Exchange charge model calculations of crystal field parameters and crystal field energy levels for [N(CH3)4]2CoCl4 and [N(CH3)4]2MnCl4 single crystals

Complex study of [N(CH3)4]2MCl4 (M = Co, Mn) crystals (crystal growth, optical spectroscopy, crystal field analysis) is presented. Exchange charge model of crystal field was used to calculate the crystal field parameters (CFPs) and energy levels for both Co2+ and Mn2+ ions. Effects of the covalent bond formation between Co2+(Mn2+) and Cl− ions are treated from the point of view of overlap of the corresponding wave functions. Dependence of the CFPs values on the number of ions included into the crystal lattice summation was analyzed. Comparison between the calculated energy levels and corresponding absorption spectra is discussed; on the basis of the calculations, assignment of the absorption bands in the experimental spectra was done.