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An ordered structure is found in the composition range VN0.74-VN0.84 of the cubic mononitride phase by means of electron diffraction/microscopy. The lattice constant of this structure is twice as large as that of the original NaCl type cell. At the composition VN0.81, or V32N26, six nitrogen atoms are missing from the unit cell. The vacancy arrangement has tetragonal symmetry, and the superstructure belongs to the space group P42/nmc. Disordering of this structure occurs at about 520 °C. The transition entropy determined from heat-capacity measurements agrees well with a calculation based on the crystal structure proposed here. A tentative phase diagram for the composition range VN0.6-VN1.0 is presented.