Effect of hard-sphere structure on pure-component equation of state calculations

Abstract

Hard-sphere fluid structure is shown to be important in describing the thermodynamic properties of the square-well fluid. A simple local composition model using the exponential approximation (EXP) of Anderson and Chandler (1972) for the pair correlation function is developed. The hard-sphere pair correlation function is determined using the analytic solution to the Percus-Yevick theory (Wertheim, 1964). The model is shown to predict the properties of the square-well fluid that are in good agreement with molecular dynamics data. The equation is used to predict the properties of argon and methane. The equation is also incorporated into the Simplified-Perturbed-Hard-Chain Theory (SPHCT), and the new equation improves calculations of vapor pressures and saturated densities for non-polar and polar fluids.