Theory of alkali metal adsorption on close-packed metal surfaces

Results of recent density-functional-theory calculations for alkali-metal adsorbates on close-packed metal surfaces are discussed. Single adatoms on the (111) surface of Al and Cu are studied with the self-consistent surface Green-function method by which the pure adsorbate-substrate interaction may be analyzed. Higher coverage ordered adlayers of K on Al(111), Na on Al(111), and Na on Al(001) are treated using the ab initio pseudopotential plane-wave method which affords the prediction of coverage-dependent stable and metastable adsorbate geometries and phase transitions of the adsorbate layers. Together, these studies give insight and understanding into current key issues in alkali-metal adsorption, namely, the nature of the adsorbate-substrate bond at low coverage and the occurrence of hitherto unanticipated adsorbate geometries, and the associated electronic properties.