Chair-like N66− in AlN3 with high-energy density

The search for stable novel polynitrogen clusters has garnered significant attention in the field of energetic materials due to their potential applications as high-energy-density materials. In this study, a chair-like N 6 6 − ring with N–N single bonds in the AlN3 compound is theoretically predicted through first-principles calculations in conjunction with an unbiased structure searching method. The predicted AlN3 phase exhibits high kinetic and thermodynamic stability, along with a high energy density of 5.04 kJ/g relative to AlN and N2 gas. Additionally, its detonation velocity and pressure are estimated to reach 12.93 km/s and 1009.63 kbar, respectively. These values are greater than those of TNT and HMX, positioning it as a promising candidate for high-energy-density materials in the field of explosive combustion. The analysis of electronic properties and the related chemical bonding patterns indicates that the compounds are stabilized by both Coulomb interactions and covalent bonds. More importantly, the calculated formation of enthalpy indicates that the N 6 6 − anions within AlN3 can be synthesized by compressing AlN and N2 at a moderate pressure (46 GPa). These findings present a viable approach for synthesizing and stabilizing the all-nitrogen N 6 6 − anions.