Comment on the electronic structure of the neutral vacancy in silicon

From a comparison of three calculations, we conclude that the unrelaxed vacancy in Si introduces a T₂ bound level in the gap and two A₁ resonances in the valence band. The lower one, in the first minimum of the density of states, is only weakly localized and the other, near the valence-band edge, corresponds to the symmetric combination of the dangling bonds. Preliminary results for the relaxed vacancy are also discussed.