Small gold species at hydroxylated alumina surfaces. A computational study using embedded-cluster models of α-Al2O3(0001)

We calculated equilibrium structures for adsorption complexes of gold monomers, dimers, and trimers on a α-Al2O3(0001) model surface, partially covered by μ1 and μ3 hydroxyl groups. We applied a scalar-relativistic gradient-corrected density functional method to cluster models of the support that were embedded in an elastic polarizable environment. The most stable structures, with calculated adsorption energies in the range 0.81–1.74 eV, feature coordination bonds to surface μ1-OH group and are 0.24–0.79 eV more stable than the corresponding Aun complexes on a dehydrated surface. Isomeric rearrangements of the most stable complexes are hindered by barriers of 0.65–1.08 eV.