It has previously been reported that under a pressure of greater than 110 GPa, H₂S is converted into a superconductor at a remarkably high temperature of approximately 200 K.

The groups of Arndt Simon and Jürgen Kohler, both at the Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany, and Myung-Hwan Whangbo, North Carolina State University, USA, now propose that this superconducting phase is not body-centered cubic H₃S, as previously surmised, but that it is formed by the decomposition of 2 H₂S into H₃S⁺ and SH^–.

This process, which was suggested in analogy to the dissociation of water into H₃O⁺ and OH^–, leads to the formation of the perovskite (SH^–)(H₃S⁺), which consists of corner-sharing SH₆ octahedra with an SH^– ion at the center of each S₈ cube. Calculations suggest that the hydrogen atoms of these SH^– ions are fluxional even at the critical temperature.

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• Structure and Composition of the 200 K-Superconducting Phase of H₂S at Ultrahigh Pressure: The Perovskite (SH^–)(H₃S⁺),
  E. E. Gordon, K. Xu, H. Xiang, A. Bussmann-Holder, R. K. Kremer, A. Simon, J. Köhler, M.-H. Whangbo,
  Angew. Chem. Int. Ed. 2016.
  DOI: 10.1002/anie.201511347

 

Previous Report

• Superconductivity Record
  ChemistryViews.org, August 2015.
  New high temperature record for conducting electricity without resistance
• Conventional superconductivity at 203 kelvin at high pressures in the sulfur hydride system,
  A. P. Drozdov, M. I. Eremets, I. A. Troyan, V. Ksenofontov, S. I. Shylin,
  Nature 2015, 525, 73–76.
  DOI: 10.1038/nature14964