EPR theoretical investigation of substitution site and local lattice structure of tetragonal Cr2+ in cadmium thiogallate

By analyzing the experimental EPR zero-field-splitting (ZFS) parameters a, D and F, the substitution position and the local lattice structure of tetragonal Cr2+ center in cadmium thiogallate (CdGa2S4) crystal have been studied on the basis of the complete energy matrix for a d4 configuration in a tetragonal ligand-field within a strong-field-representation. Our results show that the Cd2+ site is the only substitutional position for Cr2+ in CdGa2S4 and the local structure around the Cr2+ is a compression distortion. From EPR calculations, the local lattice structure parameters R = 2.44 A and θ = 57.74° are determined.