Refinement of the experimental dynamic structure factor for liquid para-hydrogen and ortho-deuterium using semi-classical quantum simulation

Kyle K G Smith; Jens Aage Poulsen; A Cunsolo; Peter J Rossky

doi:10.1063/1.4851997

Refinement of the experimental dynamic structure factor for liquid para-hydrogen and ortho-deuterium using semi-classical quantum simulation

J Chem Phys. 2014 Jan 21;140(3):034501. doi: 10.1063/1.4851997.

Authors

Kyle K G Smith¹, Jens Aage Poulsen², A Cunsolo³, Peter J Rossky¹

Affiliations

¹ Institute for Computational Engineering and Sciences and Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, USA.
² Department of Physical Chemistry, Goteborg University, S-412-96 Goteborg, Sweden.
³ Photon Sciences Directorate, Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973, USA.

PMID: 25669394
DOI: 10.1063/1.4851997

Abstract

The dynamic structure factor of liquid para-hydrogen and ortho-deuterium in corresponding thermodynamic states (T = 20.0 K, n = 21.24 nm(-3)) and (T = 23.0 K, n = 24.61 nm(-3)), respectively, has been computed by both the Feynman-Kleinert linearized path-integral (FK-LPI) and Ring-Polymer Molecular Dynamics (RPMD) methods and compared with Inelastic X Ray Scattering spectra. The combined use of computational and experimental methods enabled us to reduce experimental uncertainties in the determination of the true sample spectrum. Furthermore, the refined experimental spectrum of para-hydrogen and ortho-deuterium is consistently reproduced by both FK-LPI and RPMD results at momentum transfers lower than 12.8 nm(-1). At larger momentum transfers the FK-LPI results agree with experiment much better for ortho-deuterium than for para-hydrogen. More specifically we found that for k ∼ 20.0 nm(-1) para-hydrogen provides a test case for improved approximations to quantum dynamics.