Comparative study of crystal field effects for Ni2+ ion in LiGa5O8, MgF2 and AgCl crystals

Exchange charge model (ECM) of crystal field was used to calculate the crystal field parameters (CFPs) and model the energy levels for Ni2+ ion in LiGa5O8, MgF2 and AgCl crystals. Calculated energy levels (including splitting of the orbital triplets) are in good agreement with experimental absorption spectra. Covalent effects were shown to play an important role in all considered crystals. Bilinear forms built up from the overlap integrals between (Ni2+–Cl−)→(Ni2+–O2−)→(Ni2+–F−) pairs were considered a quantitative measure of the covalent (nephelauxetic) effects.