A simple method for constructing effective Hamiltonians for the 4fN and 4fN-15d 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.
@article{arxiv.1011.1709,
title = {Extraction of crystal-field parameters for lanthanide ions from quantum-chemical calculations},
author = {L. Hu and M. F. Reid and C. K. Duan and S. Xia and M. Yin},
journal= {arXiv preprint arXiv:1011.1709},
year = {2012}
}