TiO2-SiO2复合氧化物结构和红外光谱的量子化学研究

 构建了TiO2-SiO2复合氧化物晶胞结构,采用HyperChem量子化学程序中的从头计算方法以3-21G*基组对其进行了全优化计算,并进行了振动分析,预测了TiO2-SiO2复合氧化物各化学键的红外特征吸收频率. 采用IR谱对TiO2-SiO2复合氧化物进行了表征,通过理论计算与实验数据相结合的方法确定了TiO2-SiO2复合氧化物的分子结构,对其平衡几何构型、IR谱、电子结构和Lewis酸性进行了讨论.

Study on Structure and IR Spectra of TiO2-SiO2 Composite Oxide by Quantum Chemistry

The crystal structure of TiO 2-SiO 2 composite oxide was constructed and calculated by the Ab initio method of HyperChem quantum chemistry procedure at 3-21G * level, and its optimized structure was obtained. The calculated bond length of Ti-O, Si-O and H-O was 0.1802 , 0.1632 and 0.0953 nm, respectively, which was in good agreement with the experimental values of 0.180, 0.160 and 0.095 nm. The analysis of the optimized structure and the predictions of IR characteristic frequency of different chemical bonds were made, which were confirmed by the experimental results: frequency of 1148 and 1142 cm -1 was assigned to symmetric and asymmetric stretching mode of Si-O, respectively, frequency of 1069 and 910 cm -1 was assigned to symmetric and asymmetric stretching mode of Ti-O-Si, and frequency of 932 cm -1 was assigned to stretching mode of Ti-O. All the above conclusions prove that the constructed structure of TiO 2-SiO 2 composite oxide was reasonable. In addition, the frontier molecular orbitals showed that the HOMO orbits of TiO 2-SiO 2 composite oxide were mainly contributed by O atoms of Ti-O-Si, while the LUMO orbits were contributed by d-orbits of Ti atoms. Molecular electrostatic potential and electric charge distribution showed that Ti atoms, the catalytic sites of Lewis acid, had bigger positive electrostatic potential and strong electron-accepting ability.