Ce $^{3+}$掺杂镧硅氮磷光体的第一性原理研究：中性激发、Stokes位移和发光中心识别
First-principles study of Ce$^{3+}$ doped lanthanum silicate nitride phosphors: Neutral excitation, Stokes shift, and luminescent center identification
摘要：
我们从第一性原理出发研究了两种镧硅氮化合物LaSi $_{3}$ N $_{5}$和LaPDMATHABMM Si $_{6}$ N $_{11}$，原始的以及掺杂Ce离子的$^{3+}$，以解释它们不同的发射颜色，并表征发光中心。两种未掺杂基质的电子结构相似，并且没有给出定量描述这种差异的暗示。Ce $^{3+}$离子的$4f\rightarrow 5d$中性激发通过约束密度泛函理论方法与$Δ$ SCF分析的总能量相结合来模拟，产生吸收能。之后，原子的位置在激发态放松，产生的发射能量和斯托克斯位移。在此基础上，确定了$_{3}$ N $_{5}$：Ce和$_{3}$ Si $_{6}$ N $_{11}$：Ce中的发光中心.计算量与实验数据的一致性是相当合理的，并解释了发射光的不同颜色。同时，得到的斯托克斯位移与实验值相差在20%以内.
英文摘要：
We study from first principles two lanthanum silicate nitride compounds, LaSi$_{3}$N$_{5}$ and La$_{3}$Si$_{6}$N$_{11}$, pristine as well as doped with Ce$^{3+}$ ion, in view of explaining their different emission color, and characterising the luminescent center. The electronic structures of the two undoped hosts are similar, and do not give a hint to quantitatively describe such difference. The $4f\rightarrow 5d$ neutral excitation of the Ce$^{3+}$ ions is simulated through a constrained density-functional theory method coupled with a $Δ$SCF analysis of total energies, yielding absorption energies. Afterwards, atomic positions in the excited state are relaxed, yielding the emission energies and Stokes shifts. Based on these results, the luminescent centers in LaSi$_{3}$N$_{5}$:Ce and La$_{3}$Si$_{6}$N$_{11}$:Ce are identified. The agreement with the experimental data for the computed quantities is quite reasonable and explains the different color of the emitted light. Also, the Stokes shifts are obtained within 20\% difference relative to experimental data.
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