A Refined EOS of bcc Bi up to 260 GPa*

We present diamond anvil cell x-ray diffraction measurements of body-centered cubic Bi, stable above 10 GPa, up to 260 GPa in a neon pressure medium. The simple structure and high compressibility of bcc Bi make it appealing as a pressure calibrant in ultrahigh compression experiments. With these data we have been able to refine the equation of state over a wider pressure range than has previously been covered, and our new EOS parameters show a notable difference from previous work by our maximum pressure. Examination of the stress state of Bi and deviations from reported P-V curves attest to the importance of a soft pressure medium in reducing pressure anisotropy at extreme compression.