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  • Title: Phase transitions in KIO(3).
    Author: Bayarjargal L, Wiehl L, Friedrich A, Winkler B, Juarez-Arellano EA, Morgenroth W, Haussühl E.
    Journal: J Phys Condens Matter; 2012 Aug 15; 24(32):325401, 1-11. PubMed ID: 22787136.
    Abstract:
    The high-pressure behavior of KIO(3) was studied up to 30 GPa using single crystal and powder x-ray diffraction, Raman spectroscopy, second harmonic generation (SHG) experiments and density functional theory (DFT)-based calculations. Triclinic KIO(3) shows two pressure-induced structural phase transitions at 7 GPa and at 14 GPa. Single crystal x-ray diffraction at 8.7(1) GPa was employed to solve the structure of the first high-pressure phase (space group R3, a = 5.89(1) Å, α = 62.4(1)°). The bulk modulus, B, of this phase was obtained by fitting a second order Birch-Murnaghan equation of state (eos) to synchrotron x-ray powder diffraction data resulting in B(exp,second) = 67(3) GPa. The DFT model gave B(DFT,second) = 70.9 GPa, and, for a third order Birch-Murnaghan eos, B(DFT,third) = 67.9 GPa with a pressure derivative of [Formula: see text]. Both high-pressure transformations were detectable by Raman spectroscopy and the observation of second harmonic signals. The presence of strong SHG signals shows that all high-pressure phases are acentric. By using different pressure media, we showed that the transition pressures are very strongly influenced by shear stresses. Earlier work on low- and high-temperature transitions was complemented by low-temperature heat capacity measurements. We found no evidence for the presence of an orientational glass, in contrast to earlier dielectric studies, but consistent with earlier low-temperature diffraction studies.
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