Accommodation coefficients for molecular hydrogen on a graphite surface

On the basis of the molecular dynamics simulation method the trajectories of hydrogen molecules reflected from a graphite surface are calculated with account for its structure and the thermal motion of carbon atoms. The velocity distribution after the reflection is obtained as a function of the velocity magnitude and direction of the incident molecules and the surface temperature. In the case of heat transfer between symmetric surfaces in the free-molecular regime, the energy accommodation coefficients are calculated for hydrogen on graphite as functions of the gas and wall temperatures. The results obtained are in agreement with experimental data.