A G3B3 study of N4H4 isomers

A Gaussian-3 theory investigation using B3LYP geometries is carried out to examine N4H4 isomers. Eleven species are found, six of which are reported for the first time. The structures, stabilities, thermochemical properties, and tautomerism between them are studied and discussed. The most stable N4H4 isomer is the straight-chain tetrazene (NH2NNNH2). The results show that N4H4 isomers have high positive heats of formation (ΔHf298) and are highly energetic. The calculated ΔHf298 values are about 300-600 kJ/mol. If synthesized, they would be possible candidates of high-energy-density materials (HEMDs).