Capturing High-Energy Polymeric Nitrogen Structures Stabilized by Lutetium at Ambient Conditions.

Polynitrogen with high energy and environmental friendliness has exhibited potential application in military and civilian fields. In this study, first-principle calculations were employed to conduct a comprehensive investigation of the nitrogen-rich Lu-N compounds. The research yielded ten novel polynitrides: P21/c-LuN2, P1̅-LuN3, P1̅-LuN4, P21/m-LuN4, P1̅-LuN5, P1̅-LuN6, P1̅-LuN8, Cm-LuN9, I4/m-LuN10, and Cmcm-LuN10. It is noteworthy that two novel polymeric nitrogen structures have been observed in our prediction: an infinite tripodic-N4 chain formed in P21/m-LuN4, and a heart-shaped N12 ring band formed in Cm-LuN9. Excellent stabilities were observed in the calculated Lu-N compounds; P21/m-LuN4 and P1̅-LuN8 are quenchable under ambient conditions. Meanwhile, the polynitrogen structures of P1̅-LuN6 and Cm-LuN9 are calculated to decompose into thermally stable N6 rings and infinite N-chains under ambient conditions, respectively. Cmcm-LuN10 is thermodynamically stable due to its high symmetry and efficient packing of the chain-like N10 cage. Moreover, the Lu-N compounds, which display favorable energy density (mass energy density (Ed) = 1.60-3.59 kJ/g; volumetric energy density (EV) = 11.32-15.65 kJ/cm3), are prospective candidates for environmentally friendly high-energy density materials. These results provide a good theoretical guide for the experimental synthesis of new energetic materials.