X-ray diffraction study of metallic VO2

Refinement of the crystal structure of VO₂ at 360 and 470 K in the metallic rutile phase shows that both the vanadium and oxygen thermal displacements are larger than those found in rutile phases of TiO₂ and CrO₂ or monoclinic phases of VO₂ or V₀.₉₇₆Cr₀.₀₂₄O₂. The vanadium-vanadium distance along the rutile V₀.₉₇₆Cr₀.₀₂₄O₂ axis is anomalously short when compared with neighboring rutile phases while the other nearest-neighbor metal-metal and metal-oxygen distances vary smoothly across the series. A comparison of Debye temperatures calculated from heat-capacity and x-ray data suggests the presence of low-lying vibrational modes in metallic VO₂.