Computer simulation of 〈001〉 tilt grain boundaries in nickel oxide

Atomistic simulation methods have been used to calculate the structures end energies of a series of 〈001〉 symmetrical tilt grain boundaries in NiO. The configurations studied were all coincident twin boundaries, but the relaxation displaces the two crystal halves from the perfectly coincident structure. The (n 10) boundaries are all qualitatively similar, and can be considered as arrays of [100] dislocations. Boundaries such as (320) end (430) consist of [110] dislocations. The boundary energies very smoothly with angle, except for a cusp where the structure changes from [100] to [110] dislocations. All the boundaries are stable with respect to dissociation. The Coulomb interaction makes these boundaries qualitatively different from the analogous interfaces in f.c.c. metals. The significance of the structures for grain-boundary diffusion is discussed.