Li Qian Shu, Yang Jing, Zhang Shaowen
School of Chemistry and Environment, South China Normal University, Guangzhou 510006, People's Republic of China.
J Phys Chem A. 2006 Sep 28;110(38):11113-9. doi: 10.1021/jp0626317.
We present a theoretical study of the hydrogen abstraction reactions from CH(3)F and CH(2)F(2) by an ozone molecule. The geometries and harmonic vibrational frequencies of all stationary points are calculated at the MPW1K, BHandHLYP, and MPWB1K levels of theory. The energies of all of the stationary points were refined by using both higher-level (denoted as HL) energy calculations and QCISD(T)/6-311++G(2df,2pd) calculations based on the optimized geometries at the MPW1K/6-31+G(d,p) level of theory. The minimum energy paths (MEPs) were obtained by the MPW1K/6-31+G(d,p) level of theory. Energetic information of the points along the MEPs is further refined by the HL method. The rate constants were evaluated on the basis of the MEPs from the HL level of theory in the temperature range 200-2500 K by using the conventional transition-state theory (TST), the canonical variational transition-state theory (CVT), the microcanonical variational transition-state theory (microVT), the CVT coupled with the small-curvature tunneling (SCT) correction (CVT/SCT), and the microVT coupled with the Eckart tunneling correction (microVT/Eckart) based on the ab initio calculations. A general agreement was found among the TST, CVT, and microVT theories. The fitted three-parameter Arrhenius expressions of the calculated forward CVT/SCT and microVT/Eckart rate constants of the ozonolysis of fluoromethane are k(CVT/SCT)(T) = 2.76 x 10(-34)T(5.81)e((-13975/)(T)) and k(microVT/Eckart)(T) = 1.15 x 10(-34)T(5.97)e((-14530.7/)(T)), respectively. The fitted three-parameter Arrhenius expressions of the calculated forward CVT/SCT and microVT/Eckart rate constants of the ozonolysis of difluoromethane are k(CVT/SCT)(T) = 2.29 x 10(-36)T(6.42)e((-15451.6/)(T)) and k(microVT/Eckart)(T) = 1.31 x 10(-36)T(6.45)e((-15465.8/)(T)), respectively.
我们给出了臭氧分子从CH(3)F和CH(2)F(2)中夺取氢反应的理论研究。在MPW1K、BHandHLYP和MPWB1K理论水平下计算了所有驻点的几何结构和谐振频率。所有驻点的能量通过基于MPW1K/6-31+G(d,p)理论水平优化几何结构的更高水平（记为HL）能量计算和QCISD(T)/6-311++G(2df,2pd)计算进行了优化。通过MPW1K/6-31+G(d,p)理论水平获得了最小能量路径（MEP）。沿着MEP的点的能量信息通过HL方法进一步优化。在200-2500 K温度范围内，基于从头算计算，使用传统过渡态理论（TST）、正则变分过渡态理论（CVT）、微正则变分过渡态理论（microVT）、结合小曲率隧穿（SCT）校正的CVT（CVT/SCT）以及结合埃卡特隧穿校正的microVT（microVT/Eckart），根据HL理论水平的MEP评估了速率常数。在TST、CVT和microVT理论之间发现了总体一致性。氟甲烷臭氧分解反应计算得到的正向CVT/SCT和microVT/Eckart速率常数的拟合三参数阿伦尼乌斯表达式分别为k(CVT/SCT)(T) = 2.76 x 10^(-34)T^(5.81)e^((-13975/)(T))和k(microVT/Eckart)(T) = 1.15 x 10^(-34)T^(5.97)e^((-14530.7/)(T))。二氟甲烷臭氧分解反应计算得到的正向CVT/SCT和microVT/Eckart速率常数的拟合三参数阿伦尼乌斯表达式分别为k(CVT/SCT)(T) = 2.29 x 10^(-36)T^(6.42)e^((-15451.6/)(T))和k(microVT/Eckart)(T) = 1.31 x 10^(-36)T^(6.45)e^((-15465.8/)(T))。
