A molecular dynamics study was made, using Pt and Ag as examples, of the self-diffusion of adatoms on (100) face-centered cubic metal surfaces. The metals were modelled by means of surface embedded-atom potentials. It was found that, as well as the familiar exchange diffusion mechanism, another one appeared which involved the diffusion of an ad-dimer. This was explained by the so-called concerted-motion model which involved strong bonds that formed in the transition state. It was expected that this mechanism could often operate, even at room temperature, and make adatoms more mobile on (100) face-centered cubic surfaces.

Exchange Mechanism for Adatom Diffusion on Metal FCC (100) Surfaces J.Zhuang, L.Liu: Physical Review B, 1998, 58[3], 1173-6