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本文利用高温拉曼光谱技术和从头计算的方法,研究了LiB3O5和CsB3O5晶体高温熔融体的结构,分析了碱金属阳离子对熔体结构的影响,以及熔体结构的差异与LiB3O5和CsB3O5晶体结晶习性的联系.结果表明:LiB3O5和CsB3O5晶体高温熔融体中的结构基团主要为B37和B36两种不同类型的硼氧六元环;环内B4四面体的数量影响了六元环呼吸振动峰的拉曼频率,随B4四面体数量的增加六元环呼吸振动峰向低频移动;LiB3O5晶体高温熔融体中,B4四面体含量相对较多;然而,离子半径相对较大的Cs+离子却阻碍了熔体中B4四面体的形成,造成CsB3O5晶体高温熔融体中B4/B3比值的降低.结合LiB3O5和CsB3O5晶体生长动力学过程的分析(Wang D,Wan S Metal.2011 Cryst.Eng.Comm.13 5239),阳离子的不同导致高温熔体中B4四面体数量的差异,被认为是影响LiB3O5和CsB3O5晶体结晶习性的重要因素,有效降低高温熔体中B4四面体的数量,将是实现LiB3O5晶体生长的关键条件.
In this paper, the structure of LiB3O5 and CsB3O5 crystals at high temperature was studied by means of high temperature Raman spectroscopy and ab initio calculations. The effects of alkali metal cations on the melt structure were analyzed. The difference of melt structure and the crystal habit of LiB3O5 and CsB3O5 The results show that the main structural groups in the high temperature melt of LiB3O5 and CsB3O5 crystal are two different types of boron-oxygen six-membered rings, B37 and B36. The number of B4 tetrahedrons in the ring affects six The Raman frequency of the ring respiration vibration peak shifted to the low frequency with the increase of the number of B4 tetrahedrons, and the content of B4 tetrahedron was relatively higher in the LiB3O5 crystal melt. However, the ionic radius The relatively large Cs + ions impede the formation of B4 tetrahedra in the melt and decrease the B4 / B3 ratio in the high temperature melt of CsB3O5 crystal. Combining the analysis of the growth kinetics of LiB3O5 and CsB3O5 crystals Wang D, Wan S Metal. 2011. Cryst. Eng. Comm. 13, 5239). The difference in the number of B4 tetrahedra in the high temperature melt due to the different cations is considered to be an important factor influencing the crystal habit of LiB3O5 and CsB3O5 crystals. Lower high temperature melt The number of B4 tetrahedrons will be the key to achieving the crystal growth of LiB3O5.