Molecular Dynamics Analysis on Gas-Surface Interaction

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The scattering process of a gas molecule on a clean and complete surface is simulated and analyzed by the molecular dynamics method. First, a thermal equilibrium state of a thin solid film is calculated using 864 molecules of Lennard-Jones type, and then the gas molecule, whose potential parameters and its mass is changed, has collide on to this surface. For one case of parameters hundreds of scattering is simulated. In some cases the Morse type potential is used for gas-solid interaction potential. The numerical results are :1. The scattering behavior of gas molecule is differ from that in the diffuse model or Maxwell model.2. The sticking probability of gas molecule is affected mainly by the initial gas velocity and the potential well depth.3. The average of normal momentum of non-sticking molecules is very correlated with the initial normal momentum of them.4. Using the Morse potential for the Xe-Pt (111) system, the sticking probability is agree with the experiment of Tully et al.5. The energy transfer of gas to surface is limited in a certain period, that between the two maximum of kinetic energy of gas molecule in one collision. The amount of this energy transfer for one collision is very correlated to the kinetic energy at first maximum and its distribution function is controlled by the tangential momentum of gas molecule.