First-principles density-functional calculations were performed for basal-plane stacking faults in sapphire (α-phase Al2O3). The present results confirmed the predictions of empirical atomistic studies, where these faults were found to have high energies. Examination of the cation-layer stacking sequences along [00•1] showed that important changes in the Al-Al coordination occurred; with respect to the bulk, several cations have additional or no cation nearest neighbours in adjacent basal cation layers. The obtained generalized stacking-fault energies for displacement paths along the close-packed <1010> directions of the oxygen sub-lattice are discussed in connection with existing theories of basal slip and twinning.

Density-Functional And Shell-Model Calculations of The Energetics of Basal-Plane Stacking Faults In Sapphire. A.G.Marinopoulos, C.Elsässer: Philosophical Magazine Letters, 2001, 81[5], 329-38