2026/01/26 by Evgeny Nazarchuk, E.V. Nazarchuk, Oleg I. Siidra +3
Earth and Planetary Sciences · Materials Science · #High-pressure geophysics and materials #Solid-state spectroscopy and crystallography #Thermal Expansion and Ionic Conductivity
paper · pdf · doi:10.1180/mgm.2026.10192
crossref issued 2026/01/26 · crossref published 2026/01/26 · crossref published-online 2026/01/26 · openalex created_date 2026/01/26 · openalex publication_date 2026/01/26 · crossref created 2026/01/26 · crossref published-print 2026/06/01 · openalex updated_date 2026/06/24 · crossref deposited 2026/07/17 · crossref indexed 2026/07/30
Abstract Hydrated sodium and magnesium sulfates are fairly common minerals. This study is focused on löweite from the fumaroles of the Tolbachik volcano in Kamchatka. The crystal structure of löweite was refined using single-crystal X-ray diffraction, and the hydrogen atoms were localized for the first time. In situ single-crystal (temperature range –173 to 227°C) and powder (temperature range –173 to 900°C) X-ray studies were performed. Both techniques show that löweite remains stable up to ∼220°C without showing any signs of potential phase transitions. The mineral is also stable under a vacuum of ∼600 Pa. The following transformation sequence for löweite was observed upon heating: löweite → metathénardite + vanthoffite + ‘x-phase’ → metathénardite + periclase. The thermal expansion of löweite demonstrates two distinct patterns in two temperature ranges. There is virtually no expansion in the structure until –93°C. Following this, the structure rapidly expands, exhibiting a highly anisotropic behaviour. Shear deformations of the soft S–O–Mg and S–O–Na hinges explain the structural flexibility and adaptability of löweite to changes in physicochemical environments.