Communication: Virial coefficients and demixing in highly asymmetric binary additive hard-sphere mixtures

TL;DR

This paper investigates whether fluid-fluid demixing occurs in highly asymmetric binary additive hard-sphere mixtures, comparing virial expansion results for finite size ratios and the extreme case of point particles, questioning the existence of such transitions.

Contribution

It provides a comparative analysis of virial expansion results across different size ratios, including the extreme point-particle limit, to assess the likelihood of demixing in asymmetric mixtures.

Findings

Critical constants behave similarly across size ratios.

Point-particle system does not exhibit fluid-fluid segregation.

Results cast doubt on the existence of demixing in highly asymmetric mixtures.

Abstract

The problem of demixing in a binary fluid mixture of highly asymmetric additive hard spheres is revisited. A comparison is presented between the results derived previously using truncated virial expansions for three finite size ratios with those that one obtains with the same approach in the extreme case in which one of the components consists of point particles. Since this latter system is known not to exhibit fluid-fluid segregation, the similarity observed for the behavior of the critical constants arising in the truncated series in all instances, while not being conclusive, may cast serious doubts as to the actual existence of a demixing fluid-fluid transition in disparate-sized binary additive hard-sphere mixtures.