Prediction of a {1122} hcp stacking fault using a modified generalized stacking-fault calculation

We present a new approach for calculating generalized stacking-fault energies, which allows for in-plane relaxation of atoms. When applied to the {112} slip plane in hcp materials, our approach predicts that a stable stacking fault occurs, associated with a slip of 1/6 (11 ) ≡ ½ (c + a). This is consistent with the edge dislocation with b = (c + a) breaking into two partial dislocations, each with b = 1/2 (c + a), observed in previous simulations of the dislocation cores. The resulting generalized stacking-fault energy profile may be useful in understanding the competition between {112} (11 ) twinning (observed in Zr and Ti) and the related slip mode, observed in Mg, Co and Zn.