Five stable points on the N sub 6 energy hypersurface: Structures, energies, frequencies, and chemical shifts
- Los Alamos National Lab., NM (USA)
Five stationary points on the N{sub 6} energy hypersurface have been located by use of ab initio self-consistent field (SCF) methods. These five points correspond to the N{sub 6} analogues of the (CH){sub 6} structures: (a) benzene (1), (b) Dewar benzene (2), (c) benzvalene (3), (d) triprismane (4), and (e) trans-3,3{prime}-bicyclopropenyl (5). The points of the energy hypersurface are calculated in the restricted Hartree-Fock approximation, using 4-31G and 4-31G* basis sets. At the stationary points, vibrational frequencies have also been calculated at the RHF/4-31G and RHF/4-31G* levels. Within the RHF/4-31G* model, all the structures are stable. For trans-3,3{prime}-bicyclopropenyl, no corresponding stationary point is found with the RHF/4-31G model. The five structures are higher in energy than three N{sub 2} molecules by (1) 243, (2) 289, (3) 303, (4) 382, and (5) 286 kcal/mol with the RHF/4-31G* model. The effect of electron correlation on the energies is examined by use of the MP2-FC/4-31G*//RHF/4-31G* and MP2=FC/4-31G//RHF/4-31G models. In most cases, the inclusion of correlation stabilizes the structures to dissociation into three N{sub 2} molecules by 30-50 kcal/mol (relative to the mean field results). The lowest (nontorsional) RHF/4-31G* vibrational frequency for 2-5 is significantly larger than that of 1, indicating that the geometries of 2-5 are more rigidly defined by the energy hypersurface than is 1. Nitrogen chemical shifts are also presented; these were calculated at the RHF/4-31G level using gauge-invariant atomic orbitals and SCF perturbation theory. Most calculations were also performed on diatomic nitrogen (N{sub 2}), diimide (N{sub 2}H{sub 2}), and hydrazine (N{sub 2}H{sub 4}); these results are used as an aid in the interpretation of the N{sub 6} results.
- OSTI ID:
- 7108552
- Journal Information:
- Journal of Physical Chemistry; (USA), Vol. 93:15; ISSN 0022-3654
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
NITROGEN
ENERGY MODELS
ANALOG SYSTEMS
BENZENE
CALCULATION METHODS
SELF-CONSISTENT FIELD
THEORETICAL DATA
AROMATICS
DATA
ELEMENTS
HYDROCARBONS
INFORMATION
NONMETALS
NUMERICAL DATA
ORGANIC COMPOUNDS
400000* - Chemistry
400200 - Inorganic
Organic
& Physical Chemistry
400102 - Chemical & Spectral Procedures