Transition Metal Atoms on Oxide Supports Density Functional Calculations

摘要

The adsorption properties of Cu, Ag, Ni, and Pd atoms on O2-, Fand F+ sites of MgO, CaO, SrO, and BaO (001) surfaces have been studied by means of density functional calculations. The examined dusters were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The adsorption properties have been analyzed with reference to the basicity and energy gap of the oxide support in addition to orbital interactions. While the free Ni d(9)s(1) triplet ground state is preserved on adsorption on the O2- sites of MgO, CaO, and SrO surfaces, it is no longer preserved on the O2- site of BaO. For all adsorbates considered, adsorption is found to be stronger on F+ sites compared with regular O2- sites. While on the O2- site, Pd and Ni form the most stable complexes, on the F site, Pd and Cu form the most stable counterparts. On the F+ site, die single valence electron of Cu and Ag atoms couples with the unpaired electron of the vacancy forming a covalent bond. As a result, the adsorption energies of these atoms on the F+ site are stronger than those on the F and O2- sites. The adsorption properties correlate linearly with the basicity and energy gap of the oxide support in addition to orbital interactions. (C) 2008 Wiley Periodicals, Inc. Int J Quantum Chem 109: 1094-1102, 2009