Complex evolution of dislocation core structure in a process of motion: model analysis with ab-initio parameterization

We extend the Peierls-Nabarro (PN) model to eliminate the "continuum" appro ximation for the misfit energy, and use it to analyze features of the evolu tion of the dislocation core structure under various stress conditions (gli de and Escaig stress). We show that the core may assume competing multiple structures with their marked dependence on the dislocation axis position. A s we demonstrate for ordinary dislocations in fee Ir and the ordered Ll(0) CuAu calculated using ab-initio generalized stacking fault energies, these lattice discreteness effects, missing in the original PN model, significant ly affects the evolution of the dislocation under stress. In particular, th ese effects may result in the ladder-like dependence of the partial separat ion under Escaig stress conditions, and dramatic changes in the shape and a mplitude of the Peierls barrier. Thus, we find that lattice discreteness ef fects can be significant not only in ordered alloys with a deep Peierls val ley but also in fee metals under stress and futher, these effects result in the evolution of dislocation structure which is more complex than previous ly thought. (C) 2001 Published by Elsevier Science B.V.