  Fermionic path integral Monte Carlo simulations have been applied to study
the equilibrium properties of the hydrogen and deuterium in the density and
temperature range of 1.6 < rs < 14.0 and 5000K < T < 167000K. We use this
technique to determine the phase diagram by identifying the plasma, the
molecular, atomic and metallic regime. We explain how one can identify the
phases in the path integral formalism and discuss the state of hydrogen for 5
points in the temperature-density plane. Further we will provide arguments for
the nature of the transitions between the regimes.
