A PHASE-TRANSITION FOR SOLID METHANE

The phase behaviour for solid methane has been investigated by a latti ce sum minimization method. The potential energy between a pair of CH, molecules as a function of volume is calculated at five different tem peratures for both the body centered cubic lattice and the orthorhombi c structure using an HFD potential with different parameters for each temperature. The sublimation energy at each temperature, the equation of state (P-V diagram) and the pressure at the phase transition for ea ch temperature are estimated.