Shock melting of cerium

Abstract

Shock-wave experiments were performed to examine the melt transition for cerium. Despite past work which points to a higher-pressure transition, the large volume collapse associated with the low-pressure $\ensuremath{\gamma}\text{\ensuremath{-}}\ensuremath{\alpha}$ phase transition is expected to result in a low-pressure melt transition. Multiple experimental configurations including front-surface impact and transmission experiments using velocimetry were used to obtain Hugoniot data and sound-speed data for impact stresses up to approximately 18 GPa. Sound-speed data exhibit a structured release consisting of a longitudinal wave followed by a slower plastic wave. The difference between these two wave speeds is observed to decrease with increasing impact stress until a single shock wave is observed indicating the onset of the melt transition which was estimated to be $10.24\ifmmode\pm\else\textpm\fi{}0.34\text{ }\text{GPa}$. Additional data show that the sound speed is in agreement with liquid data at approximately 18 GPa likely indicating the completion of the melt transition. Further results and implications are discussed.