Models for adatom diffusion on fcc (001) metal surfaces

We present a class of models that describe self-diffusion on fcc (001) metal substrates within a common framework. The models are tested for Cu(001), Ag(001), Au(001), Ni(001), and Pd(001), and found to apply well for all of them. For each of these metals the models can be used to estimate the activation energy of any diffusion process using a few basic parameters that may be obtained from experiments, ab initio or semiempirical calculations. To demonstrate the approach, the parameters of the models are optimized to describe self- diffusion on the (001) surface, by comparing the energy barriers to a full set of barriers obtained from semiempirical potentials via the embedded atom method (EAM). It is found that these models with at most four parameters, provide a good description of the full landscape of hopping energy barriers on fcc (001) surfaces. The main features of the diffusion processes revealed by EAM calculations are quantitatively reproducible by the models.