Single neutral and positively charged O vacancies (F and F+ centers) in α-Al2O3 were investigated by using the super-cell model at the Hartree-Fock and density functional theory level and the cyclic cluster model implemented in the semi-empirical MSINDO method. Results of super-cell and cyclic cluster calculations for the cohesive energy of the perfect Al2O3 crystal were compared with the experimental value for the heat of atomization. The defect formation energy of the unrelaxed F center was calculated with the super-cell model. The super-cell model was used to calculate the defect formation energy of the F and the F+ centers. Relaxation effects for the nearest neighbors and the next-nearest neighbors of the F and F+ centers were investigated. The obtained values were compared to other theoretical literature data.

First-Principles Periodic and Semi-Empirical Cyclic Cluster Calculations for Single Oxygen Vacancies in Crystalline Al2O3. F.Janetzko, R.A.Evarestov, T.Bredow, K.Jug: Physica Status Solidi B, 2004, 241[5], 1032-40