ALKALI-METAL ADSORBATES ON ALUMINUM (111) - THE INTERPLAY AND COMPETITION OF ADSORBATE SUBSTRATE AND ADSORBATE-ADSORBATE INTERACTIONS

We investigated the chemisorption of Na and K alkali-metal atoms on the Al(111) surface from very low coverages (THETA = 1/16) up to a full monolayer. The calculations predict site and bond-length 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 unexpectedly complex behavior of the adsorbate layer is shown to have important consequences on the coverage dependence of the work function.