NaF-AlF3二元系铝氟四面体团簇结构的拉曼光谱表征与量子化学从头计算

本文构建了一系列NaF-AlF3二元系铝氟四面体团簇结构模型, 应用量子化学从头计算方法, 采用Restricted Hatree-Fock(RHF)自洽场方法和6-31G(d)基组对结构进行优化, 并用相同的方法和基组进行分子振动模式的模拟计算。考虑相邻铝氟四面体的影响, 引入四面体应力指数(SIT)的概念分析和讨论该二元系高频区非桥氟对称伸缩振动及中频区桥氟对称弯曲振动模式。研究表明, 高频区铝氟四面体非桥氟对称伸缩振动频率与其铝氟四面体的种类(Qi)密切相关, 且铝氟四面体非桥氟对称伸缩振动频率的值随SIT值的增大而增大, 呈现较好的线性关系。同时, NaF-AlF3二元系团簇结构的中频区桥氟对称弯曲振动频率主要受桥氟角度的影响。并采用高温拉曼仪测定了分子比为NaF:AlF3 =1∶2体系的升温拉曼光谱, 随着温度的升高NaF:AlF3 =1∶2体系的主峰逐渐向低频移动, 观察到Q0、Q1、Q2峰位的变化。

Characteristic Raman Spectra and Quantum Chemistry ab initio Calculation on Aluminum-Fluorine Tetrahedral Model Clusters of NaF-AlF3 Binary

Quantum chemistry ab initio calculation was applied to optimize a series of aluminum-fluorine tetrahedral model clusters and calculate their molecular vibrational modes in terms of Restricted Hatree-Fock(RHF) method with the basis sets of 6-31G(d).Considering the effect of neighboring aluminum-fluorine tetrahedral,SIT(Stress Index of Tetrahedron) was introduced to analyze the Al-Fb-Al symmetric bending vibrational modes in intermediate wavenumber range and the symmetric stretching vibrational modes of non-bridging fluorine in high wavenumber range.It suggested that the symmetric stretching vibrational wavenumber of non-bridging fluorine depends mainly on the species of aluminum-fluorine tetrahedral(Qi) and appears linear relationship with the value of SIT.It was also demonstrated that the Al-Fb-Al symmetric bending vibrational wavenumber is dominated by the Al-Fb-Al angle.Raman spectra of NaF: AlF3 =1∶2 were determined with the increasing temperature.Various microstructure units including Q0,Q1,and Q2were observed and the main peaks shift to low-frequency with the increasing temperature.