Molecular thermodynamics of a quantum Lennard-Jones fluid using an effective Mie potential and the SAFT-VR-Mie approach

Abstract

The SAFT-VR-Mie approach is applied to model quantum fluids following a method presented previously on the combined use of thermodynamic perturbation theory (TPT) and path-integral Monte Carlo (PIMC) simulations to describe a quantum square-well (QSW) fluid. In this communication we consider a system of N particles contained within a volume V interacting via a quantum Lennard-Jones potential (QLJ) with de Broglie's thermal wavelength , where m denotes the particle's mass, T is the temperature and h and k are the Planck's and Boltzmann's constants, respectively. The method is based on the exact analogy between the discretised path-integral formalism of Quantum Mechanics and the partition function of a classical system composed of necklace molecules. The Zwanzig's expansion is implemented in order to obtain the QLJ's first-perturbation term, , from PIMC simulations. An effective Mie potential with a variable repulsive parameter range and fixed attractive parameter, , is obtained by mapping to the classical expression provided by the SAFT-VR-Mie value, . The thermodynamics of the QLJ system is obtained using the SAFT-VR-Mie equation of state and applied to obtain accurate predictions for molecular hydrogen's isotherms when .

GRAPHICAL ABSTRACT

Keywords:

• Perturbation theory
• quantum fluids
• path-integral Monte Carlo
• semiclassical methods

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

We gratefully acknowledge financial support from CONA CYT (México) through Ph.D. scholarships (S.C. and C.S.), and from the University of Guanajuato, Convocatoria Institucional de Investigación Científica 2018 (grant CIIC 292/2018).