Synthesis and Stability of Lanthanum Superhydrides

ORAL

Abstract

Recent theoretical calculations predict that megabar pressure stabilizes very hydrogen-rich simple compounds having new clathrate-like structures and remarkable electronic properties including room-temperature superconductivity. We report x-ray diffraction and optical studies demonstrating that superhydrides of lanthanum can be synthesized with La atoms in an fcc lattice at 170 GPa upon heating to ~1000 K. The results match the predicted cubic metallic phase of LaH10 having cages of thirty-two hydrogen atoms surrounding each La atom. Upon decompression, the fcc-based structure of LaH10 undergoes a rhombohedral distortion of the La sublattice. The superhydride phases consist of an atomic hydrogen sublattice with H-H distances of ~1.1 Å, which are close to predictions for solid atomic metallic hydrogen at these pressures.

*This research was supported by EFree, an EFRC funded by the US DOE (DE-SC0001057). The infrastructure and facilities used are supported by the US DOE/NNSA (Awards DE-NA-0002006, CDAC; and DE-NA0001974, HPCAT).

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Presenters

  • Zachary Geballe

    • Geophysical Laboratory, Carnegie Institution of Washington
    • Geophysical Laboratory, Carnegie Inst of Washington

Authors

  • Zachary Geballe

    • Geophysical Laboratory, Carnegie Institution of Washington
    • Geophysical Laboratory, Carnegie Inst of Washington

  • Hanyu Liu

    • Geophysical Laboratory, Carnegie Institution for Science
    • Geophysical Laboratory, Carnegie Institution of Washington
    • Geophysical Laboratory, Carnegie Inst of Washington

  • Ajay Mishra

    • Geophysical Laboratory, Carnegie Institution of Washington
    • Geophysical Laboratory, Carnegie Inst of Washington
    • Carnegie Inst of Washington

  • Muhtar Ahart

    • Geophysical Laboratory, Carnegie Institution of Washington
    • Carnegie Inst of Washington
    • Extreme Materials Initiative, Geophysical Lab, Carnegie Institution for Science

  • Maddury Somayazulu

    • Geophysical Laboratory, Carnegie Institution of Washington
    • Geophysical Laboratory, Carnegie Inst of Washington
    • Carnegie Inst of Washington

  • Yue Meng

    • HPCAT, Carnegie Institution of Washington
    • Geophysical Laboratory, Carnegie Inst of Washington
    • Carnegie Institution of Washington, High Pressure Collaborative Access Team (HPCAT), Geophysical Laboratory

  • Maria Baldini

    • Geophysical Laboratory, Carnegie Institution of Washington
    • Geophysical Laboratory, Carnegie Inst of Washington
    • Carnegie Institution of Washington

  • Russell Hemley

    • Institute of Materials Science and Civil and Environmental Engineering, George Washington University
    • School of Engineering and Applied Science, George Washington University
    • George Washington University
    • Department of Civil and Environmental Engineering, The George Washington University