach. The fermionic sign problem is circumvented by using a guiding wave function in Fock space. The method provides an upper bound on the ground-state energy whose tightness depends on the choice of the guiding wave function. We argue that the antisymmetric geminal product class of wave functions is a good choice for guiding wave functions. We demonstrate our method for the trapped two-species fermionic cold atom system in the unitary regime of infinite scattering length using the particle-number projected Hartree-Fock-Bogoliubov wave function as the guiding wave function. We estimate the ground-state energy and energy-staggering pairing gap as a function of the number of particles. Our results compare favorably with exact numerical diagonalization results and with previous coordinate-space Monte Carlo calculations.

Mukherjee, Abhishek

2013-01-01T23:59:59.000Z

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.


441

Configuration-interaction Monte Carlo method and its application to the trapped unitary Fermi gas  

E-Print Network (OSTI)

We develop a quantum Monte Carlo method to estimate the ground-state energy of a fermionic many-particle system in the configuration-interaction shell model approach. The fermionic sign problem is circumvented by using a guiding wave function in Fock space. The method provides an upper bound on the ground-state energy whose tightness depends on the choice of the guiding wave function. We argue that the antisymmetric geminal product class of wave functions is a good choice for guiding wave functions. We demonstrate our method for the trapped two-species fermionic cold atom system in the unitary regime of infinite scattering length using the particle-number projected Hartree-Fock-Bogoliubov wave function as the guiding wave function. We estimate the ground-state energy and energy-staggering pairing gap as a function of the number of particles. Our results compare favorably with exact numerical diagonalization results and with previous coordinate-space Monte Carlo calculations.

Abhishek Mukherjee; Y. Alhassid

2013-04-05T23:59:59.000Z

442

Automatic Mesh Adaptivity for Hybrid Monte Carlo/Deterministic Neutronics Modeling of Fusion Energy Systems  

SciTech Connect

Three mesh adaptivity algorithms were developed to facilitate and expedite the use of the CADIS and FW-CADIS hybrid Monte Carlo/deterministic techniques in accurate full-scale neutronics simulations of fusion energy systems with immense sizes and complicated geometries. First, a macromaterial approach enhances the fidelity of the deterministic models without changing the mesh. Second, a deterministic mesh refinement algorithm generates meshes that capture as much geometric detail as possible without exceeding a specified maximum number of mesh elements. Finally, a weight window coarsening algorithm decouples the weight window mesh and energy bins from the mesh and energy group structure of the deterministic calculations in order to remove the memory constraint of the weight window map from the deterministic mesh resolution. The three algorithms were used to enhance an FW-CADIS calculation of the prompt dose rate throughout the ITER experimental facility and resulted in a 23.3% increase in the number of mesh tally elements in which the dose rates were calculated in a 10-day Monte Carlo calculation. Additionally, because of the significant increase in the efficiency of FW-CADIS simulations, the three algorithms enabled this difficult calculation to be accurately solved on a regular computer cluster, eliminating the need for a world-class super computer.

Ibrahim, Ahmad M [ORNL; Wilson, P. [University of Wisconsin; Sawan, M. [University of Wisconsin; Mosher, Scott W [ORNL; Peplow, Douglas E. [ORNL; Grove, Robert E [ORNL

2013-01-01T23:59:59.000Z

443

A Deterministic-Monte Carlo Hybrid Method for Time-Dependent Neutron Transport Problems  

Science Conference Proceedings (OSTI)

A new deterministic-Monte Carlo hybrid solution technique is derived for the time-dependent transport equation. This new approach is based on dividing the time domain into a number of coarse intervals and expanding the transport solution in a series of polynomials within each interval. The solutions within each interval can be represented in terms of arbitrary source terms by using precomputed response functions. In the current work, the time-dependent response function computations are performed using the Monte Carlo method, while the global time-step march is performed deterministically. This work extends previous work by coupling the time-dependent expansions to space- and angle-dependent expansions to fully characterize the 1D transport response/solution. More generally, this approach represents and incremental extension of the steady-state coarse-mesh transport method that is based on global-local decompositions of large neutron transport problems. An example of a homogeneous slab is discussed as an example of the new developments.

Justin Pounders; Farzad Rahnema

2001-10-01T23:59:59.000Z

444

GUINEVERE experiment: Kinetic analysis of some reactivity measurement methods by deterministic and Monte Carlo codes  

Science Conference Proceedings (OSTI)

The GUINEVERE experiment (Generation of Uninterrupted Intense Neutrons at the lead Venus Reactor) is an experimental program in support of the ADS technology presently carried out at SCK-CEN in Mol (Belgium). In the experiment a modified lay-out of the original thermal VENUS critical facility is coupled to an accelerator, built by the French body CNRS in Grenoble, working in both continuous and pulsed mode and delivering 14 MeV neutrons by bombardment of deuterons on a tritium-target. The modified lay-out of the facility consists of a fast subcritical core made of 30% U-235 enriched metallic Uranium in a lead matrix. Several off-line and on-line reactivity measurement techniques will be investigated during the experimental campaign. This report is focused on the simulation by deterministic (ERANOS French code) and Monte Carlo (MCNPX US code) calculations of three reactivity measurement techniques, Slope ({alpha}-fitting), Area-ratio and Source-jerk, applied to a GUINEVERE subcritical configuration (namely SC1). The inferred reactivity, in dollar units, by the Area-ratio method shows an overall agreement between the two deterministic and Monte Carlo computational approaches, whereas the MCNPX Source-jerk results are affected by large uncertainties and allow only partial conclusions about the comparison. Finally, no particular spatial dependence of the results is observed in the case of the GUINEVERE SC1 subcritical configuration. (authors)

Bianchini, G.; Burgio, N.; Carta, M. [ENEA C.R. CASACCIA, via Anguillarese, 301, 00123 S. Maria di Galeria Roma (Italy); Peluso, V. [ENEA C.R. BOLOGNA, Via Martiri di Monte Sole, 4, 40129 Bologna (Italy); Fabrizio, V.; Ricci, L. [Univ. of Rome La Sapienza, C/o ENEA C.R. CASACCIA, via Anguillarese, 301, 00123 S. Maria di Galeria Roma (Italy)

2012-07-01T23:59:59.000Z

445

Topics in Noncommutative Gauge Theories and Deformed Relativistic Theories  

E-Print Network (OSTI)

This is my PhD thesis. In this thesis we study the gauge theories on noncommutative Moyal space. We find new static solitons and instantons in terms of the so called generalized Bose operators. Generalized Bose operators are constructed to describe reducible representation of the oscillator algebra. They create/annihilate $k$-quanta, $k$ being a positive integer. We start with giving an alternative description to the already found static magnetic flux tube solutions of the noncommutative gauge theories in terms of generalized Bose operators. The Nielsen-Olesen vortex solutions found in terms of these operators reduce to the already found ones. On the contrary we find a class of new instaton solutions which are unitarily inequivalant to the the ones found from ADHM construction on noncommutative space. The charge of the instaton has a description in terms of the index representing the reducibility of the Fock space, i.e., $k$. After studying the static solitonic solutions in noncommutative Minkowski space and the instaton solutions in noncommutative Euclidean space we go on to study the implications of the time-space noncommutativity in Minkowski space. To understand it properly we study the time-dependent transitions of a forced harmonic oscillator in noncommutative 1+1 dimensional spacetime. We also try to understand the implications of the found results in the context of quantum optics. We then shift to the so called DSR theories which are related to a different kind of noncommutative ($\\kappa$-Minkowski) space. DSR (Doubly/Deformed Special Relativity) aims to search for an alternate relativistic theory which keeps a length/energy scale (the Planck scale) and a velocity scale (the speed of light scale) invariant. We study thermodynamics of an ideal gas in such a scenario.

Nitin Chandra

2013-01-17T23:59:59.000Z

446

Theory  

Science Conference Proceedings (OSTI)

Table 4   Line intensity...Identification (qualitative analyses) d-I search/match (PDF Hanawalt) Intensity changes with element substitution Crystal structure analysis Differences in fine grained state from single crystal state Structures of materials which only occur in fine grained state Quantitative analysis Phase...

447

RunMC - an object-oriented analysis framework for Monte Carlo simulation of high-energy particle collisions  

E-Print Network (OSTI)

RunMC is an object-oriented framework aimed to generate and to analyse high-energy collisions of elementary particles using Monte Carlo simulations. This package, being based on C++ adopted by CERN as the main programming language for the LHC experiments, provides a common interface to different Monte Carlo models using modern physics libraries. Physics calculations (projects) can easily be loaded and saved as external modules. This simplifies the development of complicated calculations for high energy physics in large collaborations.This desktop program is open-source licensed and is available on the LINUX and Windows/Cygwin platforms.

S. Chekanov

2004-11-05T23:59:59.000Z

448

Diffeomorphisms in group field theories  

SciTech Connect

We study the issue of diffeomorphism symmetry in group field theories (GFT), using the noncommutative metric representation introduced by A. Baratin and D. Oriti [Phys. Rev. Lett. 105, 221302 (2010).]. In the colored Boulatov model for 3d gravity, we identify a field (quantum) symmetry which ties together the vertex translation invariance of discrete gravity, the flatness constraint of canonical quantum gravity, and the topological (coarse-graining) identities for the 6j symbols. We also show how, for the GFT graphs dual to manifolds, the invariance of the Feynman amplitudes encodes the discrete residual action of diffeomorphisms in simplicial gravity path integrals. We extend the results to GFT models for higher-dimensional BF theories and discuss various insights that they provide on the GFT formalism itself.

Baratin, Aristide [Triangle de la Physique, CPHT Ecole Polytechnique, IPhT Saclay, LPT Orsay and Laboratoire de Physique Theorique, CNRS UMR 8627, Universite Paris XI, F-91405 Orsay Cedex (France); Girelli, Florian [School of Physics, University of Sydney, Sydney, New South Wales 2006 (Australia); Oriti, Daniele [Max Planck Institute for Gravitational Physics, Albert Einstein Institute, Am Muehlenberg 1, 14467 Golm (Germany)

2011-05-15T23:59:59.000Z

449

Fundamental constants in effective theory  

E-Print Network (OSTI)

There is a discussion between L. B. Okun, G. Veneziano and M. J. Duff, concerning the number of fundamental dimensionful constants in physics [1]. They advocated correspondingly 3, 2 and 0 fundamental constants. Here we consider this problem on example of the effective relativistic quantum field theory, which emerges in the low energy corner of quantum liquids and which reproduces many features of our physics including chiral fermions, gauge fields and dynamical gravity. 1 Introduction. The effective relativistic quantum field theory (RQFT) arising as emergent phenomenon in quantum liquids [2], or in other condensed matter systems [3], allows us to look at the problem of fundamental constants from the outside, i.e. from the point of view of an external observer who does not

G. E. Volovik

2008-01-01T23:59:59.000Z

450

Theory of magnetoresistance in multilayers  

Science Conference Proceedings (OSTI)

Recently it has been found that metallic multilayer films exhibit novel phenomena, particularly giant magnetoresistance in Fe/Cr, Co/Cu, Co/Cu/NiFe/Cu, and other multilayers. In this review, the authors explicate the theory of the giant magnetoresistance effect, placing emphasis on its mechanism and dependence on the constituent materials of multilayers. Some relations between the giant magnetoresistance, the electrical resistivity of the magnetic alloys, and the anisotropic magnetoresistance are also discussed.

Inoue, J.; Maekawa, S. (Nagoya Univ. (Japan))

1993-06-01T23:59:59.000Z

451

A Simple Thermodynamical Theory for Dust Devils  

Science Conference Proceedings (OSTI)

Based on the heat engine framework, a simple scaling theory for dust devils is proposed and compared to observations. This theory provides a simple physical interpretation for many of the observed characteristics of dust devils. In particular, it ...

Nilton O. Rennó; Matthew L. Burkett; Matthew P. Larkin

1998-11-01T23:59:59.000Z

452

BLG theory with generalized Jordan triple systems  

E-Print Network (OSTI)

We use a generalized Jordan algebra of the second kind to study the recently proposed BLG theory of multiple M2-branes. We find the restriction imposed on the ternary product from its consistency with the BLG theory.

Sudipto Paul Chowdhury; Subir Mukhopadhyay; Koushik Ray

2009-03-17T23:59:59.000Z

453

Generalized Stability Theory. Part I: Autonomous Operators  

Science Conference Proceedings (OSTI)

Classical stability theory is extended to include transient growth processes. The central role of the nonnormality of the linearized dynamical system in the stability problem is emphasized, and a generalized stability theory is constructed that ...

Brian F. Farrell; Petros J. Ioannou

1996-07-01T23:59:59.000Z

454

Translational-invariant noncommutative gauge theory  

Science Conference Proceedings (OSTI)

A generalized translational-invariant noncommutative field theory is analyzed in detail, and a complete description of translational-invariant noncommutative structures is worked out. The relevant gauge theory is described, and the planar and nonplanar axial anomalies are obtained.

Ardalan, F. [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Studies in Theoretical Physics and Mathematics (IPM), School of Physics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Sadooghi, N. [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of)

2011-01-15T23:59:59.000Z

455

Scissors congruence and K-theory  

E-Print Network (OSTI)

In this thesis we develop a version of classical scissors congruence theory from the perspective of algebraic K-theory. Classically, two polytopes in a manifold X are defined to be scissors congruent if they can be decomposed ...

Zakharevich, Inna (Inna Ilana)

2012-01-01T23:59:59.000Z

456

Northern Winter Stationary Waves: Theory and Modeling  

Science Conference Proceedings (OSTI)

A review is provided of stationary wave theory, the theory for the deviations from zonal symmetry of the climate. To help focus the discussion the authors concentrate exclusively on northern winter. Several theoretical issues, including the ...

Isaac M. Held; Mingfang Ting; Hailan Wang

2002-08-01T23:59:59.000Z

457

Quantum Mechanics and Representation Theory Columbia University  

E-Print Network (OSTI)

Quantum Mechanics and Representation Theory Peter Woit Columbia University Texas Tech, November 21 2013 Peter Woit (Columbia University) Quantum Mechanics and Representation Theory November 2013 1 / 30 #12;Does Anyone Understand Quantum Mechanics? "No One Understands Quantum Mechanics" "I think

Woit, Peter

458

Seeking String Theory in the Cosmos  

E-Print Network (OSTI)

We review the existence, formation and properties of cosmic strings in string theory, the wide variety of observational techniques that are being employed to detect them, and the constraints that current observations impose on string theory models.

Copeland, Edmund J; Vachaspati, Tanmay

2011-01-01T23:59:59.000Z

459

Fast library for number theory: an introduction  

Science Conference Proceedings (OSTI)

We discuss FLINT (Fast Library for Number Theory), a library to support computations in number theory, including highly optimised routines for polynomial arithmetic and linear algebra in exact rings.

William B. Hart

2010-09-01T23:59:59.000Z

460

A unified theory of superconductivity  

E-Print Network (OSTI)

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

Xiuqing Huang

2008-04-10T23:59:59.000Z

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461

Spatially Resolved Porous Electrode Theory for Rechargeable ...  

Science Conference Proceedings (OSTI)

Symposium, Nanostructured Materials for Lithium Ion Batteries and for Supercapacitors. Presentation Title, Spatially Resolved Porous Electrode Theory for ...

462

Supersymmetric extensions of K field theories  

E-Print Network (OSTI)

We review the recently developed supersymmetric extensions of field theories with non-standard kinetic terms (so-called K field theories) in two an three dimensions. Further, we study the issue of topological defect formation in these supersymmetric theories. Specifically, we find supersymmetric K field theories which support topological kinks in 1+1 dimensions as well as supersymmetric extensions of the baby Skyrme model for arbitrary nonnegative potentials in 2+1 dimensions.

Adam, C; Sanchez-Guillen, J; Wereszczynski, A

2012-01-01T23:59:59.000Z

463

Quantum Theory Event-Probability Interpretation  

Science Conference Proceedings (OSTI)

In this article the propagation of pointlike event probabilities in space is considered. New interpretation of Quantum Theory is formulated.

Quznetsov, Gunn [Chelyabinsk State University, Chelyabinsk, Ural (Russian Federation)

2011-03-28T23:59:59.000Z

464

1994 International Sherwood Fusion Theory Conference  

SciTech Connect

This report contains the abstracts of the paper presented at the 1994 International Sherwood Fusion Theory Conference.

NONE

1994-04-01T23:59:59.000Z

465

Algebraic methods for biochemical reaction network theory  

E-Print Network (OSTI)

theory [BBCQ04, CFR08]. Convex geometry and differential geometry have also played a role in chemical reactor

Shiu, Anne

2010-01-01T23:59:59.000Z

466

A solution manual for Polchinski's "String Theory"  

E-Print Network (OSTI)

We present detailed solutions to 81 of the 202 problems in J. Polchinski's two-volume textbook "String Theory".

Headrick, Matthew

2008-01-01T23:59:59.000Z

467

A solution manual for Polchinski's "String Theory"  

E-Print Network (OSTI)

We present detailed solutions to 81 of the 202 problems in J. Polchinski's two-volume textbook "String Theory".

Matthew Headrick

2008-12-23T23:59:59.000Z

468

Nuclear Dynamics with Effective Field Theories  

E-Print Network (OSTI)

These are the proceedings of the international workshop on "Nuclear Dynamics with Effective Field Theories" held at Ruhr-Universitaet Bochum, Germany from July 1 to 3, 2013. The workshop focused on effective field theories of low-energy QCD, chiral perturbation theory for nuclear forces as well as few- and many-body physics. Included are a short contribution per talk.

Evgeny Epelbaum; Hermann Krebs

2013-09-05T23:59:59.000Z

469

Nuclear Dynamics with Effective Field Theories  

E-Print Network (OSTI)

These are the proceedings of the international workshop on "Nuclear Dynamics with Effective Field Theories" held at Ruhr-Universitaet Bochum, Germany from July 1 to 3, 2013. The workshop focused on effective field theories of low-energy QCD, chiral perturbation theory for nuclear forces as well as few- and many-body physics. Included are a short contribution per talk.

Epelbaum, Evgeny

2013-01-01T23:59:59.000Z

470

Is There a Nonrecursive Decidable Equational Theory?  

Science Conference Proceedings (OSTI)

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

Benjamin Wells

2002-05-01T23:59:59.000Z

471

Towards Dark Energy from String-Theory  

E-Print Network (OSTI)

We discuss vacuum energy in string and M-theory with a focus on heterotic M-theory. In the latter theory a mechanism is described for maintaining zero vacuum energy after supersymmetry breaking. Higher-order corrections can be expected to give a sufficiently small amount of vacuum energy to possibly account for dark energy.

Axel Krause

2007-12-31T23:59:59.000Z

472

Thermodynamics, Hydrodynamics and Critical Phenomena in Strongly Coupled Gauge Theories.  

E-Print Network (OSTI)

??The gauge theory / string theory correspondence has led to great progress in the study of strongly-coupled gauge theories. In this work, we start with… (more)

Pagnutti, Christopher

2011-01-01T23:59:59.000Z

473

Overview of Geometry Representation in Monte Carlo Codes Ronald P. Kensek  

National Nuclear Security Administration (NNSA)

Overview of Geometry Representation Overview of Geometry Representation in Monte Carlo Codes Ronald P. Kensek Brian C. Franke Thomas W. Laub Leonard J. Lorence Matthew R. Martin Sandia National Laboratories Steve Warren Kansas State University Joint Russian-American Five-Laboratory Conference on Computational Mathematics / Physics Vienna, Austria June 19-23, 2005 Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States National Nuclear Security Administration and the Department of Energy under contract DE-AC04-94AL85000. 2 Problem Setup: Engineering designs CG vs. CAD Combinatorial Geometry (CG) * Engineering designs are not typically created in this format * No general automatic translation from CAD to CG yet exists * Problem setup is difficult: Creation

474

State and parameter estimation using Monte Carlo evaluation of path integrals  

E-Print Network (OSTI)

Transferring information from observations of a dynamical system to estimate the fixed parameters and unobserved states of a system model can be formulated as the evaluation of a discrete time path integral in model state space. The observations serve as a guiding potential working with the dynamical rules of the model to direct system orbits in state space. The path integral representation permits direct numerical evaluation of the conditional mean path through the state space as well as conditional moments about this mean. Using a Monte Carlo method for selecting paths through state space we show how these moments can be evaluated and demonstrate in an interesting model system the explicit influence of the role of transfer of information from the observations. We address the question of how many observations are required to estimate the unobserved state variables, and we examine the assumptions of Gaussianity of the underlying conditional probability.

John C. Quinn; Henry D. I. Abarbanel

2009-12-08T23:59:59.000Z

475

Validation of the Monte Carlo Criticality Program KENO V. a for highly-enriched uranium systems  

SciTech Connect

A series of calculations based on critical experiments have been performed using the KENO V.a Monte Carlo Criticality Program for the purpose of validating KENO V.a for use in evaluating Y-12 Plant criticality problems. The experiments were reflected and unreflected systems of single units and arrays containing highly enriched uranium metal or uranium compounds. Various geometrical shapes were used in the experiments. The SCALE control module CSAS25 with the 27-group ENDF/B-4 cross-section library was used to perform the calculations. Some of the experiments were also calculated using the 16-group Hansen-Roach Library. Results are presented in a series of tables and discussed. Results show that the criteria established for the safe application of the KENO IV program may also be used for KENO V.a results.

Knight, J.R.

1984-11-01T23:59:59.000Z

476

Suppressing nonphysical overheating with a modified implicit Monte Carlo method for time-dependent radiative transfer  

SciTech Connect

In this note we develop a robust implicit Monte Carlo (IMC) algorithm based on more accurately updating the linearized equilibrium radiation energy density. The method does not introduce oscillations in the solution and has the same limit as {Delta}t{yields}{infinity} as the standard Fleck and Cummings IMC method. Moreover, the approach we introduce can be trivially added to current implementations of IMC by changing the definition of the Fleck factor. Using this new method we develop an adaptive scheme that uses either standard IMC or the modified method basing the adaptation on a zero-dimensional problem solved in each cell. Numerical results demonstrate that the new method alleviates both the nonphysical overheating that occurs in standard IMC when the time step is large and significantly diminishes the statistical noise in the solution.

Mcclarren, Ryan G [Los Alamos National Laboratory; Urbatsch, Todd J [Los Alamos National Laboratory

2008-01-01T23:59:59.000Z

477

Cation dopant distributions in nanostructures of transition-metal doped ZnO:Monte Carlo simulations  

SciTech Connect

The path from trace doping to solid solution formation involves an intermediate regime in which the doping level is a few to several atomic percent. In this regime, dopant-dopant interactions, which are driven by the spatial arrangement of dopants, are critical factors in determining the resulting properties. Conventional wisdom counts on simple probabilistic methods for predicting dopant distributions. Here, we use Monte Carlo simulations to show that widely used, straightforward statistical models, such as that of Behringer1, are accurate only in the limit of infinitesimally small surface–to-volume ratio. For epitaxial films and nanoparticles, where much of the current interest resides, dopant distributions depend strongly on the surface-to-volume ratio. We present empirical expressions that accurately predict dopant bonding configurations as a function of film or particle size, shape and dopant concentration for doped ZnO, a material of particular interest in semiconductor spintronics.

Droubay, Timothy; Kaspar, Tiffany C.; Kaspar, Bryce P.; Chambers, Scott A.

2009-02-01T23:59:59.000Z

478

MaGe - a Geant4-based Monte Carlo framework for low-background experiments  

E-Print Network (OSTI)

A Monte Carlo framework, MaGe, has been developed based on the Geant4 simulation toolkit. Its purpose is to simulate physics processes in low-energy and low-background radiation detectors, specifically for the Majorana and Gerda $^{76}$Ge neutrinoless double-beta decay experiments. This jointly-developed tool is also used to verify the simulation of physics processes relevant to other low-background experiments in Geant4. The MaGe framework contains simulations of prototype experiments and test stands, and is easily extended to incorporate new geometries and configurations while still using the same verified physics processes, tunings, and code framework. This reduces duplication of efforts and improves the robustness of and confidence in the simulation output.

Yuen-Dat Chan; Jason A. Detwiler; Reyco Henning; Victor M. Gehman; Rob A. Johnson; David V. Jordan; Kareem Kazkaz; Markus Knapp; Kevin Kroninger; Daniel Lenz; Jing Liu; Xiang Liu; Michael G. Marino; Akbar Mokhtarani; Luciano Pandola; Alexis G. Schubert; Claudia Tomei

2008-02-06T23:59:59.000Z

479

MC++: A parallel, portable, Monte Carlo neutron transport code in C++  

SciTech Connect

MC++ is an implicit multi-group Monte Carlo neutron transport code written in C++ and based on the Parallel Object-Oriented Methods and Applications (POOMA) class library. MC++ runs in parallel on and is portable to a wide variety of platforms, including MPPs, SMPs, and clusters of UNIX workstations. MC++ is being developed to provide transport capabilities to the Accelerated Strategic Computing Initiative (ASCI). It is also intended to form the basis of the first transport physics framework (TPF), which is a C++ class library containing appropriate abstractions, objects, and methods for the particle transport problem. The transport problem is briefly described, as well as the current status and algorithms in MC++ for solving the transport equation. The alpha version of the POOMA class library is also discussed, along with the implementation of the transport solution algorithms using POOMA. Finally, a simple test problem is defined and performance and physics results from this problem are discussed on a variety of platforms.

Lee, S.R.; Cummings, J.C. [Los Alamos National Lab., NM (United States); Nolen, S.D. [Texas A & M Univ., College Station, TX (United States)

1997-03-01T23:59:59.000Z