Core structure of a screw dislocation in a diamond-like structure

The core structure of a screw dislocation in the diamond lattice has been calculated with the Stillinger-Weber potential for the interatomic interaction. The non-dissociated screw dislocation positioned at the centre of a unit hexagon normal to the dislocation line is a stable configuration A. A perfect screw centred on a longer edge of the unit hexagon is also a stable configuration B. Configuration B is more stable and has a lower energy than configuration A. Dissociated configurations of width w = na (a is the repeat distance in the slip direction and n = 1, 2, 3,…) are also stable. The geometrical feature of configuration B explains the cross-slip observed in III-V compounds at low temperatures. The Peierls stress of the perfect screw dislocation is 0.044G, where G is the shear modulus. This value corresponds to the experimental values of III-V compounds deduced from the temperature dependence of the critical shear stress at low temperatures.