Electronic effects of light impurities on edge dislocation motion in iron at T = 0 K

The first principles discrete variational method is employed to study the effect of some light impurities, such as B, C, N and O, on the edge dislocation motion in bcc iron at T = 0 K. The results of the simulation to the dislocation motion show that a dislocation line, when crossing an atom on the slip plane, must surmount an energy barrier, and that the impurity atoms trapped in the dislocation core can raise this energy barrier. This indicates the resistance of the lattice and light impurities to dislocation motion. According to the degree by which the energy barrier is raised, C has the strongest, O the weakest and B and N a medium resisting effect, which may explain the solid solute hardening of B, C and N in iron. B, C and N also have strong site-competition abilities against O in the dislocation core as they do in the grain boundary. The interactions between the impurities and their first nearest neighbor Fe atoms play an important role in the above effect, while the 2p-3d hybridization is the major part of the bonding.