Ab initio molecular orbital calculations have been carried out on 2,4,6,8-tetranitro-1,3,5,7-tetraazacyclooctatetraene, the tetramer of the series (NO2CN), where n = 1-4, using the Hartree-Fock theory with the 6-31 G(d) basis set. These calculations yield three conformers for the tetramer with D-4h, C-4h and C-2 symmetries. The nonplanar conformer with the C-2 symmetry turns out to be 99.0 and 164.4 U mol(-1), respectively, lower in energy than the C-4h and D-4h conformers. The electron density topography-the density at the bond critical point-has been used as a measure of the C-NO2 strengths. Based on these bond strengths, heats of formation [obtained from the parametric model 3 (PM3) method] and specific decomposition energies, it may be concluded that (NO2CN)(4) is a promising candidate in the class of high energy molecules. Theoretically computed explosive (velocity of detonation, detonation pressure, etc.) and ballistic (characteristic velocity, specific impulse, etc.) parameters support these conclusions. (c) 2005 Elsevier B.V. All rights reserved.