Abstract
Based on density functional theory and the crystal structure prediction methods, USPEX and AIRSS, stable intermediate compounds in the Ni-X (X = B, C, and N) systems and their structures were determined in the pressure range of 0-400 GPa. It was found that in the Ni-B system, in addition to the known ambient-pressure phases, the new nickel boride, Ni(2)B(3)-Immm, stabilizes above 202 GPa. In the Ni-C system, Ni(3)C-Pnma was shown to be the only stable nickel carbide which stabilizes above 53 GPa. In the Ni-N system, four new phases, Ni(6)N-R3̄, Ni(3)N-Cmcm, Ni(7)N(3)-Pbca, and NiN(2)-Pa3̄, were predicted. For the new predicted phases enriched by a light-element, Ni(2)B(3)-Immm and NiN(2)-Pa3̄, mechanical and electronic properties have been studied.