Accurate Coupled Cluster Calculations of the Reaction Barrier Heights of Two CH3• + CH4 Reactions

Wim Klopper,*,§ Rafal A. Bachorz,§ David P. Tew,§ Jorge Aguilera-Iparraguirre,§ Yannick Carissan,⊥ Christof Hättig‡
Institut für Physikalische Chemie, Universität Karlsruhe (TH), D-76128 Karlsruhe, Germany, Universités d'Aix-Marseille I, II & III–CNRS, UMR 6263: Institut des Sciences Moléculaires de Marseille (iSm2), F-13397 Marseille Cedex 20, France, and Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

J. Phys. Chem. A 113,11679-11684 (2009).
Received: March 26, 2009; Revised Manuscript Received: July 3, 2009

We have computed barrier heights of 71.8 +/- 2.0 and 216.4 +/- 2.0 kJ mol-1 for the reactions CH4 + CH3• → CH3• + CH4 and CH4 + CH3• → H-center dot + C2H6, respectively, using explicitly correlated coupled cluster theory with singles and doubles combined with standard coupled cluster theory with up to connected quadruple excitations. Transition-state theory has been used to compute the respective reaction rate constants in the temperature interval of 250-1500 K. The computed rates for the reaction to ethane are orders of magnitude slower than those used in the mechanism of Norinaga and Deutschmann (Ind. Eng. Chem. Res. 2007, 46, 3547.) for the modeling of the chemical vapor deposition of pyrolytic carbon.

† Part of the ``Walter Thiel Festschrift''.
* To whom correspondence should be addressed. E-mail: klopper@chem-bio.uni-karlsruhe.de.
§ Universität Karlsruhe (TH).
⊥ Universtités d'Aix-Marseille I, II & III–CNRS.
‡ Ruhr-Universität Bochum.

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