Molecular dynamics study of the migration kinetics of asymmetric grain boundaries

Classical molecular dynamics (MD) simulations are commonly used to explore the migration of grain boundaries. Our previous research on low sigma symmetric boundaries has shown that at conditions of low driving forces as found in actual experimental setups and when going towards system sizes exceeding those commonly employed in MD a novel mechanism becomes operational that is based on mesoscopic island nucleation. In the present study we extend our research towards grain boundaries deviating from the perfect and symmetric arrangement to investigate the kinetics of asymmetric, defective boundaries. Such grain boundaries constitute in fact the majority of experimentally observed moving boundaries. We introduce defects by deviating the boundary plane from a symmetric equilibrium boundary. The results of the simulations show how the fundamental atomistic mechanisms change as the nucleation driven motion shifts towards a step propagating one.