Advanced Boundary Conditions to Enable Quantification of Uncertainty in Atomistic Simulation of Defects

材料缺陷演化过程中能量势垒的精确模型对于理解高性能合金的许多过程至关重要，例如核反应堆屏蔽层辐射损伤的热演化。这个问题极具挑战性，因为它既需要量子力学精度来重新排列缺陷核心附近的原子，又需要足够大的系统来包含远程弹性响应。该项目建立在一种新的嵌入方法上，使用非标准连续统理论来确定边界条件，从而在DFT水平上直接模拟位错核心的缺陷-位错反应。在这个博士项目中，将扩展反平面螺旋位错案例的原理验证实现，并与现有的QM/MM方法进行比较，并应用于预测fcc和bcc金属（如Ni和W）的扭结成核和推进以及裂纹扩展等三维位错过程的能量势垒。该项目将与共同研究人员合作，并与主管的EPSRC相关拨款EP/R043612/1关于材料缺陷原子模拟的边界条件的合作伙伴，即伦敦大学学院的Richard Catlow教授和Alexey Sokol博士以及伊利诺伊大学厄巴纳香槟分校的Dallas Trinkle教授合作。该项目与EPSRC的凝聚态物理、连续介质力学、数学分析、数值分析和材料表征的研究主题保持一致。

Accurate models for energy barriers involved in material defect evolution are essential to understand many processes in high performance alloys, for example thermal evolution of radiation damage in nuclear reactor shields. This problem is extremely challenging because it requires both quantum-mechanical precision for the rearrangement of atoms near the defect core and sufficiently large systems to include the long-range elastic response.This project builds on a new approach to embedding using non-standard continuum theories to determine boundary conditions, bringing direct simulations of defect-dislocation reactions at dislocation cores at the DFT level within reach. In this PhD project, a proof-of-principle implementation for the anti-plane screw dislocation case will be extended and compared with existing QM/MM approaches, and applied to predict energy barriers for 3D dislocation processes such as kink nucleation and advance in fcc and bcc metals (e.g. Ni and W) and crack propagation.The project will involve collaboration with co-investigators and partners in the supervisors' related EPSRC grant EP/R043612/1 on Boundary Conditions for Atomistic Simulation of Material Defects, namely Prof. Richard Catlow and Dr Alexey Sokol at University College London and Prof. Dallas Trinkle at the University of Illinois at Urbana Champaign.The project is aligned with EPSRC research topics of Condensed Matter Physics, Continuum Mechanics, Mathematical Analysis, Numerical Analysis and Materials Characterisation.