Carbon at Extreme Conditions

Properties of carbon at extreme pressures and temperatures are of critical importance for constructing interior models of carbon-rich exoplanets. Among the questions that have long perplexed the scientific community are the existence and potential synthesis of high-pressure post-diamond carbon phases, and the inelastic response of diamond to strong shock compression. In particular, very recent ramp compression and X-Ray diffraction experiments at the National Ignition Facility (NIF) challenged the theoretical prediction of the existence of a high-pressure BC8 post-diamond phase by compressing diamond to gigantic pressures up to 20 Mbar. In this project, we uniquely couple quantum-accurate, billion-atom MD simulations on exascale DOE computers with cutting-edge experiments at NIF to uncover the atomic-scale mechanisms and kinetics of solid-solid and solid-liquid phase transitions and nature of inelastic deformations in diamond. We also design the compression pathways towards the successful synthesis of the elusive post-diamond BC8 phase. The research is supported by DOE/NNSA and computational campaign at Frontier and Aurora exascale supercomputers through DOE’s The Innovative and Novel Computational Impact on Theory and Experiment (INCITE) and an experimental campaign via the NIF/LLNL Discovery Science program.