Nucleation of elementary $\{\bar {1}\,0\,1\,1\}$ and $\{\bar {1}\,0\,1\,3\}$ twinning dislocations at a twin boundary in hexagonal close-packed crystals

In this paper, we study the kinetics and energetics involved in the nucleation and propagation of and twinning dislocations (TDs) in Mg using atomistic simulations. We demonstrate that for both twins, a 2-layer TD of mixed character nucleates as a result of the interaction of a basal dislocation with a twin boundary. The favorability of the 2-layer TD over a 4-layer TD of edge character can be explained by its greater mobility. The twin boundary likely translates by nucleating and propagating 2-layer TDs with opposite-signed screw components in equal amounts on average.