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arXiv · 2505.16799

Synthesis of Y$_3$Fe$_4$H$_{20}$ as a new prototype structure for ternary superhydrides recoverable at ambient pressure

M. Caussé·L. Toraille·G. Geneste·P. Loubeyre
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Abstract

Reaching pressures in the 100 GPa range enables the synthesis of hydrogen-rich compounds, with nontraditional H stoichiometries and H sublattices, called superhydrides. Record-breaking superconductivity temperature in some superhydrides have attracted great interest. A crucial next step is to stabilize superhydrides outside of high-pressure environments, leading to a search beyond binary hydrides to ternary hydrides. Here, we report the synthesis of Y$_3$Fe$_4$H$_{20}$ at pressures starting at 60 GPa by compressing an hydrogenated Y-Fe compound, embedded in hydrogen in a laser-heated diamond anvil cell. Single-crystal X-ray diffraction allowed us to resolve the Y$_3$Fe$_4$ lattice skeleton, and a constrained ab initio structural search was used to position the hydrogen atoms. FeH$_8$ cubic molecular units form building blocks which are connected edge-to-edge by sharing two hydrogen atoms, creating a framework that hosts Y cations. Remarkably, Y$_3$Fe$_4$H$_{20}$ maintains its structure through decompression, making it the first superhydride recovered metastable under ambient conditions.

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M. Caussé, L. Toraille, G. Geneste, P. Loubeyre. 2025-05-22. Synthesis of Y$_3$Fe$_4$H$_{20}$ as a new prototype structure for ternary superhydrides recoverable at ambient pressure. https://doi.org/10.1038/s41467-026-74232-4

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