The crystallographic aspects that governed the general features of the cores of <111> screw dislocations in body-centered cubic metals were considered. The analysis was performed by comparing the results of 2 atomistic calculations of dislocations in Mo. One was carried out by using many-body central force potentials, and the other by using bond-order potentials that included the angular dependence of the interatomic interactions. In both cases, the core spread onto three {110} planes of the [111] zone. However, in one case it was unique and invariant with respect to the <101>-type dyad; a symmetry operation of the body-centered cubic lattice. In the second case, 2 distinct configurations existed that were related by the dyad operation. The decision as to which of the structures was found depended upon interatomic interactions, and it was shown that the γ-surface for {110} planes could be used to predict the type of core spreading. It was then demonstrated that both core structures could lead to very similar responses, of the dislocation to applied stresses, since the strained crystal lost the original symmetry; in particular, the corresponding <101>-type dyad. The distinction between the 2 types of core therefore vanished.

Core Structure of Screw Dislocations in Body-Centred Cubic Metals - Relation to Symmetry and Interatomic Bonding. V.Vitek: Philosophical Magazine, 2004, 84[3], 415-28