title: The H + CO ⇌ HCO reaction studied by ab initio benchmark calculations.
abstract: The title reaction has been calculated using complete active space self-consistent field and internally contracted multi-reference configuration interaction, including Davidson correction, calculations. Dunning's correlation consistent atomic basis sets, together with several complete basis set extrapolation schemes, were employed. Core-valence and scalar relativistic effects were also taken into account, as well as anharmonicity of the vibrational modes. Core-valence correlation appears to have a large impact on the calculated frequencies, spectroscopic constants, and on the energetics. In particular, the best estimate for the HCO (DCO) formation barrier height at 0 K, 4.54 ± 0.14 (4.43 ± 0.14) kcal mol(-1) is larger than previous theoretical works and well above the usually accepted value of 2.0 ± 0.4 kcal mol(-1), measured at room temperature. Inclusion of temperature and entropy at 298 K does not seem to be able to solve this discrepancy. The present theoretical barrier height is therefore the recommended value. The exo-ergicity of the HCO (DCO) dissociation reaction, predicted to be -13.36 ± 0.57 (-14.72 ± 0.57) kcal mol(-1), is slightly below the experimental value. Finally, all tested density functionals fail to reproduce accurately both the formation and dissociation barriers.
authors.affiliation: Laboratoire de Physique des Lasers, Atomes et Molecules (PhLAM), UMR CNRS 8523, Université Lille 1 Sciences et Technologies, Villeneuve d'Ascq F-59655, France.
authors.forename: Phillip S
authors.initials: PS
authors.lastname: Peters
authors.forename: Denis
authors.initials: D
authors.lastname: Duflot
authors.forename: Laurent
authors.initials: L
authors.lastname: Wiesenfeld
authors.forename: Céline
authors.initials: C
authors.lastname: Toubin