Search results for "Atmospheric reactions"
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Ab Initio Study of the Mechanism and Thermochemistry of the Atmospheric Reaction NO + O3 → NO2 + O2
2002
The atmospheric reaction between NO and ozone has been investigated using ab initio methods. The structures of all reactants, products, intermediates, and transition states of reaction 1 have been optimized and characterized at the UMP2(full) level of theory. The 6-31G(d), 6-311G(d), and 6-311G(df) basis sets have also been used to calibrate the effect of the basis set functions on the optimized structures and energies of all stationary points. Finally, we have reoptimized at the UMP4(SDQ, full)/6-31G(d) and 6-311G(d) levels. The energetics of the reaction has been studied more accurately within the G2 and G2(MP2) schemes. Also, QCISD(T)/6-311G(d) single-point calculations have been perform…
Ab initio study on the mechanism of the atmospheric reaction OH + O3--HO2 + O2.
2003
The atmospheric reaction (1) OH + O 3 → + O 2 was investigated theoretically by using MP2, QCISD, QCISD(T), and CCSD(T) methods with various basis sets. At the highest level of theory, namely, QCISD, the reaction is direct, with only one transition state between reactants and products. However, at the MP2 level, the reaction proceeds through a two-step mechanism and shows two transition states, TS1 and TS2, separated by an intermediate, Int. The different methodologies employed in this paper consistently predict the barrier height of reaction (1) to be within the range 2.16 - 5.11 kcal mol -1 , somewhat higher than the experimental value of 2.0 kcal mol -1 .