Alkali metals adsorption on the Mg(0 0 0 1) surface

Density functional theory and a pseudopotential plane-wave approach are applied to study the structural properties and energetics of low-coverage of Na and K adatoms on the Mg(0 0 0 1) surface. The stability of the (2 × 2) structures formed by alkali atoms adsorbed in different sites is determined. We found that at coverage 0.25 monolayer a substitution of Na atom in place of one of the Mg surface atoms is energetically most favored. For K atoms adsorption the on-surface fcc-hollow sites are most favorable. This chemical trend is in line with that reported previously by Neugebauer and Scheffler for alkali metal adsorption on the Al(1 1 1) surface. The differences between the adsorption on these two different substrates are also discussed.