Differences between Finnis-Sinclair potentials and bond-order potentials (BOPs) were considered while studying ½〈111〉 screw dislocations in body-centered cubic transition metals; specifically Mo and W. These two types of potentials differ in that the former was central-force, whereas the latter include angular bonding. The cores of ½〈111〉 screw dislocations have two variants, one invariant with respect to the 〈101〉 diad and the other not. Hence, the latter core was degenerate. The BOPs always lead to the invariant type, whereas for Finnis-Sinclair potentials both variants occur. However, the symmetry of the core does not play a decisive role in the glide of dislocations. It was the description of interatomic forces that governs both the core structure and the glide behaviour of dislocations. The general characteristics of dislocation glide, the twinning-anti-twinning asymmetry and a lower Peierls stress for tension than compression were the same for both types of potentials. Whereas the results obtained with BOPs were similar for the two cases studied, Finnis-Sinclair potentials lead to a broader variety. Particularly, the slip plane at 0K was always {110} for BOPs but it was either {110} or {112} for Finnis-Sinclair potentials. The reason was that, in the latter case, the core configuration and core transformations were less constrained than in the former case. Hence, in body-centered cubic transition metals the BOPs were a more reliable description of atomic interactions than Finnis-Sinclair potentials, but when the d band does not play any important role, the Finnis-Sinclair potentials were fully applicable.

Directional Versus Central-Force Bonding in Studies of the Structure and Glide of ½<111> Screw Dislocations in BCC Transition Metals. R.Gröger, V.Vitek: Philosophical Magazine, 2009, 89[34-36], 3163-78