High-temperature, high-pressure behavior of lithium fluoride

Lithium fluoride (LiF) is used extensively as optical windows in dynamic compression experiments and is also used as pressure media and thermal insulation in diamond-anvil cell (DAC) experiments. In order to better understand this important high-pressure standard and ubiquitous window material, we present high-temperature isothermal equations of state of LiF below its melting curve as measured in a laser-heated DAC. These measurements complement already measured low-T isotherms [Myint et al., JCP, 2019] performed with resistively-heated DACs and will be used to generate phase-aware, thermally accurate equations of state for LiF. Above its previously determined melting curve [Boehler et al., PRL, 1997], LiF exhibits strong changes in absorption, similar to other alkali halides [Arveson et al., PRB, 2018]. We explore these changes in optical properties and the significant consequences they have for temperature measurements measured spectroscopically.