Theoretical study of N2O adsorption and decomposition at regular and defect sites of MgO(001) surface

The adsorption of N2O at regular and defect sites of MgO (001) surface has been studied systematically using cluster models embedded in a large array of point charges by density functional method. The calculated results show that the MgO (001) surface with oxygen vacancies exhibits high catalytic reactivity toward N2O adsorptive-decomposition at variance with the regular MgO surface or the surface with magnesium vacancies. Much elongation of O-N bond of N2O after adsorption at oxygen vacancy site with O end of N2O down indicates that O-N bond has been broken with concurrent production of N-2, leaving a regular site instead of the original oxygen vacancy site (F center). Besides, the MgO (001) surface with magnesium vacancies hardly exhibits catalytic reactivity. It can be concluded that N2O dissociation is likely occurred at MgO (001) surface oxygen vacancy sites, which is consistent with the generally accepted viewpoint in the experiment.