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Ab initio Study on Spectral Properties of Charge-Compensated Ce3+ in NaF
Nai-yu Ma,Feng Yang,Xian-chun Shen,Yu-cheng Huang,Li-xin Ning*
Author NameAffiliationE-mail
Nai-yu Ma Department of Physics, Anhui Normal University, Wuhu 241000, China  
Feng Yang Department of Physics, Anhui Normal University, Wuhu 241000, China  
Xian-chun Shen Department of Physics, Anhui Normal University, Wuhu 241000, China  
Yu-cheng Huang Department of Physics, Anhui Normal University, Wuhu 241000, China  
Li-xin Ning* Department of Physics, Anhui Normal University, Wuhu 241000, China ninglx@mail.ahnu.edu.cn 
Abstract:
We report an ab initio>/I> study of spectral properties of Ce3+ doped at Na+ site of the NaF crys-tal, with the charge imbalance compensated by two oxygen substitutions for fluoride (OF') in the first coordination shell or two sodium vacancies (VNa') in the second coordination sphere. Density functional theory calculations within the supercell model are first performed to op-timize the local structures of the charge-compensated Ce3+, based on which Ce-centered embedded clusters are constructed and wave function-based CASSCF/CASPT2/RASSI-SO calculations are carried out to obtain the energies of 4f1 and 5d1 levels. By comparing the calculated 4f→5d transition energies with experimental excitation spectra at low temper-atures, the lowest 4f→5d transition band peaked at 390 nm is assigned to the Ce3+ with charge compensation by two coordinating OF' substitutions, rather than to the Ce3+ with compensation by two VNa0 vacancies, as proposed earlier. The electronic reason for the large redshift (by ~8000 cm-1) of the lowest 4f→5d transition as induced by the two nearby OF' substitutions is analyzed in terms of the changes in the centroid shift and crystal-field splitting.
Key words:  Ab initio calculation, NaF:Ce3+, Local structure, Transition
FundProject:
NaF晶体中电荷补偿掺杂Ce3+离子光谱性质的从头算
马乃玉,杨峰,沈先春,黄玉成,宁利新*
摘要:
用从头算研究NaF晶体中Ce3+占据Na+格位时的光谱性质,电荷补偿由占据格位第一配位壳层的两个氟原子被氧取代 (OF') 或第二配位壳层的两个Na空位(Na') 来提供. 首先采用基于DFT的超单胞模型方法优化了Ce3+的局域结构,并构造以Ce为中心的镶嵌团簇,对其进行基于波函数理论的CASSCF/CASPT2/RASSI-SO计算,获得Ce3+的4f1和5d1组态分裂能级能量. 通过将4f→5d跃迁能量计算值与低温实验激发光谱比较,发现实验观测到的最低4f→5d跃迁谱带(390 nm)来自于两个最近邻OF'补偿的Ce3+离子,并不是文献中的两个次近邻VNa' 补偿的Ce3+. 最后从5d1组态能级重心位移和晶场分裂两方面分析了由两个最近邻OF'取代造成最低4f→5d 跃迁红移约8000 cm-1的原因.
关键词:  从头算, NaF:3+, 局域结构, 4f→5d 跃迁
DOI:10.1063/1674-0068/27/05/512-518
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