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. N-6-1 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 N-6-2 (d: 1.58 g cm(-3); D: 10 093 m s(-1); P: 41.3 GPa) has higher density and detonation performance than N-6-3 (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 N-6-1 can be compared to those of octanitrocubane (ONC, D: 10100 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.