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

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.

Impact on Students. The primary impact will be on the 50+ PhD students trained by the Centre. They will be high-quality computational scientists who can develop and implement new methods for modelling complex systems in collaboration with scientists and end-users, who are comfortable working in interdisciplinary environments, have excellent communication skills and be well prepared for a wide range of future careers. The students will tackle and disseminate results from exciting PhD projects with strong potential for direct impact. Exemplar research themes we have identified together with our industrial and international partners: (i) design of electronic devices, (ii) catalysis across scales, (iii) high-performance alloys, (iv) direct drive laser fusion, (v) future medicine exploration, (vi) smart nanofluidic interfaces, (vii) composite materials with enhanced functionality, (viii) heterogeneity of underground systems.

Impact on Industry. Students trained by HetSys will make a significant impact on UK industry as they will be ideally prepared for R&D careers to help to address the skills shortage in science and engineering. They will be in high demand for their ability to (i) work across disciplines, (ii) perform calculations that come along with error estimates, and (iii) develop well-designed software that other researchers can readily use and modify which implements novel solutions to scientific problems. More generally, incorporating error bars into models to take account of incomplete data and insufficient models could lead to significantly enhanced adoption of materials modelling in industry, reducing trial and error, and costly/time-consuming R&D procedures. The global market for simulation software is expected to more than double from now to 2022 indicating a very strong absorptive capacity for graduates. Moreover, a recent European Materials Modelling Consortium report identified a typical eight-fold return on investment for materials modelling research, leading to cost savings of 12M Euros per industrial project.

Impact on Society. Scarcity of resources and high energy requirements of traditional materials processing techniques raise ever-increasing sustainability concerns. Limitations on jet engine fuel efficiency and the difficulties of designing materials for fusion power stations reflect the social and economic cost of our incomplete knowledge of how complex heterogeneous systems behave. High costs of laboratory investigations mean that theory must aid experiment to produce new knowledge and guidance. By training students who can develop the new methodology needed to model such issues, HetSys will support society's long term need for improved materials and processes.

There will also be a direct impact locally and regionally through engagement by HetSys in outreach projects. For example we will encourage CDT students to be involved with annual 'Inspire' residential courses at Warwick for Year 11 girls, which will show what STEM subjects are like at degree level. CDT students will present highlights from projects to secondary-school pupils during these courses and also visit local schools, particularly in areas currently under-represented in the student body, in coordination with relevant professional bodies.

Impact on collaboration. Our international partners have identified the same urgent challenges for computational modelling. We will build flourishing links with research institutes abroad with long term benefit on UK research via our links to computational science networks. Shared research projects will strengthen links between academic staff and industry R&D personnel and across disciplines. The work will also lead to accessible, robust and reusable software. The Centre will achieve cross-disciplinary academic impact on the physical and materials sciences, engineering, manufacturing and mathematics communities at Warwick and beyond, and on the generation of new ideas, insights and techniques.