The HF/3s2pld and MP2/3s2pld structures, energies and vibrational frequencies were calculated for ten N8 isomers, corresponding to ten analogous CH structures. Comparative calculations using density functional theory (DFT), with a cc-pVTZ basis set, were also performed. All ten structures were found to be local minima on the energy hypersurface at the Hartree-Fock (HF) level, whereas at the second-order Möller-Plesset (MP2) level nine structures were stable. At the DFT level, eight local minima were found. The total energies were recomputed using 4s3p2dlf basis sets at the HF and MP2 levels of theory.