title: Possible "Magnéli" Phases and Self-Alloying in the Superconducting Sulfur Hydride.
abstract: We theoretically give an infinite number of metastable crystal structures for the superconducting sulfur hydride H_{x}S under pressure. Previously predicted crystalline phases of H_{2}S and H_{3}S have been thought to have important roles for experimentally observed low and high T_{c}, respectively. The newly found structures are long-period modulated crystals where slablike H_{2}S and H_{3}S regions intergrow on a microscopic scale. The extremely small formation enthalpy for the H_{2}S-H_{3}S boundary indicated by first-principles calculations suggests possible alloying of these phases through the formation of local H_{3}S regions. The modulated structures and gradual alloying transformations between them not only explain the peculiar pressure dependence of T_{c} in sulfur hydride observed experimentally, but also could prevail in the experimental samples under various compression schemes.
authors: Department of Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors: Ryosuke
authors: R
authors: Akashi
authors: Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.|RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan.
authors: Wataru
authors: W
authors: Sano
authors: RIKEN Center for Emergent Matter Science, Wako, Saitama 351-0198, Japan.|JST ERATO Isobe Degenerate π-Integration Project, Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai, Miyagi 980-8577, Japan.
authors: Ryotaro
authors: R
authors: Arita
authors: Department of Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.|Institute of Solid State Physics, The University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
authors: Shinji
authors: S
authors: Tsuneyuki