Undissociated screw dislocations in silicon: Calculations of core structure and energy

The stability of the perfect screw dislocation in silicon has been investigated using both classical potentials and first-principles calculations. Although a recent study by Koizumi et al. stated that the stable screw dislocation was located in both the 'shuffle' and the 'glide' sets of {111} planes, it is shown that this result depends on the classical potential used, and that the most stable configuration belongs to the 'shuffle' set only, in the centre of one (amp;1tilde;01) hexagon. We also investigated the stability of an sp² hybridization in the core of the dislocation, obtained for one metastable configuration in the 'glide' set. The core structures are characterized in several ways, with a description of the three-dimensional structure, differential displacement maps and derivatives of the disregistry.