Order–order transition structural state in titanium monoxide TiO1.0

Resumo

A new class of defect structures in which point defects of a crystal lattice simultaneously occupy sites of two different superstructures is proposed. The formation of these structural modifications is due to a second-order order–order phase transition that does not occur to the end. The allowable relation between the long-range order parameters in the structural modification formed by a combination of the monoclinic (M₅X₅)_mon (space group C2/m (A2/m)) and the cubic (M₅X₅)_cub (space group Pm3m) of the superstructures is studied using an atom–vacancy ordering in titanium monoxide TiO_1.0. The thermodynamic calculations show that the proposed structural modification is equilibrium and must form instead of assumed high-temperature cubic phase (Ti₅O₅)_cub.