Virial coefficients, thermodynamic properties, and fluid-fluid transition of nonadditive hard-sphere mixtures

TL;DR

This paper compares various theoretical models for predicting thermodynamic properties and phase behavior of nonadditive hard-sphere mixtures, providing explicit formulas and validating them against simulation data.

Contribution

It unifies multiple existing theories and introduces a new nonlinear extension, offering explicit expressions and comprehensive comparison with simulation results.

Findings

The new nonlinear MIX1 extension improves accuracy for certain properties.

Explicit virial coefficient formulas facilitate practical calculations.

Theories show varying strengths and limitations when compared to Monte Carlo data.

Abstract

Different theoretical approaches for the thermodynamic properties and the equation of state for multicomponent mixtures of nonadditive hard spheres in $d$ dimensions are presented in a unified way. These include the theory by Hamad, our previous formulation, the original MIX1 theory, a recently proposed modified MIX1 theory, as well as a nonlinear extension of the MIX1 theory proposed in this paper. Explicit expressions for the compressibility factor, Helmholtz free energy, and second, third, and fourth virial coefficients are provided. A comparison is carried out with recent Monte Carlo data for the virial coefficients of asymmetric mixtures and with available simulation data for the compressibility factor, the critical consolute point, and the liquid-liquid coexistence curves. The merits and limitations of each theory are pointed out.