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 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.