Probabilities of octahedral clusters depending on long-range order parameters and composition in nonstoichiometric titanium monoxide Ti[O.sub.y]

A method for calculating the probabilities of cluster configurations in ordered superstructures of strongly nonstoichiometric compounds depending on the composition and the order parameter is described using the [Ti.sub.5][O.sub.5] superstructure of nonstoichiometric titanium monoxide Ti[O.sub.y]. Analytic expressions are derived for the dependences of the probabilities of the main cluster configurations in the [Ti.sub.5][O.sub.5] superstructure on the fraction of atomic positions in the titanium and oxygen sublattices and on the long-range order parameter. The probabilities of configurations are calculated for various long-range order parameters taking into account experimental data on the concentration of structural vacancies in the titanium and oxygen sublattices. The dependences of the probabilities of cluster configurations on the short- range order parameter are established from the relations between the superstructure long-range and short- range order parameters.