Simple analytic equations of state for Sutherland fluids and square-well fluids

Abstract

A simple analytic expression satisfying the limitation condition at low density for the radial distribution function of hard spheres is developed in terms of a polynomial expansion of nonlinear base functions and the Carnahan–Starling equation of state. The simplicity and precision for the expression is superior to the well-known Percus–Yevick expression. The coefficients contained in the expression were determined by fitting the Monte-Carlo data for the first coordination shell, and by fitting both the Monte-Carlo data and the numerical results of the Percus–Yevick expression for the second coordination shell. The expression has been applied to develop analytic equations of state for Sutherland fluids and square-well fluids. The numerical results are in good agreement with computer-simulation data. PACS Nos.: 61.20.Gy, 64.10.+h, 05.70.Ce