Calculated structures and energies of grain boundaries in alpha -Al sub 2 O sub 3

Static-lattice calculations of the energies and structures of {10 minus 1n} (n=0, 1, and 4) and {0001} grain boundaries in alpha -Al sub 2 O sub 3 using three different potentials are reported. The energies of boundaries perpendicular to the < 0001 > direction are 0.3-0.9 J center dot m sup - sup 2 . These compare favorably to experimental values, and results are not sensitive to the choice of potential. Energies of the other boundaries depend on the potential, but their relaxed structures do not. Using the most reliable potential, the energies of boundaries studied by HREM are 1-1.7 J center dot m sup - sup 2 . Simulated images of the calculated structures compare favorably with HREM micrographs of these boundaries. 38 refs.