The disordered vanadium monoxide VOx contains oxygen vacancies, metal vacancies and metal interstitials. The clustering and ordering of these defects has been studied throughout the composition range VO0.78–VO1.27 using electron diffraction, especially diffuse scattering due to defect ordering.

The concentration of V atoms at interstitial tetrahedral sites in VO1.23 above the ordering temperature has been determined through structure-factor measurements. Using an electron diffraction method which utilizes the splitting of weak Kikuchi lines near their crossing with strong bands, the 002 structure factor has been determined to within 3% accuracy. The value obtained is explained by the existence of a fraction of interstitial atoms close to that of the ordered phase. This supports the assumption that the defect cluster typical of the ordered phase persists above the ordering temperature.