Prediction of erbium–nitrogen compounds as high-performance high-energy-density materials

To explore high-energy-density materials, intense attention has been focused on how to stabilize the N–N bond in nitrogen-rich compounds. Here, we report several stable phases of erbium–nitrogen compounds ErN _x as high-energy-density materials. Specifically, the phase diagrams of stable high-pressure structures Immm-ErN₂, C2-ErN₃, P 1 ˉ -ErN₄, and P 1 ˉ -ErN₆, are theoretically studied by combining first-principles calculation with particle swarm optimization algorithm. In these erbium–nitrogen compounds, the N–N bonds are stabilized as diatomic quasi-molecule N₂, helical-like nitrogen chains, armchair nitrogen chains, and armchair–anti-armchair nitrogen chains, respectively. Among them, the P 1 ˉ -ErN₆ harbors excellent stability at high thermal up to 1000 K. More importantly, the P 1 ˉ -ErN₆ has outstanding explosive performance with high-energy-density of 1.30 kJ g⁻¹, detonation velocity of 10.87 km s⁻¹, and detonation pressure of 812.98 kbar, which shows its promising application prospect as high-energy-density materials.