Distribution, structures and nonlinear properties of noncentrosymmetric titanates

The difference has been revealed between the statistical distributions of centrosymmetric and noncentrosymmetric titanates over crystal symmetry systems. Space formations of Ti-O polyhedra has been analyzed for 52 noncentrosymmetric titanates. The type of Ti-O polyhedra space formations is dependent on the stoichiometric ratio, SR = n(O)/n(Ti), where n(O) is the number of oxygen and n(Ti) is the number of titanium atoms in formal composition of the compound. Individual (Ti-O) polyhedra are found for SR ≥ 3.5 (SR ≥ 6 for octahedra), chains and layers of the polyhedra exist in the range stoichiometric ratio, SR = 3.5-7.0. Only framework formations are possible at SR ≤ 3.5.