S and O adsorption on pure and Ge doped Ag(1 1 1)

We have studied the possibility of preventing the sulphur poisoning of silver surfaces by doping them with Ge. Our first principles calculations show that the presence of Ge at the topmost surface layer does not affect the adsorption characteristics of S much, yet Ge helps to bind oxygen much more strongly. We thus predict that Ge doping induces a protective O layer which helps to prevent the poisoning caused by sulphur.