The simple model for 4f-5d transitions of lanthanide ions in crystals was extended to deal with the case of the octahedral crystal field,where for the t_(2)component of 5d orbitals the spin-orbit interaction could not be neglected due to incomplete quenching of the 5d orbital angular momentum.The energy levels for the 4f^(N-1)5d configuration and the relative line strengths for the 4f^(N)\4f^(N-1)5d transition were calculated in detail.The result was applied to the interpretation of the low-temperature 4f-5d excitation spectrum of Cs_(2)NaYCl_(6)∶Tb^(3+).
Ma ChonggengM F.ReidDuan ChangkuiXia ShangdaYin Min
The ab initio self-consistent DV-Xa （discrete variational Xa） method was used in its relativistic and spin-polarized model to investigate the ground-state electronic structttres of the crystal YPO4 and YPO4：RE^3＋ （RE=Ce, Pr and Sm） and f-d transition energies of the lattice. The calculation was performed on the clusters Y5P10O32 and REY4P10O32 embedded in a microcrystal containing about 1500 ions, respectively. The ground-state calculation provided the locations of the 4f and 5d crystal-field one-electron levels of RE^3＋ relative to the valence and conduction bands of host, the curve of total and the partial density of states, and the corresponding occupation numbers, etc. Especially, the transition-state calculation was performed to obtain the 4f→5d transition energies of RE^3＋ in comparison to the experimental observations. The lattice relaxation caused by the dopant ion RE3＋ was discussed based on the total energy calculation and the transition-state calculation of the f-d transition energies.
