Density-functional theory and freezing of simple liquids

Abstract

A theory for the Helmholtz free-energy functional F of inhomogeneous simple liquids is presented in which hard-sphere perturbation theory is utilized to separate F into primarily entropic and internal-energy contributions. The entropy of the hard-sphere reference system is obtained from the weighted-density approximation and the internal energy is determined from an expansion about the uniform-liquid value. The thermodynamic functions of a model Lennard-Jones solid, liquid, and vapor are then calculated and the resulting ρ-T phase diagram is found to be in good agreement with all aspects of simulation studies, including the Lindemann parameter along the freezing curve.