Alkali adsorption on the Al(001) surface - A theoretical study

The chemisorption of Na on the Al(001) surface has been studied by 2D bandstructure calculations on slab models using a density functional STO-LCAO method. Two slab models of three and five layers of substrate atoms have been used. Overlayers of the structures p(2×2), c(2×2) and p(1×1), representing coverages of a quarter, a half and a full atomic monolayer of sodium atoms, respectively, have been investigated. The electronic structure of the adatoms and the charge transfer to the substrate are discussed. Satisfactory agreement with experiment is obtained for the adsorption induced change of the work function, correctly reproducing its monotonic character.