CaSeO<sub>4</sub>·0.625H<sub>2</sub>O – water channel occupation in a bassanite related structure

Fritz, Susanne A.; Schmidt, Horst; Paschke, Iris; Dinnebiér, Robert E.; Freyer, Daniela; Voigt, Wolfgang

doi:10.1107/s0108768111018544

Cited by 13 publications

(3 citation statements)

References 29 publications

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“…The single-crystal structure solution of CaSeO 4 Á0.625H 2 O (Fritz et al, 2011) demonstrated that water contents higher than 0.5H 2 O are possible in bassanite analogous structures, although the unit cell of the selenate is 10% larger compared with the sulfate. As a consequence of the smaller unit-cell volume of CaSO 4 Á0.5H 2 O the distances between water molecules are short.…”

Section: Introductionmentioning

confidence: 99%

Water channel structure of bassanite at high air humidity: crystal structure of CaSO₄·0.625H₂O

Schmidt

Paschke

Freyer

et al. 2011

Acta Crystallogr B Struct Sci

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Structure analysis using single-crystal diffraction was carried out as a contribution to the dispute about the nature of the water channel structure of bassanite (CaSO(4)·0.5H(2)O). A recent result of Weiss & Bräu (2009) for the crystal structure of bassanite (monoclinic, space group C2) at ambient conditions of air humidity was confirmed. In the presence of high relative air humidity the crystal structure of bassanite transformed due to the incorporation of additional water of hydration. The crystal structure of CaSO(4)·0.625H(2)O was solved by single-crystal diffraction at 298 K and 75% relative air humidity. The experimental results provided an insight into both crystal structures. A model explaining the phase transition from CaSO(4)·0.625H(2)O to CaSO(4)·0.5H(2)O was derived. The monoclinic cell setting of CaSO(4)·0.5H(2)O and the trigonal cell setting of CaSO(4)·0.625H(2)O were confirmed by powder diffraction.

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Section: Introductionmentioning

confidence: 99%

Water channel structure of bassanite at high air humidity: crystal structure of CaSO₄·0.625H₂O

Schmidt

Paschke

Freyer

et al. 2011

Acta Crystallogr B Struct Sci

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“…To the best of our knowledge, there is not a previous study of Raman or infrared spectroscopy of CaSeO 4 . In contrast, there are some reports about the Raman and infrared spectra of CaSeO 4 · n H 2 O. , On the other hand, there are some reports of vibrational properties under pressure for similar compounds to CaSeO 4 , such as CaSO 4 and PbSO 4 , which identified the phase transitions driven by pressure with the help of Raman spectroscopy. Here, the frequencies of the Raman and IR active modes for the Cmca , monazite, scheelite, and AgMnO 4 -type structures have been calculated as well as their pressure dependences.…”

Section: Results and Discussionmentioning

confidence: 99%

Polymorphs of CaSeO₄ under Pressure: A First-Principles Study of Structural, Electronic, and Vibrational Properties

et al. 2015

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In this paper we report a theoretical study of the CaSeO4 compound at ambient pressure and under pressure. Here we made a structural analysis of its three known polymorphs--orthorhombic (Cmca), monoclinic monazite, and tetragonal scheelite--where direct comparison with experimental measurements is done. Besides, the electronic and vibrational structures are reported for the first time for those structures. In addition, the behavior of CaSeO4 as a function of pressure is studied, where phase transitions are investigated by considering a quasiharmonic approximation at 300 K. After a total energy study of 14 possible high-pressure phases of CaSeO4, the following sequence of pressure-driven structural transitions has been found: orthorhombic (Cmca) → tetragonal scheelite → monoclinic AgMnO4-type structure. It was observed that monazite is less stable as temperature increases, while the opposite occurs for the AgMnO4-type structure, this being a novel polymorph. This high-pressure structure is a distortion of the monazite structure and resembles the distorted barite-type structure (P2(1)/n) of CaSO4. The equation of state and the pressure evolution of the structural, electronic, and vibrational properties are also reported.

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“…Similarly, the existence of only one bending mode at 1615 cm -1 could be correlated to the quasi-equivalent nature of the water molecules in the rhabdophane structure. Also, as in the case of churchite, a parallel can be drawn [43] but without investigating the typical wavenumber range of water molecules vibration. In these conditions, the FTIR and Raman data collected in this study for GdPO4•0.667H2O rhabdophane can be considered as a potential firstbasis approach to forecast the spectral characteristics of water in these compounds.…”

Section: Water Moleculesmentioning

confidence: 99%

Monazite, rhabdophane, xenotime & churchite: Vibrational spectroscopy of gadolinium phosphate polymorphs

Clavier

Mesbah

Szenknect

2018

Spectrochimica Acta Part A: Molecular and Biomolecular Spectros

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Rare-earth phosphates with the general formula REEPO4•nH2O belong to four distinct structural types: monazite, rhabdophane, churchite, and xenotime. We report herein the first direct comparison between vibrational spectra of these compounds for the same metal cation i.e. gadolinium. The four GdPO4•nH2O samples were prepared through wet chemistry methods and first characterized by X-Ray Diffraction. Three distinct spectral domains, associated to the deformation and stretching modes of phosphate tetrahedra (PO4) and to water molecules vibrations were then analyzed from FTIR and Raman data, and discussed regarding the structural characteristics of each sample. The most obvious differences between the spectra were associated to (H2O) and s(PO4) modes and led to propose a simple method to rapidly and unambiguously discriminate the four polymorphs.

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CaSeO₄·0.625H₂O – water channel occupation in a bassanite related structure

Cited by 13 publications

References 29 publications

Water channel structure of bassanite at high air humidity: crystal structure of CaSO₄·0.625H₂O

Water channel structure of bassanite at high air humidity: crystal structure of CaSO₄·0.625H₂O

Polymorphs of CaSeO₄ under Pressure: A First-Principles Study of Structural, Electronic, and Vibrational Properties

Monazite, rhabdophane, xenotime & churchite: Vibrational spectroscopy of gadolinium phosphate polymorphs

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CaSeO4·0.625H2O – water channel occupation in a bassanite related structure

Cited by 13 publications

References 29 publications

Water channel structure of bassanite at high air humidity: crystal structure of CaSO4·0.625H2O

Water channel structure of bassanite at high air humidity: crystal structure of CaSO4·0.625H2O

Polymorphs of CaSeO4 under Pressure: A First-Principles Study of Structural, Electronic, and Vibrational Properties

Monazite, rhabdophane, xenotime & churchite: Vibrational spectroscopy of gadolinium phosphate polymorphs

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CaSeO₄·0.625H₂O – water channel occupation in a bassanite related structure

Water channel structure of bassanite at high air humidity: crystal structure of CaSO₄·0.625H₂O

Water channel structure of bassanite at high air humidity: crystal structure of CaSO₄·0.625H₂O

Polymorphs of CaSeO₄ under Pressure: A First-Principles Study of Structural, Electronic, and Vibrational Properties