Modelling of electronic and structural strain effects in grain boundaries of semiconducting oxides

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The influence of mechanical stress conditions on the electronic conductivity of doped and undoped grain boundaries in piezoelectric oxides is investigated by means of electronic structure calculations based on density functional theory (DFT) and atomistic modelling. The calculations aim for modelling the chemical and structural reconstruction of grain boundaries (GB) of different orientations as function of mechanical strain, temperature and oxygen partial pressure. The goal is to simulate the influence of external strain on the electronic density of states within the GB. Here, it is of special interest, how mechanical and electrical fields couple to the distribution of dopants, open volume and the electronic structure of grain boundaries. Detailed examinations of bicrystal-arrangements for grain boundaries of different orientation (tilt and twist boundaries) upon uniaxial and multi-axial mechanical load are planned. Additionally, the influence of heat treatment under mechanical load on grain boundary properties as well as the characteristic time scales for structural rearrangement processes will be estimated by means of calculated activation barriers for diffusive transport of intrinsic and extrinsic defects in the area of mechanically loaded grain boundaries. In order to model the influence of microstructural parameters on the observed effects, molecular statics and molecular dynamics simulations base on classical interatomic potentials are planned. In perspective, the simulations aim to identify and to quantify those physical parameters, which are necessary to model the characteristics of mechanically tunable components