Abstract
We report a significantly stronger suppression of the phonon contribution to the thermal conductivity in VOx than can be accounted for by disorder of the 16% atomic vacancies present in VO. Since the transition from localized to itinerant electronic behavior is first order and has been shown to be characterized by bond length fluctuations in several transition-metal oxides with the perovskite structure, we propose that cooperative V–V bond length fluctuations play a role in VO similar to the M–O bond length fluctuations in the perovskites. This model is able to account for the strong suppression of the thermal conductivity, the existence of a pseudogap confirmed by thermoelectric power, an anomalously large Debye-Waller factor, the temperature dependence of the magnetic susceptibility, and the inability to order atomic vacancies in VO.