关键词: ternary nitride, crystal structure, CALYPSO, high pressure

Abstract: Transition metal nitrides have attracted significant attention due to their outstanding properties; however, studies on ternary systems under high pressure remain limited. In this work, we systematically investigated the structures and properties of NiMoN compounds in the pressure range of 0-100 GPa by combining crystal structure analysis by particle swarm optimization (CALYPSO) structure prediction with first-principles calculations. To explore more structural possibilities, a large number of candidate structures were predicted and those with potential stability were selected. Among the newly predicted structures, a stable phase $P$2$_{1}$3-NiMo$_{4}$N and a low-energy metastable phase $I$4$_{1}$32-NiMo$_{3}$N are proposed for the first time. The metastable structure $I$4$_{1}$32-NiMo$_{3}$N lies 0.007 eV/atom above the convex hull, whereas the energy of the experimentally synthesized structure Fd3$m$-Ni$_{3}$Mo$_{3}$N is 0.036 eV/atom above the convex hull. Therefore, $I$4$_{1}$32-NiMo$_{3}$N can likely be obtained through experimental synthesis. Phonon and elastic constant calculations confirm the stability of $P$2$_{1}$3-NiMo$_{4}$N and $I$4$_{1}$32-NiMo$_{3}$N, while electronic structure calculations indicate that both exhibit metallic behavior, with Mo-4d orbitals making the primary contribution at the Fermi level. Mechanical property evaluations reveal that $P$2$_{1}$3-NiMo$_{4}$N exhibits high hardness, whereas $I$4$_{1}$32-NiMo$_{3}$N shows relatively lower hardness but enhanced ductility. Under different pressures, both structures exhibit comparable ideal tensile strengths, but their failure mechanisms differ. This study broadens the known structural diversity of NiMoN ternary nitrides and provides theoretical insights into the exploration of high-pressure ternary nitrides.

Key words: ternary nitride, crystal structure, CALYPSO, high pressure