Computer-simulation study of melting in dense oxygen layers on graphite

Abstract

The thermodynamic, structural, and dynamical properties of oxygen adsorbed on graphite have been simulated using a molecular-dynamics algorithm. The simulations were run at temperatures ranging from 30 to 70 K and at nominal coverages of one (dense) layer, ∼1.7 layers, two layers, and three layers. Melting behavior was characterized in all cases. Enthalpies, layer densities (solid and liquid), and temperatures of melting were obtained. The temperature for first-layer melting was found at 55–60 K and was not very dependent upon total coverage. This melting appeared to be sharp for most cases studied. Second-layer melting behavior depended very strongly on the layer density, and compound liquid-solid layers were observed. The simulation results are found to be in good agreement with experiment. The importance of orientational changes in determining the properties of these systems is demonstrated and discussed.