Compressibility, Structure, and Melting of Platinum to 500 GPa*

Platinum is used as a pressure standard in both static and dynamic compression experiments, due in part to the stability of the face-centered cubic (fcc) phase over wide pressure–temperature states. To address discrepancies in the reported melting curves as well as a predicted phase transformation between 35 and 300 GPa [1], x-ray diffraction and optical pyrometry characterized shock and shock-ramped platinum. The fcc phase was measured for initial shocks between 83 and 200 GPa and subsequent compression up to 500 GPa. On the Hugoniot, the fcc phase remained stable upon compression until liquid diffraction was observed. From these results, a melt curve is constructed incorporating previous melt measurements in static and dynamic compression experiments. Optical pyrometry provides a lower bound on the Hugoniot melting temperature.  This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0003856.

[1] L. Burakovsky, S. P. Chen, D. L. Preston, and D. G. Sheppard, J. Phys.: Conf. Ser. 500, 162001 (2014).