MECHANISMS OF ISLAND FORMATION OF ALKALI-METAL ADSORBATES ON AL(111)

Using density functional theory total-energy calculations we investigate the chemisorption of Na and K alkali metals on the (111) surface of aluminum from very low coverages (THETA = 1/16) up to a full monolayer. The calculations predict site changes of the adsorbate atoms, as well as a condensation into islands with increasing coverage. Some processes are activated, which implies a possibly irreversible temperature dependence. This is shown to have important consequences for the coverage dependence of the work function change.