Isothermal equations of state for H2O-VII and D2O-VII

Lattice parameters and cell volumes at room temperature are reported for H2O-VII to 36 GPa and for D2O-VII to 32 GPa. The data are fitted to seven isothermal equations of state from which are derived averaged values of the isothermal bulk moduli (B) and their pressure derivatives (dB/dP) as a function of pressure. For H2O over the range 2.33⩽P⩽30.9 GPa, B increases from 22.3 to 141.0 GPa while dB/dP decreases from 4.9 to 3.7. For D2O over the range 2.8⩽P⩽30.27 GPa, B increases from 30.0 to 129.0 GPa while dB/dP decreases from 4.1 to 3.1. An independent determination of B and dB/dP using a piecewise regression analysis gives B = 15.78+4.11 P, GPa with no distinction between H2O and D2O over the observed pressure ranges. The procedures employed for treating the data and the reliability of the derived results are assessed for both materials.