Potential energy surface and quasiclassical trajectory studies of the CN+H{sub 2} reaction
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113 (United States)
- Chemical Dynamics Group, Argonne National Laboratory, Argonne, Illinois 60439 (United States)
We present dynamical studies of the CN+H{sub 2} reaction based on an empirical potential energy surface that is derived from high quality {ital ab} {ital initio} calculations. The {ital ab} {ital initio} calculations, which use a multireference configuration interaction method with large correlation consistent basis sets, indicate that the linear HHCN barrier is about 4.3 kcal/mol above CN+H{sub 2}, and that there is no reaction path which connects CN+H{sub 2} to the stable intermediate H{sub 2}CN, although there is a path for dissociation of H{sub 2}CN to H+HCN. The empirical surface is written as a sum of two-, three-, and four-body terms, with the two- and three-body terms for HCN based on an accurate global surface that describes both the HCN and HNC force fields. The four-body terms are developed so as to describe the HHCN linear saddle point and the H{sub 2}CN minimum accurately, as well as dissociation of H{sub 2}CN into HCN+H, and the ridge which separates the abstraction and H{sub 2}CN dissociation pathways. Other features of the potential surface, such as the HCNH {ital cis} and {ital trans} minima, and the pathways leading to the formation of HNC+H are also described, though less accurately. Three different choices for the HHCN saddle point properties are considered. We find that the surface which matches the {ital ab} {ital initio} barrier energy most accurately gives rate constants that are too low. Much better agreement is obtained using a 3.2 kcal/mol barrier. The trajectory results show typical dependence of the CN+H{sub 2} reactive cross sections on initial translational energy and initial vibration/rotation state, with CN behaving as a spectator and H{sub 2} playing an active role in the reaction dynamics. Analysis of the H+HCN products indicates that both the C-H stretch and bend modes are significantly excited, with bend excitation showing strong sensitivity to the saddle point properties and to reagent translational energy.
- DOE Contract Number:
- W-31-109-ENG-38
- OSTI ID:
- 367140
- Journal Information:
- Journal of Chemical Physics, Vol. 105, Issue 2; Other Information: PBD: Jul 1996
- Country of Publication:
- United States
- Language:
- English
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