Atomistic structure of Σ=3, (111) grain boundaries in strontium titanate

This paper presents the results of experimental and theoretical studies on the atomistic structure of Sigma = 3, (111) grain boundaries in SrTiO3 (strontium titanate). By means of high-resolution transmission electron microscopy (HRTEM) we have imaged the structure of such gain boundaries in cross-sectional view, using specimens that we prepared from a macroscopic SrTiO3 bicrystal. By quantitative evaluation of HRTEM images that we recorded along the common [110] direction of the two adjoining half crystals we hale determined the positions of the atom (ion) columns near the grain boundary plane with an average precision of 0.015 nm. We compare the experimental structure with model structures we have obtained by molecular statics calculations, employing empirical potentials. The equilibrium structure obtained bg thf calculations reproduces the characteristic features of the experimental grain boundary structure. Concerning the atom positions close to the grain boundary plane. however, the theoretical structure and the experimental structure exhibit significant discrepancies, which we discuss at the end of this paper.