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

TL;DR

This paper reports the synthesis of a new ternary superhydride, Y3Fe4H20, at high pressure, which remains stable at ambient conditions, opening pathways for practical applications of superhydrides outside of high-pressure environments.

Contribution

The study introduces a novel ternary superhydride structure, Y3Fe4H20, synthesized at high pressure and recoverable at ambient conditions, advancing superhydride stabilization methods.

Findings

Y3Fe4H20 synthesized at 60 GPa

Structure remains stable after decompression

First metastable superhydride recovered at ambient conditions

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.