Molecular dynamics methods, using embedded atom potentials, were used to investigate the effect of steps and H impurities upon the diffusion of a Ag adatom on the Pt(111) surface. The calculations showed that even a very low H coverage could appreciably increase the apparent diffusion barrier to Ag. The steps bound the Ag adatoms in a potential well of more than 0.2eV, and acted as sinks for adatoms up to high temperatures. After adsorption at the step, the Ag atoms underwent slow 1-dimensional diffusion, with an apparent activation barrier that was some 5 times higher than that on the terraces. On the basis of the simulations, an effective 2-body interaction for Ag with H and steps was derived.

P.Blandin, P.Ballone: Surface Science, 1995, 331-333, 891-5