New features of the core structure of screw dislocations in b.c.c. transition metals using non-local potentials

The core structure of a screw dislocation has been calculated using the Finnis and Sinclair n-body potentials. Three-dimensional relaxations have shown that the split-core solution is not a universal feature of any non-'pathological' potential and that inter-row potentials can be inadequate in bringing about the desired relaxation by a rigid-body-like rotation of the core necessary to initiate the displacements along the (111) direction. The first observation of a local variation in the pitch of the screw dislocation is reported and physical mechanisms which can account for the occurrence of the split-core configuration are analysed.