Molecular dynamics studies of the dissociated screw dislocation in silicon

Characterizing the motion of dislocations through covalent, high Peierls barrier materials is a key problem in materials science, while despite the progress in experimental studies the actual observation of the atomistic behaviour involved in core migration remains limited. We have applied a hybrid embedding scheme to investigate the dissociated screw dislocation in silicon, consisting of two 30° partials separated by a stacking fault ribbon, under the influence of a constant external strain. Our 'learn on the fly' hybrid technique allows us to calculate the forces on atoms in the vicinity of the core region using the tight binding Kwon potential, whilst the remainder of the bulk matrix is treated within a classical approximation. Applying a 5% strain to the dissociated screw dislocation, for a simulation time of 100 ps at a temperature of 600 K, we observe movement of the partials through two different mechanisms: double kink formation and square ring diffusion at the core. Our results suggest that in these conditions, the role of solitons or anti-phase defects in seeding kink formation and subsequent migration is an important one, which should be taken into account in future studies.