Rigid body translations at grain boundaries

Abstract
Arguments are presented suggesting that the energy of a grain boundary may be minimized by the adoption of constant rigid body translations over facets of different inclination, continuously curved segments and/or adjacent structural units of different types within a given facet or curved segment. Consequently, a general high angle grain boundary should contain a network of dislocations bordering areas of constant rigid body translation. Observations by transmission electron microscopy of such translations in faceted and curved incoherent twin boundaries support the proposed ideas.