Spin-density study of the silicon divacancy

The possible charge states of the silicon divacancy V₂ are studied using the local spin-density pseudopotential method. The ionic coordinates are relaxed without any symmetry constraints. We obtain the formation and binding energies as well as the ionization levels from total-energy calculations and use them to discuss several experiments. We find using the 216-atom-site supercell that V₂⁰ and V₂^- have a ``mixed'' structure that includes both pairing and resonant-bond characters, V₂⁰ being more of the pairing type and V₂^- more of the resonant-bond type.