High-Pressure sound velocity of PbF2: a high-impedance standard blackbody 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, we investigated the Hugoniot data and sound velocity of single-crystal lead fluoride (PbF₂) in the pressure range of 64-198 GPa by combining dynamic compression techniques with quantum molecular dynamics simulations. The theoretical simulation results are in excellent agreement with the experimental data. Our findings indicate that PbF₂ undergoes a melting phase transition at approximately 56 GPa and transforms into a liquid metal at 89.5 GPa, which enables efficient laser reflection at the shock front. Using a high-precision laser velocity measurement system, 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 blackbody windows.