Phase diagram of a tetrahedral patchy particle model for different interaction ranges

We evaluate the phase diagram of the Kern-Frenkel patchy model with four interaction sites for four different values of the radial interaction range (all in the single-bond-per-patch regime) keeping the area of the interaction patches fixed. Four stable crystal phases are investigated, namely diamond cubic (DC), bcc, fcc, and plastic fcc. The DC is favored at low temperatures and pressures, while the bcc is favored at low temperatures and intermediate to high pressures. At low temperatures and very high pressures an ordered fcc phase is found, while-as expected-at high temperatures, the only stable crystal is a plastic fcc phase. We find a rich phase diagram with several re-entrant coexistence lines, which can be brought in the equilibrium phase diagram by a proper choice of the range. We also show that the gas-liquid phase separation becomes metastable as the range narrows, and it takes place in a region of the phase diagram where the low density diamond crystal is the thermodynamically stable phase. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3393777]