The electronic, structural, and optical properties of 2 red phosphors, Rb₂HfF₆:Mn⁴⁺ and Cs₂HfF₆:Mn⁴⁺, are evaluated using the first‐principles and crystal field theory methods. The calculated trigonal splitting of the Mn⁴⁺ orbital triplets perfectly matches the experimental excitation spectra. The structural and electronic properties of the mixed compound RbCsHfF₆ are also studied theoretically. In the mixed compound, the inversion center symmetry around the Hf site is removed. This symmetry lowering may result in an increase in the Mn^{4+ 2}E→⁴A₂ zero phonon line (ZPL) intensity, which is very weak in the 2 end members. This finding may be of interest for increasing the phosphor luminosity. It is believed that such a mechanism of local site symmetry lowering by preparing solid solutions may be used for other systems as well, to gain ZPL intensity and perhaps to minimize thermal losses, eventually leading to improved phosphor materials.

中文翻译：

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两种新型红色荧光粉Rb2HfF6：Mn4 +和Cs2HfF6：Mn4 +的电子和光学性质的第一性原理和晶体场计算

使用第一性原理和晶体场理论方法对2种红色荧光粉Rb ₂ HfF ₆：Mn ⁴⁺和Cs ₂ HfF ₆：Mn ⁴⁺的电子，结构和光学性质进行了评估。计算出的Mn ⁴⁺轨道三重态的三角分裂与实验激发光谱完全匹配。还从理论上研究了混合化合物RbCsHfF ₆的结构和电子性能。在混合的化合物中，去除了Hf部位周围的反转中心对称性。这种对称性降低可能导致Mn ^{4+ 2} E→ ⁴ A _2的增加零声子线（ZPL）强度，在两个末端成员中非常弱。该发现对于增加磷光体的发光度可能是有意义的。可以相信，通过制备固溶体来降低局部对称性的这种机理也可以用于其他系统，以获得ZPL强度并且可能使热损失最小化，最终导致改进的磷光体材料。