Systematics of adsorption near a step

Abstract

Local-density-functional (LDF) calculations show that on Al(331), a surface whose narrow (111)-like terraces are separated by (110)-like steps, a trivalent Al adatom is strongly attracted to step bottoms, while a monovalent H adatom prefers step edges. H-adatom potential energies in the three-fold terrace sites on Al(331) and Al(111) differ by only about 0.1 eV. This is because H atoms are small and must sit close to substrate atoms, where step effects are rapidly screened. Al adatoms, being larger, prefer the terrace sites of Al(331) by more than 0.25 eV.