THEORY OF ALKALI-METAL ADSORPTION ON CLOSE-PACKED METAL-SURFACES

Results of recent density-functional-theory calculations for alkali-me tal adsorbates on close-packed metal surfaces are discussed. Single ad atoms on the (111) surface of Al and Cu are studied with the self-cons istent surface Green-function method by which the pure adsorbate-subst rate interaction may be analyzed. Higher coverage ordered adlayers of K on Al(111), Na on Al(111), and Na on A1(001) are treated using the a b initio pseudopotential plane-wave method which affords the predictio n of coverage-dependent stable and metastable adsorbate geometries and phase transitions of the adsorbate layers. Together, these studies gi ve insight and understanding into current key issues in alkali-metal a dsorption, namely, the nature of the adsorbate-substrate bond at low c overage and the occurrence of hitherto unanticipated adsorbate geometr ies, and the associated electronic properties.