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Vergasovaite to cupromolybdite topotactic transformation with crystal shape preservationстатья
- Авторы: Nazarchuk Evgeni V., Siidra Oleg I., Charkin Dmitri O., Nikolaevich Gleb V., Borisov Artem S., Ugolkov Valery L.
- Журнал: American Mineralogist
- Год издания: 2023
- Издательство: Mineralogical Society of America
- Местоположение издательства: United States
- DOI: 10.2138/am-2022-8753
- Аннотация: Thermal behavior of vergasovaite, ideally Cu3O(SO4)(MoO4), and its synthetic analog has been studied by high-temperature single crystal X-ray diffraction in the temperature range of 300-1100K. The natural mineral is stable until 950±15K; at 975 K, the unit cell parameters and volume increase abruptly due to topotactic transformation of vergasovaite into cupromolybdite, Cu3O(MoO4)2. The transformation is accompanied by loss of sulfur (and excess copper) without destruction of the crystal. The thermal expansion of the vergasovaite structure is strongly anisotropic, being minimal along the [O2Cu6]8+ chains comprised of vertex-sharing OCu4 tetrahedra. The peculiarities of the thermal expansion of vergasovaite can be explained by the anisotropy of bond length evolution in the Cu1O6 and Cu3O6 octahedra and flexibility of the S-O-Cu and Mo-O-Cu bond angles. Synthetic Zn- and V-free analogue demonstrates negative thermal expansion at 425-625 K and melts at as low temperature as 700 K with no indication to (re)crystallization at least below 1200 K.
- Добавил в систему: Чаркин Дмитрий Олегович