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., NeN6, NeN10, and NeN22) 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, NeN22 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 NeN10 and NeN22 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 NeN10 (11.1 kJ/g), NeN22 (11.5 kJ/g), tetragonal t-N-22 (11.6 kJ/g), and t-N-20 (12.0 kJ/g) produced from NeN22, which are more than twice the value of trinitrotoluene (TNT). Meanwhile, their explosive performance is superior to that of TNT. Therefore, NeN10, NeN22, 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.