Wen Jun, Ning Lixin, Duan Chang-Kui, Zhan Shengbao, Huang Yucheng, Zhang Jie, Yin Min
†School of Physics and Electronic Engineering, Anqing Normal University, Anqing 246011, People's Republic of China.
‡Center for Nano Science and Technology, Department of Physics, Anhui Normal University, Wuhu 241000, People's Republic of China.
J Phys Chem A. 2015 Jul 23;119(29):8031-9. doi: 10.1021/acs.jpca.5b02873. Epub 2015 Jul 9.
In the present work, geometric structures, electronic properties, and 4f → 5d transitions of γ-Ca2SiO4:Ce(3+) phosphors have been investigated by using first-principles calculations. Four categories of typical substitutions (i.e., the doping of the Ce(3+) without the neighboring dopants/defects and with the neighboring VO(••), AlSi', and VCa″) are taken into account to simulate local environments of the Ce(3+) located at two crystallographically different calcium sites in the γ-Ca2SiO4. Density functional theory (DFT) geometry optimization calculations are first performed on the constructed supercells to obtain the information about the local structures and preferred sites for the Ce(3+). On the basis of the optimized crystal structures, the electronic properties of γ-Ca2SiO4:Ce(3+) phosphors are calculated with the Heyd-Scuseria-Ernzerhof screened hybrid functional, and the energies and relative oscillator strengths of the 4f → 5d transitions of the Ce(3+) are derived from the ab initio embedded cluster calculations at the CASSCF/CASPT2/RASSI-SO level. A satisfactory agreement with the available experimental results is thus achieved. Moreover, the relationships between the dopants/defects and the electronic as well as spectroscopic properties of γ-Ca2SiO4:Ce(3+) phosphors have been explored. Such information is vital, not least for the design of Ce(3+)-based phosphors for the white light-emitting diodes (w-LEDs) with excellent performance.
在本工作中，通过第一性原理计算研究了γ-Ca2SiO4:Ce(3+) 荧光粉的几何结构、电子性质和4f→5d跃迁。考虑了四类典型取代（即Ce(3+) 掺杂且无相邻掺杂剂/缺陷以及有相邻VO(••)、AlSi' 和VCa″），以模拟位于γ-Ca2SiO4中两个晶体学不同钙位点的Ce(3+) 的局部环境。首先对构建的超胞进行密度泛函理论（DFT）几何优化计算，以获得关于Ce(3+) 的局部结构和优选位点的信息。基于优化后的晶体结构，采用Heyd-Scuseria-Ernzerhof筛选混合泛函计算γ-Ca2SiO4:Ce(3+) 荧光粉的电子性质，并在CASSCF/CASPT2/RASSI-SO水平上通过从头算嵌入簇计算得出Ce(3+) 的4f→5d跃迁的能量和相对振子强度。从而与现有的实验结果取得了令人满意的一致性。此外，还探索了掺杂剂/缺陷与γ-Ca2SiO4:Ce(3+) 荧光粉的电子及光谱性质之间的关系。这些信息至关重要，尤其是对于设计具有优异性能的用于白光发光二极管（w-LEDs）的Ce(3+) 基荧光粉。
