Hydrogen sublattice in LaH12: structural stability and possible ordering motifs
Abstract
Lanthanum polyhydrides, synthesized under extreme pressure, exhibit near-room-temperature superconductivity. Finding a precise arrangement of the hydrogen sublattice that is critical for understanding the strong electron-phonon coupling remains experimentally unresolved due to the small X-ray scattering form factor of hydrogen atoms. In this work, we attempt to computationally reconstruct hydrogen sublattices of the LaH12 at 100-200 GPa combining unconstrained evolutionary searches and structure generation with fixed lanthanum sublattice. By implementing a similarity metric, we screen the computationally generated configurations against experimental powder X-ray diffraction data. We specifically identify the trigonal R3̅-LaH12 and pseudo-hexagonal C2221-La2H24 phases, which demonstrate close agreement with the experimental X-ray diffraction data. First-principles calculations confirm the metallic and superconducting nature of these hydrides. Crucially, our lattice dynamics analysis using the stochastic self-consistent harmonic approximation (SSCHA) indicates that these structures are dynamically stable. We reveal the presence of molecular H2 units and soft phonon modes in the trigonal LaH12 that suppresses superconductivity (Tc ≥ 30 K), while the hydrogen clathrate network in the C2221 phase drives strong electron-phonon interactions, yielding the coupling parameters of λ≈ 1.83, ωlog ≈ 87.5 meV and transition temperature of Tc≈ 150 K at 150 GPa.
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BibTeX
@misc{akhmadiev2026hydrogen,
title = {{Hydrogen sublattice in LaH$_12$: structural stability and possible ordering motifs}},
author = {Khasan Akhmadiev and Di Zhou and Viktor V. Struzhkin and Alexander G. Kvashnin and Dmitrii V. Semenok},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2611.06424},
eprint = {2611.06424},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2611.06424},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Hydrogen sublattice in LaH_12: structural stability and possible ordering motifs
AU - Khasan Akhmadiev
AU - Di Zhou
AU - Viktor V. Struzhkin
AU - Alexander G. Kvashnin
AU - Dmitrii V. Semenok
PY - 2026
DA - 2026/11/04
PB - arXiv
DO - 10.48550/arxiv.2611.06424
UR - https://arxiv.org/abs/2611.06424
AB - Lanthanum polyhydrides, synthesized under extreme pressure, exhibit near-room-temperature superconductivity. Finding a precise arrangement of the hydrogen sublattice that is critical for understanding the strong electron-phonon coupling remains experimentally unresolved due to the small X-ray scattering form factor of hydrogen atoms. In this work, we attempt to computationally reconstruct hydrogen sublattices of the LaH_12 at 100-200 GPa combining unconstrained evolutionary searches and structure generation with fixed lanthanum sublattice. By implementing a similarity metric, we screen the computationally generated configurations against experimental powder X-ray diffraction data. We specifically identify the trigonal R3̅-LaH_12 and pseudo-hexagonal C222_1-La_2H_24 phases, which demonstrate close agreement with the experimental X-ray diffraction data. First-principles calculations confirm the metallic and superconducting nature of these hydrides. Crucially, our lattice dynamics analysis using the stochastic self-consistent harmonic approximation (SSCHA) indicates that these structures are dynamically stable. We reveal the presence of molecular H_2 units and soft phonon modes in the trigonal LaH_12 that suppresses superconductivity (T_c ≥ 30 K), while the hydrogen clathrate network in the C222_1 phase drives strong electron-phonon interactions, yielding the coupling parameters of λ≈ 1.83, ω_log ≈ 87.5 meV and transition temperature of T_c≈ 150 K at 150 GPa.
ER -