An elastic perfect edge dislocation, with a (c+a) Burgers vector, was introduced into a crystal which was then relaxed by using molecular dynamics methods and a Lennard-Jones type of pair potential. It was found that 2 types of core were stable at 0K. One was a perfect dislocation, and the other was two ½(c+a) partial dislocations. Whereas the core that spread into two ½(c+a) partial dislocations remained stable at higher temperatures, the core of the perfect dislocation extended parallel to the basal plane. The changes in these core structures which occurred upon applying a shear stress were also investigated. The two ½(c+a) partial dislocations glided separately on the slip plane. On the other hand, the extended core emitted a ½(c+a) partial dislocation and expanded a stacking fault, with increasing stress, while the remainder of the dislocation did not move. The results suggested that the (c+a) edge dislocation glided on the plane as two ½(c+a) partial dislocations, and became sessile due to a change in core structure. It was suggested that such a change in core structure, from glissile to sessile, caused the anomalous temperature dependence of the yield stress which was observed in hexagonal close-packed metals.

Molecular Dynamics Simulations of the (c+a) Edge Dislocation Core Structure in an Hexagonal Close-Packed Crystal. S.Ando, K.Takashima, H.Tonda: Materials Transactions, 1996, 37[3], 319-22