Bulk Modulus of H2O Across the Ice VII–ice X Transition Measured by Time-Resolved X-Ray Diffraction in Dynamic Diamond Anvil Cell Experiments

We have studied the H2O ice VII-ice X phase transition at room temperature by performing three quasi-continuous synchrotron time-resolved x-ray-diffraction experiments in a dynamic diamond anvil cell, reaching pressures of 180 GPa. The dense pressure coverage of our volume data allows us to directly derive the bulk modulus for H2O over the entire pressure range. Our data document three major changes in compression behavior in the ranges of 35-40,50-55, and 90-110 GPa, likely corresponding to the formation of pretransition dynamically disordered ice VII and ice X, and static ice X, respectively. Our results confirm that ice X has a very high bulk modulus.