Potentiai Energy Surfaces and Dynamics of Chemical Reactions in Solution

基于溶质分子的参考相互作用位点自洽场（RISM-SCF）电子结构计算，结合大量溶剂的分子动力学（MD）模拟计算，建立了溶液中化学反应的反应路径哈密顿量。将该方法应用于S_N2反应CH_3Cl + Cl^-和Menshutkin型反应NH_3+CH_3X (X=Cl, Br， I)，考察了溶剂动力学对反应速率的影响。前者的透射系数为0.71，与前面的仿真计算结果一致。我们还利用我们之前提出的电荷响应核模型（charge response kernel， CRK）研究了电子极化对溶液中分子动力学的影响。建立了水分子的三、五点CRK模型，计算了水分子的红外光谱和拉曼光谱。结果表明，五点模型能较好地再现实验光谱特征。进一步应用该五位点模型计算了水溶液中n -甲基乙酰胺（NMA）的红外光谱。最后，我们提出了一种新的定义CRK的方法，避免了在确定原子位置有效电荷时的模糊性。

We have developed a method to construct a reaction path Hamiltonian for chemical reactions in solution based on the reference interaction site self-consistent field (RISM-SCF) electronic structure calculations of reacting solute molecule combined with molecular dynamic (MD) simulation calculations for bulk solvent. We applied this method to the S_N2 reaction CH_3Cl + Cl^- and the Menshutkin type reactions NH_3+CH_3X (X=Cl, Br, I) and examined the effect of solvent dynamics on the reaction rates. The transmission coefficient for the former was 0.71, which was consistent with the previous simulation calculations. We have also investigated the electronic polarization effect on the dynamics of molecules in solution with the use of charge response kernel (CRK) model, which was proposed previously by us. Three and frve site CRK models for water molecule were developed and the infrared and Raman spectra for bulk water were calculated. The five site model was shown to well reproduce the experimental spectral features. The present five site model was further applied to calculate the infrared spectrum of N-Methylacetamide (NMA) in aqueous solution. Finally, we proposed a new method to define the CRK which avoid the ambiguity in determining the effective charges at atomic sites.