Ab initio calculations of rigid-body displacements at the Sigma 5 (210) tilt grain boundary in TiO2

Through extensive ab initio total energy calculations of the Sigma 5 (210) grain boundary in TiO2 (rutile), the remarkably large rigid-body contractio ns found by high resolution electron microscopy and Z-contrast imaging are explored. Unlike previous calculations, this work emphasizes the importance of the displacements of the two halves of the bicrystal towards one anothe r. Previous experimental work suggests that the stochiometry and ionic char ges at the boundary are preserved at their bulk values and therefore vacanc ies and impurities within the grain boundary core were not considered. The calculations predict no significant rigid-body contraction or expansion. Th e implications of this result for both computational and experimental studi es of rigid-body displacements at grain boundaries are discussed.