First principle calculations of elastic and thermodynamic properties of Ir3Nb and Ir3V with L12 structure under high pressure

The structural and elastic properties of the L1₂ structure Ir₃Nb and Ir₃V under pressure have been investigated by means of the first principles calculations based on the density functional theory within the generalized gradient approximation. The lattice parameters of Ir₃Nb and Ir₃V obtained by minimization of the total energy are consistent with the available experimental and other theoretical results. In addition, the elastic constants (C₁₁, C₁₂, C₄₄) of Ir₃Nb and Ir₃V show that they are mechanical stable structures under pressure. The values of B/G exhibit an upward trend with increasing pressure, which means its ductility increased. When the pressure reaches 45 GPa, the Cauchy pressures and B/G values reveal that Ir₃Nb and Ir₃V change from brittle to ductile. Finally, through quasi-harmonic Debye model, the temperature and pressure dependences of thermodynamic properties are predicted in a wide pressure (0–50 GPa) and temperature (0–1200 K) ranges.