The diffusion of a surface vacancy on Fe(100) was studied at various temperatures by means of molecular-dynamics simulations in conjunction with a many body potential in the context of the embedded atom method. This interatomic potential was constructed by fitting its parameters to both experimental and first-principles results. From the analysis of the vacancy jumps, three main diffusion mechanisms were investigated. The first one corresponds to the migration of the vacancy on the surface layer (intra-layer jumps) by hopping to a neighboring site, while the two others involved the participation of an atom of the second layer (inter-layer jumps) as well. The temperature dependence of the associated diffusion coefficients follows an Arrhenius behavior, from which the migration energies and pre-exponential factors were deduced. It was found that one of the mechanisms corresponding to inter-layer jumps was energetically slightly favored over the two other processes and in addition, its diffusivity was about six times higher than that of the two others. The results showed that the contribution of vacancy diffusion to mass transport was large.

Diffusion of a Vacancy on Fe(100): a Molecular-Dynamics Study. Papanicolaou, N.I., Chamati, H.: Computational Materials Science, 2009, 44[4], 1366-70