Understanding Warm Dense Matter Beyond Density Functional Theory

Warm dense matter (WDM) is an exotic state of matter found in stars and inertial confinement experiments. Since WDM encompasses the overlap of plasma and condensed phases, it is challenging to successfully model its various properties. Density functional theory (DFT) models have been able to successfully model the equation of state in dense plasmas but fail to consider multiconfigurational effects that are important for understanding opacity. Here, we build upon the Tartarus algorithm, which employs an average-atom DFT framework, by incorporating these multiconfigurational effects into the opacity calculations. Additionally, we implement a new stress-tensor formalism for calculating the pressure. We compare our model's predictions with a recent NIF experiment that measured the equation of state and opacity of C9H10 at extreme pressures. We found that our modeled Hugoniot is within one standard error of the experimental Hugoniot, suggesting that our average-atom DFT model is able to accurately model the equation of state for dense plasmas for a wide range of pressures. Our modeled opacity is within one standard error of the experimental opacity up to 250 MBar, after which it falls just outside of that threshold.