Gas–liquid phase coexistence in a tetrahedral patchy particle model

Abstract

We evaluate the location of the gas–liquid coexistence line and of the associated criticalpoint for the primitive model for water (PMW), introduced by Kolafa and Nezbeda (1987Mol. Phys. 61 161). Besides being a simple model for a molecular network formingliquid, the PMW is representative of patchy proteins and novel colloidal particlesinteracting with localized directional short-range attractions. We show that thegas–liquid phase separation is metastable, i.e. it takes place in the region of the phasediagram where the crystal phase is thermodynamically favoured, as in the caseof particles interacting via short-range attractive spherical potentials. We donot observe crystallization close to the critical point. The region of gas–liquidinstability of this patchy model is significantly reduced as compared to that fromequivalent models of spherically interacting particles, confirming the possibility ofobserving kinetic arrest in a homogeneous sample driven by bonding as opposed topacking.