Prediction of metastable phase of the Sc–N system in the N-rich region under high pressure

The prediction of the high-pressure structure of the ScNx system enriches the phase diagram of the Sc–N system: three metastable phase structures (P-ScN8, P1-ScN9 and P1-ScN11) are proposed in the N-rich region. These structures have novel polymeric nitrogen structures, and enrich the structural types of polymeric nitrogen under pressure. Interestingly, the P1-ScN11 phase can be quenched to ambient conditions, and release energy at a relatively mild temperature of 800 K. The larger charge transfer plays an important role in the structural stability by inducing the Sc–N ionic bond interaction and N–N covalent bond interaction. The prominent energy properties of P-ScN8, P1-ScN9 and P1-ScN11 make them potential candidates in the application of propellants and explosives.