| Autor: |
Wildner, Manfred, Ende, Martin, Meusburger, Johannes M., Kunit, Roland, Matzinger, Philipp, Talla, Dominik, Miletich, Ronald |
| Zdroj: |
Zeitschrift für Kristallographie - Crystalline Materials; October 2021, Vol. 236 p225-237, 13p |
| Abstrakt: |
The kieserite-type compound cobalt(II) sulfate monohydrate, CoSO4·H2O, has been investigated under isothermal (T= 295 K) hydrostatic compression up to 10.1 GPa in a diamond anvil cell by means of single-crystal X-ray diffraction and Raman spectroscopy. The monoclinic α-phase (space group C2/c) undergoes a second-order ferroelastic phase transition at Pc= 2.40(3) GPa to a triclinic β-phase (space group P1‾$‾{1}$ ). Lattice elasticities derived from fitting third-order Birch-Murnaghan equations of state to the pressure dependent unit-cell volume data yield V0= 354.20(6) Å3, K0= 53.0(1.7) GPa, K′ = 5.7(1.8) for the α-phase and V0= 355.9(8) Å3, K0= 45.2(2.6) GPa, K′ = 6.6(6) for the β-phase. Crystal structure data of the high-pressure polymorph were determined at 2.98(6) and 4.88(6) GPa. The most obvious structural feature and thus a possible driving mechanism of the phase transition, is a partial rearrangement in the hydrogen bonding system. However, a comparative analysis of pressure-induced changes in the four kieserite-type compounds investigated to date suggests that the loss of the point symmetry 2 at the otherwise rather rigid SO4tetrahedron, allowing symmetrically unrestricted tetrahedral rotations and edge tiltings in the β-phase, could be the actual driving mechanism of the phase transition. |
| Databáze: |
Supplemental Index |
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