Unexpected compound reformation in the dense selenium-hydrogen system

Year: 2025

Authors: Hu HX., Kuzovnikov MA., Shuttleworth HA., Marqueso T., Yan JW., Osmond I., Gorelli FA., Gregoryanz E., Dalladay-Simpson P., Ackland GJ., Pesa-Alvarez M., Howie RT.

Autors Affiliation: Ctr High Pressure Sci & Technol Adv Res, Shanghai, Peoples R China; Univ Edinburgh, Ctr Sci Extreme Condit, Sch Phys & Astron, Edinburgh, Scotland; SHARPS Shanghai Adv Res Phys Sci, Shanghai, Peoples R China; CNR, Ist Nazl Ott, INO, Sesto Fiorentino, Italy; Inst Solid State Phys, Key Lab Mat Phys, Hefei, Peoples R China.

Abstract: The H2Se molecule and the van der Waals compound (H2Se)2H2 are both unstable upon room temperature compression, dissociating into their constituent elements above 22 GPa. Through a series of high pressure-high temperature diamond anvil cell experiments, we report the unexpected formation of a novel compound, SeH2(H2)2 at pressures above 94 GPa. X-ray diffraction reveals the metallic sublattice to adopt a tetragonal (I41/amd) structure with density functional theory calculations finding a small distortion due to the orientation of H2 molecules. The structure comprises of a network of zig-zag H-Se chains with quasi-molecular H2 molecular units hosted in the prismatic Se interstices. Electrical resistance measurements demonstrate that SeH2(H2)2 is non-metallic up to pressures of 148 GPa. Investigations into the Te-H system up to pressures of 165 GPa and 2000 K yielded no compound formation. The combined results suggest that the high pressure phase behavior of each chalcogen hydride is unique and more complex than previously thought.

Journal/Review: COMMUNICATIONS MATERIALS

Volume: 6 (1)      Pages from: 193-1  to: 193-7

More Information: The work was supported by the European Research Council (ERC) under the European Union’s Hor izon 2020 research and innovation program (Grant agreement no. 948895, MetElOne), and the UKRI Future Leaders fellowship Mrc-Mr/T043733/1. For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising from this submission. G.J.A. acknowledges funding from the ERC project HECATE and EPSRC for the UKCP consortium, grant ref EP/P022561/1. We acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of beamline P02.2 at PETRA-III, allocated under proposal I-20230232, and we would like to thank Hanns-Peter Liermann and Timofey Fedotenko for their assistance. The ESRF (Grenoble, France) is acknowledged for providing access to beamline ID15B for proposal HC-5457. We thank M. Hanfland, G. Garbarino and S. Gallego-Parra for beamline support. Portions of this work were performed at GeoSoilEnviroCARS (The University of Chicago, Sector 13), Advanced Photon Source, Argonne National Laboratory. GeoSoilEnviroCARS is supported by the National Science Foundation-Earth Sciences via SEES: Synchrotron Earth and Environmental Science (EAR -2223273). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. We acknowledge SPring-8 (Japan), where portions of this work were performed at the BL10XU beamline with the approval of JASRI (2024A1404 and 2024A1415). We thank S. Kawaguchi for beamline support.
KeyWords: Crystal-structure; Sulfur; Diffraction; Pressures; Diamond; Program; State
DOI: 10.1038/s43246-025-00899-9