Hydrogen interactions with quasicrystalline Al-Pd-Mn surfaces

In this work we examine the interaction of molecular and atomic deuterium with the fivefold surface of an icosahedral ( i -) Al-Pd-Mn alloy using angle-resolved low-energy ion scattering under ultrahigh vacuum conditions. i -Al-Pd-Mn has been studied extensively and is known to form a laterally-bulk-terminated surface that is Al-rich. The density of Al atoms on the clean surface of fivefold i -Al-Pd-Mn is about that of Al(111) and hence we compare our results to studies of molecular and atomic hydrogen adsorbed on Al(111). We find that molecular deuterium does not adsorb or dissociate on i -Al-Pd-Mn, as on Al(111). Atomic D, however, readily adsorbs on both surfaces and on i -Al-Pd-Mn attenuates the scattering signals from Al, Pd and Mn substrate atoms. It thus appears that D chemisorbs on the outer layer of i -Al-Pd-Mn and bonds with Al atoms.