Localized orbital approach to chemisorption. I. H on W(100)

Abstract

Atomic (s- and d-) orbitals and an atomic approximation to the potential are used in the chemical pseudopotential secular equation to calculate the covalent binding of an adsorbed monolayer on a transition-metal slab. After showing that the method provides a realistic description of the d-bands in bulk W and Pt the changes which accompany adsorption of hydrogen on W(100) in various surface arrangements are examined. Maximum coverage is found to correspond to occupation of all bridge sites on the W(100) surface ( beta1phase). Bridge sites also provide maximum covalent binding at lower coverage but energy differences between alternative sites are small ( approximately 0.2 eV per H-atom) and ionic effects may stabilize adsorption above atoms in the beta2phase.