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

The core structure of a screw dislocation in the diamond lattice has been c alculated with the Stillinger-Weber potential for the interatomic interacti on. The non-dissociated screw dislocation positioned at the centre of a uni t hexagon normal to the dislocation line is a stable configuration A. A per fect screw centred on a longer edge of the unit hexagon is also a stable co nfiguration B. Configuration B is more stable and has a lower energy than c onfiguration 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 geo metrical feature of configuration B explains the cross-slip observed in III -V compounds at low temperatures. The Peierls stress of the perfect screw d islocation 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.