Simple volume-explicit equation of state for mixtures of non-additive hard-spheres

A simple volume-explicit equation of state (EOS) for hard sphere mixtures has been developed on the basis of the pressure form of the virial expansion. The resulting equation yields the dependence of the compressibility factor on the packing fraction and mole fraction for different size ratios within the error estimates of simulation data in most cases. The new equation also gives the exact second and third pressure virial coefficients. An advantage of such equations of state is the fact that they yield easily the Gibbs energies and consequently hard-sphere diagrams. The equations also predict with good accuracy the compressibility factor of non-additive hard sphere mixture with a small negative or positive value of non-additivity parameter (Δ).