First-principles search for metallic and superconducting phases in compressed solid hydrogen

2016 Fiscal Year Final Research Report

• Project/Area Number: 15K17707
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Condensed matter physics II
• Research Institution: Osaka University
• Principal Investigator: Ishikawa Takahiro 大阪大学, 基礎工学研究科, 特任助教(常勤) (40423082)
• Project Period (FY): 2015-04-01 – 2017-03-31
• Keywords: 固体水素 / 水素化合物 / 金属化 / 高温超伝導 / 第一原理計算 / 結晶構造予測 / ポテンシャルエネルギー面トレッキング / 遺伝的アルゴリズム

Outline of Final Research Achievements

I theoretically searched for novel metallic and room-temperature superconducting phases in solid hydrogen under high-pressure using potential energy surface trekking. New high-pressure phases have not been discovered yet, whereas a new finding was obtained in the metallic phase from 500 to 600 GPa, in which Cs-IV-type structure takes shuttlewise distortion. In addition, I also investigated hydrogen compounds expected to have a potential for high-temperature superconductivity, using genetic algorithm technique. A novel sulfur-hydrogen compound H5S2 was predicted to be thermodynamically stable phase at around 110 GPa and show the superconducting critical temperature of 50-70 K, reproducing the experimental data. These results suggest that room-temperature superconductivity at pressures accessible by experiments, i.e. less than 360 GPa, is difficult to be obtained in pure solid hydrogen, whereas it is sufficiently expected in hydrogen compounds.

Free Research Field

高圧物性理論