| Abstract
| - Quantum mechanical methods have been used to examine isomers ofN8. In addition to the previously studiedoctaazacubane structure (Oh symmetry,1), we have investigated two new structures, ofD2h (2) andC2v (3)symmetry, without NN double bonds. TheC2v structure may be designatedoctaazacuneane. The followingbasis sets and methods have been employed to optimize geometries: (1)(SCF, CISD, CCSD)/DZP; (2) (SCF,MP2, B3LYP, B3P86, BHLYP)/6-31G*; (3) B3LYP/6-311+G*. Thesingle-point energies have also beenestimated at the CISD+Q/DZP level of theory with CISD/DZP geometriesand at the CCSD(T)/DZP levelwith CCSD/DZP geometries. The harmonic vibrational frequencies andtheir infrared intensities have alsobeen predicted with the SCF, MP2, and DFT methods. The resultsshow that the two new isomers are bothminima on the N8 potential energy hypersurface and ofhigher energy than isomers containing NN doublebonds. Among the three isomers with only single bonds, the oneswith the higher symmetry have higherenergies.
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