High-pressure x-ray diffraction studies on rhenium up to 216 GPa (2.16 Mbar)

Energy-dispersive x-ray diffraction techniques using a synchrotron source were used to study rhenium. The hcp structure is stable up to the highest pressure used 216 GPa (volume fraction V/$V_0$=0.734), and the axial ratio (c/a) is independent of pressure within experimental errors. The present study represents the first x-ray measurement above 2 Mbar, and diffraction patterns with 12 peaks were used to confirm the structure. This is also the first case in which x rays were used to obtain a pressure profile across the diamond face. The suitability of rhenium as a gasket material in ultrahigh-pressure experiments is also discussed.