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

Abstract

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 3rd 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.