Insights into the energetic performance from structures: a density functional theory study on N6

Abstract

In this study, in order to compare the energetic performance of poly-nitrogen compounds with different structures, N₆ was taken as an example, and three bi-ring structures of N₆ were presented and calculated by using density functional theory (DFT) methods. N₆-1 with 3D caged structures exhibits the highest density (1.64 g cm⁻³), highest heat of formation (1262.2 kJ mol⁻¹), best detonation performance (D: 10 899 m s⁻¹; P: 50.7 GPa) and best specific impulse (422.7 s) among the three N₆ isomers. V-shaped N₆-2 (d: 1.58 g cm⁻³; D: 10 093 m s⁻¹; P: 41.3 GPa) has higher density and detonation performance than N₆-3 (d: 1.50 g cm⁻³; D: 9714 m s⁻¹; and P: 44.6 GPa) with a chair-like structure. All three designed materials show a better precited detonation performance and specific impulses (387.2–422.7 s) than CL-20 (D: 9406 m s⁻¹; P: 44.6 GPa; and I_sp: 272.6 s), and the detonation properties of N₆-1 can be compared to those of octanitrocubane (ONC, D: 10 100 m s⁻¹; and P: 50.0 GPa). The surface electrostatic potentials, frontier molecular orbitals, and weak interactions were also analyzed to further understand the structure–performance relationship.