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Ab initio study of the mechanism of the atmospheric reaction: NO 2 + O 3 → NO 3 + O 2
Author(s) -
PeiróGarcía Julio,
NebotGil Ignacio
Publication year - 2003
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.10299
Subject(s) - hypersurface , chemistry , ab initio , enthalpy , standard enthalpy change of formation , potential energy , reaction mechanism , transition state , ab initio quantum chemistry methods , thermodynamics , range (aeronautics) , potential energy surface , computational chemistry , atomic physics , molecule , standard enthalpy of formation , physics , materials science , mathematics , catalysis , organic chemistry , composite material , mathematical analysis , biochemistry
Abstract The atmospheric reaction NO 2 + O 3 → NO 3 + O 2 (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 × 10 −18 cm 3 molecule −1 s −1 . Both results can be regarded also as accurate predictions of the methodology employed in this article. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 1657–1663, 2003