Intercomparison of pressure scales up to 140 GPa and 2500 K

Figure caption: Differences in pressure among the Pt (red), Au (blue), and MgO (dashed lines) at 1500–2500 K at various pressures. (a), (b), (c), (d) present data at different sample combinations.
Figure caption: Differences in pressure among the Pt (red), Au (blue), and MgO (dashed lines) at 1500–2500 K at various pressures. (a), (b), (c), (d) present data at different sample combinations.

Accurate pressure scales remain a challenging subject in compression science. Intercomparison of the pressure standards provides important information on their accuracies and reconciles discrepancies between experimental results based on different pressure scales. In order to intercalibrate the equations of state (EOSs) of the three widely used pressure standards, gold, platinum, and MgO, a research group has measured their unit cell volumes using the laser-heated diamond anvil cell up to 140 GPa and 2500 K. The simultaneous measurements of Au+MgO and Pt+MgO allow to compare the EOSs of Au, Pt, and MgO directly at high P-T and further refine them for consistency. At 300 K, three standards agree with each other within ±2.5 GPa to 135 GPa in quasi-hydrostatic media. Refined EOSs have been obtained at 300 K, making the measured results consistent with each other within ±1 GPa up to 135 GPa. At high temperature, the Au, Pt, and MgO scales are in agreement with each other within ±1 GPa at pressures between 40 and 130 GPa when the scales by Dorogokupets and Dewaele [2007] are used. While these data sets provide accurate comparison of the widely used pressure standards, Au, Pt, and MgO, it is cautiously noted that they do not provide information on absolute pressure scales. More in Ye et al, J. Geophys. Res., 122, 3450, 2017.