Multicoefficient Gaussian-3 calculation of the rate constant for the OH + CH 4 reaction and its 12C/ 13C kinetic isotope effect with emphasis on the effects of coordinate system and torsional treatment

Benjamin A. Ellingson, Jingzhi Pu, Hai Lin, Yan Zhao, Donald G. Truhlar

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27 Scopus citations

Abstract

Rate constants and 12CV 13C kinetic isotope effects are calculated by direct dynamics for the OH + CH 4 → H 2O + CH 3 reaction. The electronic structure calculations required to generate the implicit potential energy surface were carried out by the high-level multicoefficient Gaussian-3/version-3 (MCG3) method and compared to two other multilevel methods, MC3BB and MC3MPW, and three density functional methods, M06-2X, BB1K, and MPW1K. The rate constants and 12C/ 13C kinetic isotope effects are shown to depend strongly on the coordinate system used to calculate the frequencies as well as on the method used to account for the torsional anharmonicity of the lowest-frequency vibrational mode of the generalized transition states.

Original languageEnglish (US)
Pages (from-to)11706-11717
Number of pages12
JournalJournal of Physical Chemistry A
Volume111
Issue number45
DOIs
StatePublished - Nov 15 2007

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