Computer simulation of general grain boundaries in rocksalt oxides

The structures and energies of a series of tilt grain boundaries and corres ponding surfaces were calculated to obtain a general relationship between t he grain boundary energy and the tilt angle for NiO and MgO. We show that t he simple elastic expressions for the grain boundary energy give reasonable results for low-angle grain boundaries. We investigate the assumptions tha t lie behind thermal grooving experiments and show that the torque terms sh ould be large, even when far from a major pole [the (100), (110), or (111) directions]. However, the measured angles agree better with the calculation s when torque terms are ignored. We discuss this effect in terms of facetin g and oxidation of the surface. [S0163-1829(99)06627-8].