Technical Session - 1

Title:            Computational study on the potential energy surface for the reaction HO2 + NO
Authors:       Ngoc N. Ho, Hong-Uyen T. Nguyen, Lam K. Huynh
Abstract:     The reaction between two radicals HO2 and NO plays a key role in both atmospheric and combustion chemistry [1, 2], relevant to several environmental concerns. In this work, the gas-phase chemical reaction HO2 + NO has been investigated by state-of-the-art ab initio calculations. The rigorous singlet potential energy surface (PES) was constructed at accurate composite CBS-QB3 level of theory, which reveals the three possible pathways for the formation of HO + NO2 from HO2 + NO: (i) the direct oxygen abstraction reaction which is the novel pathway, or (ii) the direct O-O dissociation of the peroxynitrous acid, HOONO intermediate, or (iii) the O–N bond breaking reaction after the isomerization of HOONO to nitric acid (HO-NO2). Multiple pathways was explored to occur via isomerization and decomposition reactions of HOONO intermediate leading to a variety of intermediates and products, HNO + O2, HON + O2, and HONO + O. Our result indicates that nitric acid HO-NO2 is thermodynamically the most stable species followed by the peroxynitrous acid HOONO. The calculated bond lengths, harmonic vibrational frequencies, and the bond dissociation energy for cis,cis-HOONO are in good agreement with available theoretical and experiment data. Our predicted data are valuable information for further investigation on a detailed kinetic analysis of this system.

Keywords:  Combustion and Atmospheric Chemistry, Potential Energy Surface, HO2, NO, Radicals, CBS-QB3
Pages:        026-030

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