It was recalled that a recent paper had tentatively attributed 2 new infra-red bands, at 914 and 1000/cm in neutron irradiated Czochralski-grown material, to a [VO+Oi] structure that was suggested to develop as an intermediate stage in the conversion of a VO center to a VO2 complex during heat treatment. A further investigation was made here of the [VO+Oi] structure, and of the formation of intermediate defects. Semi-empirical calculations were also made of the localized vibrational mode frequencies of the [VO+Oi] defect. The results were consistent with experimental observations.

C.A.Londos, N.Sarlis, L.G.Fytros, K.Papastergiou: Physical Review B, 1996, 53[11], 6900-3