Shock response of magnesium difluoride to 130 GPa along the <i>c</i>-axis

Magnesium difluoride (MgF₂) is an archetypal simple ionic crystal that is extensively used as an optical material. It is also of significant interest to geophysics, and therefore, well studied under static high-pressure loading, because its ambient rutile-type structure is isomorphic to SiO₂ (stishovite). In this work, plate impact experiments were carried out to shock compress single crystal MgF₂ samples to 130 GPa along the c-axis. Resulting wave profile and shock velocity through the sample were measured using laser velocimetry (PDV). Shocked MgF₂ exhibits a nonlinear elastic response up to ~10 GPa, beyond which a two-wave structure, consisting of an elastic wave and an inelastic wave, was observed. A single overdriven wave was observed for peak longitudinal stresses greater than 90 GPa. Measured wave profiles and the calculated longitudinal stress – particle velocity Hugoniot do not indicate any phase transition, such as those reported under static high-pressure loading (rutile → orthorhombic → distorted fluorite → cotunnite). The optical response of shocked MgF₂ along the c-axis will also be discussed in this talk. LA-UR-20-29023