Electron-Ion Path Integral Monte Carlo with Hard Core

We performed numerical (restricted) path integral Monte Carlo experiments on metallic Hydrogen from first principles. We study a quantum two component plasma where one component is made of pointwise particles of negative unitary charge and the other is made of charged hard spheres of positive unitary charge. We study both the additive mixture and a nonadditive mixture where we only keep a hard core between unlike species. We specialize to the case of the electron-proton plasma with a 1:1 ratios between the molar fraction of the two species. We measured thermodynamic and structural properties of the plasma. From an analysis of the structure we see a transition from a metallic Hydrogen phase, to a molecular Hydrogen phase as the temperature is lowered. As expected at high density the correlations are diminished.