Synthesis of Weaire-Phelan Barium Polyhydride

By combining pressures up to 50 GPa and temperatures of 1200 K, we synthesize the novel barium hydride, Ba8H46, stable down to 27 GPa. We use Raman spectroscopy, X-ray diffraction, and first-principles calculations to determine that this compound adopts a highly symmetric Pm (3) over barn structure with an unusual 53/4:1 hydrogen-to-barium ratio. This singular stoichiometry corresponds to the well-defined type-I clathrate geometry. This clathrate consists of a Weaire-Phelan hydrogen structure with the barium atoms forming a topologically closepacked phase. In particular, the structure is formed by H-20 and H-24 clathrate cages showing substantially weakened H-H interactions. Density functional theory (DFT) demonstrates that cubic Pm (3) over barn Ba8H46 requires dynamical effects to stabilize the H-20 and H-24 clathrate cages.

Automated summary

This study successfully synthesized a novel rare gas compound Ba8H46 under high pressure and high temperature conditions, which has a unique cage structure with a hydrogen-to-barium ratio of 53/4:1, exhibiting weakened hydrogen-hydrogen interactions.