Unique structure and high energy properties of lithium-nitrogen compound in the N-rich region

The structure and properties of the Li-N system in the nitrogen-rich region have been systematically studied at 50 GPa. We propose four stable novel phases: P1-LiN₇, Pm-LiN₈, P1-LiN₉ and P1-LiN₁₀. The polynitrogen polymeric structure in the P1-LiN₁₀ phase is discovered for the first time: the N atoms exist in the form of nitrogen chains, which contain N₅ rings, and every two the N₅ rings are connected by five N atoms. The analysis of electrical properties shows that the P1-LiN₇, Pm-LiN₈ and P1-LiN₉ phases are semiconductor, while the P1-LiN₁₀ phase is a superconductor with 0.23 K at 50 GPa. The N atoms in the P1-LiN₁₀ phase all exist in the sp³ hybrid form. The high energy density, and excellent detonation pressure, detonation velocity performance of the P1-LiN₁₀ phase make it good candidate for high energy density materials.