title: Structure and Composition of the 200 K-Superconducting Phase of H2 S at Ultrahigh Pressure: The Perovskite (SH(-) )(H3 S(+) ).
abstract: At ultrahigh pressure (>110 GPa), H2 S is converted into a metallic phase that becomes superconducting with a record Tc of approximately 200 K. It has been proposed that the superconducting phase is body-centered cubic H3 S (Im3‾ m, a=3.089 Å) resulting from the decomposition reaction 3 H2 S→2 H3 S+S. The analogy between H2 S and H2 O led us to a very different conclusion. The well-known dissociation of water into H3 O(+) and OH(-) increases by orders of magnitude under pressure. H2 S is anticipated to behave similarly under pressure, with the dissociation process 2 H2 S→H3 S(+) +SH(-) leading to the perovskite structure (SH(-) )(H3 S(+) ). This phase consists of corner-sharing SH6 octahedra with SH(-) ions at each A site (the centers of the S8 cubes). DFT calculations show that the perovskite (SH(-) )(H3 S(+) ) is thermodynamically more stable than the Im3‾ m structure of H3 S, and suggest that the A site hydrogen atoms are most likely fluxional even at Tc  .
authors: Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, USA.
authors: Elijah E
authors: EE
authors: Gordon
authors: Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai, 200433, P. R. China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, P. R. China.
authors: Ke
authors: K
authors: Xu
authors: Key Laboratory of Computational Physical Sciences (Ministry of Education), State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai, 200433, P. R. China.|Collaborative Innovation Center of Advanced Microstructures, Nanjing, 210093, P. R. China.
authors: Hongjun
authors: H
authors: Xiang
authors: Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569, Stuttgart, Germany.
authors: Annette
authors: A
authors: Bussmann-Holder
authors: Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569, Stuttgart, Germany.
authors: Reinhard K
authors: RK
authors: Kremer
authors: Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569, Stuttgart, Germany. j.koehler@fkf.mpg.de.
authors: Arndt
authors: A
authors: Simon
authors: Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569, Stuttgart, Germany. a.simon@fkf.mpg.de.
authors: Jürgen
authors: J
authors: Köhler
authors: Department of Chemistry, North Carolina State University, Raleigh, NC, 27695-8204, USA. mike_whangbo@ncsu.edu.
authors: Myung-Hwan
authors: MH
authors: Whangbo
keywords: electronic structure; high-pressure chemistry; hydrogen sulfide; perovskite phases; superconductors