Improved first order mean-spherical approximation for simple fluids

A perturbation approach based on the first-order mean-spherical approximation (FMSA) is proposed. It consists in adopting a hard-sphere plus short-range attractive Yukawa fluid as the novel reference system, over which the perturbative solution of the Ornstein-Zernike equation is performed. A choice of the optimal range of the reference attraction is discussed. The results are compared against conventional FMSA/HS theory and Monte-Carlo simulation data for compressibility factor and vapor-liquid phase diagrams of the medium-ranged Yukawa fluid. The proposed theory keeps the same level of simplicity and transparency as the conventional FMSA/HS approach does, but turns out to be more accurate.