CALCULATED STRUCTURES AND ENERGIES OF GRAIN-BOUNDARIES IN ALPHA-AL2O3

Static-lattice calculations of the energies and structures of (10 $$($ ) over bar 1n) (n = 0, 1, and 4) and (0001) grain boundaries in alpha- Al2O3 using three different potentials are reported. It was found that the energies of boundaries perpendicular to the (0001) direction vary between 0.3 and 0.9 J.m(-2). These compare favorably to experimental values, and the results are not sensitive to the choice of potential. The energies of the other boundaries do depend on the potential, but t heir relaxed structures do not. Using the most reliable potential, the energies of boundaries which have been studied by high-resolution ele ctron microscopy range from 1.0 to 1.7 J.m(-2) Simulated images of the calculated structures compare favorably with high-resolution electron microscope micrographs of these boundaries.