Bulk modulus of osmium: High-pressure powder x-ray diffraction experiments under quasihydrostatic conditions

High-pressure powder x-ray diffraction experiments have been carried out on Os at room temperature under quasihydrostatic conditions with a He-pressure medium. By fitting the pressure-volume data up to 580.3em0exGPa, the bulk modulus and its pressure derivative are determined to be B₀=395(15)0.3em0exGPa and B₀^'=4.5(5). The bulk modulus of Os is smaller than that for diamond, in contrast with the conclusion drawn in a recent work [H. Cynn, et al. Phys. Rev. Lett. 88, 135701 (2002)].