Thermodynamics of phase transitions in the system ice VI-ice VII-water

The paper presents an analysis of experimental results on phase equilibria in the system ice VI-ice VII-water. The mathematical processing of the experimental data makes it possible to further constrain the location of phase transition boundaries between crystalline ices VI and VII and liquid water. Based on the standard thermodynamic properties of H₂O, an equation was derived for the free energy of formation of liquid water in its stability fields. The equations thus obtained were then utilized to calculate the standard thermodynamic properties (free energy, enthalpy, and entropy) of water ice VI and VII and the free energy of their formation at pressures of 6.3–25 kbar.