Symmetry-Modelling of Rare Earth Compounds with Kramers Ions: II. Erbium(III) in Various Solids

The »truncated crystal field method« which allows determination of the microsymmetry of the crystal field around Kramers . ions is applied to erbium(III) in five different host crystals. The starting data for the calculations are taken from carefully interpreted optical spectra. In the first step, crystal field narameters for various assumed test symmetries are chosen in order to give the best fit to the splitting of the ground state multiplet. Then, a truncated crystal field calculation involving only a limited number of Stark levels is performed. The microsymmetry of the earth ion in the compounds is suggested in terms of the standard deviation between the calculated and experimental Stark splittings, All the calculations including the optimization of parameters have been performed on a personal computer. Tables of crystal field parameters and standard deviations are given for the following compounds with optical data taken from the literature: Er(C2H"S04h . 9H20, Er(IIJ) :LuP04, Er(III) : :HfSi04, Er(III) :LaC13and Er(III) :Y203.