密度泛函理论研究SiFCl自由基和异硫氰酸的反应机理

A Theoretical Study on the Multi-channel Reaction Mechanism of SiFCl Radical with HNCS in Density Functional Theory

采用密度泛函理论(DFT)的B3LYP方法对SiFCl自由基和HNCS的反应机理进行研究,在B3LYP/6-311++G**水平上对反应势能面上的所有稳定点(反应物、过渡态和中间体)进行了全几何参数优化,通过简谐振动频率分析和內禀反应坐标(IRC)确定中间体和过渡态。应用G3方法计算了在B3LYP/6-311++G**水平优化后的各个驻点的相对能量以获得更精确的能量值,化学反应过程中主要化学键的生成和断裂通过自然键轨道理论(NBO)和电子密度拓扑分析(AIM)进行详细讨论;依据统计热力学和用Winger校正的Eyring过渡态理论,计算了低势垒反应在不同温度下的平衡常数和速率常数。结果表明,单重态的SiFCl自由基与HNCS的反应有8条可能的反应通道,其中单重态反应通道SiFCl+HNCS→IM5→TS7→SSiFClCNH(P2)为主反应通道。

The reaction mechanism of SiFCl radical with HNCS has been explored by the B3LYP method of density functional theory(DFT),while all stationary points on the potential energy surface have been calculated at the B3LYP/6-311++G**level.The stationary point energies were calculated at the G3 levelso as to obtain more precise energy result.The thermodynamic and kinetic characters of the channel with low energy barrier range from 100 to 1000 Kwere investigated through the statistical thermodynamics and Eyring transition state theory with Winger correction.In addition,the analysis on the combining interaction between SiFCl radical and HNCS was performed by atom-in-molecules theory(AIM)and natural bond orbitals(NBO)analysis.The calculation results showed that the reaction of SiFCl radical with HNCS had eight channels;S-atom abstraction channel(SiFCl+HNCS→IM5→TS7→SSiFClCNH)in singlet state was the main channel with low potential energy,high equilibrium constant and reaction rate constant;SSiFClCNH was the main product.