The non-degenerate core structure of a 1/2 < 111 > screw dislocation in bcc transition metals modelled using Finnis-Sinclair potentials: The necessary and sufficient conditions

It is shown that semi-empirical potentials for bcc metals based on the non-directional second-moment Finnis-Sinclair approximation are able to predict, as a matter of routine, the non-degenerate core structure for the perfect 1/2 < 111 > dislocation if they correctly describe the inter-string pair potential of a rigid multi-string Frenkel-Kontorova model for the corresponding ideal bcc lattice. We prove this by inspecting the previously published empirical potentials, and also by performing an extensive search in functional parameter space for an optimal parameterisation of the magnetic potential formalism for bcc ferromagnetic Fe.