Phase equilibria in model mixtures of spherical molecules of different sizes

Abstract

Phase boundaries have been calculated for model binary mixtures comprising spheres of different sizes, between which there are long-range attractive forces. Particular attention has been paid to the case in which the ratio of sizes is infinite. The systems show a wide variety of behaviour that includes liquid–liquid and gas–gas immiscibility and the formation of negative azeotropes. The model systems are shown to reproduce some of the behaviour of aqueous solutions of surfactants if it assumed that the large spheres are models of the micelles and the small spheres models of the solvent molecules.