Phase transition kinetics of superionic H₂O ice phases revealed by Megahertz X-ray free-electron laser-heating experiments.

ABSTRACT: H₂O transforms to two forms of superionic (SI) ice at high pressures and temperatures, which contain highly mobile protons within a solid oxygen sublattice. Yet the stability field of both phases remains debated. Here, we present the results of an ultrafast X-ray heating study utilizing MHz pulse trains produced by the European X-ray Free Electron Laser to create high temperature states of H₂O, which were probed using X-ray diffraction during dynamic cooling. We confirm an isostructural transition during heating in the 26-69 GPa range, consistent with the formation of SI-bcc. In contrast to prior work, SI-fcc was observed exclusively above ~50 GPa, despite evidence of melting at lower pressures. The absence of SI-fcc in lower pressure runs is attributed to short heati

SUBMITTER: Husband RJ 

PROVIDER: S-EPMC11420352 | biostudies-literature | 2024 Sep

REPOSITORIES: biostudies-literature