Empty liquid state and self-assembly of high valence non-spherical colloidal systems

Abstract

A vapour–liquid phase coexistence with vanishing critical volume fraction (empty liquid) is predicted in some model systems of attractive hard ellipsoids. The trends in critical density and temperature do not depend on the ellipsoid shape and the range of the square-well attraction. Our theoretical and simulation studies show transparently that the empty liquid limit is due to the competition between the anisotropic attractive and repulsive interactions. Additionally, the nematic phase is destabilized by the square-well attraction for both prolate and oblate shapes. The demand to maximize the number of bonds while keeping a relatively low excluded volume leads to special structures such as the cubatic and star-shaped cluster phases at low temperatures. The liquid branch of the vapour–liquid binodal is always isotropic for oblates, while it can be isotropic or cluster-like for prolates. Our results predict the occurrence of an empty liquid state in high valence anisotropic colloidal systems.