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Issue 18, 2011
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Theoretical study of the dynamics of Cl + O3 reaction I. Ab initio potential energy surface and quasiclassical trajectory results

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Abstract

We present a global full dimensional potential energy surface (PES) for the Cl + O3 → ClO + O2 reaction, which is an elementary step in a catalytic cycle that leads to the destruction of ozone in the stratosphere. The PES is constructed by interpolation of quantum chemistry data using the method developed by Collins and co-workers. Ab initio data points (energy, gradients and Hessian matrix elements) have been calculated at the UQCISD/aug-cc-pVDZ (unrestricted quadratic configuration interaction with single and double excitations) level of theory. The ab initio calculations predict a markedly non-coplanar (dihedral angle of 80°) transition state for the reaction, located very early in the reactant valley and slightly below the energy of the reactants as long as the spin–orbit splitting is neglected. Quasiclassical trajectory (QCT) calculations have been carried out at several collision energies to investigate the reaction dynamics. The QCT excitation function shows no threshold, displays a minimum at a collision energy of 2.5 kcal mol−1, and then increases monotonically at larger collision energies. This behaviour is consistent with a barrierless reaction dominated by an oxygen-abstraction mechanism. The calculated product vibrational distributions (strongly inverted for ClO) and rate constants are compared with experimental determinations. Differential cross sections (DCS) summed over all final states are found to be in fairly good agreement with those derived from crossed molecular beam experiments.

Graphical abstract: Theoretical study of the dynamics of Cl + O3 reaction I. Ab initio potential energy surface and quasiclassical trajectory results

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Publication details

The article was received on 06 Dec 2010, accepted on 07 Mar 2011 and first published on 24 Mar 2011


Article type: Paper
DOI: 10.1039/C0CP02793F
Citation: Phys. Chem. Chem. Phys., 2011,13, 8537-8548
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    Theoretical study of the dynamics of Cl + O3 reaction I. Ab initio potential energy surface and quasiclassical trajectory results

    J. F. Castillo, F. J. Aoiz and B. Martínez-Haya, Phys. Chem. Chem. Phys., 2011, 13, 8537
    DOI: 10.1039/C0CP02793F

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