High Energy Density Materials based on N₄ Molecules: Synthesis Routes from First-principles Calculations

To explore the routes for synthesizing and stabilizing polymeric nitrogen in molecules or crystals, two methods for synthesizing high energy density materials (HEDM) based on N₄ molecules were proposed based on the first-principles calculations. The first route is to adsorb N₄(T_d) molecule on single crystal metal surfaces, and the second method is to use structural search to obtain stable N₄-related structures. Three N₄-containing crystals, P-43m-N₄, P4/m-LiN₄ and Amm2-G/N₄ were proposed, and their energy densities, thermodynamic and kinetic stabilities, as well as their electronic properties were calculated. The results show that under ultra-high vacuum and low temperature conditions, N₄(T_d) can be stabilized by losing the T_d symmetry on the metal surfaces. AIMD simulations indicate that they are stable at 50GPa and 50 or 300K. Through coordination bond between N₄ and metal atoms, polymerized N₄ can be synthesized at high pressure and stabilized at low temperature conditions.