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Synthesis and Stability of Lanthanum Superhydrides
Author(s) -
Geballe Zachary M.,
Liu Hanyu,
Mishra Ajay K.,
Ahart Muhtar,
Somayazulu Maddury,
Meng Yue,
Baldini Maria,
Hemley Russell J.
Publication year - 2018
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201709970
Subject(s) - lanthanum , metallic hydrogen , hydrogen , metal , crystallography , chemistry , diffraction , hydrogen atom , atom (system on chip) , hydrogen storage , solid hydrogen , phase (matter) , chemical physics , materials science , inorganic chemistry , physics , alkyl , organic chemistry , computer science , optics , embedded system
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. X‐ray diffraction and optical studies demonstrate that superhydrides of lanthanum can be synthesized with La atoms in an fcc lattice at 170 GPa upon heating to about 1000 K. The results match the predicted cubic metallic phase of LaH 10 having cages of thirty‐two hydrogen atoms surrounding each La atom. Upon decompression, the fcc‐based structure undergoes a rhombohedral distortion of the La sublattice. The superhydride phases consist of an atomic hydrogen sublattice with H−H distances of about 1.1 Å, which are close to predictions for solid atomic metallic hydrogen at these pressures. With stability below 200 GPa, the superhydride is thus the closest analogue to solid atomic metallic hydrogen yet to be synthesized and characterized.