The (√3X√3) R30° sulfur over layer on the iridium(111) surface: A DFT study

Iridium (Ir) is used as a selective reducing exhaust gas catalyst in the lean-burn car engine technology. In this paper we investigated the energetics of adsorption of adatom sulfur on the iridium (111) surface for the (√3X√3) R30° structure at .33 monolayer coverage using first-principles calculations. We have calculated electronic structure and total energy for three possible sites i.e. on-top site, threefold site in the hollow(substrate atom located beneath) and threefold site in the hollow(vacancy located beneath). We found threefold site, with a vacancy located beneath it in the second layer, is the most stable which is in good agreement with the experimental results.