Simultaneous compression of NaCl, Au, and ruby: toward mutually consistent pressure scales

ABSTRACT

We evaluate pressure consistency of equations of state (EOS) for NaCl and Au at 300 K. The simultaneous measurements of unit-cell volumes (V) with ruby R1 line shifts (Δλ) in a helium (He) loaded diamond cell effectively remove potential systematic errors. Compression and decompression data were automatically collected at 1 sec interval, yielding a dense dataset with >8,000 (V, Δλ) pairs each for NaCl and Au. Solidification of He has noticeable effects on both V and Δλ (hence P). Only data up to ~14 GPa, or 6000 (V, P) pairs, can be considered hydrostatic within the resolution. The P–V data are fitted to the Rydberg-Vinet and the 3^rd order Birch-Murnaghan EOS. Predicted pressures of these EOSs agree with those given by the Ruby2020 ruby scale to within ±0.05 GPa. Overall, pressures predicted by the Rydberg-Vinet EOS are in better agreement with the average of commonly used NaCl and Au pressure scales.

KEYWORDS:

• High pressure X-ray diffraction
• hydrostaticity
• Rydberg-Vinet equation of state
• Birch-Murnaghan equation of state
• ruby pressure scales

Acknowledgements

This work was performed at HPCAT (Sector 16), APS, Argonne National Laboratory. We thank Richard Ferry for his help with loading helium and two anonymous reviewers for constructive comments which improved the manuscript. Y.W. thanks Simon Hunt for valuable discussions. HPCAT operations are supported by DOE-NNSA's Office of Experimental Sciences. Portions of this work were performed at GeoSoilEnviroCARS (The University of Chicago, Sector 13), Advanced Photon Source (APS), Argonne National Laboratory. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

GeoSoilEnviroCARS is supported by the National Science Foundation – Earth Sciences [EAR – 1634415].