Shock response of low-density silica aerogel in the multi-Mbar regime

Low-density silica aerogels have found several applications in high-pressure research due to the ability for aerogel to be made over a wide range of initial densities with very small and uniform pore sizes. Here, we present plate-impact, shock wave experiments on nominally 110 and 200 mg/cc silica aerogel over the pressure range of ∼30-100 and ∼30-200 GPa, respectively. Direct measurement of the shock velocity in the aerogel using velocity interferometry enabled the Hugoniot to be inferred with very high precision, more than an order of magnitude improvement with respect to previously reported data for similar density silica aerogel. These results establish aerogel as a useful low impedance shock wave standard and provide data at high-entropy, high-pressure, and relatively low-density states to aid in the development of wide range equations of state for silica, a major constituent in the Earth's crust and mantle. Such models are crucial for accurate simulations of high-velocity giant impacts that are thought to be prevalent in the final stages of terrestrial planet formation.