MOLECULAR PACKING ANALYSIS OF BENZENE CRYSTALS .2. PREDICTION OF EXPERIMENTAL CRYSTAL-STRUCTURE POLYMORPHS AT LOW AND HIGH-PRESSURE

Benzene crystal structures were obtained by pseudoannealing initial st ructures sampled from a trajectory of constant moles, volume, and temp erature molecular dynamics (NVT MD). The crystal structure of the obse rved low pressure phase I was reproduced as the most stable state and other crystal structures, which included high pressure phase III, were obtained as metastable states at zero pressure. The pressure dependen ce of enthalpy was analyzed for these crystal structures, and the rela tive stability among these crystal structures is discussed, at pressur es up to 4 GPa. The observed low pressure phase I was the most stable state up to 1.4 GPa and the high pressure phase III was the most stabl e state above 1.4 GPa. The reported high pressure phase II was not obt ained in this work at any pressure up to 4 GPa.