Core structure of a screw dislocation in the b.c.c. lattice and its relation to slip behaviour of α-iron

Using various interatomic row potentials, the atomistic structure of the core of a screw dislocation in the b.c.c. lattice has been computed. Stable core structure is either of a degenerate or a non-degenerate type depending on the shape of the interatomic row potential; the criterion for the core type is presented. A non-degenerate stable core is always accompanied by the existence of a metastable core structure of a split type. Characteristic features of slip in α-iron are reasonably interpreted based on the translation of a non-degenerate core over a camel-hump Peierls potential.