A SELF-CONSISTENT SURFACE-GREEN-FUNCTION (SSGF) METHOD

We describe the basic aspects of a new, self-consistent Green-function method which allows to calculate the density of states, electron density, and related quantities for a localized perturbation (e.g. an isolated adsorbate or an intrinsic surface defect) at a crystal surface. The method is based on the density-functional theory and combines several ideas from recent theoretical developments, as, for example, from the layer-KKR Green-function method, from ab-initio pseudopotential theory, and from the self-consistent defect-Green-function method. Two applications of the method are presented (S on Pd(100) and Na on Al(100)) in order to demonstrate its efficiency and to address a recent controversial discussion concerning the nature of the bonding of alkali adsorbates on metals at very low coverage (THETA --> 0).