A new equation of state for $\alpha$-quartz

Quartz (SiO$_2$) is often used as an optically transparent window for visar signals in shock experiments and is itself an active component of the experiments. Therefore, the shock response of quartz is an important input that must be known to high fidelity for precise measurement of other materials. We describe on-going work to develop a wide-range equation of state table that includes multiple phases and incorporates the latest high quality experimental and density functional theory (DFT) calculations. The emphasis in this work is the proper description of $\alpha$-quartz along its principal Hugoniot through Stishovite and liquid phases. While molecular dissociation occurs at high pressures and temperatures, we find that an additional dissociation model is unnecessary. Although SiO$_2$ possesses a number of solid phases, we restrict our focus to $\alpha$-quartz and Stishovite as these two provide the density change along the Hugoniot path. We compare the model to recently measured data on Sandia's Z-machine. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE