Theoretical study on Al_nO₂ (n = 1-10) clusters and O₂ adsorption on the Al(111) surface

The structural properties of neutral and ionic Al_nO₂ (n = 1-10) clusters have been systematically investigated using the density functional method B3LYP with a standard 6-311+G(d) basis set. The calculated results show that in the Al_nO₂⁺, Al _nO₂, and Al_nO₂^- (n ≥ 3) clusters, O atoms tend to penetrate into the aluminum clusters with some Al atoms moving outward. The binding energies and natural charges populations indicate that the oxygen-etching is generally stronger in the order Al _n⁺ < Al_n < Al_n^- for n < 3, and Al_n⁺ > Al_n > Al _n^- for n ≥ 3. To further understand the mechanism of interaction between Al and O₂, the adsorption of O₂ on the Al(111) surface was studied using the density functional theory with plane wave pseudopotential method. The calculated results are consistent with the experimental observation that the O₂ molecule would dissociate on the Al(111) surface and be adsorbed in adjacent hollow sites, forming a local structure of Al₃O-Al₃O.