The ring hexavacancy, V6, had been found – by theoretical modelling - to be a particularly stable defect but had not been identified with any observed center. First-principles calculations were used here to deduce the structure and properties of 2 forms of V6H2 and to identify these defects with the trigonal optical centres, B41 and B711, which were known to contain two H atoms in equivalent and inequivalent sites, respectively. It followed, from the calculations, that V6 should also be optically active and it was identified with the B804 (J-line) center. This placed the acceptor level of V6 at Ec - 0.04eV.

Identification of the Hexavacancy in Silicon with the B804 Optical Center B.Hourahine, R.Jones, A.N.Safonov, S.Oberg, P.R.Briddon, S.K.Estreicher: Physical Review B, 2000, 61[19], 12594-7