Stress-dependence of kinetic transitions at atomistic defects

SL Ball and KC Alexander and CA Schuh, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, 26, 015007 (2018).

DOI: 10.1088/1361-651X/aa9587

The full second-rank activation volume tensors associated with vacancy migration in FCC copper and HCP titanium as well as transition events in the Sigma 5 (2 1 0) grain boundary in copper are calculated and analyzed. The full tensorial results quantitatively illustrate how the conventional use of an activation volume scalar in atomistic studies of the kinetic processes of complex defects can miss important stress dependencies, in that neither hydrostatic pressure nor deviatoric stress dependencies can be considered alone as dominating the response. The results speak to the importance of anisotropies in the stress-dependence of atomistic kinetics, including crystal structure anisotropy, elastic anisotropy, and defect structure or migration-path anisotropies.

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