On high pressure phase transitions in solid methane

The structure behavior of solid methane has been investigated under pressure by a technique which minimizes the lattice energy at different volumes. The potential energy between a pair of CH4 molecules as a function of volume is calculated at five different temperatures for both the face centered cubic (f.c.c.) lattice and the hexagonal structure using a Hartree-Fock dispersion (HFD) potential with different parameters for each temperature. The sublimation energy at each temperature, the equation of state (P - V diagram), bulk modulus and the pressure at the phase transition for each temperature are estimated. (C) 2002 Published by Elsevier Science B.V.