First-principles calculations of the energy barrier to dislocation motion in Si and GaAs

The single kink formation and migration energies Fₖ and Wₘ of 90^∘{} glide partial dislocations in Si and GaAs are calculated using an ab initio local density-functional cluster method. Kink migration occurs via a concerted exchange of an atom at a dislocation core with one of its glide plane nearest neighbors. By constraining these atoms to sit in high-energy positions and relaxing a surrounding cluster of atoms, sufficient points in configuration space can be sampled for the energy barrier for the first step in kink pair formation to be estimated. By including an estimate of the elastic energy of the interaction of kink pairs, the single kink formation energy is calculated. It is found that Fₖ and Wₘ for Si are 0.1 and 1.8 eV, respectively. For the 90^∘{} {α} glide partial in GaAs, these quantities are 0.07 and 0.7 eV, respectively, and 0.3 and 1.1 eV for {β} partials.