Atom-by-atom and concerted hopping of ad-dimers on the open (100) surface of face-centered cubic metals were studied by means of density functional calculations. It was noted that the adatom interaction was relatively short-ranged and that, beyond the next-nearest neighbours, the ad-dimers were effectively dissociated. Diffusion took place via a simple shearing process which was preferred because it maximized the adatom coordination at the transition state. This was expected to be a general result because geometrical arguments predominated over the details of the electronic structure. It was also shown that even complicated collective processes could be accounted for by using a simple pair-wise model that was based upon the adatom diffusion barrier and the ad-dimer binding energy.

Atom-by-Atom and Concerted Hopping of Adatom Pairs on an Open Metal Surface. A.Bogicevic, S.Ovesson, B.I.Lundqvist, D.R.Jennison: Physical Review B, 2000, 61[4], R2456-9