The core structure of a 1/3〈1123〉 screw dislocation in h.c.p. metals

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Abstract
Atomistic calculations are made for a 1/3〈1 123〉 screw dislocation, using a truncated Lennard-Jones (12–6) potential. A variety of core configurations are formed depending on initial conditions. They can be interpreted as combinations of two types of elementary structures; one corresponds to an extension of the core along {1011}, and the other along 〈1122〉 planes, each bounded by partial dislocations with the Burgers vectors b/2 (= 1/6〈1 123〉). The fault energies on the {1011} and {1122} planes are almost the same, which is consistent with the appearance of various core configurations. The planar fault bounded by partials is not a simple stacking fault but has transition layers, which are caused by shuffling movements of atoms normal to the fault vector. The shear displacement accompanying the fault, however, occurs stepwise at the fault and the partials are not zonal. This is in sharp contrast to the dissociation models for the dislocation so far proposed.