Density functional theory studies on two novel poly‐nitrogen compounds: N₅⁺N₃⁻ and N₅⁺N₅⁻

Abstract

Density functional theory (DFT) methods with B3LYP/6‐311++g(d,p) level of theory were employed to study two poly‐nitrogen salts N5+N3− and N5+N5−. The optimized geometries and thermochemical parameters, frontier molecular orbitals, molecular electrostatic potential, and predicted infrared (IR) spectra were calculated for inspecting the molecular stabilities, electronic structures, and chemical reactivity. The energetic properties including densities, solid state heats of formation, heats of detonation, detonation velocities, and detonation pressures of N5+N3− and N5+N5− were also calculated. Results show that the planar N5+N3− and N5+N5− have higher heats of formation (>1000 kJ mol−1) than that of HMX (116.1 kJ mol−1) and CL‐20 (365.4 kJ mol−1). The detonation velocity of N5+N3− is 9.29 km s−1, which is comparable with HMX (9.22 km s−1). Especially, N5+N5− has a higher detonation velocity (10.21 km s−1) than HMX and CL‐20, which means it could be an excellent high‐energy‐density material (HEDM). However, they have a very small energy gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), which predicts that they have poor stabilities.

Density functional theory studies on N4 and N8 species: Focusing on various structures and excellent energetic properties

“…All the all-nitrogen materials presented in this work has much higher energy density than CL-20 (D: 9445 m s −1 , p : 46.7 GPa). And compared to N 5 + N 3 − in our previous work ( Xu et al, 2020b ), N 8 -2 (ρ: 1.669 g cm −3 , D: 9747 m s −1 , p : 38.0 GPa) exhibits higher density and higher detonation performance based on the same structural composition of pentazole ring and azide (N 5 + N 3 − : ρ: 1.55 g cm −3 , D: 9290 m s −1 , p : 34.67 GPa). The above discussion not only confirms that all-nitrogen materials have the great prospects because of the huge energy, but also that covalent poly-nitrogen compounds would be more powerful than all-nitrogen salts.…”