Multiscale modelling of materials chemomechanics: from stress corrosion cracking to catastrophic brittle fracture

Fracture is one of the most challenging ‘multi-scale’ problems to model: since crack propagation is driven by the concentration of a long-range stress field at an atomically sharp crack tip, an accurate description of the chemical processes occurring in the small crack tip region is essential, as is the inclusion of a very large model systems. Both these requirements can be met by combining a quantum mechanical description of the crack tip with a classical atomistic model that captures the long-range elastic behaviour of the surrounding crystal matrix. Examples of the application of these techniques to fracture problems include: low-speed dynamical fracture instabilities in silicon [1]; interactions between moving cracks and material defects such as dislocations or impurities [2]; the crossover from thermally activated to catastrophic fracture; very slow crack propagation via kink formation and migration; chemically activated fracture, where cracks advance under the concerted action of stress and corrosion by chemical species such as oxygen or water [3].

[1]. J. R. Kermode et al., Nature 455, 1224-1227 (2008).
[2]. J. R. Kermode, et al., Nat. Commun. 4, 2441 (2013).
[3]. A. Gleizer et al. Phys. Rev. Lett. 112 115501 (2014).