First‐Principles Study of Nb–Si‐(Co, Rh, Ir) Ternary Compounds

This study employs first‐principles calculations to systematically investigate the effects of platinum group elements (Co, Rh, Ir) on the structural, mechanical, thermal, and electronic properties of Nb–Si‐based ternary compounds. All NbSiX phases exhibit negative formation enthalpies and dynamically stable phonon spectra. Among them, NbSiIr demonstrates the most superior overall performance, possessing the highest bulk modulus (268.1 GPa) and Young's modulus (345.4 GPa), along with a predicted melting point of 3359 K. Its good ductility is reflected in a Pugh's ratio (B/G) of 1.99. Electronic structure analysis reveals that the excellent properties of NbSiIr originate from its lowest density of states at the Fermi level and enhanced metallic bonding character. This work identifies Ir as the most effective alloying element and provides theoretical guidance for developing next‐generation Nb–Si‐based ultrahigh‐temperature structural materials.