Crystal field analysis of the absorption spectra and electron-phonon interaction in Ca₃Sc₂Ge₃O₁₂:Ni ²⁺

Exchange charge model of crystal field [B.Z. Malkin, in: A.A. Kaplyanskii, B.M. Macfarlane (Eds.), Spectroscopy of Solids Containing Rare-earth Ions, North-Holland, Amsterdam, 1987, pp. 33-50.] was used to analyze the energy level schemes of Ni²⁺ ion at both possible positions (octahedral and tetrahedral) in Ca₃Sc₂Ge₃O₁₂. The crystal field parameters were calculated from the crystal structure data; the crystal field Hamiltonian was diagonalised in the complete basis consisting of 25 wave functions of all LS terms of the Ni²⁺ ion. Results of calculations are in a good agreement with experimental data. From the experimental spectra available in the literature, the Huang-Rhys parameter S=3.5 and effective phonon energy ℏω=200cm-1 were evaluated for the octahedral Ni²⁺ ion.