Bi4B2O9晶体及其熔体结构的高温原位拉曼光谱研究

High-temperature in situ Raman Spectroscopic Study on the Micro-structure of Bi4B2O9 Crystal and Melt

利用密度泛函理论计算了Bi4B2O9晶体的常温拉曼光谱,并通过与实验拉曼光谱对比,对其振动模式进行了归属.利用高温原位拉曼光谱研究了Bi4B2O9从常温到750℃升温过程中微结构的变化.随着温度的升高,晶体的平均键长变长,键角分布变宽,熔化后晶体中的BiO4和BiO5多面体解体,BO3构型则保持三配位不变.运用量子化学从头算法模拟了Bi4B2O9的熔体结构并与实验拉曼光谱进行了对比分析,发现在Bi4B2O9熔体中B原子团簇为孤立的BO3构型,Bi^3+游离于BO3之间,并结合未参与形成BO3的O原子起到平衡电荷的作用.

Raman spectrum of Bi4B2O9 crystal at ambient temperature was measured and calculated via density functional theory and vibration modes of all the peaks were assigned. Then high temperature in situ Raman spectroscopic technique was utilized to measure Raman spectra of Bi4B2O9 crystal from room temperature to750 ℃( above the melting point) to investigate its micro-structure’s evolution. With the temperature increasing,the lattice lengthens in bond length and broadens in bond angle. After melting,BiO4 and BiO5 polyhedron in crystal tends to convert,while BO3 triangle stays constant. Ab initio method was used to simulate the microstructure of Bi4B2O9 melt cluster,calculate and analyze its Raman spectra. It is found that B atoms in Bi4B2O9 melt form isolated BO3 triangle structure and Bi^3+ cation among BO3,connecting O atoms out of BO3,functions as charge balancer.