کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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1333292 | 979072 | 2007 | 12 صفحه PDF | دانلود رایگان |
We performed the single-crystal X-ray diffraction study of a perovskite-type gold mixed-valence compound, Cs2AuIAuIIICl6, under high pressures up to 18 GPa by using a diamond-anvil-cell with helium gas as an ideal hydrostatic pressure-transmitting medium. The lattice parameters and the variable atomic positional parameters were obtained with reasonable accuracy at various pressures. A structural phase transition at ca. 12.5 GPa from I4/mmm to Pm3m was found. The lattice parameters a0 and c0, denoted in the tetragonal cell setting, result in the relationship 21/2a0=c0, and the superstructure reflections h k l (l is odd), caused by the shift of the Cl ions from the midpoint of the Au ions, disappeared at pressures above the phase transition. Both elongated [AuIIICl6] and compressed [AuICl6] octahedra in the low-pressure phase smoothly approach regular octahedra with increasing pressure. Above the structural phase transition at 12.5 GPa, all the [AuCl6] octahedra are crystallographically equivalent, which shows that the tetragonal-to-cubic phase transition accompanies the valence transition from the AuI/AuIII mixed-valence state to the AuII single-valence state.
Single-crystal X-ray diffraction study under high pressures up to 18 GPa by using a diamond-anvil-cell with helium gas as an ideal hydrostatic pressure medium has revealed that a perovskite-type gold mixed-valence compound, Cs2AuIAuIIICl6, exhibits the structural phase transition from tetragonal to cubic at 12.5 GPa accompanying gold valence transition.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 180, Issue 4, April 2007, Pages 1353–1364