As the core of all-solid-state lasers, the second harmonic generation (SHG) inorganic crystals exclusively require a noncentrosymmetric (NCS) structure. However, the vast majority of the known inorganic compounds, approximately 79%, are centrosymmetric (CS). Herein, we report a unique concentration-driven isomerization of the and phases of Cd(NH)(POF)·2HO, -CdNPF (2, NCS) and -CdNPF (2/, CS). The NCS -CdNPF is generated at a higher mother solution concentration ( vs. phase: 0.20 vs. 0.15 M), which allows the [CdO] octahedron accommodate higher number of the [POF] ligand with a weak crystal field (CN = 4 vs. 3), leading to a dipole moment reduction (1.06 D vs. 1.60 D) that eventually eliminates the unwanted symmetric center trap induced by the antiparallel dipole-dipole interactions between the [CdO] octahedra in the CS -CdNPF. Interestingly, such a slight - vs. -[CdO] geometry difference in the and phases, also makes the Cd-fluorescence red-shift slightly (437 vs. 431 nm) and narrows slimly (cal.: 4.01 vs. 4.05 eV). More interestingly, -CdNPF exhibits excellent NLO properties (relatively strong phase matching SHG: 0.78 × KDP at 1064 nm; deep ultraviolet (DUV) transparent ( < 200 nm); high laser induced damage threshold: 1.48 × KDP), indicating a promising DUV NLO application potential.

中文翻译：

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异构Cd(NH4)2(PO3F)2·2H2O：溶液浓度驱动消除反平行偶极子-偶极子相互作用，产生SHG β相


作为全固态激光器的核心，二次谐波产生（SHG）无机晶体只需要非中心对称（NCS）结构。然而，绝大多数已知的无机化合物（约 79%）是中心对称的 (CS)。在此，我们报道了 Cd(NH)(POF)·2HO、-CdNPF (2, NCS) 和 -CdNPF (2/, CS) 的独特的浓度驱动异构化和相。 NCS -CdNPF 是在较高的母液浓度（相对于相：0.20 vs. 0.15 M）下生成的，这使得 [CdO] 八面体能够容纳更多数量的具有弱晶体场的 [POF] 配体（CN = 4 vs . 3)，导致偶极矩减小（1.06 D vs. 1.60 D），最终消除了由 CS -CdNPF 中的 [CdO] 八面体之间的反平行偶极-偶极相互作用引起的不需要的对称中心陷阱。有趣的是，在 和 相中如此轻微的 - 与 -[CdO] 几何形状差异，也使得 Cd 荧光轻微红移（437 与 431 nm）并略微变窄（校准：4.01 与 4.05 eV）。更有趣的是，-CdNPF表现出优异的NLO性能（相对较强的相位匹配SHG：1064 nm处0.78 × KDP；深紫外（DUV）透明（< 200 nm）；高激光诱导损伤阈值：1.48 × KDP），表明DUV是一种有前途的材料非线性光学应用潜力。