Pressure-Induced Phase Transformations of IrSb from First-Principles Calculations

Based on first-principle calculations and the structure prediction method CALYPSO of particle swarm optimization algorithms, phase transition behaviors and physical properties of IrSb in the pressure range of 0–100 GPa have been systematically studied. At ambient pressure, the space group of $\alpha $-IrSb phase with cubic structure is P6₃/mmc, in consistency with experimental results. A new cubic structure, $\beta $-IrSb phase, is found at 16.4 GPa with the space group of C2/c. When the pressure is above 76.5 GPa, the space group becomes P-1. The phonon dispersion shows that $\alpha $-, $\beta $- and $\gamma $-IrSb phases have no virtual frequency in the whole Brillouin zone, thus the three phases are dynamically stable. Calculated results show that the formation enthalpy of three phases are less than zero, indicating that all the three phases have the thermodynamic stability. Band structure calculations show that all the three phases have the overlapping of conduction bands and valence bands near Fermi surface, thus are metallic phases. The charge transfer of each phase is calculated and discussed, in which Ir atoms are the acceptor and Sb atoms are the donor.