Phase stability and mechanical properties of ternary equiatomic arsenides

Abstract The ternary system of equiatomic transition-metal arsenides offers promise for topological superconductors, but their structural stability and mechanical properties remain largely unexplored. By means of the first-principles calculations, the Co 2 P-type orthorhombic structure is predicted to stable ground states of TT ′As ( T = Ti, Zr, or Hf; T ′ = Ru or Os), and the experimentally reported ZrRuAs and HfRuAs with the Fe 2 P-type hexagonal structure only is the high-temperature phases. Although the Fe 2 P-type structure of ideally stoichiometric TiRuAs, TiOsAs, ZrOsAs, and HfOsAs exhibits the thermodynamic and elastic stability, their phonon spectrums always have some imaginary frequencies below 2,500 K, indicating dynamical instability. The calculations on their mechanical properties indicate that these TT ′As compounds are a class of low-compressible and ductile materials. Moreover, they also possess moderately high shear stiffness and hardness. The electronic structures of representative HfRuAs are analyzed to reveal the underlying origin of the intriguing physical properties.