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

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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.