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 e ffect of some light impurities, such as B, C, N and O, on the edge dislocat ion motion in bcc iron at T=0 K. The results of the simulation to the dislo cation motion show that a dislocation line, when crossing an atom on the sl ip plane, must surmount an energy barrier, and that the impurity atoms trap ped in the dislocation core can raise this energy barrier. This indicates t he resistance of the lattice and light impurities to dislocation motion. Ac cording to the degree by which the energy barrier is raised, C has the stro ngest, O the weakest and B and N a medium resisting effect, which may expla in the solid solute hardening of B, C and N in iron. B, C and N also have s trong 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. (C) 2000 Elsevier Science B.V. All rights reserved.