First-Principles Equation of State Calculations of First- and Second-Row Plasmas

Abstract:

Theoretical studies of high energy density matter are a key component to improving our knowledge related to interiors of giant planets and stars, astrophysical processes, and new plasma energy technologies, such as inertial confined fusion. Path integral Monte Carlo (PIMC) and density functional theory molecular dynamics (DFT-MD) are simulation methods that provide consistent, first-principles descriptions of warm, dense matter and plasmas over a wide range of density and temperature conditions. Here, we report simulation results using these two methods for a number of first- and second-row elements. DFT-MD algorithms are well-suited for low temperatures, while PIMC has been restricted to relatively high temperatures due to the free-particle approximation of the nodal surface. For first-row elements, we find that the free-particle approximation is sufficient as long as the temperature is high enough to sufficiently ionize the second electronic shell of the atoms. For heavier, second-row elements, we have developed a new, localized nodal surface, which allows us to treat bound states within the PIMC formalism. By combining PIMC and DFT-MD pressures and internal energies, we produce a coherent, first-principles equation of state, bridging the entire warm dense matter regime. Pair-correlation functions and the density of electronic states reveal an evolving plasma structure. The degree of ionization is affected by both temperature and density. Finally, shock Hugoniot curves show an increase in compression as the first and second shells are ionized.