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在G3B3,CCSD(T)/6-311++G(d,p)//B3LYP/6-311++G(d,p)水平上详细研究了CH3SH与基态NO2的微观反应机理.在B3LYP/6-311++G(d,p)水平得到了反应势能面上所有反应物、过渡态和产物的优化构型,通过振动频率分析和内禀反应坐标(IRC)跟踪验证了过渡态与反应物和产物的连接关系.在CCSD(T)/6-311++G(d,p)和G3B3水平计算了各物种的能量,得到了反应势能面.利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT),分别计算了在200～3000K温度范围内的速率常数kTST,kCVT和kCVT/SCT.研究结果表明,该反应体系共存在5个反应通道,其中N进攻巯基上H原子生成CH3S+HNO2的通道活化势垒较低,为主要反应通道.动力学数据也表明,该通道在200～3000K计算温度范围内占绝对优势,拟合得到的速率常数表达式为k1CVT/SCT=1.93×10-16T0.21exp(-558.2/T)cm3·molecule-1·s-1.
The microscopic reaction mechanism of CH3SH with ground state NO2 has been studied in detail at the level of G3B3, CCSD (T) / 6-311 ++ G (d, p) // B3LYP / 6-311 ++ G (d, p) The optimal configurations of all the reactants, transition states and products on the reaction potential energy surface were obtained at the level of 6-311 ++ G (d, p). Vibrational frequency analysis and intrinsic reaction coordinate (IRC) The energy of each species was calculated at the level of CCSD (T) / 6-311 ++ G (d, p) and G3B3, and the reaction potential energy surface was obtained.Using the classical transition state theory (TST) and (CVT) combined with small curvature tunneling effect model (SCT) were used to calculate the rate constants kTST, kCVT and kCVT / SCT in the temperature range of 200-3000 K. The results show that the reaction system coexists with 5 Reaction channels, in which N attack on the H atom to generate CH3S + HNO2 channel activation barrier lower, as the main reaction channel.Kinetic data also showed that the channel in the 200 ~ 3000K calculation temperature range accounted for an absolute advantage, fitting The obtained rate constant expression is k1CVT / SCT = 1.93 × 10-16 T0.21exp (-558.2 / T) cm3 · molecule-1 · s-1.