Density functional study of the Sigma 3 (111) [1(1)over-bar0] symmetrical tilt grain boundary in SrTiO3

Density functional supercell calculations were carried out by a mixed-basis pseudopotential method for the Sigma3 (111) [110] symmetrical tilt grain b oundary in strontium titanate, SrTiO3, as a prototype planar defect in an e lectroceramic material. A low grain boundary energy of 0.52 J m(-2) was obt ained. Minor structural relaxations compared to the coincidence site lattic e model are obtained close to the grain boundary plane by theory and previo us experiment. Within the Limits of the rather small supercell model employ ed in the calculations, the calculated geometric structure agrees well with the experimental one. An analysis of calculated local electron densities o f states shows that the perturbation due to the grain boundary is localized in the near vicinity of the boundary plane. From the present results for t he small supercell model, there is no evidence for the build-up of a space- charge layer at this highly ordered and undoped twin boundary in SrTiO3.