The core structures of three-fold dissociated ½<111> screw dislocations, situated near to a mode-III crack-tip, were studied by means of molecular dynamics simulations; using the J2 potential. In the case of dislocations which were situated a few atomic distances away from the crack tip, the core transformation behaviour under stress was almost identical to that in a bulk crystal; except for the presence of a Volterra image-force. However, the effective Peierls stress which was felt by a dislocation ahead of a crack tip was significantly smaller than the bulk value.

Atomistic Simulation of Screw Dislocation Mobility Ahead of a Mode III Crack Tip in the BCC Structure. H.F.Zhang, A.H.W.Ngan: Scripta Materialia, 1999, 41[7], 737-42