Localization of water in hexasodium hexakis(aluminosilicate)–deuterium oxide (1/8), Na6[AlSiO4]6.8D2O. A neutron powder diffraction Rietveld profile analysis at 10 K

Felsche, J.; Luger, Selina M.; Fischer, P.

doi:10.1107/s0108270187093983

Cited by 17 publications

(11 citation statements)

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“…On the other hand, the reversible dehydration/hydration phenomena and the consequent anomalous effect on framework geometry are only known from hydro sodalites [7,11,12]. Although very many hydro sodalites have been reported within a vast range of chemical compositions, their compositional variations were mostly confined to either topotactic manipulation of the guest species or complete replacement of the framework T-atoms [7,[11][12][13][14][15][16][17][18]. In contrast, partial T-sites substitution in the sodalite frameworks [19][20][21][22] remains little explored whereas extensive commercial successes have been achieved through partial T-sites substitution in zeolites [23,24].…”

Section: Introductionmentioning

confidence: 99%

Gallium substitution in the alumosilicate framework: synthesis and structural studies of hydro sodalites

Murshed¹,

Gesing²

2008

Zeitschrift Für Kristallographie - Crystalline Materials

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A series of hydro sodalites of composition Na 6 [Al 1Ày Ga y SiO 4 ] 6 (H 2 O) 8 (0 y 1) have been prepared from Na 6þx [Al 1Ày Ga y SiO 4 ] 6 (OH Á H 2 O) x (H 2 O) 8À4x sodalites by NaOH/H 2 O exchange methods carried out in acidic aqueous media. One of the end members (y ¼ 1) Na 6 [GaSiO 4 ] 6 (H 2 O) 8 is obtained from Na 8 [GaSiO 4 ] 6 I 2 by a hydrothermal transformation process. The polycrystalline samples are characterized by Rietveld refinements using X-ray powder diffraction data. The cell parameter fluctuates slightly from the [AlSiO 4 ] 6 to the [GaSiO 4 ] 6 framework with an average value of 884.8 pm. The occurrence of an almost constant cell parameter has been explained as a combined effect of hydrogen bonding between the oxygen atoms of the entrapped water (or the occluded [Na 3 & (H 2 O) 4 ] 3þ complex in the b-cage as a whole), and the framework together with six-ring window deformation. During XRD refinements both aluminium and gallium atoms have been converged to a single crystallographic site. The Al/Ga--O bond distance therefore indicates the mean of Al--O and Ga--O distances, which increases with increasing gallium content in the framework. However, the Si--O distance remains almost constant at 162.9 pm at any Ga/Al ratio. The coupled twisting of the (Al,Ga)O 4 and SiO 4 tetrahedra confirms the increase of tilt angles and decrease of six-ring pore dimension upon aluminium replacement by gallium in the framework. Results of 1 H and 29 Si MAS NMR as well as FTIR spectroscopy are also discussed in terms of successive gallium incorporation in the alumosilicate hydro sodalite frameworks.

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Section: Introductionmentioning

confidence: 99%

Gallium substitution in the alumosilicate framework: synthesis and structural studies of hydro sodalites

Murshed¹,

Gesing²

2008

Zeitschrift Für Kristallographie - Crystalline Materials

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“…The position of the last hydrogen could not be established [40]. In this structure there is effectively no hydrogen bonding between the OH and H 2 O moieties with the framework oxygen [31].…”

Section: Discussionmentioning

confidence: 94%

“…As a result each cage in the sodalite structure contains four Na, one OH, and two H 2 O species. Different authors have reported on the positional variations of oxygen, hydrogen, and the sodium in hydroxy sodalite upon partial and full loss of framework water [39][40][41]. In the fully hydrated form the tetrahedrally coordinated Na cations are located close to the 6-membered ring faces on the corners of a cubical structure as presented in Fig.…”

Section: Discussionmentioning

confidence: 95%

Thermostability of hydroxy sodalite in view of membrane applications

Khajavi

Sartipi

Gascón

et al. 2010

Microporous and Mesoporous Materials

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“…Shannon et al, using both classical force field energy minimization and DFT methods, report a similar result. Felsche and Luger, writing at least five articles in the mid-1980s, have probably contributed the most toward our understanding of Na 6 [SOD]·(H 2 O) n . ,,, In the end, two independent, experimental studies 33,45 were chosen by which to validate the simulation results.…”

Section: Resultsmentioning

confidence: 99%

“…Whereas most sodalite materials contain eight monovalent cation (M + ) and two monovalent anion species (X - ), the so-called “class A” sodalites, this study examines a particularly unique sodalite materialNa 6 [SOD]·(H 2 O) n . First reported as a “sodium poor”' sodalite in 1947 by Borchert and Keidel, the presence of only six extraframework cations invokes unique unit cell distortions and asymmetric ring configurations for which considerable adsorption and exchange properties have been reported …”

Section: Sodalite Structurementioning

confidence: 99%

Molecular Simulations of Anhydrous Na₆[Al₆Si₆O₂₄] Sodalite

et al. 2004

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An empirical energy force field, one that combines previously published force field parameters with a flexible SPC water model, is used to examine the structures and dynamical properties of the hydrosodalite family of zeolitic materials. In this paper, we present the results for Na6[Al6Si6O24], one of two anhydrous end-members in this family. Experimentally derived unit cell volumes, T−O bond lengths, and T−O−T and O−T−O bond angles are used to validate the force field. Supplemental plane-wave pseudopotential density functional calculations fully support the potential-based models. Although sodalite materials usually possess P4̄3n symmetry, the direct modeling results from both simulation techniques employed in this study suggest the formation of volume-doubled C2/c supercells. The loss of symmetry is due to the presence of only six monovalent ions in the unit cell, rather than the usual eight. This result stands in partial agreement with recent simulation and experimental studies that report volume-doubled Pcn2 and orthorhombic supercell structures, respectively. More specifically, Le Bail profile and Rietveld refinementswhen compared to the synchrotron-based XRD data from the recent experimental studyfavor P2/c symmetry, a sub-group of C2/c. Le Bail profile agreement indices of R P = 6.18% and R WP = 7.92% for P2/c are lower than those reported for the orthorhombic cases, and Rietveld refinement indices of R P = 7.91% and R WP = 10.50% are lower than those reported for Pcn2. We further propose a new S6R ring structure that can be explained in terms of two crystallographically and energetically distinct oxygen sites. These structural and energetic results offer explicit evidence to support the hypothesis that “vacant ring avoidance” drives supercell formation. The new S6R structure leads to the formation of two enantiomeric β-cages, which, in turn, leads to the volume-doubled supercell. Finally, the periodic DFT calculations suggest that the sodium ions occupy the centers of the six-membered rings, in full agreement with the force field results. This arrangement, however, stands in contrast to the results of a recent DFT study, where a significant offset of the sodium ions out of the planes of the S6Rs is observed.

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Localization of water in hexasodium hexakis(aluminosilicate)–deuterium oxide (1/8), Na6[AlSiO4]6.8D2O. A neutron powder diffraction Rietveld profile analysis at 10 K

Abstract: (4)]11. These findings are contrary to the behaviour of the water molecules in the basic sodalites Naa[A1SiO416(OH)2.nH20, 0 < n < 4, which show no hydrogen bonding to the framework O atoms.

Cited by 17 publications

References 7 publications

Gallium substitution in the alumosilicate framework: synthesis and structural studies of hydro sodalites

Gallium substitution in the alumosilicate framework: synthesis and structural studies of hydro sodalites

Thermostability of hydroxy sodalite in view of membrane applications

Molecular Simulations of Anhydrous Na₆[Al₆Si₆O₂₄] Sodalite

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Localization of water in hexasodium hexakis(aluminosilicate)–deuterium oxide (1/8), Na6[AlSiO4]6.8D2O. A neutron powder diffraction Rietveld profile analysis at 10 K

Abstract: (4)]11. These findings are contrary to the behaviour of the water molecules in the basic sodalites Naa[A1SiO416(OH)2.nH20, 0 < n < 4, which show no hydrogen bonding to the framework O atoms.

Cited by 17 publications

References 7 publications

Gallium substitution in the alumosilicate framework: synthesis and structural studies of hydro sodalites

Gallium substitution in the alumosilicate framework: synthesis and structural studies of hydro sodalites

Thermostability of hydroxy sodalite in view of membrane applications

Molecular Simulations of Anhydrous Na6[Al6Si6O24] Sodalite

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Product

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Molecular Simulations of Anhydrous Na₆[Al₆Si₆O₂₄] Sodalite