Experimental Evidence for a High-Pressure Isostructural Phase Transition in Osmium

Florent Occelli (1) , Daniel L Farber (1) , James M Badro (1, 2) , Chantel M Aracne (1) , David M Teter (3) , Michael M Hanfland (4) , Bernard M Canny (2) , Bernard M Couzinet (2)

1 Earth Science Division, Energy and Environment Directorate
2 IMPMC - Institut de minéralogie et de physique des milieux condensés
3 Organization 9753
4 ESRF - European Synchrotron Radiation Facility

We have measured the isothermal equation of state (EOS) of osmium to 75 GPa under hydrostatic conditions at room temperature using angle-dispersive x-ray diffraction. A least-squares fit of this data using a third-order Birch-Murnaghan EOS yields an isothermal bulk modulus K 0 ˆ 411 6 GPa, showing osmium is more compressible than diamond. Most importantly, we have documented an anomaly in the compressibility around 25 GPa associated with a discontinuity in the first pressure derivative of the c=a ratio. This discontinuity plausibly arises from the collapse of the small hole-ellipsoid in the Fermi surface near the L point.

Keywords: osmium, high-pressure solid-state phase transformations, equations of state, X-ray diffraction, elastic moduli

Domains: Condensed Matter [cond-mat]; Mineralogy

Florent Occelli, Daniel L Farber, James M Badro, Chantel M Aracne, David M Teter, et al.. Experimental Evidence for a High-Pressure Isostructural Phase Transition in Osmium. Physical Review Letters, 2004, 93, pp.095502. ⟨10.1103/PhysRevLett.93.095502⟩. ⟨insu-01387809⟩