A theoretical investigation of Ti3+ in yttrium borophosphate glass materials: Local structures and optical properties.

• Local structure of Ti3+ in CFCYBPT glasses are investigated. • Five coordinated [TiO 5 ]7‒ is more suitable than six coordinated [TiO 6 ]9‒ in view of better fitting results. • Fitting E 2 with the experimental data, inflection point at x (= 0.58 mol%) is acceptable. • The microscopic mechanisms of the variation rules of the relevant quantities are explained related with NBO. • Conventional and local optical basicities are studied to represent local environment of Ti3+ in CFCYBPT glasses. Local structure and g factors for (20-x)CaF 2 -10CaO-5Y 2 O 3 -10B 2 O 3 -55P 2 O 5 : x TiO 2 (x = 0.2, 0.4, 0.6, 0.8 and 1.0 mol%) glasses are theoretically studied by using the perturbation formulae for a tetragonally elongated octahedral 3d1 cluster. Six coordinated [TiO 6 ]9‒ and five coordinated [TiO 5 ]7‒ clusters are evaluated in view of the Jahn-Teller effect and the charge compensation of impurity Ti3+ for host Ti4+. d -d transition bands of E 2 (2B 2g →2A 1g) and E 3 (2B 2g →2B 1g) of the [TiO 5 ]7‒ cluster is obtained with the piecewise linear fitting function of x. The microscopic mechanisms of the varying rules of relevant quantities g // , E 2 and N with x are related with NBO. The role of various TiO 2 concentrations in local structure and optical spectra is also comprehensively studied from the local optical basicity Λ loc , which can represent the local environment and covalency of the Ti3+ center. [ABSTRACT FROM AUTHOR]