High‐Pressure Stability and Electronic Properties of Sodium‐Rich Nitrides: Insights from First‐Principles Calculations

Abstract Using first‐principles structure search calculations, we investigated the phase stability of sodium‐nitrogen (Na−N) compounds under high pressure. Our study reveals that increasing pressure promotes the formation of Na‐rich nitrides, leading to the prediction of three previously unreported stoichiometries: Na 2 N, Na 5 N, and Na 8 N. Notably, the electride Na 5 N undergoes a pressure‐induced structural transition from a P 6/ mmm to a P 6 3 / mmc phase. This transformation is characterized by spatial reorientation and redistribution of interstitial anionic electrons (IAEs). In the P 6 3 / mmc phase, IAEs adopt a zero‐dimensional, triangular‐like configuration, whereas in the low‐pressure P 6/ mmm phase, they form an interconnected, graphene‐like network. With increasing pressure, P 6 3 / mmc phase undergoes a transition from metallic to semiconducting behavior due to the increased interaction between sodium and IAEs. Additionally, C 2/ m Na 8 N, featuring triangular‐ and ship‐like IAEs, is predicted to exhibit superconductivity. Our findings provide new insights into the behavior and stability of Na‐rich nitrides under high‐pressure conditions.