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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 ,这些都较好地改善了体系能量的计算
Using the energy gradient technique, we have optimized the equilibrium geometry of the hydrated silicic acid molecule with the aid of seven kinds of basic groups in the minimum and extension bases, (631G basis set), the optimal configuration of the geometry is determined.The self-consistent field (RHF), configuration interaction (CI), ground-state interaction (Mller Plesset MP2 and MP4). The energy of the first excited state (S1, T1) of the hydrated silicate molecular system was calculated by the CI method. The results show that the system energy calculated by the 631G basis set combined with MP4 is the lowest. From the analysis of the ab initio basis set effect, the calculation mode of the hydrated silicate molecular system is confirmed as follows: the 631G basis set is the optimized geometric configuration, then the 631G basis set is used to calculate the energy and the relevant energy is corrected by using MP4, These are better to improve the calculation of system energy