Abstract
We review first-principles calculations of dislocation core structure in diamond, and draw out similarities with and differences from silicon. Primary differences are in hybridization changes in carbon and in the different behaviour of H interacting with dislocations. In both materials, condensation of a homogeneous distribution of H atoms should result, first, in formation of small H aggregates with the appearance of a glide dislocation dipole and, second, in formation of larger platelets based on the half-stacking-fault model.