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<p>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 (<i>I</i>4<sub>1</sub>/<i>a</i><i>m</i><i>d</i>) 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.</p>

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Unexpected compound reformation in the dense selenium-hydrogen system

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年8月21日

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  • Huixin Hu,
  • Mikhail A. Kuzovnikov,
  • Hannah A. Shuttleworth,
  • Tomas Marqueño,
  • Jinwei Yan,
  • Israel Osmond,
  • Federico A. Gorelli,
  • Eugene Gregoryanz,
  • Philip Dalladay-Simpson,
  • Graeme J. Ackland,
  • Miriam Peña-Alvarez,
  • Ross T. Howie

摘要

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.