Thermodynamic and Optical Properties of Warm Dense Carbon

The high-fidelity prediction of thermophysical properties of light elements at extreme pressures is essential for interpreting the results of laboratory experiments involving particle beams, short-pulsed lasers, and Z-pinches. In particular, carbon (C) is used as an ablator in inertial confinement fusion targets and a tamping material in laser compression experiments. The equation of state (EOS) of C in the warm dense matter (WDM) regime is the fundamental ingredient for characterizing C properties. The Hartree-Fock-Slater - Collisional-Radiative Steady-State (HFS-CRSS) model and Density Functional Theory Molecular Dynamics (DFT-MD) are used to predict the WDM EOS of C. HFS-CRSS model implements the ab initio HFS methods accounting for the near-degenerate states and the effects of dense plasma environment. DFT-MD combines the classical MD for nuclei and DFT for electrons. The abundances of C ions, level populations, and fractions of bound and free electrons, EOS of solid-density strongly coupled warm C plasma, and radiative emissivity are predicted using the HFS-CRSS model. The differences in the EOS of C in the WDM regime are quantified by comparing the HFS-CRSS and DFT-MD results.