Pair correlation function from the Barker–Henderson perturbation theory of fluids: the structure of square-well and square-shoulder potentials

Abstract

The Barker–Henderson perturbation theory is employed to modify the mean spherical approximation direct correlation function. It then leads to an improved version of the optimised random phase approximation by fulfilling the core condition of the resulting radial distribution function. The resulting theory is employed to find the pair correlation functions of moderate- to long-ranged square-well and square-shoulder potentials. Comparisons with the results of computer simulations and other theories show that the present approach gives a reliable structure for these potentials especially with the moderate to long-ranged tails.