title: Superconducting H5S2 phase in sulfur-hydrogen system under high-pressure.
abstract: Recently, hydrogen sulfide was experimentally found to show the high superconducting critical temperature (Tc) under high-pressure. The superconducting Tc shows 30-70 K in pressure range of 100-170 GPa (low-Tc phase) and increases to 203 K, which sets a record for the highest Tc in all materials, for the samples annealed by heating it to room temperature at pressures above 150 GPa (high-Tc phase). Here we present a solid H5S2 phase predicted as the low-Tc phase by the application of the genetic algorithm technique for crystal structure searching and first-principles calculations to sulfur-hydrogen system under high-pressure. The H5S2 phase is thermodynamically stabilized at 110 GPa, in which asymmetric hydrogen bonds are formed between H2S and H3S molecules. Calculated Tc values show 50-70 K in pressure range of 100-150 GPa within the harmonic approximation, which can reproduce the experimentally observed low-Tc phase. These findings give a new aspect of the excellent superconductivity in compressed sulfur-hydrogen system.
authors.affiliation: Center for Science and Technology under Extreme Conditions, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Center for Science and Technology under Extreme Conditions, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Akitaka
authors.initials: A
authors.lastname: Nakanishi
authors.affiliation: Center for Science and Technology under Extreme Conditions, Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Katsuya
authors.initials: K
authors.lastname: Shimizu
authors.affiliation: Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Katayama-Yoshida
authors.affiliation: Institute of Science and Engineering, Kanazawa University, Kakuma, Kanazawa, Ishikawa 920-1192, Japan.
authors.forename: Tatsuki
authors.initials: T
authors.lastname: Oda
authors.affiliation: Department of Pure and Applied Physics, Kansai University, 3-3-35 Yamate, Suita, Osaka 564-8680, Japan.
authors.forename: Naoshi
authors.initials: N
authors.lastname: Suzuki