Study on high-pressure sound velocity of PbF₂: discovery of a high-impedance standard window material

Accurate sound velocity measurement under high pressure requires high-impedance window materials. However, no ideal candidates have been reported to date. In this study, the Hugoniot data and sound velocity of single-crystal lead fluoride (PbF₂) in the pressure range from 64 GPa to 198 GPa were investigated by applying shock compression techniques and quantum molecular dynamics simulations. The theoretical simulation results of Hugoniot data and sound velocities are in excellent agreement with the experimental data. Along the Hugoniot curve, the sound velocities of liquid FbF₂ increase linear with particle velocity. The signal from a displacement interferometer system for any reflector (DISAR) and simulation results confirm that PbF₂ transforms into a liquid metal at 89.6 GPa, which enables efficient laser reflection at the shock front. Using a DISAR, both the shock wave velocity and the catch-up time of rarefaction waves can be accurately measured, providing critical technical support for the precise determination of sound velocity in materials under extremely high pressure. These superior properties, including high impedance, structural stability under high pressure, and pressure-induced metallization, enable PbF₂ fully meet the core requirements for high-impedance standard windows.