Polyhydride CeH₉ with an atomic-like hydrogen clathrate structure

Area of Science:

• Materials Science
• Condensed Matter Physics
• High-Pressure Physics

Background:

• High-pressure compression of hydrogen-rich materials is a key strategy for achieving metallic hydrogen and high-temperature superconductors.
• Synthesizing polyhydrides with high hydrogen-to-metal ratios remains a significant challenge in materials discovery.

Purpose of the Study:

• To synthesize novel cerium (Ce) polyhydrides under high pressure.
• To investigate the structural and electronic properties of these polyhydrides.
• To explore the potential of cerium polyhydrides in achieving metallic hydrogen states.

Main Methods:

• Direct reaction of cerium (Ce) and hydrogen (H2) at high pressures (above 100 GPa).
• Analysis of structural properties using electron localization function (ELF) calculations.
• Electronic band structure calculations to determine metallic character.

Main Results:

• Successful synthesis of a series of cerium polyhydrides, including CeH9.
• CeH9 exhibits a stable three-dimensional hydrogen network with clathrate H29 cages.
• Electronic structure calculations confirm the metallic nature of CeH9 due to weak electron localization.
• Ce atom doping in CeH9 facilitates the realization of metallic hydrogen structures.

Conclusions:

• Cerium polyhydrides, particularly CeH9, represent a promising pathway towards synthesizing metallic hydrogen.
• The stabilizing role of Ce atoms in hydrogen cage structures is highlighted, drawing parallels to lanthanum hydride superconductors.
• This study advances the understanding of high-pressure hydrides and their potential for novel superconducting materials.