Prof. James Kermode (Warwick University, UK)

Multiscale Modelling of Materials Chemomechanics
When Jan 23, 2017
from 02:00 PM to 03:00 PM
Where LR8
Contact Name
Contact Phone 01865-283446
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‘Chemomechanical’ processes involving complex and interrelated chemical and mechanical processes that originate at the atomic scale often determine the ultimate behaviour of materials. Fracture and dislocation creep are prominent examples, and remain some of the most challenging ‘multi-scale’ modelling problems, typically requiring both an accurate description of chemical processes and the inclusion of very large model systems.
I will explain how these requirements can be met simultaneously by combining a quantum mechanical description of crack tips and/or dislocation cores with a classical atomistic model that captures the long-range elastic behaviour of the surrounding crystal matrix, using a QM/MM (quantum mechanics/molecular mechanics) approach such as the `Learn on the Fly’ (LOTF) scheme.
The situation is further complicated when the relevant failure processes are also rare events, e.g. thermally activated crack propagation or dislocation climb. While QM/MM schemes help to address multiple length scales, they don’t do much to address the timescale issue. I will demonstrate that kinetic Monte Carlo models based on barriers computed from first principles offer one solution, and describe a novel machine learning implementation of the LOTF scheme which reduces the number of expensive QM calculations to provide another. Methodological aspects will be illustrated with applications, focussing in particular on slow processes such as thermally or chemically activated fracture.