The nitrogen-rich transition metal nitrides have attracted considerable attention due to their potential application as high energy density materials. Here, a systematic theoretical study of PtNxcompounds has been performed by combining first-principles calculations and particle swarm-optimized structure search method at high pressure. The results indicate that several unconventional stoichiometries of PtN2, PtN4, PtN5, and Pt3N4compounds are stabilized at moderate pressure of 50 GPa. Moreover, some of these structures are dynamically stable even when the pressure release to ambient pressure. TheP1-phase of PtN4and theP1-phase of PtN5can release about 1.23 kJ g-1and 1.71 kJ g-1, respectively, upon the decomposition into elemental Pt and N2. The electronic structure analysis shows that all crystal structures are indirect band gap semiconductors, except for the metallic Pt3N4withPcphase, and the metallic Pt3N4is a superconductor with estimated critical temperatureTcvalues of 3.6 K at 50 GPa. These findings not only enrich the understanding of transition metal platinum nitrides, but also provide valuable insights for the experimental exploration of multifunctional polynitrogen compounds.
Keywords: first-principles calculations; high pressure; high-energy-density; phase diagram; superconductor; transition-metal nitride.
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