The Hugoniot curve and sound velocity of forsterite to 1200 GPa

The comprehension of the composition and physical state of the deep interiors of large planets, as well as the impact events pertinent to planetary formation and evolution, necessitates an understanding of the properties of planetary materials under extreme conditions. Forsterite (Mg₂SiO₄), a significant geological mineral, has not been fully characterized in terms of its behavior under shock compression due to a lack of consensus among previous experiments and simulations aimed at determining its Hugoniot, as well as the absence of knowledge of sound velocity at high pressures, a critical parameter indicative of phase transformation and melting.
In this study, we delineated the Hugoniot curve of the mineral forsterite up to immense pressures of 1200 GPa. For the first time, we successfully constrained its sound velocity along the Hugoniot curve up to 760 GPa by combining laser-driven shock experiments with first-principles molecular dynamics simulations. The measured Hugoniot data for forsterite corroborated previous findings and suggested the occurrence of incongruent melting during shock compression. Remarkably, along their respective Hugoniot curves, the sound velocity of forsterite was observed to fall between that of the minerals bridgmanite and periclase. The remarkable agreement between the experimental results and simulation data provides reliable sound velocity measurements on the forsterite Hugoniot, which is critical for comprehensively understanding the phase transition and melting behavior of forsterite under ultra-high pressures. This knowledge sheds invaluable light on the behavior of this significant geological mineral under extreme conditions akin to those found in the interiors of planets.