Sound Velocities of Generalized Lennard-Jones (n − 6) Fluids Near Freezing

Abstract

In a recent paper [S. Khrapak, Molecules 25, 3498 (2020)], the longitudinal and transverse sound velocities of a conventional Lennard–Jones system at the liquid–solid coexistence were calculated. It was shown that the sound velocities remain almost invariant along the liquid–solid coexistence boundary lines and that their magnitudes are comparable with those of repulsive soft-sphere and hard-sphere models at the fluid–solid phase transition. This implies that attraction does not considerably affect the magnitude of the sound velocities at the fluid–solid phase transition. This paper provides further evidence to this by examining the generalized Lennard–Jones (n− 6) fluids with n ranging from 12 to 7 and demonstrating that the steepness of the repulsive term has only a minor effect on the magnitude of the sound velocities. Nevertheless, these minor trends are identified and discussed.

Elastic properties of dense hard-sphere fluids

“…This is a generalization of the conventional Cauchy identity for isotropic solids made of molecules interacting with two-body central forces, which is now valid for fluids at any temperature and pressure [176]. Note that similar relations can be derived for the generalized n-m LJ potential [178]. Thus, knowledge of thermodynamic parameters c v , u ex , and p ex is sufficient to evaluate the thermal conductivity coefficient within the vibrational paradigm.…”

Excess entropy determines the applicability of Stokes-Einstein relation in simple fluids

“…( 11) above. The sound velocities of LJ liquids near the liquid-solid phase transition have been recently evaluated [52,53]. Expressed in units of thermal velocity v T = T /m they turn out to be c l /v T 11.5 and c t /v T 6.…”