Equation of state of non-additive $d$-dimensional hard-sphere mixtures

TL;DR

This paper introduces a simple, natural extension of the equation of state for additive hard spheres to non-additive mixtures in multiple dimensions, based on known virial coefficients and the compressibility factor.

Contribution

It proposes a new equation of state for non-additive hard-sphere mixtures that extends previous models and aligns well with exact and simulation data across various dimensions.

Findings

Good agreement with virial coefficients and compressibility factors

Effective for high asymmetries and positive nonadditivities

Applicable in 1, 2, and 3 dimensions

Abstract

An equation of state for a multicomponent mixture of non-additive hard spheres in $d$ dimensions is proposed. It yields a rather simple density dependence and constitutes a natural extension of the equation of state for additive hard spheres proposed by us [A. Santos, S. B. Yuste, and M. L\'opez de Haro, Mol. Phys. 96, 1 (1999)]. The proposal relies on the known exact second and third virial coefficients and requires as input the compressibility factor of the one-component system. A comparison is carried out both to another recent theoretical proposal based on a similar philosophy and to the available exact results and simulation data in $d=1$, 2, and 3. Good general agreement with the reported values of the virial coefficients and of the compressibility factor of binary mixtures is observed, especially for high asymmetries and/or positive nonadditivities.