An X-ray diffraction study of semiconductor and metallic vanadium dioxide

Powder diffraction data for semiconductor and metallic states of vanadium dioxide are presented. The structures are refined by Rietveld methods using a monoclinic cell ( a = 5.7529Å, b = 4.5263Å, c = 5.3825Å, β = 122.61°) and space group P2 1 / c for the room temperature data, and a tetragonal cell ( a =4.5540Å, c = 2.8557Å) and space group P4 2 /mnm for data collected at 400 K. The similarity between the corresponding X-ray diffraction patterns is discussed. The transition process from the monoclinic to tetragonal phase is investigated and initial evidence for the coexistence of phases over a small temperature range is presented.