SURFACE MODELS FOR GAMMA-AL2O3 FROM MOLECULAR-DYNAMICS SIMULATIONS

Molecular dynamics simulations for gamma-Al2O3 and La3+-doped gamma-Al2O3 crystals have been performed. From bulk simulations a description of the crystal-terminating layers in both doped and pure alumina solids is reported. The molecular dynamics simulations allow us to describe systematically for the first time the surface of the gamma-Al2O3 crystal, taking into account the actual stoichiometry of the solid. This description results in a model in which the number of different surface sites is increased with respect to the previously reported models. The number of different surface sites may account for the IR spectra of hydroxy groups adsorbed on gamma-Al2O3.