CsLiB_6O_(10)晶体及熔体微结构的高温拉曼光谱研究

High Temperature Raman Spectroscopic Study on the Micro-structures of CsLiB_6O_(10) Crystal and Its Melt

本文利用高温原位拉曼光谱技术,测定了非线性光学晶体硼酸铯锂(CsLiB6O10,CLBO)晶体及其熔体的变温拉曼光谱。利用密度泛函理论计算了基本单元为(B3O7)5-六元环的CLBO晶体的拉曼光谱,并对振动模式进行了分析归属。在升温过程中,CLBO晶体的拉曼光谱出现展宽和红移,无相变发生;在熔化过程中,CLBO晶体微结构中(B3O7)5-六元环的[BO4]四面体发生异构化反应,转变为[BO3]三角形,即晶体相中的(B3O7)5-环变为熔体中的(B3O6)3-环。利用量子化学从头计算方法计算分析了熔体中结构基元的拉曼光谱谱学特征,结合熔体实测结果,表明CLBO熔体的阴离子基元为四个(B3O6)3-六元环组成的大四元环超级结构。

Temperature dependent Raman spectra of the nonlinear optical crystal, CsLiBrOlo （CLBO） and its melt were recorded by in situ high temperature Raman spectroscopic technique. The vibrational modes of the CLBO crystal with （B3O7 ）5- ring as basic unit were simulated and assigned by density functional theory（DFF） method. As the temperature increasing, nearly all of the peaks of CLBO crystal broadened and decreased in wavenumber, without phase transition. An isomerization reaction from [ BO4 ] tetrahedron to [ BO3 ] triangle occurred during the melting process, that is, （B3O7 ）5- in CLBO crystal structure translated into （B3O6） 3- groups in CLBO melt. The spectroscopy characteristics of the Raman spectrum of structure unit in melt were caculated by quantum chemistry ab initio. It can be concluded that there exists super ring structure which contains four （ B3O6 ） 3 - rings connected by each other, which agreed well with the experimental result.