Ab initio multireference configuration interaction study of CH sub 2 NNO sub 2. HONO elimination vs NN bond fragmentation
- Naval Research Laboratory, Washington, DC 20375-5000 (USA)
- Ballistic Research Laboratory, Aberdeen Proving Ground, MD 21005 (USA)
- Lawrence Livermore National Laboratory, Livermore, CA 94550 (USA)
Features of the potential energy surface pertinent to the thermal decomposition mechanism of methylenenitramine (CH{sub 2}NNO{sub 2}) are investigated. At issue are the activation energies both for concerted molecular dissociation leading to HCN and HONO and for the simple NN bond cleavage leading to CH{sub 2}N and NO{sub 2}. We use multiconfiguration (MC)SCF wave functions with double-zeta and double-zeta plus polarization quality basis sets to locate minimum energy and transition state structures as well as determine harmonic vibrational frequencies and resulting zero-point vibrational energies. The energetics are determined using configuration interaction wave functions which include single and double excitations from a selected set of reference configurations constructed with the MCSCF molecular orbitals. Our best calculations, without adjustment, predict the molecular dissociation to have an activation energy slightly lower than that for simple bond rupture. Calculations at the level of those reported here are known, however, to underestimate bond dissociation energies by several kcal/mol. Based on trends from past calculations, and new calculations on a related compound, we estimate the activation energy for the HONO elimination path to be 31{plus minus}4 kcal/mol and the NN bond dissociation energy to be 35{plus minus}4 kcal/mol. This reverses the energetic ordering of previous theoretical predictions and is consistent with recent molecular beam experiments.
- OSTI ID:
- 7069209
- Journal Information:
- Journal of Chemical Physics; (USA), Vol. 93:3; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMINES
DECOMPOSITION
HYDROCYANIC ACID
CHEMICAL REACTION YIELD
NITROUS ACID
ACTIVATION ENERGY
CHEMICAL BONDS
CONFIGURATION INTERACTION
DISSOCIATION ENERGY
CHEMICAL REACTIONS
CYANIDES
ENERGY
HYDROGEN COMPOUNDS
INORGANIC ACIDS
ORGANIC COMPOUNDS
YIELDS
400201* - Chemical & Physicochemical Properties