Quantum-chemical ab initio study of the crystal-field and charge transfer energies of nanocrystalline Y2O3: Eu

The 4f energy levels and crystal-field parameters for several clusters representing the local coordination surroundings of Eu³⁺ in the bulk and nanocrystalline cubic Y₂O₃: Eu³⁺ crystals are obtained by using a method based on the combination of the DV-X_α calculation and the effective Hamiltonian method initialized by M.F. Reid et al. (J. Phys.: Condens. Matter, 2011, 23: 045501). The results are in reasonable agreement with the measured energy levels and the crystal-field parameters obtained from the least-square fitting. The charge transfer energies are also obtained for all the clusters from the DV-X_α calculation. The results indicate that, compared with the bulk Y₂O₃: Eu³⁺ crystal, the charge transfer band in the excitation spectra is red-shifted in the nanocrystal.