On the Stability of N₅⁺N₅⁻

We investigate the stability of N 5 + N 5 - as an isolated species and in a potential periodic structure. Its barriers toward loss of N 3 · from the N 5 + ion or addition to form N 10 are 25 and 15 kcal/mol. The barrier toward loss of N 2 from the N 5 - ion is 15 kcal/mol. Increasingly positive charges of the N 5 species in N 5 ·, “N 5 + N 3 - ”, N 5 + N 5 -, and N 5 + are correlated with increased dissociation barriers. Preliminary calculations on quasi-periodic (N 5 + N 5 - ) 2 clusters and periodic DFT calculations agree on a density of ∼1.9 g/cm 3 and a lattice energy of ∼130 kcal/mol. If a crystalline form of N 5 + N 5 - could be stabilized, it would be an ideal monopropellant since its density is nearly twice that of hydrazine while the energy densities (heat of reaction per gram) are comparable.