A Stress-Induced Tetragonal Distortion in K2OsCl6 under Pressure
Abstract
The structural behaviour of cubic (Fm-3m) K2OsCl6 under compression was investigated to 35.4 GPa using angle-dispersive synchrotron powder X-ray diffraction. Upon increasing pressure, K2OsCl6 undergoes a sequence of structural transformations from the ambient-pressure cubic phase to a tetragonal (P4/mnc) phase above 9.5(3) GPa, followed by a transition to a monoclinic (P21/n) phase beginning at approximately 14.2 GPa. The tetragonal and monoclinic phases coexist over the pressure range 14.2-17.2 GPa, while the monoclinic phase is observed as the sole phase at 17.9 GPa and remains stable up to the maximum pressure investigated. Analysis of the diffraction profiles and unit-cell parameters indicates that the intermediate tetragonal structure is likely associated with stress-induced symmetry lowering rather than a distinct thermodynamic phase. This distortion, which is adequately described by the tetragonal P4/mnc space group, is attributed to non-hydrostatic deviatoric stresses arising from the pressure-transmitting medium. Equation-of-state analysis reveals a pronounced reduction in compressibility across the structural transitions, with the bulk modulus increasing from 26(2) GPa for the cubic phase to 71(3) GPa for the monoclinic phase. The pressure-induced structural sequence is analogous to that reported for related compounds such as K2IrCl6, although the transitions in K2OsCl6 occur at lower pressures. All structural transformations are reversible upon decompression.
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BibTeX
@misc{bura2026stressinduced,
title = {{A Stress-Induced Tetragonal Distortion in K2OsCl6 under Pressure}},
author = {Neha Bura and Peije Zhang and Ganesh Bera and Catalin Popescu and Caleb J. Bennett and Brendan J. Kennedy and Daniel Errandonea},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25913},
eprint = {2610.25913},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25913},
}
RIS
TY - UNPB
TI - A Stress-Induced Tetragonal Distortion in K2OsCl6 under Pressure
AU - Neha Bura
AU - Peije Zhang
AU - Ganesh Bera
AU - Catalin Popescu
AU - Caleb J. Bennett
AU - Brendan J. Kennedy
AU - Daniel Errandonea
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.25913
UR - https://arxiv.org/abs/2610.25913
AB - The structural behaviour of cubic (Fm-3m) K2OsCl6 under compression was investigated to 35.4 GPa using angle-dispersive synchrotron powder X-ray diffraction. Upon increasing pressure, K2OsCl6 undergoes a sequence of structural transformations from the ambient-pressure cubic phase to a tetragonal (P4/mnc) phase above 9.5(3) GPa, followed by a transition to a monoclinic (P21/n) phase beginning at approximately 14.2 GPa. The tetragonal and monoclinic phases coexist over the pressure range 14.2-17.2 GPa, while the monoclinic phase is observed as the sole phase at 17.9 GPa and remains stable up to the maximum pressure investigated. Analysis of the diffraction profiles and unit-cell parameters indicates that the intermediate tetragonal structure is likely associated with stress-induced symmetry lowering rather than a distinct thermodynamic phase. This distortion, which is adequately described by the tetragonal P4/mnc space group, is attributed to non-hydrostatic deviatoric stresses arising from the pressure-transmitting medium. Equation-of-state analysis reveals a pronounced reduction in compressibility across the structural transitions, with the bulk modulus increasing from 26(2) GPa for the cubic phase to 71(3) GPa for the monoclinic phase. The pressure-induced structural sequence is analogous to that reported for related compounds such as K2IrCl6, although the transitions in K2OsCl6 occur at lower pressures. All structural transformations are reversible upon decompression.
ER -