Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction

Fortes, A. Dominic

doi:10.1107/s2056989015011354

Cited by 6 publications

(2 citation statements)

References 35 publications

(39 reference statements)

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“… Note. ν exp /cm −1 , ν cal /cm −1 , and ν ref /cm −1 refer to the room temperature Raman bands experimentally observed, calculated using CASTEP, and reported in the literature, respectively, for NWHO crystal.…”

Section: Resultsmentioning

confidence: 99%

“…Busey et al pointed out an asymmetric stretching vibrational mode of H 2 O in the NWHO Raman spectrum (~3,300 cm −1 ) and two bending vibrational modes in its infrared spectrum (1,680 and 1,695 cm −1 ). Having studied Raman spectrum of NWHO, Fortes observed the bending vibrational mode of H 2 O at 1,683 cm −1 and considered that the envelope corresponding to stretching vibrational mode of H 2 O approximately at 3,300 cm −1 can be divided into four peaks (3,100, 3,297, 3,358, and 3,455 cm −1 ). Saraiva et al recorded Raman spectra of polycrystalline NWHO at low temperatures between 13 and 295 K and found that the envelope of H 2 O in the region between 3,175 and 3,450 cm −1 splits as temperature decreases, indicating the evidence of the conformational changes of the crystal.…”

Section: Introductionmentioning

confidence: 99%

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In‐situ high‐temperature Raman spectroscopic studies of the vibrational characteristics and microstructure evolution of sodium tungstate dihydrate crystal during heating and melting

Wang

You

Wang

et al. 2018

J Raman Spectroscopy

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In-situ studies of the vibrational characteristics and microstructure evolution of the Na 2 WO 4 ·2H 2 O (sodium tungstate dihydrate) crystal during the temperature-induced solid-state phase transformation and melting process were carried out using high-temperature Raman spectroscopic technique. Results showed that the thermal decomposition process of the Na 2 WO 4 ·2H 2 O crystal takes place mainly within the temperature range of 348-383 K, along with the structure transforming from the orthorhombic to cubic symmetry. As the sample temperature increased further, another solid-state phase transformation from the cubic to orthorhombic structure was observed approximately at 893 K before melting occurred at 1023 K. Although the isolated [WO 4 ] 2− tetrahedron was preserved within the entire temperature range from room temperature to 1023 K, subtle changes were observed with the mean bond length of W-O bonds in the tetrahedron unit. Furthermore, Raman active vibrational modes of Na 2 WO 4 ·2H 2 O, two Na 2 WO 4 crystal phases, and corresponding melt were assigned based on the density functional theory simulation and compared with the literature data. Finally, four-molecule cluster arranged as T d symmetry is considered to be the most likely configuration in the molten state according to density functional theory simulation based on the different multimolecular clusters proposed.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

In‐situ high‐temperature Raman spectroscopic studies of the vibrational characteristics and microstructure evolution of sodium tungstate dihydrate crystal during heating and melting

Wang

You

Wang

et al. 2018

J Raman Spectroscopy

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Fine structures and their impacts on the characteristic Raman spectra of molten binary alkali tungstates

Wang

You

et al. 2021

J Raman Spectroscopy

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Comparing with the crystalline tungstate compounds, little work has been carried out and reported on the relation among the microstructure, W–O bond lengths, and characteristic Raman‐active vibration wavenumber of the molten tungstates, which allows us to diagnose and determine the structure of unknown clusters existing in and further predict the physicochemical properties of molten binary alkali tungstates. Raman spectra of an ensemble of eight model clusters were simulated in the present work by density functional theory (DFT) to establish the effect of the fine structures and W–Onb (non‐bridging oxygen) bond lengths of W–O complexes on the characteristic wavenumber of W–Onb Raman‐active vibration modes of the molten tungstates. Results show that the characteristic wavenumbers of the symmetric stretching vibration modes of W–Onb bonds increase almost linearly with the decreasing bond length. The characteristic wavenumbers of W–Onb symmetric stretching vibration modes generally follow [WO4]2− > [WO5]4− > [WO6]6− present in the melt simultaneously. The characteristic wavenumbers were also found to increase with the number of bridging oxygen for the same W–O complex. In situ Raman spectra of molten A2WnO3n + 1 (A = Li, Na, K; n = 1, 2, 3) were then measured in order to verify the correlation observed among the microstructure, W–O bond lengths, and characteristic Raman‐active vibration mode wavenumbers. The correlation was successfully applied to deconvolute the in situ Raman spectrum of the molten Na2W3O10.

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Microwave dielectric properties and thermal conductivities of low-temperature sintered (Na1-K )2MoO4 (x ≤ 0.2) ceramics

Gupta

Kim

2022

Ceramics International

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Crystal structures of deuterated sodium molybdate dihydrate and sodium tungstate dihydrate from time-of-flight neutron powder diffraction

Abstract: High-precision structural parameters for Na2MoO4·2D2O and Na2WO4·2D2O are reported based on refinement of high-resolution time-of-flight neutron powder diffraction data. Complementary Raman spectra are also provided.

Cited by 6 publications

References 35 publications

In‐situ high‐temperature Raman spectroscopic studies of the vibrational characteristics and microstructure evolution of sodium tungstate dihydrate crystal during heating and melting

In‐situ high‐temperature Raman spectroscopic studies of the vibrational characteristics and microstructure evolution of sodium tungstate dihydrate crystal during heating and melting

Fine structures and their impacts on the characteristic Raman spectra of molten binary alkali tungstates

Microwave dielectric properties and thermal conductivities of low-temperature sintered (Na1-K )2MoO4 (x ≤ 0.2) ceramics

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