Dynamic experiments to examine the high-pressure, solid phases of cerium

The ability to understand and predict the response of matter at extremes requires knowledge of a materials equation-of-state including the location of phase boundaries, transition kinetics, and the evolution of material strength. Cerium metal exhibits a rich phase diagram at moderate pressures that continues to attract scientific interest as an ideal material for studies focused on the dynamic multiphase properties of materials. Recent dynamic experiments have provided information on the shock-melt transition, and the Hugoniot that spans two solid phases and the liquid. Despite these efforts, the high-pressure, solid region of the phase diagram remains largely unexplored dynamically. Static data have identified the ε phase which exists up to Mbar pressures along a room temperature isotherm. At higher temperatures (greater than 600 K), a direct α-ε transition has been reported although there are disagreements in both slope and location of the boundary. In this work, double-shock loading was used to access the α-ε region of the phase diagram to obtain equation-of-state (EOS) information, and to determine the location of the epsilon phase boundary for shock loading (LA-UR-18-30153).