Peiró-García Julio, Nebot-Gil Ignacio
Facultad de Química, Universidad de Valencia, c/ Dr. Moliner, 50, E-46100 Burjasot, Valencia, Spain.
J Comput Chem. 2003 Oct;24(13):1657-63. doi: 10.1002/jcc.10299.
The atmospheric reaction NO2 + O3 --> NO3 + O2 (1) has been investigated theoretically by using the MP2, G2, G2Q, QCISD, QCISD(T), CCSD(T), CASSCF, and CASPT2 methods with various basis sets. The results show that the reaction pathway can be divided in two different parts at the MP2 level of theory. At this level, the mechanism proceeds along two transition states (TS1 and TS2) separated by an intermediate, designated as A. However, when the single-reference higher correlated QCISD methodology has been employed, the minimum A and the transition state TS2 are not found on the hypersurface of potential energy, which confirms a direct reaction mechanism. Single-reference high correlated and multiconfigurational methods consistently predict the barrier height of reaction (1) to be within the range 2.5-6.1 kcal mol(-1), in reasonable agreement with experimental data. The calculated reaction enthalpy is -24.6 kcal mol(-1) and the reaction rate calculated at the highest CASPT2 level, of k = 6.9 x 10(-18) cm(3) molecule(-1) s(-1). Both results can be regarded also as accurate predictions of the methodology employed in this article.
通过使用MP2、G2、G2Q、QCISD、QCISD(T)、CCSD(T)、CASSCF和CASPT2方法以及各种基组，对大气反应NO2 + O3 --> NO3 + O2 (1)进行了理论研究。结果表明，在MP2理论水平上，反应途径可分为两个不同部分。在此水平上，该反应机理沿着由一个称为A的中间体隔开的两个过渡态（TS1和TS2）进行。然而，当采用单参考更高相关的QCISD方法时，在势能超曲面上未找到最小值A和过渡态TS2，这证实了一种直接反应机理。单参考高相关方法和多组态方法一致预测反应(1)的势垒高度在2.5 - 6.1 kcal mol(-1)范围内，与实验数据合理吻合。计算得到的反应焓为 -24.6 kcal mol(-1)，在最高CASPT2水平计算得到的反应速率为k = 6.9 x 10(-18) cm(3) molecule(-(1)) s(-1)。这两个结果也可视为本文所采用方法的准确预测。
