The diffusion of various adatoms on the (211) plane of W was studied by means of field ion microscopy. Diffusion appeared to occur in accord with the simplest of models, and the pre-exponential factor differed little between adatoms (19.2 for Re, 19.0 for W, 16.4 for Mo, 15.4 for Ir, and 12.4kcal/mol for Rh). The data for Rh could be described by:

D (cm2/s) = 0.0033 exp[-12.4(kcal/mol)/RT]

There was no sign of any anomaly in the diffusion dynamics. It was suggested that the activation energies for diffusion over a flat surface could be correlated with bulk thermodynamic data for vaporization.

S.C.Wang, G.Ehrlich: Surface Science, 1988, 206[3], 451-74