Using first-principles calculations based on density-functional theory, mechanisms and energy barriers for atomic diffusion on Al(110), Al(100), and Al(111), up and down (100) and (111) steps on Al(110), and between the (100), (111), and (110) facets of Al were investigated. It was found that the energetically preferred mechanism for adatom diffusion on Al(110) was a diagonal exchange between the adatom and the substrate, which leads to isotropic diffusion on this anisotropic surface. Similarly, diagonal exchange involving three atoms was the preferred mechanism for atoms to ascend and descend the (100) and (111) steps. The descent of atoms over the (100) steps was hindered by diffusion to the step edge while for the (111) steps, it was hindered by diffusion over the edge. Energy barriers to ascend from (110) to (100) or (111) facets depend on facet height. Neighbouring adatoms could significantly influence diffusion-energy barriers and simple approaches cannot predict this complex behavior. The energy barriers for dimers to climb from the (110) to the (100) and (111) facets were lower than those for isolated adatoms.

Mechanisms of Atomic Diffusion on the Flat, Stepped, and Faceted Surfaces of Al(110). Y.Tiwary, K.A.Fichthorn: Physical Review B, 2010, 81[19], 195421