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

准确的材料缺陷演化能垒模型对于理解高性能合金中的许多过程是至关重要的，例如核反应堆屏蔽中辐射损伤的热演化。这个问题极具挑战性，因为它既需要缺陷核附近原子重排的量子力学精度，也需要足够大的系统来包括长程弹性响应。这个项目建立在一种新的嵌入方法上，使用非标准连续介质理论来确定边界条件，使直接模拟位错核上的缺陷-位错反应变得容易。在这个PHD项目中，反平面螺位错情况的原理证明实现将被扩展并与现有的QM/MM方法进行比较，并应用于预测三维位错过程的能垒，例如面心立方和体心立方金属(例如，Ni和W)中的扭结形核和推进以及裂纹扩展。该项目将涉及与合作调查人员和合作伙伴在主管的相关EPSRC补助金EP/R043612/1上进行合作，以用于原子模拟材料缺陷的边界条件，他们是伦敦大学学院的Richard Catlow教授和Alexey Sokol博士以及伊利诺伊大学香槟分校的Dallas Trinkle教授。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等研究课题保持一致。

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.