Atomistic modeling of Ag deposition on the low-index faces of Al and Al deposition on Ag

The deposition of Ag on low-index surfaces of Al, and the symmetric case of Al on Ag surfaces, are studied by means of a simple modeling approach based on a quantum approximate technique, the BFS method for alloys. For submonolayer deposits of Ag on Al, a preference is seen for growth of close-packed chains along nearest-neighbor directions on (1 0 0) and (1 1 0) surfaces, while cluster formation is preferred for growth on Al(1 1 1). For Al deposition on all three low-index Ag surfaces, diffusion of Al into the Ag surface layers is favored. The behavior seen on the various surfaces is attributed to a competition between the preference for Ag atoms to favor an Al environment, while Al atoms tend to avoid the increased energy associated with having Ag neighbors. The energies of the various atomic configurations are then determined by how the two competing effects manifest themselves for the corresponding geometric arrangements considered.