Formation of H2-rich iodine-hydrogen compounds at high pressure

We have used synchrotron x-ray and Raman spectroscopic studies combined with molecular dynamics to investigate the I-2-H-2 system at high pressure. By laser heating the mixture above 25 GPa we synthesized the molecular compound HI(H-2)(13), with the AB(13) structure type and unusually high volumetric hydrogen content. The isolation of HI molecules by (H-2)(13) supramolecular clusters stabilizes the compound over a remarkable pressure range from 9 to at least 130 GPa. At lower pressures and 300 K another compound, hydrogen diiodane H-2(HI)(2), spontaneously forms, being stable up to 12.5 GPa.