透闪石结构的Raman光谱

RAMAN SPECTRA FOR STRUCTURE OF TREMOLITE

将硅氧“四面体应力指数(stressindexoftetrahedron,SIT)”值的计算和透闪石矿物Raman光谱的实际测定与量子化学自洽场分子轨道“从头计算”的方法相结合,用以探讨透闪石的Raman光谱在800～1200cm–1高频区间内特征Raman谱峰的位移和结构含义,为深入理解链状硅酸盐矿物的结构特征提供理论依据。研究表明:实际测定的透闪石Raman光谱高频区的特征峰值1030cm–1和1061cm–1与用SIT计算和用量子化学“从头计算”方法对透闪石晶体模拟结构Si6O17Na10计算所获得的结果基本一致,证明了链状硅酸盐矿物透闪石的晶体结构中Q2和Q3两种结构单元所对应的特征Raman谱峰应分别位于1033cm–1和1059cm–1处,代表了Q2和Q3两种结构单元中非桥氧的对称伸缩振动。实际测定的透闪石Raman光谱中930cm–1附近的谱峰,可能为Si—Onb间伸缩振动的反映。在SIT的计算和量子化学“从头计算”结果中都缺乏这个谱峰,初步的解释是与透闪石晶体中Q2的2个非桥氧与金属阳离子的配位互不等价,导致Q2非桥氧的伸缩振动发生分裂有关。

The methods of stress index of tetrahedron （SIT） calculation, Raman spectra testing of tremolites and ＂ab initio＂ quantum chemical calculation for the silicon-oxygen tetrahedral model were combined to analyze the characteristics and structural meaning of the characteristic Raman peaks of tremolite at the scale of 800-1 200 cm^-1, and to provide a theoretical foundation for a deep understanding of the structural characteristics of chain silicate minerals. For the characteristic Raman peaks of tremolite, at both seats of 1 033 cm^-1 and 1 059 cm^-1, the results of experiments were consistent with the SIT calculations and silicon-oxygen tetrahedral model cluster Si6O17Na10, which proved the structure species Q2 and Q3 correspond to both seats of the characteristic Raman peaks 1 033 cm^-1 and 1 059 cm^-1, respectively. The characteristic Raman peaks of tremolite may be a reflection of the symmetry stretching vibrations of the non-bridge oxygen in both Q2 and Q3 structure species of thermolite. The Raman peak of the thermolite at 930 cm^-1 tested by experiments may be a stretching vibration of Si-Onb and short of the 930 cm^-1 Raman peak in the calculation of SIT and silicon-oxygen tetrahedral model cluster Si6O17Na10. An initial explanation is the coordination of non-isovalent ions between both non-bridge-oxygen in Q2 structure species and the metal cation of the tremolite crystal, which caused the symmetry stretching vibrations of Q2 non-bridge-oxygen to break off.