Atomic-scale study of nucleation of dislocations from fcc-bcc interfaces

Using atomistic simulations, we reveal the role of the atomic interface structure on the nucleation of glissile dislocations from a low-energy, atomically flat, incoherent face-centered cubic-body-centered cubic interface with a Kurdjumov-Sachs orientation relationship. Several loading states are simulated to systematically probe the selection of slip systems. Contrary to conventional expectation, the preferred nucleation sites are not always associated with pre-existing misfit dislocations, and the preferred slip systems are not determined solely by the Schmid factor. Amongst the two or more systems that may be geometrically favored, the activated slip system depends on the structure of the nucleation site. The system-site combination is such that the dislocation deposited in the interface after the nucleation event lowers the interfacial energy and has a relatively low self-energy. The fundamental correlations established here apply to interfaces of other orientation relationships that are also flat and have spatially non-uniform shear resistance.