Phase transitions in simple fluids: an application of a one-phase entropic criterion to Lennard-Jones and point Yukawa fluids

Abstract

A recently proposed entropic criterion [P.V. Giaquinta and G. Guinta, Physica A 187, 145 (1992)] for the determination of phase transitions in simple fluids is applied to two-fluid models, a purely repulsive point Yukawa fluid, and a 6-12 Lennard-Jones system. Both the gas-liquid and the freezing transitions are investigated by means of integral equation theory, and assessed with simulation data available in the literature. Our results indicate that the entropic criterion is a reasonable tool for predicting the freezing transition at low temperatures, in particular for purely repulsive potentials. Comparison with other melting rules is less favorable when there is an important attractive component in the interaction. On the other hand, the determination of the gas-liquid critical point and the liquid side of the gas-liquid coexistence curve is merely qualitative. Our results, however, show the existence of a correlation between the gas-liquid transition and the location of one of the inflection points of the density-dependent excess residual entropy.