Molecules ionization at phase transition in warm dense hydrogen

Abstract

An idea is suggested that the fluid–fluid phase transition in warm dense hydrogen is related to the partial ionization of molecules H2 with formation of molecular ions . Conventional ab initio quantum modeling is applied. Proton pair correlation functions (PCF) obtained are used for the nonconventional diagnostics of the phase transition and elucidation of its nature for temperatures 700–1500 K. Short- and long-range changes of PCFs are studied. H2 molecules ionization and molecular ions appearance is revealed. The validity of the soft sphere model is tested for the long-range order.