Structure and phase behavior of Widom-Rowlinson mixtures: Integral equation approach

We have proposed a new approximation for Widom-Rowlinson mixtures that relies on incorporating an analytical direct correlation function for like particles into the Percus-Yevick closure approximation for unlike particles. We provide an analytical expression for the direct correlation functions for like particles with the fit parameters as a function of the density, which is accurate up to the critical density. The theoretical predictions for the structural properties and phase behaviors are in good agreement with the computer simulations. However, the accuracy between the theory and the simulations deteriorates with increasing density and mole fraction. These results are meant to provide a guide in the search for a manageable, simple, analytic parameterization of the structure of mixtures of nonadditive hard spheres.