MELTING TRANSITION OF ETHYLENE ON GRAPHITE

The melting behavior of submonolayer patches of physisorbed ethylene molecules on the graphite basal plane has been investigated by molecular dynamics calculations. The simulation results reveal the significant role played by the substrate in determining the behavior of the incommensurate overlayer. The competition between the ethylene-ethylene intermolecular interactions and the two-dimensional solid-substrate interactions causes the solid overlayer to be farther away from the surface than in the case of a liquid film. This competition may be related to the observed continuous melting transition. In the transition region, the adsorbate forms solid patches connected by liquidlike domain walls. The coherence (correlation) length of the ordered domains and the structural relaxation time are estimated.