Liu Juhe, Lee Ming-Hsien, Li Chunxiao, Meng Xianghe, Yao Jiyong
Beijing Center for Crystal Research and Development, Key Lab of Functional Crystals and Laser Technology, Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China.
Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, P. R. China.
Inorg Chem. 2022 Dec 5;61(48):19302-19308. doi: 10.1021/acs.inorgchem.2c03083. Epub 2022 Nov 17.
In this paper, a revised structure determination of an already known compound CsNbOBO with new structural insights was performed and the detailed characterization of its optical properties was reported for the first time. CsNbOBO was synthesized by spontaneous crystallization. It crystallizes in the 2 space group, and the unit lattice parameters are = 7.5220(7) Å, = 3.9881(4) Å, = 9.7167(9) Å, and = 2. In the structure of CsNbOBO, a [NbO] square pyramid and [BO] unit are linked to constitute an infinitely extended two-dimensional [NbOBO] layer via sharing oxygen atoms. Between these two-dimensional layers, there are no covalent bonds perpendicular to their planes based on Mulliken bond order analysis. CsNbOBO has a wide band gap (4.52 eV) and a large second-harmonic-generation (SHG) response (1.2 × KDP) and demonstrates type-I phase-matchable behavior. First-principles simulations reveal that the birefringence is approximately 0.10. Moreover, SHG-weighted charge density analysis shows that the primary source of the nonlinearity of the title compound is the distorted NbO square pyramids.
本文对已知化合物CsNbOBO进行了结构测定修订，获得了新的结构见解，并首次报道了其光学性质的详细表征。CsNbOBO通过自发结晶合成。它属于2空间群，晶胞参数为 = 7.5220(7) Å， = 3.9881(4) Å， = 9.7167(9) Å， = 2。在CsNbOBO结构中，一个[NbO]四方锥和[BO]单元通过共享氧原子相连，构成无限延伸的二维[NbOBO]层。基于穆利肯键级分析，在这些二维层之间，不存在垂直于其平面的共价键。CsNbOBO具有宽带隙（4.52 eV）和大的二次谐波产生（SHG）响应（1.2×KDP），并表现出I型相位匹配行为。第一性原理模拟表明双折射约为0.10。此外，SHG加权电荷密度分析表明，标题化合物非线性的主要来源是扭曲的NbO四方锥。
