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2026 Mereiter Swartzite Phase Transition

Kurt Mereiter

2026enswartziteuranium mineralscrystal structurephase transitionhydrogen bondingx‑ray diffraction

Abstract

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The uranyl tricarbonate mineral swartzite, CaMg[UO 2(CO3)3]·12H2O, was investigated using single−crystal X − ray diffraction on synthetic material between 295 and 100 K. Swartzite is composed of Mg(H 2O)6 octahedra and {Ca(H2O)6[UO2(CO3)3]} complexes linked into a three–dimensional framework through an extensive hydrogen–bond network. At room temperature, the compound crystallizes in the monoclinic space group P21/m with specific parameters, and subtle disorder in water groups affects hydrogen bonds. A reversible phase transition occurs at approximately 238 K, leading to a low−temperature structure with space group P21/c, where all water groups become ordered with changes in symmetry. This phase transition involves atomic displacements and distortions across temperature ranges, with final refinements indicating convergence of results for various reflections at different temperatures. Neutron diffraction data are also presented to complement X−ray measurements, providing insights into hydrogen−bond geometries above the phase transition temperature.

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Cite This Work

@article{1c5b741c-a45e-4c15-9377-106e74c2f4d1,
  title={2026 Mereiter Swartzite Phase Transition},
  author={Kurt Mereiter},
  year={2026},
  language={en}
}
TY  - JOUR
TI  - 2026 Mereiter Swartzite Phase Transition
AU  - Kurt Mereiter
PY  - 2026
LA  - en
ER  -

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