Silicon carbide at exoplanetary core conditions*

Silicon carbide (SiC) is a major planetary material of carbon-rich exoplanets. Understanding the high pressure-temperature behavior of SiC s at high P-T conditions is urgently sought to develop models of the exoplanetary cores. Our joint experimental and simulation studies of SiC focus on the phase transitions between ambient zinc-blende B3 and high pressure rock-salt B1 phases with the goal to resolve the discrepancy between static and dynamic compression experiments, which have produced conflicting results about the pressure at which the transition occurs. The B3-B1 phase transition is accompanied by a significant 20% volume collapse, leading to a novel hypothesis of "kinematic Hugoniot frustration," which refers to the inability to satisfy the Hugoniot jump conditions at the thermodynamic B3/B1 phase boundary. Our predictive molecular dynamics simulations and experiments with the SNL Z machine and STAR gas gun provide new insights into the underlying mechanisms of phase transitions in dynamically compressed materials.