Distribution of Vacancies in a Hybrid M_(5–11/18)X_(5–11/18) Superstructure of a High-Temperature Ordered β-TiO Phase

A new structural model of the high-temperature ordered β-TiO phase of titanium monoxide with vacancies in metallic and nonmetallic sublattices has been proposed. The model suggests that the vacancies are simultaneously distributed over sites of two partially disordered superstructures: monoclinic M₅X_5(mon) (space group C2/m (A2/m)) and cubic M₅X_5(cub) (space group Pm$\overline{3}$m). The hybrid superstructure belongs to space group P1m1 of the monoclinic system. The proposed notation M_(5–11/18)X_(5–11/18) of the hybrid superstructure takes into account an expansion of the vacancy sublattice due to the superposition of initial $M_5{X}_{5^{-}}$ type superstructures. It is shown that the arrangements of the superstructure reflections in the diffraction spectra of the M_(5–11/18)X_(5–11/18) and M₅X_5(cub) superstructures are identical.