Abstract : From first-principles molecular dynamics, we investigate the relation between the superionic proton conduction and the behavior of the O-H ... O bond (ice VII' to ice X transition) in body-centered-cubic (bcc) H2O ice between 1300 and 2000 K and up to 300 GPa. We bring evidence that there are three distinct phases in the superionic bcc stability field. A first superionic phase characterized by extremely fast diffusion of highly delocalized protons (denoted VII\textquotedblright hereinafter) is stable at low pressures. A first-order transition separates this phase from a superionic VII\textquotedblright, characterized by a finite degree of localization of protons along the nonsymmetric O-H ... O bonds. The transition is identified in structural, energetic, and elastic analysis. Upon further compression a second-order phase transition leads to the superionic ice X with symmetric O-H-O bonds.
https://hal-univ-lyon1.archives-ouvertes.fr/hal-02333289 Contributor : Depot 2 Lyon 1Connect in order to contact the contributor Submitted on : Wednesday, November 24, 2021 - 9:03:54 AM Last modification on : Wednesday, November 24, 2021 - 9:03:57 AM Long-term archiving on: : Friday, February 25, 2022 - 6:14:26 PM