DIFFUSION OF ATOMS AND DIMERS ON METAL-SURFACES

Experiments from literature have shown that the diffusion coefficients of dimers of rhenium atoms on tungsten are larger than those of the s ingle rhenium atoms for the cross-channel configuration of the dimer a nd smaller for the in-channel configuration. In the present paper, exp ressions are derived for the diffusion coefficient which explain the a bove observations. They are based on Langevin equations of the motion of a single atom and dimer on a metal surface, in which the relation d erived previously by the authors for the friction coefficient is emplo yed. It is also demonstrated that the diffusion coefficient of the dim ers exhibits a periodical dependence upon the ratio between the dimer length and the metal lattice parameter, phenomenon which is called res onant diffusion.