Li2B4O7晶体及其熔体结构的拉曼光谱研究

采用高温原位拉曼光谱技术，研究了Li₂B₄O₇从常温至1 373 K温度范围内的拉曼光谱。在升温过程中，晶体的拉曼光谱出现展宽和红移现象，且强度降低。晶体熔化时，由2个BO₄]和2个BO₃]组成的B₄O₉]环状结构转变成(B₃O₆)3- 六元环和BO₃]结构，BO₄]结构减少直至消失。基于密度泛函理论，计算了Li₂B₄O₇晶体的拉曼光谱，对其振动模式进行了分析归属。利用量子化学从头计算法计算了由B₃O₆-BO₃]为基础相互连接形成的x(Li₂B₄O₇)(x=2, 3, …, 9)的环状团簇模型的拉曼光谱，对Li₂B₄O₇熔体的结构进行了模拟分析。计算结果表明Li₂B₄O₇熔体的阴离子基元为三个(B₃O₆-BO₃)组成的大三元环超级结构。

Raman Spectroscopic Study of Li2B4O7 Crystal and Melt Structure

Raman spectra of Li₂B₄O₇ at different temperatures up to 1 373 K were recorded by using in situ high temperature Raman spectroscopic technique. With the increase of temperature, Raman spectra of crystal broaden and decrease in wavenumber and intensity. During the melting process, B₄O₉] rings which consist of two BO₄] and two BO₃] turned into (B₃O₆)3- six-membered ring and BO₃], BO₄] species decreased and then disappeared. In addition, the vibrational modes of the Li₂B₄O₇ crystal were simulated and assigned by using density functional theory(DFT)method. Raman spectra of x(Li₂B₄O₇)(x=2, 3, …, 9) rings which consist of (B₃O₆-BO₃) were calculated by using quantum chemistry ab initio method, to analyze the cluster in melt. It can be concluded that there exists super ring structure which contains three (B₃O₆-BO₃) rings connected with each other.