Energy-level calculations for the 5f26d1 configuration of U3+ in Cs2NaYCl6 single crystals

Energy levels and the 5f3 → 5f26d(t2g)1 transition intensities of U3+ in Cs2NaYCl6 were calculated using a theoretical model for nfN energy levels extended for interactions related with the presence of d-electron, proposed by Reid et al. [M.F. Reid, L. van Pieterson, R.T. Wegh, A. Meijerink, Phys. Rev. B 62 (2000) 14744]. The Fk(fd) and Gj(fd) parameters for f-d Coulomb interactions, the ζ(dd) spin-orbit interactions parameter for 6d electron as well as B04(ff)andB06(ff) crystal-field parameters for 5f2 core electrons were adjusted, and a very good agreement between calculated and experimental spectrum has been achieved. The F2(fd), G1(fd) and ζ(dd) parameters were reduced to 37.5%, 45.3% and 77.2% of the ab initio calculated free-ion values, respectively. The values of Bqk(ff) parameters determined for 5f26d1 configuration are closer to those of 5f2 configuration of U4+ than 5f3 configuration of U3+. The results of calculations performed in the frame of the semi-empirical Hamiltonian model are in a very good accordance with those of ab initio theoretical analysis, reported by Seijo and Barandiarán [L. Seijo, Z. Barandiarán, J. Chem. Phys. 118 (2003) 5335].