High-pressure lattice dynamic and thermodynamic properties of Ir by first-principles calculation

Lattice dynamic and thermodynamic properties of Ir under high pressure are studied by using density-functional theory (DFT) within quasiharmonic approximation. Several possible phases under pressure have been investigated by comparing their corresponding total energies at different volumes and no transition within these structures occurs above 60 GPa. Phonon dispersion relations of Ir under different pressures are computed. With thermal equation of state being investigated, thermal pressure, linear thermal expansion coefficient, bulk modulus and Grueneisen parameter of Ir are calculated as function of temperature and pressure. Also, the dependence of the Debye temperature on pressure is computed. The calculation results are compared to the experimental data whenever they exist to guarantee the validity. Some of these results may have their application in the study of Doppler-broadened neutron resonance spectroscopy.