| Rare earth ions have unique electronic configurations, and theirmaterials exhibit rich optical, electrical, magnetic properties, which havewide applications in metallurgy, medical treatment, lighting and so on. Inthis thesis, we focus on one of the rare earth luminescent materials,Ce3+-doped La2CaB10O19crystal, for which first-principles wereperformed to study electronic properties and4fâ†'5d transitions. Thecontent is organized as follows:The first chapter is the introduction, in which we briefly review thehistory of discovery of rare earth elements, and try to explain rare earthmaterials’ strategic position from the aspects of their unique electronicproperties. In addition, the wide applications and promising prospectivesrare earth materials are highlighted.The second chapter is concerned with the theoretical methodsinvolved in this article, mainly containing the hybrid density functionaltheory (DFT) and the wave function-based embedded cluster calculations.The theoretical methods and ab initio software relevant to the study ofluminescent materials are emphasized.The third chapter constitutes the main part of this thesis, mainlyabout the details of first-principles calculations on Ce3+-doped LCBcrystal. We first constructed a supercell model theory for the pure LCBand LCB:Ce3+crystals. Then, three DFT functionals, PBE, PBE0and HSE06, were used to optimize their geometries and calculate theelectronic structures. By comparison with experiments, the DFTfunctional PBE0was selected with best performance. Later, with thePBE0-optimized LCB:Ce3+geometries, Ce3+-centered embedded clusters(CeLaO10)17-and (CeCaO18)3-, were constructed, for which the wavefunction-based calculations at the CASSCF/CASPT2level with thespin-orbit effect were conducted to obtain the4f1and5d1levels of Ce3+.Finally, the4fâ†'5d transition of Ce3+located at the La3+or Ca2+site,were discussed in association with the coordination geometry. |
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