Calculation of energy levels of cerium in inorganic scintillator crystals

Fully relativistic ab initio calculations have been performed on energy levels of cerium in BaF2, LaF3, YAP (yttrium aluminum perovskites) and YAG. Also nonrelativistic calculations were done on cerium in LSO (lutetium oxy orthosilicate). The results are in fair agreement with experiment. Both the splitting of the 4f and 5d levels and the 4f-5d energy gap can be explained in the high symmetry crystal BaF2 as well as in the low symmetry crystals LaF3, YAP, YAG and LSO. The more traditional nonrelativistic approach is not capable to handle 4f-5d energy differences but can be used for the description of the 5d state and other properties which do not critically depend on the 4f state. The authors have estimated the position of the cerium levels in the gap of the host materials. So important information for luminescence of cerium centers is obtained