Equation of states for dense ice up to 80 GPa at low-temperature conditions

We have measured the lattice volume of ice VIII in different pressure–temperature pathways and found that the volume depends on the pathway, implying that deviatoric stress makes the volume larger. Dense ice is in the ice VIII phase with the molar volume of 6.56 cm3 and in a high-pressure phase with the molar volume of 6.45 cm3 at 10 K where the pressure can be estimated as 57.0 ± 3.4 and 60.4 ± 3.6 GPa, respectively, based on the third-order Birch–Murnaghan equation with parameters determined in this study (K0 = 30.8 ± 1.3 GPa and K′0 = 3.7 ± 0.1 with V0 fixed to 12.030 cm3).