Fluid mixtures of parallel hard cubes

TL;DR

This paper derives the direct correlation function for a fluid mixture of parallel hard cubes using Rosenfeld's fundamental measure approximation, revealing stability and phase behavior consistent with simulations.

Contribution

It introduces a thermodynamically consistent approximation for the correlation function of parallel hard cube mixtures and analyzes their phase stability.

Findings

Predicts spinodal instability for large side ratios

System remains mixed in two dimensions

Results align with lattice simulation data

Abstract

The direct correlation function of a fluid mixture of parallel hard cubes is obtained by using Rosenfeld's fundamental measure approximation. This approximation is thermodynamically consistent (compressibility and virial equations of state are equal) and predicts a spinodal instability of the binary mixture for large-to-small side ratio larger than roughly 10, in qualitative agreement with simulations on the lattice version of the model. In two dimensions the system never demix, also in agreement with the simulations.