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A new class of ensemble conserving algorithms for approximate quantum dynamics: Theoretical formulation and model problems

Journal article
Authors K. K. G. Smith
Jens Aage Poulsen
Gunnar Nyman
P. J. Rossky
Published in Journal of Chemical Physics
Volume 142
Issue 24
ISSN 0021-9606
Publication year 2015
Published at Department of Chemistry and Molecular Biology
Language en
Links dx.doi.org/10.1063/1.4922887
Keywords CENTROID MOLECULAR-DYNAMICS, PHASE-SPACE, VARIABLES, SYSTEMS, HE(4), Physics, Atomic, Molecular & Chemical
Subject categories Chemical physics, Physical Chemistry

Abstract

We develop two classes of quasi-classical dynamics that are shown to conserve the initial quantum ensemble when used in combination with the Feynman-Kleinert approximation of the density operator. These dynamics are used to improve the Feynman-Kleinert implementation of the classical Wigner approximation for the evaluation of quantum time correlation functions known as Feynman-Kleinert linearized path-integral. As shown, both classes of dynamics are able to recover the exact classical and high temperature limits of the quantum time correlation function, while a subset is able to recover the exact harmonic limit. A comparison of the approximate quantum time correlation functions obtained from both classes of dynamics is made with the exact results for the challenging model problems of the quartic and double-well potentials. It is found that these dynamics provide a great improvement over the classical Wigner approximation, in which purely classical dynamics are used. In a special case, our first method becomes identical to centroid molecular dynamics. (C) 2015 AIP Publishing LLC.

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