Electronic Structure Calculation of MgO (001) Surface with Aggregated Oxygen Vacancies

The electronic structure of an MgO (001) surface with aggregated oxygen vacancies at the surface was investigated by using a density-functional embedded-cluster method using Mg45O x (x = 39−45) clusters and the B3LYP/CEP-121G level of calculation. The investigation found that the distribution of energy levels corresponding to oxygen-vacancy states strongly depends on the number and configuration of oxygen vacancies. Molecular orbitals of the oxygen vacancy states consist of orbitals at the vacancy sites and their neighboring magnesium ions. These orbitals can simply be modeled by orbitals formed from interacting pseudoatoms. A pseudoatom is an electronically neutral atom representing an oxygen vacancy and electrons of magnesium ions near the vacancy. With this model, an N-atom system having n vacancies can be modeled by n pseudoatoms. Interactions among oxygen vacancies in MgO were qualitatively reproduced by the interacting pseudoatoms model.