Surface diffusion of molecules physisorbed on dielectric substrates

Semiempirical potential calculations are performed to determine the potential surfaces experienced by a X molecule (X=Xe,CH4,N2,CO,NH3,CH3F) adsorbed on the (100) face of dielectric substrates (MgO, NaCl) and on the (111) dense face of xenon. The diffusion mechanism of X on these surfaces is then described, within the transit time concept, as a successive jump process along the diffusion coordinate, including the statical and dynamical influence of the other molecular motions. The calculated diffusion constants can serve as a test of the surface corrugation and of the admolecule dynamics.