Atomic and electronic structures of the 90° partial dislocation in silicon

Two reconstructions of the 90^∘{} partial dislocation core in silicon have been investigated using ab initio total-energy pseudopotential calculations. The asymmetric fourfold-coordinated configuration is shown to be stable and to be associated with only shallow states in the band gap. The symmetric quasi-fivefold-coordinated configuration is found to be metastable and to be associated with states that span the band gap. These results are reproduced with tight-binding Hamiltonians if the range of hopping integrals is restricted to include no more than four nearest neighbors.