The bonding and diffusion of Ba adatoms on the (001) surface were studied by using first-principles density-functional calculations. It was found that the favourable bonding site of the adatom was the 4-fold site in the trough between dimer rows. The bonding between the Ba adatoms and the surface was shown to be only slightly ionic in character; with a small charge transfer from Ba to the substrate, and with a large covalent component. The calculated jumping rates revealed a strongly anisotropic diffusivity of Ba on the surface.

Bonding and Diffusion of Ba on a Si(001) Reconstructed Surface J.Wang, J.A.Hallmark, D.S.Marshall, W.J.Ooms, P.Ordejón, J.Junquera, D.Sánchez-Portal, E.Artacho, J.M.Soler: Physical Review B, 1999, 60[7], 4968-71