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First-Principles Study on Electronic Properties and Optical Spectra of Ce-Doped La<sub>2</sub>CaB<sub>10</sub>O<sub>19</sub> Crystal
We report herein a first-principles
investigation on electronic
properties and 4f→5d transitions of Ce<sup>3+</sup> substituted
at La<sup>3+</sup> and Ca<sup>2+</sup> sites of La<sub>2</sub>CaB<sub>10</sub>O<sub>19</sub> (LCB) crystal, using the hybrid density functional
theory (DFT) and the wave function-based embedded cluster calculations,
respectively. The hybrid DFT with PBE0 functional yields a band gap
of 8.1 eV for LCB, in good agreement with the experimentally estimated
value of ∼8.3 eV. The energy gaps between the occupied Ce<sup>3+</sup> 4f states and the valence band maximum of the host are predicted
to be 1.93 ± 0.12 eV, with a slight dependence on the local environment.
Based on the results of embedded cluster calculations at the CASSCF/CASPT2
level with the spin–orbit effect, the experimentally observed
excitation bands are identified in association with the two cerium
substitutions. The difference between the lowest 4f→5d transition
energies of Ce<sup>3+</sup> located at the two dopant sites are rationalized
in terms of the variations in centroid energy and crystal-field splitting
of the 5d<sup>1</sup> configuration with the local environment