Detailed investigation of thermodynamic properties of hexagonal osmium using the ab-initio technique

The finite-temperature density functional theory and the quasiharmonic approximation are adopted to investigate thermodynamics properties of hexagonal osmium. By varying lattice volume, the anharmonic effect is part considered in present work. Phonon frequencies calculations are performed from density functional perturbation theory (DFPT). By fitting the total free energy (including both electronic and vibrational parts) to equation of states at different temperatures, some classical thermodynamic quantities and their pressure and temperature dependences are investigated systematically. The results are in good agreement with the available experimental and theoretical data.