Structural stability and elastic properties of IrSi in B31 and B20-phase from first-principles calculations

• We investigate the structural stability of IrSi in B31 and B20-phase.
• The elastic constants and moduli of IrSi are derived for the first time.
• Based on Mulliken overlap population analysis, the hardness of IrSi are evaluated.

A systematic study of the structural stability, elastic properties and electronic structures for iridium silicide (IrSi) in B31 and B20-phase has been carried out with the generalized gradient approximation (GGA) and local density approximation (LDA) in framework of density functional theory (DFT). The obtained formation enthalpies, energy–volume (E–V) curves and enthalpy–pressure (H–P) curves indicate that orthorhombic B31-IrSi is more stable than cubic B20-IrSi at both ambient and pressure conditions. The elastic stiffness constants, bulk moduli, shear moduli, Young’s moduli, Poisson’s coefficients and elastic anisotropy factors of the two phases IrSi are studied for the first time. The small elastic stiffness constant C22 of B31-IrSi induces easily compressibility along the b axis. Moreover, based on the Mulliken overlap population analysis, the hardness Hv of B31-IrSi (Hv = 11.9 GPa) and B20-IrSi (Hv = 13.4 GPa) are evaluated.