Superionicity, disorder, and bandgap closure in dense hydrogen chloride

Jack Binns, A. Hermann*, M. Pena Alvarez, Mary-Ellen Donnelly, Mengnan Wang, Saori Imada Kawaguchi, Eugene Gregoryanz, Ross T Howie, Philip Dalladay-Simpson*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


Hydrogen bond networks play a crucial role in biomolecules and molecular materials such as ices. How these networks react to pressure directs their properties at extreme conditions. We have studied one of the simplest hydrogen bond formers, hydrogen chloride, from crystallization to metallization, covering a pressure range of more than 2.5 million atmospheres. Following hydrogen bond symmetrization, we identify a previously unknown phase by the appearance of new Raman modes and changes to x-ray diffraction patterns that contradict previous predictions. On further compression, a broad Raman band supersedes the well-defined excitations of phase V, despite retaining a crystalline chlorine substructure. We propose that this mode has its origin in proton (H+) mobility and disorder. Above 100 GPa, the optical bandgap closes linearly with extrapolated metallization at 240(10) GPa. Our findings suggest that proton dynamics can drive changes in these networks even at very high densities.
Original languageEnglish
Article numbereabi9507
Pages (from-to)1-7
Number of pages7
JournalScience Advances
Issue number36
Publication statusPublished - 1 Sep 2021


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