Computational investigation of shock-driven interface physics to study material viscosity at high pressures

An accurate understanding of viscosity trends and values of materials approaching the warm dense matter regime are poorly constrained and yet are important for diverse problems including mantle dynamics of super-Earths. Mantle dynamics drive a wide range of processes that shape terrestrial planets and the viscosity of a planet's mantle at relevant pressures (>100 GPa) is a critical transport property. This work focuses on constraining the viscosity of mantle-relevant materials at such pressures. We present a theoretical and computational framework to aid in experimental design and interpretation of results. We analyze the dynamic effects of a laser-generated shock traveling through a corrugated interface. Theory suggests that the evolution of the interface (i.e. the Richtmyer- Meshkov instability) and the decay of the transmitted shock is dependent on material viscosity. Using this theory, we present a method to obtain bounds on material viscosity. Simulations are performed to study the underlying dynamics using an in-house code. We improve our simulations with a stiffened equation of state to better represent the sound and shock speeds of the experimental materials.