| People | Locations | Statistics |
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| Naji, M. |
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| Motta, Antonella |
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| Aletan, Dirar |
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| Mohamed, Tarek |
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| Ertürk, Emre |
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| Taccardi, Nicola |
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| Kononenko, Denys |
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| Petrov, R. H. | Madrid |
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| Alshaaer, Mazen | Brussels |
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| Bih, L. |
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| Casati, R. |
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| Muller, Hermance |
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| Kočí, Jan | Prague |
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| Šuljagić, Marija |
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| Kalteremidou, Kalliopi-Artemi | Brussels |
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| Azam, Siraj |
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| Ospanova, Alyiya |
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| Blanpain, Bart |
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| Ali, M. A. |
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| Popa, V. |
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| Rančić, M. |
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| Ollier, Nadège |
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| Azevedo, Nuno Monteiro |
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| Landes, Michael |
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| Rignanese, Gian-Marco |
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Kolitsch, Uwe
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Topics
Publications (5/5 displayed)
- 2021Thermessaite-(NH<sub>4</sub>), (NH<sub>4</sub>)<sub>2</sub>AlF<sub>3</sub>(SO<sub>4</sub>), a new fumarole mineral from La Fossa crater at Vulcano, Aeolian Islands, Italycitations
- 2016A single-crystal X-ray and Raman spectroscopic study of hydrothermally synthesized arsenates and vanadates with the descloizite and adelite structure typescitations
- 2011Crystal chemistry of elpidite from Khan Bogdo (Mongolia) and its K- and Rb-exchanged forms
- 2010Hydrogen bonding in coquimbite, nominally Fe2(SO4)3×9H2O, and the relationship between coquimbite and paracoquimbite
- 2009Investigations in the systems Sr-As-O-X (X = H, Cl): Preparation and crystal structure refinements of the anhydrous arsenates(V) Sr3(AsO4)2, Sr2As2O7, a- and ß-SrAs2O6, and of the apatite-type phases Sr5(AsO4)3OH and Sr5(AsO4)3Cl
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article
Hydrogen bonding in coquimbite, nominally Fe2(SO4)3×9H2O, and the relationship between coquimbite and paracoquimbite
Abstract
Using single-crystal X-ray diffraction at 293, 200 and 100 K, and neutron diffraction at 50 K, we have refined the positions of all atoms, including hydrogen atoms (previously undetermined), in the structure of coquimbite (P3_1c, a?=?10.924(2)/10.882(2) Å, c?=?17.086(3) / 17.154(3) Å, V?=?1765.8(3)/1759.2(5) Å3, at 293 / 50 K, respectively). The use of neutron diffraction allowed us to determine precise and accurate hydrogen positions. The O-H distances in coquimbite at 50 K vary between 0.98 and 1.01 Å. In addition to H2O molecules coordinated to the Al3+ and Fe3+ ions, there are rings of six "free" H2O molecules in the coquimbite structure. These rings can be visualized as flattened octahedra with the distance between oxygen and the geometric center of the polyhedron of 2.46 Å. The hydrogen-bonding scheme undergoes no changes with decreasing temperature and the unit cell shrinks linearly from 293 to 100 K. A review of the available data on coquimbite and its "dimorph" paracoquimbite indicates that paracoquimbite may form in phases closer to the nominal composition of Fe2(SO4)3·9H2O. Coquimbite, on the other hand, has a composition approximating Fe1.5Al0.5(SO4)3·9H2O. Hence, even a "simple" sulfate Fe2-x Al x (SO4)3·9H2O may be structurally rather complex.