Platinum metal was shock compressed to 660 GPa using a twohyphen;stage lighthyphen;gas gun to qualify this material as an ultrahighhyphen;pressure standard for both dynamic and static experiments. The shock velocity data are consistent with most of the previously measured lowhyphen;pressure data, and an overall linearusminus;uprelationship is found over the range 32ndash;660 GPa. As a part of this work, we have also extended the Hugoniot of the tantalum standard we use to 560 GPa; we have included these data into a new linear fit of the tantalum Hugoniot between 55ndash;560 GPa. We also present the results of a firsthyphen;principles theoretical treatment of compressed platinum. The fcc phase is predicted to remain stable to beyond 550 GPa. In addition, we have calculated the 300hyphen;K pressurehyphen;volume isotherm and the Hugoniot. The latter is in excellent agreement with experimental results and qualifies the former to at least 10percnt; accuracy.
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