Antti-Pekka Hynninen and Athanassios Z. Panagiotopoulos
Department of Chemical Engineering, Princeton University, Princeton, New Jersey 08544 and Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544

Mikael C. Rechtsman
Department of Physics, Princeton University, Princeton, New Jersey 08544

Frank H. Stillinger
Department of Chemistry, Princeton University, Princeton, New Jersey 08544

Salvatore Torquato
Department of Chemistry, Princeton University, Princeton, New Jersey 08544; Program in Applied and Computational Mathematics, Princeton University, Princeton, New Jersey 08544; Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, New Jersey 08544; and Princeton Center for Theoretical Physics, Princeton University, Princeton, New Jersey 08544

(Received 8 May 2006; accepted 22 May 2006; published online 13 July 2006)

J. Chem. Phys. 125, 024505 (2006)

Abstract

We calculate the global phase diagram using classical statistical mechanics for an isotropic pair potential that has been previously [Rechtsman et al., Phys. Rev. Lett. 95, 228301 (2005)] shown to produce the low-coordinated two-dimensional honeycomb crystal as the ground-state structure. Low-coordinated crystals are of practical interest because they have desirable photonic band-gap properties. The phase diagram is obtained from Helmholtz free energies calculated using thermodynamic integration and Monte Carlo simulations. Our results show that the honeycomb crystal remains stable in the global phase diagram even after temperature effects are taken fully into account. Other stable phases in the phase diagram are high and low density triangular phases and a fluid phase. We find no evidence of gas-liquid or liquid-liquid phase coexistence.