TIGHT-BINDING MOLECULAR-DYNAMICS STUDY OF DIFFUSION ON AU AND AG(111)

A molecular dynamics simulation of diffusion of Au on Au(111) and of Ag on Ag(111) is performed in a rather large range of temperatures, up to about one half of the melting temperature of the crystals. Au and Ag are modelized by many-body potentials derived within the second-moment approximation to the tight-binding model. The potential energy barriers (zero temperature) for diffusion are calculated by allowing a full relaxation of the crystal; those barriers result rather low in both metals and especially in Ag. However, in the temperature range considered, the activation energies, as extracted from the Arrhenius plots of the diffusion coefficient, are not significantly different from the potential energy barriers at 0 K.