The dissociation of 60° and screw dislocations was modeled by combining isotropic elasticity theory and ab initio based tight-binding total-energy calculations. Both dislocations were found to dissociate with a substantial lowering of their line energies. In the case of the 60° dislocation, an energy barrier to dissociation was found. The core structure of a screw dislocation was investigated for so-called shuffle, mixed and glide cores. The latter was found to be the most stable undissociated screw dislocation. The glide motion of 90° and 30° partials was considered in terms of a process which involved the thermal formation and subsequent migration of kinks along the dislocation line. The calculated activation barriers to dislocation motion showed that the 30° partial was less mobile than was the 90° partial. High-resolution electron microscopy was performed on high-temperature high-pressure annealed natural brown diamond, and this permitted the core regions of 60° dislocations to be imaged. Most of the dislocations were dissociated. In some cases, undissociated 60° dislocations were also observed.

Dislocations in Diamond - Dissociation into Partials and their Glide Motion. A.T.Blumenau, R.Jones, T.Frauenheim, B.Willems, O.I.Lebedev, G.Van Tendeloo, D.Fisher, P.M.Martineau: Physical Review B, 2003, 68[1], 014115 (9pp)