Density functional study of the Σ3 (111) [1bar10] symmetrical tilt grain boundary in SrTiO3

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Abstract
Density functional supercell calculations were carried out by a mixed-basis pseudopotential method for the Σ3 (111) [10] symmetrical tilt grain boundary in strontium titanate, SrTiO3, as a prototype planar defect in an electro-ceramic material. A low grain boundary energy of 0.52 J m-2 was obtained. Minor structural relaxations compared to the coincidence site lattice model are obtained close to the grain boundary plane by theory and previous experiment. Within the limits of the rather small supercell model employed in the calculations, the calculated geometric structure agrees well with the experimental one. An analysis of calculated local electron densities of 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 the 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.