Comparison of DFT-based methods for electronic stopping in warm dense aluminum

The transport properties of warm dense matter (WDM), which has temperatures and densities between condensed matter and classical plasmas, inform models of diverse objects ranging from planetary cores to inertial confinement fusion plasmas. WDM is challenging to model theoretically: classical plasma models falter at high densities, and condensed-matter models such as time-dependent density functional theory (TDDFT) become exceedingly computationally expensive at temperatures beyond the Fermi temperature. The average atom (AA) method represents a cheaper DFT-based alternative whose accuracy is conversely expected to improve as temperature approaches the plasma regime. In this talk, we benchmark AA against TDDFT for the case of electronic stopping of protons in aluminum at solid density and temperatures ranging from 100 K to 10 eV/k_B. We report good agreement for fast protons and analyze potential sources of discrepancies near and below the Bragg peak, including differing predictions for the density of states and ionization state of aluminum. Insights from this work will help improve the accuracy and speed of WDM simulations, with important implications for astrophysics and nuclear engineering.