Activation barriers and pre-factors were calculated for diffusion via hopping on the (100), (110) and (111) surfaces. The calculations revealed that, when the activation barriers decreased, there was also a decrease in the pre-factors so that the changes in the two parameters partially compensated one another with respect to the diffusivities. The thermodynamic functions which contributed to the pre-factors were estimated from the local vibrational density of states and showed that entropic contributions mainly controlled the pre-factors. The present method permitted the values obtained to be traced back to the vibrational properties of the adatoms in both minimum-energy and transition-state configurations, and led to a physical understanding of why pre-factors had certain values.

Self-Diffusion on (100), (110) and (111) Surfaces of Ni and Cu - a Detailed Study of Prefactors and Activation Energies. U.Kürpick: Physical Review B, 2001, 64[7], 075418 (7pp)