Systematical High-Pressure Study of Praseodymium Nitrides in N-Rich Region

Abstract We investigate high-pressure phase diagrams of Pr–N compounds by proposing five stable structures (Pnma-PrN,I4/mmm-PrN₂,C2/m-PrN₃,$P\overline{1}$-PrN₄, andR3-PrN₈) and two metastable structures ($P\overline{1}$-PrN₆ and$P\overline{1}$-PrN₁₀). The$P\overline{1}$-PrN₆ with the N₁₄-ring layer andR3-PrN₈ with the N₁₈-ring layer can be quenched to ambient conditions. For the$P\overline{1}$-PrN₁₀, the N₂₂-ring layer structure transfers into infinite chains with the pressure quenched to ambient pressure. Remarkably, a novel polynitrogenhR8-N designed by the excision of Pr atoms fromR3-PrN₈ is obtained and can be quenched to ambient conditions. The N-rich structures of$P\overline{1}$-PrN₆,R3-PrN₈, c-PrN₁₀ and the solid pure nitrogen structure exhibit outstanding properties of energy density and explosive performance.