Prediction of structural stability and explosive performance of N-rich Mo–N compounds under high pressures

Abstract

High-energy-density materials (HEDMs) can release enormous amounts of energy through redox reactions, exhibiting high stability, low sensitivity, and environmental friendliness, which are crucial for national defense and energy storage applications. Nitrogen-rich transition metal nitrides (TMNs) generally contain various polynitrogen structures, enabling them to store large amounts of energy, which could be potential HEDMs. Here, we systematically search the pressure-induced stable phases of Mo–N compounds under high pressure through first-principles swarm-intelligence structural search calculations. Several new molybdenum polynitride phases (e.g., P4/mbm MoN₂, P4/mnc MoN₈, and Immm MoN₁₀) are predicted to be stable or meta-stable under high pressure. The accurate structure of the experimental phase Mo₅N₆ is also proposed. The calculation of explosive performance shows that MoN₆, MoN₈ and MoN₁₀ have high energy densities (4.83, 2.51, and 2.93 kJ g⁻¹) and superior detonation velocity (18.25, 11.71, and 12.16 km s⁻¹) and detonation pressure (251.61, 94.69, and 100.21 GPa) properties, which are expected to become efficient HEDMs. In addition, MoN₆ also exhibits potential as a superhard material, with a Vickers hardness of 50.3 GPa. This theoretical exploratory research opens up opportunities to explore high-energy-density and superhard properties in N-rich Mo–N compounds.