Stable nitrogen-rich yttrium nitrides under high pressure

Polynitrides have excellent physical and chemical properties as well as have drawn wide attention. Through the first-principles calculations and CALYPSO structure searching approach, we calculated the overall structure of YN components (from 0.5 to 10) and established the pressure versus composition diagram and pressure versus structure phase diagram of the YN system. This paper focuses on the YN2 structure (space group P2(1)) which can be stable at 0 GPa and the YN10 structure with the highest nitrogen content (space group Imm2) with the intriguing chain-like N-10 cage structure appears. Under ambient conditions, the YN10 structure has a high energy density (9.33 kJ g(-1)). By calculating the phonon dispersion curve, the structure has better dynamic stability at 250 GPa. Seven structures (Y2N, YN, YN2, YN3, YN5, YN8, YN10) that appear on convex hull graphs in all YN systems are also calculated. Their dynamics, mechanics and related electronic properties are described in the appendix. We hope that our theoretical research can facilitate future experimental realization and help to advance the research on nitrogen chains.

Automated summary

Through calculations and structure searching, this study investigates various structures of YN components and establishes corresponding pressure and composition diagrams as well as phase diagrams. The YN10 structure is found to have a high energy density under ambient conditions and better dynamic stability under high pressure.