Additive and non-additive hard sphere mixtures

Abstract

Binary mixtures of additive (d ₁₂ = (d ₁ + d ₂)/2) and non-additive (d ₁₂ ≠ (d ₁ + d ₂)/2) hard spheres have been studied with new integral equations. Accurate Monte Carlo results for some non-additive cases have been generated and tables of radial distribution functions are explicitly given. Comparison of structural and thermodynamic results demonstrates that an approximate integral equation recently proposed by Martynov and Sarkisov for one-component hard spheres significantly improves on the Percus-Yevick approximation also in the mixture case, without introducing free parameters. A simple further generalization gives a very good parameterization of the computer experiment results. An analytical fit of the equation of state for symmetric non-additive systems is also given.