A density-functional study was made of the diffusion of Pt dimers on the (111) surface of Pt. The calculated activation energy of 0.37eV was in exact agreement with recent data (0.261eV for adatoms, 0.37eV for dimers) which had been obtained by using low-temperature field-ion microscopy. It was suggested that the close agreement for dimers was perhaps fortuitous because the calculations were precise to no more than a few hundredths of an eV (due to neglecting dynamic and quantum effects, finite-size limitations, and the inexact nature of the local density approximation). But the calculations established that the dimers were mobile at temperatures which were of interest with regard to adatom diffusion, and thus contributed to mass transport. The diffusion path for dimers was found to consist of a sequence of concerted 2-atom jumps plus local reorientations. Such a diffusion mechanism had been recently reported for the case of Al dimers on Al(111), on the basis of density-functional calculations.

Diffusion of Pt Dimers on Pt(111). G.Boisvert, L.J.Lewis: Physical Review B, 1999, 59[15], 9846-9