Development of an Analysis System of Gas-Surface Interaction using the Molecular Dynamics Method

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Recently, advances in engineering techniques gave more demands to analyze rarefied gas flows. The analysis of a gas molecule interacting with a surface of a film when manufacturing a semi-conductor, for example, is important. Our aim is to develop an analysis system of a more complicated system of gas-surface interaction such as a polyatomic molcule-surface interaction using the molecular dynamics method. With this system, data of adsorption rates or scattering distributions of a gas molecule are acquirable.Matsumoto, Matsui and others have expanded the system when polyatomic molecules interact or when adsorbate molecules exists, and has done calculations using a supercomputer and an exclusive software. When an adsorbate molecule exists, the simulation was done by adsorbing gas molecules to the surface and then colliding a gas molecule. At this situation, the adsorbate molecule influences the gas molecule. We have selected an oxygen molecule (diatomic molecule) to analyze the interaction of a polyatomic gas molecule and a surface. The rotational degree of freedom gave influence on the process of energy exchange between the gas atom and the surface.Shobatake and others have done experiments of gas-surface interaction using a graphite surface. The date will help estimate the from of the potential between the gas atom and the surface atom, which is essential when performing molecular dynamics simulations. Also, experimental data for comparing scattering distributions between monatomic molecules and diatomic molecules were obtained.