COMPUTER-SIMULATION STUDY OF THE PHASE-DIAGRAM OF THE CH4 MONOLAYER ON GRAPHITE - CORRUGATION EFFECTS

Molecular-dynamics simulation studies have been carried out for the two-dimensional phases of submonolayer methane physisorbed on graphite. Three methane-solid interaction potentials were used that differed by the size of the corrugation term in the molecule-solid potential function. Thermodynamic quantities were estimated throughout the commensurate-incommensurate and the melting transitions, and their dependence on the corrugation magnitude s was determined. Simulations with a corrugation magnitude 50% larger than that given by the pairwise spherical-site summation approximation to the potential give good agreement with experimental data.