Thermal equation-of-state of osmium: a synchrotron X-ray diffraction study Original Research Article

The pressure–volume–temperature behavior of osmium was studied at pressures and temperatures up to 15 GPa and 1273 K. In situ measurements were conducted using energy-dispersive synchrotron X-ray diffraction in a T-cup 6–8 high pressure apparatus. A fit of room-temperature data by the third-order Birch–Murnaghan equation-of-state yielded isothermal bulk modulus K0=435(19) GPa and its pressure derivative K′0=3.5(0.8) GPa. High-temperature data were analyzed using Birch–Murnaghan equation of state and thermal pressure approach. The temperature derivative of bulk modulus was found to be −0.061(9) GPa K−1. Significant anisotropy of osmium compressibility was observed.