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

采用基于密度泛函理论（DFT）和原子模型的电子结构计算方法，研究了机械应力条件对压电氧化物中掺杂和未掺杂晶界电子导电性的影响。计算的目的是模拟不同取向晶界随机械应变、温度和氧分压变化的化学和结构重构。目的是模拟外部应变对GB内状态电子密度的影响。在这里，它是特别感兴趣的，机械和电场如何耦合到掺杂剂的分布，开放体积和晶界的电子结构。计划在单轴和多轴机械载荷下对不同取向晶界（倾斜和扭转晶界）的双晶排列进行详细检查。此外，机械载荷下热处理对晶界性能的影响以及结构重排过程的特征时间尺度将通过计算机械载荷晶界区域内固有和外在缺陷扩散输运的激活势垒来估计。为了模拟微观结构参数对观察到的效应的影响，计划基于经典原子间相互作用势进行分子静力学和分子动力学模拟。从这个角度来看，模拟的目的是识别和量化那些物理参数，这些参数对于模拟机械可调谐部件的特性是必要的

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