%0 Journal Article
%A Hu, Huixin
%A Kuzovnikov, Mikhail A.
%A Shuttleworth, Hannah A.
%A Marqueño, Tomas
%A Yan, Jinwei
%A Osmond, Israel
%A Gorelli, Federico A.
%A Gregoryanz, Eugene
%A Dalladay-Simpson, Philip
%A Ackland, Graeme J.
%A Peña-Alvarez, Miriam
%A Howie, Ross
%T Unexpected compound reformation in the dense selenium-hydrogen system
%J Communications materials
%V 6
%N 1
%@ 2662-4443
%C London
%I Springer Nature
%M PUBDB-2025-03882
%P 193
%D 2025
%X The H<sub>2</sub>Se molecule and the van der Waals compound (H<sub>2</sub>Se)<sub>2</sub>H<sub>2</sub> 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, SeH<sub>2</sub>(H<sub>2</sub>)<sub>2</sub> at pressures above 94 GPa. X-ray diffraction reveals the metallic sublattice to adopt a tetragonal (I4<sub>1</sub>/amd) structure with density functional theory calculations finding a small distortion due to the orientation of H<sub>2</sub> molecules. The structure comprises of a network of zig-zag H-Se chains with quasi-molecular H<sub>2</sub> molecular units hosted in the prismatic Se interstices. Electrical resistance measurements demonstrate that SeH<sub>2</sub>(H<sub>2</sub>)<sub>2</sub> 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. 
%F PUB:(DE-HGF)16
%9 Journal Article
%R 10.1038/s43246-025-00899-9
%U https://bib-pubdb1.desy.de/record/637656