Supercritical phases of hydrogen

Abstract

Using experimental data from literature [1], hydrogen density-pressure (ρ-P) and density-temperature (ρ-T) phase diagrams were drawn and evaluated for various pressure and temperature intervals. Solid, liquid, vapor, gas, supercritical liquid, supercritical gas and supercritical fluid regions were identified on the obtained diagrams. There are exact equilibrium boundaries between subcritical phases. On the contrary, it is concluded that there are no such exact boundaries for supercritical phases. Formation of the supercritical fluid between liquid and gas phases explained thermodynamically with first and second order partial derivatives of chemical potential relative to pressure at constant temperature.