Compression of lithium fluoride to 92 GPa

Abstract

The equation of state and compression behavior of lithium fluoride, LiF, have been determined to 92 GPa by X-ray diffraction in a diamond anvil cell. A neon pressure-transmitting medium was used to minimize the effect of differential stress on the sample. Consistent results using multiple pressure standards were obtained. By fitting the pressure–volume data to a Birch–Murnaghan equation of state, the isothermal bulk modulus and its corresponding pressure derivative at zero pressure were determined to be K₀=70.1±0.7 GPa, and K′₀=4.3±0.1. If the bulk modulus is fixed at 66.2 GPa, a value well constrained by independent elasticity measurements, we obtain K′₀=4.6±0.1. The bulk modulus and its pressure derivative obtained from this work resolve the large discrepancy in previously reported values of K₀ and K′₀ for this material. Consequently, the equation of state of LiF is now sufficiently well constrained to allow its use as a pressure calibrant in high pressure experiments.

Keywords:

• lithium fluoride
• equation of state
• X-ray diffraction

Acknowledgements

This work was supported by the NSF and the Carnegie-DOE Alliance Center. We thank C. Stan and G. Finkelstein for their experimental assistance. High pressure gas loading was supported by COMPRES and GeoSoilEnviroCARS. Experiments were performed at GeoSoilEnviroCARS (Sector 13) and High Pressure Collaborative Access Team (HPCAT, Sector 16) at the APS. GeoSoilEnviroCARS is supported by the NSF-Earth Sciences (EAR-1128799) and DOE-Geosciences (DE-FG02-94ER14466). HPCAT is supported by CIW, CDAC, UNLV, and LLNL through funding from DOE-NNSA and DOE-BES, with partial instrumentation funding by NSF. The use of the APS was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.