Quantitative evaluation of vacancy formation energy in metal oxides

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Formation energies of neutral and charged oxygen vacancies in MgO, ZnO, A12O3, In2O3 and SnO2 have been calculated by a first principles plane-wave pseudopotential method. Two kinds of polymorphs, i.e., an ordinary phase and a high-pressure or a hypothetical negative pressure phase, have been chosen in order to see the effects of crystal structure. Theoretical calculations of vacancy-solute interactions in the selected oxides have also been examined. In conjunction to the theoretical investigations, positron lifetime experiments on Al-doped MgO samples have been made. The experiments clearly confirmed the formation of Mg-vacancies whose concentration is proportional to the amount of Al dopants, which is perfectly consistent to the theoretical predictions.The combination of first principles calculations and positron lifetime experiments should be a very powerful tool for investigation of defects in ceramic materials in general.