Like cubic TiOF 2 , NbO 2 F also adopts an average ReO 3 -type structure with oxygen and fluorine distributed over the Wyckoff 3d positions. NbO 2 F is believed to exhibit short-range ordering somewhat analogous to that predicted here for TiOF 2 , with collinear F-Ti-F units disfavoured . Electron diffraction data for NbO 2 F, however, show hk 1 3 * sheets of diffuse intensity, which has been attributed to anion ordering in one-dimensional strings along each of the three ⟨001⟩ directions . To explain this experimental observation, Brink et al. proposed a structural model for NbO 2 F in which oxygen and fluorine are ordered along ⟨001⟩ strings in repeating [F-O-O-F] sequences, but are uncorrelated between pairs of ⟨001⟩ strings, whether these strings are aligned along the same or different ⟨001⟩ directions .