Pressure-Driven Ne-Bearing Polynitrides with Ultrahigh Energy Density

Neon (Ne) can reveal the evolution of planets, and nitrogen (N) is the most abundant element in the Earth's atmosphere. Considering the inertness of neon, whether nitrogen and neon can react has aroused great interest in condensed matter physics and space science. Here, we identify three new Ne–N compounds (i.e., NeN_6, NeN_10, and NeN_22) under pressure by first-principles calculations. We find that inserting Ne into N_2 substantially decreases the polymeric pressure of the nitrogen and promotes the formation of abundant polynitrogen structures. Especially, NeN_22 acquires a duplex host-guest structure, in which guest atoms (Ne and N_2 dimers) are trapped inside the crystalline host N_20 cages. Importantly, both NeN_10 and NeN_22 not only are dynamically and mechanically stable but also have a high thermal stability up to 500 K under ambient pressure. Moreover, ultra-high energy densities are obtained in NeN_10 (11.1 kJ/g), NeN_22 (11.5 kJ/g), tetragonal t-N_22 (11.6 kJ/g), and t-N_20 (12.0 kJ/g) produced from NeN_22, which are more than twice the value of trinitrotoluene (TNT). Meanwhile, their explosive performance is superior to that of TNT. Therefore, NeN_10, NeN_22, t-N_22, and t-N_20 are promising green high-energy-density materials. This work promotes the study of neon-nitrogen compounds with superior properties and potential applications.