Effects of pressure on the two polymorphs of [Co(NH3)5NO2]I2: The anisotropy of lattice distortion and a phase transition |
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| Authors: | Elena V. Boldyreva Hans Ahsbahs Hermann Uchtmann Natalia Kashcheeva |
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| Affiliation: | 1. Institute of Solid State Chemistry and Mechanochemistry, Russian Academy of Sciences , Kutateladze, 18, Novosibirsk, 128, 630128, Russia;2. Novosibirsk State University, Chemistry Department , Pirogova, 2, Novosibirsk, 90, 630090, Russia;3. Institute of Mineralogy;4. Center of Materials Sciences;5. Center of Materials Sciences;6. Institute of Physical Chemistry Philipps-University of Marburg , Hans Meerwein Strasse, 35032, Marburg/Lahn, Germany;7. Novosibirsk State University, Chemistry Department , Pirogova, 2, Novosibirsk, 90, 630090, Russia |
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| Abstract: | ![]()
Abstract The effect of pressure on the two polymorphs of [CO(NH3)5NO2]I2 (phase I-orthorhombic, S.G. Pnma; phase II-monoclinic, S.G. C2/m) was studied by X-ray powder diffraction in a diamond anvil cell (DAC). In the presence of the ethanol-methanol-water mixture used as a pressure-transmitting liquid polymorph I was shown to undergo a phase transition at pressures between 0.45 GPa and 0.65 GPa. The diffraction pattern of the high-pressure phase (phase III) could be indexed as tetragonal with lattice parameters similar to those, which were previously reported for polymorph II in a 'pseudotetragonal setting'. The lattice distortions of phases II and III were studied at pressures up to 3.2 GPa and 3.7 GPa, correspondingly, and were shown to be very similar. Phases II and III were supposed to be very closely related. If poly(chlortrifluorethylen)-oil was used as a pressure-transmitting medium, no phase transitions were observed in phase I of [CO(NH3)5NO2I2 at least up to 1.8 GPa (the point when poly(chlortrifluorethylen)-oil becomes solid), and the anisotropy of lattice distortion could be measured. |
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| Keywords: | High pressure diamond anvil cell X-ray powder diffraction Co(III)-nitropentaammines phase transitions lattice distortion medium effects |
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