Inter-comparison of the Gold, Platinum, and MgO Pressure Scalesup to 145 GPa and 2,500 K
Abstract
In order to inter-calibrate the equations of state (EOS), we have measured the unit-cell volumes of three primary pressure scales, gold, platinum, and MgO, in the laser heated diamond-anvil cell up to 145 GPa and 2,500 K. We prepared two separate groups of samples, i.e., MgO + Au and MgO + Pt, avoiding alloying between Au and Pt while MgO in both samples enables us to com- pare the thermal EOS of all three pressure standards directly at high pressures and temperatures. At 300 K, we found that the three scales agree with each other the best up to 120 GPa if we use EOSs measured under quasi-hydrostatic media (He or Ne). At high temperature, the three standards match the best within ±1 GPa between 40 and 130 GPa, when we use the scales by Dorogokupets and Dewaele [2007]. However, even for the scales, 2-3 GPa of discrepancy remains at 20-30 GPa and 1500-2000 K, with gold estimating the highest pressure. The discrepancy persists through many different combinations of EOSs. Resolution of the discrepancy requires changes in pressure dependence of Grüneisen parameters, anharmonicity, and/or electronic effects for the EOSs. Although the pressure scales by Dorogokupets and Dewaele [2007] reduce the discrepancy in the pressures of the post-spinel and post-perovskite transitions, more than 10% of discrepancy still remains, suggesting other sources for the discrepancies. The scales by Dorogokupets and Dewaele [2007] make more significant improvement in reducing discrepancy for the Clapeyron slopes the post-spinel boundary to -2.0 -2.7 MPa/K and the post-perovskite boundary to 7 10 MPa/K, which are more consistent with seismic estimations of the 660-km and D" discontinuities.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMMR12A..05S
- Keywords:
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- 3909 Elasticity and anelasticity;
- MINERAL PHYSICSDE: 3954 X-ray;
- neutron;
- and electron spectroscopy and diffraction;
- MINERAL PHYSICSDE: 3620 Mineral and crystal chemistry;
- MINERALOGY AND PETROLOGYDE: 3694 Instruments and techniques;
- MINERALOGY AND PETROLOGY