Atomic-level theoretical and experimental study of lattice dislocations in perovskites

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The project aims to investigate the structure and energetics of dislocations in ceramic oxide materials with mixed ionic-covalent bonding by means of atomistic simulations, electronicstructure calculations, and transmission electron microscopy. We will study structural and compositional features of dislocation cores and related planar defects (stacking faults, antiphase and grain boundaries) in perovskite compounds, namely SrTiO3, BaTiO3 and PbTiO3. First-principles density functional theory will be used to calculate properties of the extended defects with high accuracy and reliability. These results will serve further to validate empirical analytic potentials for electrostatic and repulsive ion-ion interactions. With such potentials, atomistic simulations of dislocation-core models consisting of large numbers of atoms will be carried out in order to adapt and apply approaches of continuum theory and atomistic simulation developed for dislocation cores of metals to simulations of ceramic materials with prevalent ionic bonding. Special care will be given to correct handling of long-range elastic as well as electrical boundary conditions. The atomistic structure and chemical composition of dislocation cores in SrTiO3 will be studied by transmission electron microscopy. These results will serve as an important reference for the atomistic simulations. We expect that our proposed investigations will significantly improve the scientific understanding of dislocations in perovskite materials and will help to clarify the influence of dislocations on functional properties of electro-active devices.