Equation of State and Hugoniot Curve in Warm Dense Hydrogen

We investigate warm dense matter by performing quantum molecular dynamics (QMD) simulations based on density functional theory (DFT). Dense hydrogen is the main component in giant planets and, therefore, of particular interest. We present new results for the equation of state and the Hugoniot curve and compare with experiments. Density functional theory is based on the theorems of Hohenberg and Kohn [1], which state that the ground state energy of the system is a unique functional of the electron density. Actual calculations are performed within the Kohn-Sham theory [2]. The ground state energy is determined by minimizing the energy functional with respect to the electron density. With forces derived from the resulting electron density a molecular dynamics step is performed for the ions. We obtain thermodynamic data by averaging over the molecular dynamics run. This scheme is implemented within the program VASP [3] which is used in our calculations. Isotherms of the thermal equation of state (EOS) are shown in figure 1. The results are in agreement with calculations of chemical models (FVT [4], SC95 [5]) at low and high density. The EOS obtained by QMD simulations shows no phase transition behavior in the intermediate density range as some of the chemical models do.