Mixture models with weak micro-heterogeneity

Abstract

Weakly micro-heterogeneous binary systems are modelled as a mixture of a simple Lennard-Jones liquid and water-like models with reduced partial charges, hence named ‘weak-waters’. Such mixtures do not have the statistic problems of the usual micro-heterogeneous mixtures, and they allow to test how well liquid state integral equation theories are able to describe locally heterogeneous structures. It is found that such theories describe quite well the short-range structure, but fail to reproduce the heterogeneous structure in the nanometer range. In particular, it is found that the theories are not able to distinguish between micro-segregation and concentration fluctuations, a flaw apparent through the small wave vector behaviour of the structure factors. This finding helps provide further insight into both the nature of the micro-heterogeneity of aqueous mixtures in general, and the routes to improve the ability of integral equation theories to describe such mixtures.