On high pressure phase transitions in solid methane Original Research Article

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.