水合硅酸分子电子结构的从头算与基组效应研究

Study of Electronic Structures of Silicic Acid Using the Ab Initio Method

应用能量梯度技术 ,在从头算自洽场分子轨道的水平上 ,借助于最小基和扩展基中的 7种基组 ,优化得到了水合硅酸分子的平衡态几何构型 ,并与成键参数的实验值进行了比较 ,从而确定了以 6 31G基组进行几何构型优化最为合适 .对基态能量 (S0 )进行了自洽场 (RHF)、组态相互作用(CI)、M ller Plesset(MP2、MP4 )的计算 ,并利用CI法计算了水合硅酸分子体系的第 1激发态 (S1、T1)能量 ,其结果表明 ,以 6 31G 基组结合MP4计算出的系统能量最低 .通过对自洽场从头算基组效应的分析 ,确定水合硅酸分子系统的计算模式为 :以 6 31G基组为优化几何构型 ,然后利用 6 31G 基组计算能量 ,并利用MP4进行相关能量校正 。

The electronic structures of silicic acid are studied by using ab initio self consistent field molecular orbital (SCF MO) method with 7 kinds of basis sets. The geometry of silicic acid has been optimized by the energy gradient technique. The ground state energy of silicic acid has been calculated at CI, MP2 and MP4 level, while the first excited states of silicic acid have been calculated by the CI method. The basis set effects are discussed about geometry and energy of silicic acid system. It is better to use the 6?31G basis sets for optimizing the geometry and 6?31G  with MP4 for calculating the energy of silicic acid system.