Synthesis of Weaire–Phelan Barium Polyhydride

• Published in: The journal of physical chemistry letters Vol. 12; no. 20; pp. 4910 - 4916
• Main Authors: Peña-Alvarez, Miriam, Binns, Jack, Martinez-Canales, Miguel, Monserrat, Bartomeu, Ackland, Graeme J, Dalladay-Simpson, Philip, Howie, Ross T, Pickard, Chris J, Gregoryanz, Eugene
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 27.05.2021
• Subjects: Physical Insights into Materials and Molecular Properties
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.1c00826

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 P m 3̅ n structure with an unusual 5 3 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 close-packed phase. In particular, the structure is formed by H20 and H24 clathrate cages showing substantially weakened H–H interactions. Density functional theory (DFT) demonstrates that cubic P m 3̅ n Ba8H46 requires dynamical effects to stabilize the H20 and H24 clathrate cages.