Extraction of crystal-field parameters for lanthanide ions from quantum-chemical calculations

A simple method for constructing effective Hamiltonians for the 4f(N) and 4f(N-1)5d energy levels of lanthanide ions in crystals from quantum-chemical calculations is presented. The method is demonstrated by deriving crystal-field and spin-orbit parameters for Ce3+ ions doped in LiYF4, Cs2NaYCl6, CaF2, KY3F10 and YAG host crystals from quantum-chemical calculations based on the DV-X alpha method. Good agreement between calculated and fitted values of the crystal-field parameters is obtained. The method can be used to calculate parameters even for low-symmetry sites where there are more parameters than energy levels.