Application of a new ensemble conserving quantum dynamics simulation algorithm to liquid para-hydrogen and ortho-deuterium

Kyle K G Smith; Jens Aage Poulsen; Gunnar Nyman; Alessandro Cunsolo; Peter J Rossky

doi:10.1063/1.4922888

Application of a new ensemble conserving quantum dynamics simulation algorithm to liquid para-hydrogen and ortho-deuterium

J Chem Phys. 2015 Jun 28;142(24):244113. doi: 10.1063/1.4922888.

Authors

Kyle K G Smith¹, Jens Aage Poulsen², Gunnar Nyman², Alessandro Cunsolo³, Peter J Rossky⁴

Affiliations

¹ Institute for Computational Engineering and Sciences and Department of Chemistry,University of Texas at Austin, Austin, Texas 78712, USA.
² Physical Chemistry, Department of Chemistry and Molecular Biology, University of Gothenburg, SE 41296 Gothenburg, Sweden.
³ Photon Sciences Directorate, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973, USA.
⁴ Department of Chemistry, Rice University, Houston, Texas 77251, USA.

PMID: 26133416
DOI: 10.1063/1.4922888

Abstract

We apply the Feynman-Kleinert Quasi-Classical Wigner (FK-QCW) method developed in our previous work [Smith et al., J. Chem. Phys. 142, 244112 (2015)] for the determination of the dynamic structure factor of liquid para-hydrogen and ortho-deuterium at state points of (T = 20.0 K, n = 21.24 nm(-3)) and (T = 23.0 K, n = 24.61 nm(-3)), respectively. When applied to this challenging system, it is shown that this new FK-QCW method consistently reproduces the experimental dynamic structure factor reported by Smith et al. [J. Chem. Phys. 140, 034501 (2014)] for all momentum transfers considered. This shows that FK-QCW provides a substantial improvement over the Feynman-Kleinert linearized path-integral method, in which purely classical dynamics are used. Furthermore, for small momentum transfers, it is shown that FK-QCW provides nearly the same results as ring-polymer molecular dynamics (RPMD), thus suggesting that FK-QCW provides a potentially more appealing algorithm than RPMD since it is not formally limited to correlation functions involving linear operators.