An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+

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A novel method for simulating the statistical mechanics of molecular systems in which both nuclear and electronic degrees of freedom are treated quantum mechanically is presented. The scheme combines a path integral description of the nuclear variables with a first-principles adiabatic description o...

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Autores principales: Weht, R.O., Kohanoff, J., Estrin, D.A., Chakravarty, C.
Formato: JOUR
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00219606_v108_n21_p8848_Weht
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_00219606_v108_n21_p8848_Weht2023-10-03T14:23:56Z An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+ Weht, R.O. Kohanoff, J. Estrin, D.A. Chakravarty, C. A novel method for simulating the statistical mechanics of molecular systems in which both nuclear and electronic degrees of freedom are treated quantum mechanically is presented. The scheme combines a path integral description of the nuclear variables with a first-principles adiabatic description of the electronic structure. The electronic problem is solved for the ground state within a density functional approach, with the electronic orbitals expanded in a localized (Gaussian) basis set. The discretized path integral is computed by a METROPOLIS Monte Carlo sampling technique on the normal modes of the isomorphic ring polymer. An effective short-time action correct to order τ4 is used. The validity and performance of the method are tested by studying two small lithium clusters, namely Li4 and Li5+. Structural and electronic properties computed within this fully quantum-mechanical scheme are presented and compared to those obtained within the classical nuclei approximation. Quantum delocalization effects turn out to be significant as shown by the fact that quantum simulation results at 50 K approximately correspond to those of classical simulations carried out at 150 K. The scaling factor depends, however, on the specific physical property, thus evidencing the different character of quantum and thermal correlations. Tunneling turns out to be irrelevant in the temperature range investigated (50-200 K). © 1998 American Institute of Physics. Fil:Weht, R.O. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Kohanoff, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Estrin, D.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00219606_v108_n21_p8848_Weht
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description A novel method for simulating the statistical mechanics of molecular systems in which both nuclear and electronic degrees of freedom are treated quantum mechanically is presented. The scheme combines a path integral description of the nuclear variables with a first-principles adiabatic description of the electronic structure. The electronic problem is solved for the ground state within a density functional approach, with the electronic orbitals expanded in a localized (Gaussian) basis set. The discretized path integral is computed by a METROPOLIS Monte Carlo sampling technique on the normal modes of the isomorphic ring polymer. An effective short-time action correct to order τ4 is used. The validity and performance of the method are tested by studying two small lithium clusters, namely Li4 and Li5+. Structural and electronic properties computed within this fully quantum-mechanical scheme are presented and compared to those obtained within the classical nuclei approximation. Quantum delocalization effects turn out to be significant as shown by the fact that quantum simulation results at 50 K approximately correspond to those of classical simulations carried out at 150 K. The scaling factor depends, however, on the specific physical property, thus evidencing the different character of quantum and thermal correlations. Tunneling turns out to be irrelevant in the temperature range investigated (50-200 K). © 1998 American Institute of Physics.
format JOUR
author Weht, R.O.
Kohanoff, J.
Estrin, D.A.
Chakravarty, C.
spellingShingle Weht, R.O.
Kohanoff, J.
Estrin, D.A.
Chakravarty, C.
An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+
author_facet Weht, R.O.
Kohanoff, J.
Estrin, D.A.
Chakravarty, C.
author_sort Weht, R.O.
title An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+
title_short An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+
title_full An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+
title_fullStr An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+
title_full_unstemmed An ab initio path integral Monte Carlo simulation method for molecules and clusters: Application to Li4 and Li5+
title_sort ab initio path integral monte carlo simulation method for molecules and clusters: application to li4 and li5+
url http://hdl.handle.net/20.500.12110/paper_00219606_v108_n21_p8848_Weht
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