Theoretical study of O2 adsorption on perfect and defect sites of MgO (001) surface

The adsorption of O-2 on the perfect and low-coordinated sites of MgO (001) surface has been studied with the finite cluster models embedded in a large array of point charges by density functional method. The point charge value was determined by self-consistence technique. Different kinds of possible models Of O-2 adsorbed on MgO (001) surface were calculated. The optimization of the geometry, calculation of the adsorption energy, vibrational frequency and analysis of the Mulliken population to those adsorption models were carried out. The results indicate that cationic site in the lowest coordinated corner is the most advantageous position for O-2 adsorbed on MgO (001) surface. The O-O bond strength is considerably weakened when O-2 lies flatly on the Mg atom at the corner(Mg-3c). The calculated adsorption energy of O-2 on MgO(001) perfect surface is in good agreement with experimental value. For O-2 adsorbed on the perfect surface embedded in nominal +/- 2.0 e point charges and on perfect surface using the bare cluster, the adsorption energies given in this paper show that they have a large deviation from the experimental value. The vibrational frequency of adsorbed O-2, which is experimentally difficult to measure due to the existence of isotope exchange, was also calculated.