气相中Co^+催化CO与N_2O反应机理的理论计算研究

Theoretical calculations of catalyzed reaction mechanism of CO with N_2O by Co^+ in gas phase

采用密度泛函UB3LYP/6-311+G(2d)方法计算研究了Co+在基态和激发态下与N2O的反应机理,全参数优化了反应势能面上各驻点的几何构型,用频率分析方法和内禀反应坐标(IRC)方法对过渡态进行了验证,并用UB3LYP/6-311++G(3df,3pd)、单点垂直激发、Harvey等人的方法分别进行各驻点单点能校正,三重态和五重态反应势能面两个交叉点CP确定,最低能量交叉点(MECP)的优化及MECP处相应的自旋-轨道耦合常数(SOC)计算,计算结果表明,该反应为两步反应,较大的SOC值说明了在势能面上的翻转能够有效发生,且反应机理都为插入—消去反应,交叉点能够有效的降低反应的活化能,这在动力学和热力学上都是有利的。

The reaction mechanism between Co^＋in ground state and excited state with CO and N2O has been studied using the density functional theory （ DFT ） at UB3 LYP/6 -311 ＋G （2d） level. The geometries for reactant, the transition states and the products were completely optimized. All the transition states were verified by the vibration analysis and the intrinsic reaction coordinate calculations. For each stationary point, single-point energy calculations were carried out by UB3LYP/6-311 ＋＋G（3df, 3pd）method. The potential energy curve-crossing diagrams were investigated for state correlation between triplet and quintuplet state in the reaction of Co＋with CO and N2O. The results showed that the reaction is a two-step reaction and the reaction mechanism was an insertion-elimination mechanism. Every step occurs spin-forbidden between the triplet and quintuplet potential energy surfaces （PESs）. There is two crossing points（CP） between the triplet and quintuplet potential energy surfaces ,which would play a significant role in this catalytic reaction. The minimum energy crossing points（MECP） that obtained by the mathematical algorithm proposed by Harvey et al. has been also employed. The values of the SOC constants at MECP indicate that the spin crossing process in this reaction can occur efficiently due to the large SOC involved.