Role of Schottky disorder on the stability and structure of (100) twist grain boundaries in NiO

Recent calculations on (100) coincidence-site lattice (CSL) twist boundaries in the NaCl structure showed that without point defects these boundaries are only marginally stable. Following an earlier suggestion that point defects are the likely source for the considerable stability of these boundaries observed experimentally for MgO and NiO, Tasker and Duffy showed recently that the creation of a Schottky pair can, indeed, stabilize a (100) twist boundary in NiO. A variety of configurations in which one or more Schottky pairs were created in the perfect coincidence-site lattice (CSL) or anti-CSL unit cell are investigated. It is concluded that many metastable structures may exist which differ mainly with respect to their different interfacial mass densities and the relative translation of the two halves of the bicrystal.