The plasma-insulator transition of spin-polarized Hydrogen
  A mixed classical-quantum density functional theory is used to calculate pair correlations and the free energy of a spin-polarized Hydrogen plasma. A transition to an atomic insulator phase is estimated to occur around r_s=2.5 at T=10^4K, and a pressure $P\approx0.5Mbar$. Spin polarization is imposed to prevent the formation of H_2 molecules. 
Hong Xu and Jean-Pierre Hansen