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 (P1̄-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 P1̄-ScN8, P1-ScN9 and P1-ScN11 make them potential candidates in the application of propellants and explosives.