Theoretical studies of the concentration dependences of g factor and d-d transition band for Cr3 + in CdO–SrO–B2O3–SiO2 glasses

• Concentration dependences of g factor and d-d transition for Cr3 + in CSBS glasses are studied.
• Local optical basicity is introduced to describe influences of local environments on impurity Cr3 +.
• Variations of Dq and k with x are analyzed from Λloc and Sr2 + at three concentration stages.

The concentration dependences of g factor and d-d transition band are theoretically studied for Cr3 + in CdO–SrO–B2O3–SiO2 glasses in a consistent way. To determine the local structure around dopant Cr3 +, the non-bridge oxygen (NBO) occupation ratio o is calculated for different dopant concentrations x. In order to evaluate explicitly the influences of other cations (e.g., Sr2 +) and to refine the conventional bulk optical basicity of whole glass systems, a new quantity local optical basicity Λloc around dopant Cr3 + is introduced to describe the influences of local environments on the studied [CrO6] clusters. This new quantity is also theoretically characterized by o related to NBO concentration f(NBO). The concentration dependences of cubic field parameter Dq and isotropic g factor are suitably reproduced by three piecewise linear functions of Dq and orbital reduction factor k with x. The microscopic mechanisms of the relationships of crystal-field strength and covalency of [CrO6] clusters with x are analyzed in view of the variations of Λloc and high ionicity of Sr2 + nearby at different stages.