Plasma phase transition in warm dense hydrogen
A new idea is developed that the fluid–fluid phase transition in warm dense hydrogen
is related to the partial ionization of molecular hydrogen H2 with formation of
molecular ions H+2 and H+3 . Conventional ab initio quantum modelling is applied.
The proton–proton pair correlation functions (PCFs) obtained are used for the
non-conventional diagnostics of the phase transition and elucidation of its nature for
temperatures in the range 700–1500 K. Short- and long-range changes of PCFs are
studied. Ionization of H2 molecules and the appearance of molecular ions H+2and H+3
are revealed. The validity of the soft sphere model is tested for the long-range order.