First-principles calculations of intrinsic defects in Al₂O ₃

First-principles plane-wave pseudopotential calculations were performed to study electronic structures, structural relaxation, and energetics of intrinsic vacancies and interstitials in Al₂O₃. In the presence of the intrinsic point defects, extra levels appeared in the band gap. Considering various charge states for the intrinsic point defects, it was found that each point defect is most stable in its fully ionized state. From the formation energies of individual point defects, Schottky, O Frenkel, and Al Frenkel energies were also evaluated and were compared with previous results by experiment and static lattice calculations. Although previous static lattice calculations showed different relative stabilities of Schottky and Frenkel formation, depending on the choice of interatomic potentials, our calculations revealed that the relative values of formation energies are in the order of Schottky<Al Frenkel<O Frenkel, which is in good agreement with experimental data.