Li Yanqiang, Zhang Xu, Zhou Yang, Huang Weiqi, Song Yipeng, Wang Han, Li Minjuan, Hong Maochun, Luo Junhua, Zhao Sangen
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, 350002, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Angew Chem Int Ed Engl. 2022 Sep 19;61(38):e202208811. doi: 10.1002/anie.202208811. Epub 2022 Aug 17.
Birefringent materials are highly demanded for high-performance polarized optics. As compared with artificial anisotropic metamaterials, anisotropic crystals have advantages of low optical losses and easy processing, but their birefringence is still limited. Herein, based on first-principles studies, we identified a new type of functional anion units, (H C N ) (x=0, 1, 2), and then successfully synthesized a new anisotropic crystal, namely, CsH C N ⋅H O (I), whose crystal structure consists of (H C N ) anions. Remarkably, I is ultraviolet transparent and exhibits very large birefringence of about 0.55@550 nm, which is much larger than those of commercial birefringent crystals. These results make I a candidate for highly efficient manipulation of optics and light in optical modulation devices. Theoretical calculations reveal that large birefringence mainly arises from the cooperative π orbitals in (H C N ) anions. This work provides a new insight on the underlying structure-property relationships of anisotropic crystals.
双折射材料在高性能偏振光学领域有很高的需求。与人工各向异性超材料相比，各向异性晶体具有光学损耗低和易于加工的优点，但其双折射仍然有限。在此，基于第一性原理研究，我们确定了一种新型的功能阴离子单元（HCN）（x = 0, 1, 2），然后成功合成了一种新的各向异性晶体，即CsHCN·H₂O（I），其晶体结构由（HCN）阴离子组成。值得注意的是，I在紫外光下是透明的，并且在550 nm处表现出约0.55的非常大的双折射，这比商业双折射晶体的双折射大得多。这些结果使I成为光学调制器件中高效操控光学和光的候选材料。理论计算表明，大双折射主要源于（HCN）阴离子中的协同π轨道。这项工作为各向异性晶体潜在的结构-性能关系提供了新的见解。
