Equation of State Calculations With First-Principles Computer Simulations of Matter at Extreme Conditions*

The properties of materials at extreme pressure and temperature conditions are important in astrophysics and fusion science. When models for the interiors of Saturn and Jupiter are constructed to match gravity data from the NASA missions Cassini and Juno, an accurate knowledge of the equation of state of hydrogen-helium mixtures is essential. Modern dynamic compression experiments typically probe megabar and gigabar pressures. In order to provide a comprehensive theoretical description of materials at such extreme conditions, we combine results from path integral Monte Carlo (PIMC) and density functional molecular dynamics simulations. We present equation of state results for first-row elements and compounds such as boron, CH plastic, and oxygen. The shock Hugoniot curves are derived and compared with experimental data. Then we discuss how bound states can be incorporated efficiently into the nodal structure in the PIMC simulations, which enables us to simulate second row elements. We present results from equation of state computations for sodium, aluminum, silicon, and magnesiosilicates.