Atomic Structure of Symmetric Tilt Grain Boundaries in NiO

Abstract

High-resolution electron microscopy shows the coexistence of several distinct core structures for coincident-site lattice boundaries in NiO bicrystals near $\ensuremath{\Sigma}=5, (310)$, and $\ensuremath{\Sigma}=13, (510)$, where $\ensuremath{\Sigma}$ is the reciprocal density of coincident lattice sites. Lattice expansion perpendicular to the $\ensuremath{\Sigma}=5$ grain boundaries is considerably smaller than calculated theoretically. Structural units in boundaries near $\ensuremath{\Sigma}=13, (510)$ exhibit translations normal to the grain-boundary plane, resulting in a rumpling of the interface on an atomic scale. Our observations suggest the presence of a high concentration of Schottky pairs in the grain boundaries.