二元碱金属硅酸盐精细结构和拉曼光谱的从头计算研究

应用量子化学从头计算方法研究了二元碱金属硅酸盐的精细结构，对典型的系列二元碱金属硅酸盐离子簇模型采用6-31G(d)基组和闭壳层Hartree-Fock(RHF)方法优化构型，并计算了二元碱金属硅酸盐的拉曼光谱，采用硅氧四面体应力指数这一精细结构参数分析和讨论了计算得到的非桥氧高频区对称伸缩振动频率和其拉曼光学活性，以及不同阳离子对该拉曼光学活性的影响。研究表明，二元碱金属硅酸盐非桥氧高频区对称伸缩振动频率与其精细结构密切相关，而且与Q₃相连的Q₄会对该Q₃的拉曼光学活性表现出增强作用。这说明二元碱金属硅酸盐的拉曼散射等性质主要依赖于其精细结构而非其初级结构单元-硅氧四面体。研究还表明，半径较大的阳离子有利于增强离子簇的拉曼光学活性，但对于小的离子簇，过多的电荷迁移反而会起到抑制作用。

Ab Initio Calculation of Hyperfine Structure and Raman Spectra of Binary Alkali Metal Silicates

Ab initio calculation method of quantum chemistry was used to optimize several typical binary alkali metals silicates model clusters under restricted Hartree-Fock method with 6-31G(d) basis sets.The symmetric stretching vibrational frequency of non-bridging oxygen in the high frequency range,its Raman optical activity(ROA) and the influence of different cations of those model clusters were also calculated and evaluated with the concept of hyperfine micro-structure.It was shown that the symmetric stretching vibrational frequency of non-bridging oxygen in the high frequency range is related closely to the environmental hyperfine micro-structure,and ROA enhancement of Q3 species occurs as Q4 species is its nearest neighbor.It can be inferred that the Raman scattering properties of silicates might be predominantly determined by hyperfine micro-structure instead of crude SiO4 tetrahedron as primary micro-structure.It was found that large cation can enhance ROA of the symmetric stretching vibration of non-bridging oxygen by charge transfer mechanism,while ROA weakening effect can be expected on small model clusters due to the excessive charge transfer.