It was noted that nano-scale atomistic simulations could be used to study the cross-slip of a dissociated screw dislocation in a face-centered cubic metal, without suffering from the limitations that were imposed by elasticity theory. Attention was focussed on various dislocation configurations which were relevant to cross-slip via the Friedel-Escaig cross-slip mechanism. The stress-free cross-slip activation energy, and the activation length for this mechanism, were determined. It was shown that the 2 constrictions which were necessary for cross slip in the Friedel-Escaig cross-slip mechanism were not equivalent, and that a dislocation configuration with just one of these constrictions was energetically favored over 2 parallel Shockley partials. The effect of having the dislocation perpendicular to a free surface was investigated. The results were in qualitative agreement with transmission electron microscopic observations and with the predictions of linear elasticity theory, which involved recombination or repulsion of the partials near to the free surface. This recombination at the free surface was expected to be important in the context of cross-slip because it permitted, by itself, the creation of an energetically favorable constriction. It was also observed that there was a strong preference for the partials to be in a glide plane which was parallel to the surface step. Simulations were performed of 2 screw dislocations of opposite signs. One simulation led to surface-nucleated cross-slip, followed by the annihilation of the 2 dislocations. It was possible to monitor the annihilation process and thus monitor the details of dislocation reaction during annihilation.

Simulations of the Atomic Structure, Energetics and Cross-Slip of Screw Dislocations in Copper T.Rasmussen, K.W.Jacobsen, T.Leffers, O.B.Pedersen: Physical Review B, 1997, 56[6], 2977-90