Metastable water at several compression rates and its freezing kinetics into ice VII
Charles Pépin, Ramesh André, F. Occelli, Florian Dembele, A. Mozzanica, V. Hinger, Matteo Levantino, Paul Loubeyre
Abstract
Water can be dynamically over-compressed well into the stability field of ice VII. Whether water then transforms into ice VII, vitreous ice or a metastable novel crystalline phase remained uncertain. We report here the freezing of over-compressed water to ice VII by time-resolved X-ray diffraction. Quasi-isothermal dynamic compression paths are achieved using a dynamic-piezo-Diamond-Anvil-Cell, with programmable pressure rise time from 0.1 ms to 100 ms. By combining the present data set with those obtained on various ns-dynamical platforms, a complete evolution of the solidification pressure of metastable water versus the compression rate is rationalized within the classical nucleation theory framework. Also, when crystallization into ice VII occurs in between 1.6 GPa and 2.0 GPa, that is in the stability field of ice VI, a structural evolution over few ms is then observed into a mixture of ice VI and ice VII that seems to resolve apparent contradictions between previous results. Metastable water, when dynamically over-compressed, freezes into ice VII. Here the authors present a dynamic diamond anvil cell (d-DAC) study that unifies data acquired across multiple platforms, explaining the solidification pressure evolution under varying compression rates using classical nucleation theory.