First-Principles Study on Site Preference and 4f → 5d Transitions of Ce3+ in Sr3AlO4F

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• 作者：Lixin Ning ; Yongfeng Wang ; Zongcui Wang ; Wei Jin ; Shizhong Huang ; Changkui Duan ; Yongfan Zhang ; Wanping Chen ; Hongbin Liang
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：February 13, 2014
• 年：2014
• 卷：118
• 期：6
• 页码：986-992
• 全文大小：357K
• ISSN：1520-5215

文摘

The local structures and 4f 鈫?5d transition energies of Ce³⁺ located on the two crystallographic strontium sites of Sr₃AlO₄F, with charge compensation by means of nearby sodium substitutions for strontium (Na_Sr鈥? or oxygen substitutions for coordinating fluorine (O_F鈥?, have been studied using the density functional theory (DFT) within the supercell model and the wave function-based embedded cluster calculations, respectively. The DFT total energy calculations show that Ce³⁺ prefers strongly to occupy the eight-coordinated (Sr2) site over the ten-coordinate (Sr1) site. On the basis of the results from embedded cluster calculations at the CASPT2 level with the spin鈥搊rbit effect, the experimentally observed excitation bands are identified in association with the charge-compensated cerium centers. Especially, the two bands observed at 404 and 440 nm have been both assigned to the Ce³⁺ located at the Sr2 sites but with compensation by one and two nearest-neighbor O_F鈥?substitutions, respectively, rather than to the Ce³⁺ on the Sr1 and the Sr2 sites, respectively, as proposed earlier. Furthermore, the structural and electronic reasons for the red shift of the lowest 4f 鈫?5d transition caused by coordinating O_F鈥?substitutions are analyzed in terms of the variations in centroid energy and crystal-field splitting of the 5d¹ configuration with the local environment. Finally, the thermal quenching of 5d luminescence at relatively high Ce³⁺ concentrations is discussed on the basis of the electronic properties calculated with the hybrid DFT method.