Stabilization of the High-Energy-Density CuN₅ Salts under Ambient Conditions by a Ligand Effect

A series of excellent works have demonstrated that high-nitrogen-content metal pentazolate (cyclo-N₅ ^-) compounds could be stabilized by high pressure. However, under ambient conditions, low stability precludes their synthesis and application in the field of high-energy-density material. In this work, by using a constrained structure search method, we predicted two new structures as P2₁2₁2₁-CuN₅ and P2₁/c-CuN₅ containing cyclo-N₅ ^- with strong N-N and Cu-N bonds. In both structures, cyclo-N₅ ^- form four coordination with the Cu⁺ ligand, which increases the structural stability by lowering the disturbance to the aromaticity of cyclo-N₅ ^-. The calculated results show that the P2₁2₁2₁-CuN₅ and P2₁/c-CuN₅ structures exhibit high dynamic and thermal stability up to 400 K, indicating that they can be stabilized under ambient conditions. The decomposing energy of P2₁2₁2₁-CuN₅ and P2₁/c-CuN₅ can reach up to 2.40 and 2.42 kJ/g, respectively. Strikingly, the detonation velocity and the pressure of P2₁2₁2₁-CuN₅ is predicted to be up to 10.42 km/s and 617.46 kbar, respectively, indicating that they are promising high-energy candidates in the field of explosive combustion.