On the non-Gaussian corrections in the self dynamics of semi-quantum fluids

Author(s)
D. Colognesi, U. Bafile, M. Celli, M. Neumann
Abstract

This paper is devoted to the study of the limits of the well-known Gaussian approximation in the self dynamics of quantum systems. After introducing the basic formalism and shortly reviewing the methods used in classical systems to apply corrections to the Gaussian approximation, an extension to quantum fluids is devised, with a particular interest in the so-called semi-quantum fluids, i.e. those in which the single particle momentum distribution approximately retains its Maxwellian form (but not its classical width). In this case a detailed correction scheme for both the short- and the long-time behaviors of the intermediate scattering function is proposed. Subsequently, a practical test of this approach is performed on a high resolution neutron scattering spectrum derived from liquid parahydrogen at T = 14.1 K. Extracting the spectral deviations from the Gaussian approximation with the help of an accurate centroid molecular dynamics simulation, we are able to describe them precisely and to derive the first two correction coefficients in this system by means of a simple fitting procedure. These experimental findings confirm the validity of our approach and show that a description of the self dynamics beyond the Gaussian approximation is necessary even in simple liquids affected by mild quantum effects.

Organisation(s)
Computational and Soft Matter Physics
External organisation(s)
Università degli Studi di Roma "Tor Vergata"
Journal
Chemical Physics
Volume
446
Pages
57-64
No. of pages
8
ISSN
0301-0104
DOI
https://doi.org/10.1016/j.chemphys.2014.11.007
Publication date
01-2015
Peer reviewed
Yes
Austrian Fields of Science 2012
103015 Condensed matter, 103006 Chemical physics, 103019 Mathematical physics, 103008 Experimental physics
Keywords
ASJC Scopus subject areas
Physics and Astronomy(all), Physical and Theoretical Chemistry
Portal url
https://ucris.univie.ac.at/portal/en/publications/on-the-nongaussian-corrections-in-the-self-dynamics-of-semiquantum-fluids(683ecf2e-e8cf-451c-a58b-8ef2327556d0).html