Scale transition using dislocation dynamics and the nudged elastic band method

Microstructural features such as precipitates or irradiation-induced defects impede dislocation motion and directly influence macroscopic mechanical properties such as yield point and ductility. Dislocation-defect interactions involve both atomic scale and long range elastic interactions. Thermally assisted dislocation bypass of obstacles occurs when thermal fluctuations and driving stresses contribute sufficient energy to overcome the energy barrier. The Nudged Elastic Band (NEB) method is typically used in the context of atomistic simulations to quantify the activation barriers for a given reaction. In this work, the NEB method is generalized to coarse-grain continuum representations of evolving microstructure states beyond the discrete particle descriptions of first principles and atomistics. This method enables the calculation of activation energies for a 1/2[111](11¯0) glide dislocation bypassing a [001] self-interstitial atom loop of size in the range of 4-10  nm with a spacing larger than 150  nm in α-iron for a range of applied stresses and interaction geometries. Further, the study is complemented by a comparison between atomistic and continuum based prediction of barriers.