Characteristic mechanism for fast H conduction in LaH2.5O0.25

Albert Iskandarov, Tomofumi Tada, Soshi Iimura, Hideo Hosono

研究成果: ジャーナルへの寄稿学術誌査読

抄録

Solid hydrides are a new class of ionic conductors promising for future applications for hydrogen-carrier, catalysis, and energy conversion. The record-high H conductivity reported for LaH2.5O0.25 is caused by extraordinarily large pre-exponential factor, which cannot be justified within any simple diffusion picture. To reveal H dynamics in LaH2.5O0.25 on atomistic level, we developed DFT-based neural-network-potential for large-scale molecular dynamics (MD) simulation and discovered the H diffusion mechanism: the stoichiometric vacancies are ordered and almost immobile, but they can be rarely kicked-out and become fast mobile vacancies that migrate in a coupled manner with 3H ring-like rotations. The MD and DFT phonon analysis reveal that the mobile vacancy formation gives rise to an extremely large entropy leading to the anomalously large pre-exponential factor, and that the anharmonicity of H vibrations causes the large pre-exponential factor. A design concept for faster H conductor is proposed based on the present finding.

本文言語英語
論文番号117825
ジャーナルActa Materialia
230
DOI
出版ステータス出版済み - 5月 15 2022

!!!All Science Journal Classification (ASJC) codes

  • 電子材料、光学材料、および磁性材料
  • セラミックおよび複合材料
  • ポリマーおよびプラスチック
  • 金属および合金

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