PhysicoChimie des Processus de Combustion et de l'Atmosphère (PC2A), UMR 8522 CNRS/Lille1, Université Lille 1 Sciences et Technologies, Cité scientifique, Bat C11/C5, 59655 Villeneuve d'Ascq Cedex, France.
J Phys Chem A. 2010 Sep 2;114(34):9270-88. doi: 10.1021/jp104163t.
The rate constants of the reactions of iodine atoms with H(2), H(2)O, HI, and OH have been estimated using 39, 21, 13, and 39 different levels of theory, respectively, and have been compared to the available literature values over the temperature range of 250-2500 K. The aim of this methodological work is to demonstrate that standard theoretical methods are adequate to obtain quantitative rate constants for the reactions involving iodine-containing species. Geometry optimizations and vibrational frequency calculations are performed using three methods (MP2, MPW1K, and BHandHLYP) combined with three basis sets (cc-pVTZ, cc-pVQZ, and 6-311G(d,p)). Single-point energy calculations are performed with the highly correlated ab initio coupled cluster method in the space of single, double, and triple (pertubatively) electron excitations CCSD(T) using the cc-pVnZ (n = T, Q, and 5), aug-cc-pVnZ (n = T, Q, and 5), 6-311G(d,p), 6-311+G(3df,2p), and 6-311++G(3df,3pd) basis sets. Canonical transition state theory with a simple Wigner tunneling correction is used to predict the rate constants as a function of temperature. CCSD(T)/cc-pVnZ//MP2/cc-pVTZ (n = T and Q), CCSD(T)/6-311+G(3df,2p)//MP2/6-311G(d,p), and CCSD(T)/6-311++G(3df,3pd)//MP2/6-311G(d,p) levels of theory provide accurate kinetic rate constants when compared to available literature data. The use of the CCSD(T)/cc-pVQZ//MP2/cc-pVTZ and CCSD(T)/6-311++G(3df,3pd) levels of theory allows one to obtain a better agreement with the literature data for all reactions with the exception of the I + H(2) reaction R(1) . This computational procedure has been also used to predict rate constants for some reactions where no available experimental data exist. The use of quantum chemistry tools could be therefore extended to other elements and next applied to develop kinetic networks involving various fission products, steam, and hydrogen in the absence of literature data. The final objective is to implement the kinetics of gaseous reactions in the ASTEC (Accident Source Term Evaluation Code) code to improve speciation of fission transport, which can be transported along the Reactor Coolant System (RCS) of a Pressurized Water Reactor (PWR) in case of a severe accident.
碘原子与 H(2)、H(2)O、HI 和 OH 的反应速率常数分别使用 39、21、13 和 39 种不同的理论方法进行了估算，并与 250-2500 K 温度范围内的可用文献值进行了比较。这项方法学工作的目的是证明标准理论方法足以获得涉及含碘物种的反应的定量速率常数。使用三种方法 (MP2、MPW1K 和 BHandHLYP) 并结合三种基组 (cc-pVTZ、cc-pVQZ 和 6-311G(d,p)) 进行几何优化和振动频率计算。单点能计算使用高度相关的从头算耦合簇方法在单、双和三 (微扰) 电子激发 CCSD(T) 的空间中进行，使用 cc-pVnZ(n = T、Q 和 5)、aug-cc-pVnZ(n = T、Q 和 5)、6-311G(d,p)、6-311+G(3df,2p) 和 6-311++G(3df,3pd) 基组。采用简单的威格纳隧道校正的正则过渡态理论来预测温度相关的速率常数。与可用文献数据相比，CCSD(T)/cc-pVnZ//MP2/cc-pVTZ(n = T 和 Q)、CCSD(T)/6-311+G(3df,2p)//MP2/6-311G(d,p) 和 CCSD(T)/6-311++G(3df,3pd)//MP2/6-311G(d,p) 理论水平提供了准确的动力学速率常数。对于除 I + H(2)反应 R(1) 之外的所有反应，使用 CCSD(T)/cc-pVQZ//MP2/cc-pVTZ 和 CCSD(T)/6-311++G(3df,3pd) 理论水平可以更好地与文献数据吻合。该计算程序还用于预测某些无可用实验数据的反应的速率常数。因此，可以将量子化学工具的使用扩展到其他元素，并应用于开发涉及各种裂变产物、蒸汽和氢气的动力学网络，在没有文献数据的情况下。最终目标是在 ASTEC（事故源项评估代码）代码中实现气态反应动力学，以改进裂变输运的形态，在压水堆（PWR）严重事故中，裂变产物可以沿着反应堆冷却剂系统（RCS）输运。
