Molecular design and explosive properties of N₈ isomers as potential high energy density materials

Twenty novel N₈ molecular structures with different shapes of ring, cage, ladder and etc are designed. Three high-precision quantum chemistry methods are used to optimize these structures and six thermodynamic stable molecular configurations have been screened out from them. Then the reliable theoretical predictions of their structural, electronic and explosive properties are performed to obtain the optimal structural parameters, energy, density, heat of formation and detonation velocity and pressure. The results show that a planar double five-membered cyclic structure has the most thermal stability among the six N₈ isomers because it has the lowest molecular tension, the minimum total energy and the maximum HOMO-LUMO energy gap. Moreover, the double five-membered cyclic and cubic structures possess the minimum and maximum heat of formation, respectively. It is also found that the theoretical values of detonation velocity and pressure of these six N₈ molecules are greater than those of the hexogen and octogen, which are well-known explosives. Therefore, the six N₈ molecules can be considered as potential excellent pollution-free candidates for high energetic materials.