Nature of Dislocations in Silicon

Interaction between two partial 90 degrees edge dislocations is studied with atomic-scale simulations using the effective-medium tight-binding method. A large separation between the two dislocations (up to 30 Angstrom), comparable to experimental values, is achieved with a solution of the tight-binding Hamiltonian that scales linearly with the number of atoms. The partial edge dislocation is found to be very accurately described by the Peierls-Nabarro dislocation model, with generalized stacking-fault restoring forces, as reflected both in the interaction energy and in the displacement field. An asymmetric core reconstruction provides fourfold coordination, making Si behave elastically down to atomic distances.