Insights into the energetic performance from structures: a density functional theory study on N 6

In this study, in order to compare the energetic performance of poly-nitrogen compounds with different structures, N 6 was taken as an example, and three bi-ring structures of N 6 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 N 6 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.