Accurate equation of state of rhenium as pressure scale up to 130 GPa and 3200 K

Abstract

The equations of states (EOSs) of inert metals are generally used as pressure scales in a high-pressure experiment. However, the thermodynamic model and the method used to constrain the parameters of the EOSs of these metals may cause pressure deviations of up to 7% at 100 GPa and room temperature, and even higher at higher pressures and higher temperatures. In this study, we provide a new approach for obtaining accurate EOS of inert metals. First, we use a set of thermodynamic models, within the quasi-Debye framework, to describe the thermodynamics. Second, both the volume vs pressure data from the shock compression experiment and the volume vs sound velocity data from the static compression experiment are used to constrain the parameters in the EOS formula. In the fitting process, a weighted least-square method based on the uncertainty of these data is used. The calculated Grüneisen parameter shows a strong dependence not only on volume but also on temperature. The variation of the Grüneisen parameter of Re can increase by up to 7% per 103 K under the same volume, which means the previous temperature-independent approximation of the Grüneisen parameter may cause an underestimate of the pressure at high temperature. The pressure–volume–temperature EOS of Re up to 140 GPa and 3200 K is established, which can be used as a high-pressure and high-temperature pressure gauge in the future.