Structure and properties of Na‐magadiite dependent on temperature

Brandt, Astrid; Schwieger, Wilhelm; Bergk, K.‐H.; Grabner, DC Paul; Porsch, Martin

doi:10.1002/crat.2170240110

Cited by 23 publications

(31 citation statements)

References 2 publications

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“…Investigations based on FT-IR and FT-Raman spectra (Huang et al 1999) seemed to indicate that magadiite exhibits i) a centrosymmetric structure of point group symmetry 2/m, ii) has a multilayer structure with five-and six-membered rings with Si-O-Si linkages having partly large bond angles near 180 °, iii) a hydrogen bonding system, however, with some hydroxyl groups not involved. According to this model, three (pseudo) tetragonal layer-like building units consisting of 4-and 8-rings are interconnected along the c 0 -axis to form the silicate layer of magadiite (Schwieger et al 1985;Brandt et al 1987;Brandt et al 1988Brandt et al , 1989.…”

Section: Previous Structural Studiesmentioning

confidence: 99%

The crystal structure of mineral magadiite, Na2Si14O28(OH)2∙8H2O

Marler

Krysiak

Grosskreuz

et al. 2022

American Mineralogist

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Magadiite from Lake Magadi was structurally analyzed based on X-ray powder diffraction data. The idealized chemical composition of magadiite is Na16[Si112O224(OH)16]∙64H2O per unit cell. The XRD powder diffraction pattern was indexed in orthorhombic symmetry with lattice parameters a0 = 10.5035(9) Å, b0 = 10.0262(9) Å, and c0 = 61.9608(46) Å. The crystal structure was solved from a synthetic magadiite sample in a complex process using 3D electron diffraction combined with model building as presented in an additional paper. A Rietveld refinement of this structure model performed on a magadiite mineral sample in space group F2dd (No. 43) converged to residual values of RBragg = 0.031 and RF = 0.026 confirming the structure model. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and DRIFT spectroscopy further confirmed the structure. The structure of magadiite contains two enantiomorphic silicate layers of, so far, unknown topology. The dense layers exhibit no porosity or micro-channels and have a thickness of 11.5 Å (disregarding the van der Waals radii of the terminal O atoms) and possess a silicon Q4 to Q3 ratio of 2.5. 16 out of 32 terminal silanol groups are protonated, and the remaining groups compensate for the charge of the hydrated sodium cations. Bands of edge-sharing [Na(H2O)6/1.5] octahedra are intercalated between the silicate layers extending along (110) and (110). The water molecules are hydrogen bonded to terminal silanol groups with O···O distances of 2.54–2.91 Å. The structure of magadiite is slightly disordered, typical for hydrous layer silicates (HLS), which possess only weak interactions between neighboring layers. In this respect, the result of the structure refinement represents a somewhat idealized structure. Nevertheless, the natural magadiite possesses a higher degree of structural order than any synthetic magadiite sample. The structure analysis also revealed the presence of strong intra-layer hydrogen bonds between the terminal O atoms (silanol/siloxy groups), confirmed by 1H MAS NMR and DRIFT spectroscopy. The surface zone of the silicate layers, as well as the interlayer region containing the [Na(H2O)6/1.5] octahedra, are closely related to the structure of Na-RUB-18.

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Section: Previous Structural Studiesmentioning

confidence: 99%

The crystal structure of mineral magadiite, Na2Si14O28(OH)2∙8H2O

Marler

Krysiak

Grosskreuz

et al. 2022

American Mineralogist

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“…3(a)], on the basis of the reflections corresponding to the basal spacing and the width of the silicate sheet. [4][5][6][7] In order to induce pillaring of silica, octylamine is intercalated into the silicic acid sites in the first stage, leading to an increase of the basal spacing due to the formation of an octylamine-octylammonium bilayer.9 Some of the octylamine is then replaced by TEOS in the organic-pillar precursor [Fig. 3(b)].…”

Section: N E W Silica-pillared Materials Prepared From the Layered Si...mentioning

confidence: 99%

New silica-pillared material prepared from the layered silicic acid of ilerite

Kosuge¹,

Tsunashima²

1995

J. Chem. Soc., Chem. Commun.

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“…The reason is that structure analysis was hindered by the strong stacking disorder and small particle size of the material. Attempts to propose a structural model were made based on 29 Si MAS NMR and FTIR − and, recently, based on a PDF analysis . As we will show in this work, all these attempts to solve the structure of magadiite failed.…”

Section: Introductionmentioning

confidence: 98%

The Elusive Structure of Magadiite, Solved by 3D Electron Diffraction and Model Building

et al. 2021

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In addition to a great swelling ability, layered silicates also allow the functionalization of their interlayer region to form various robust green materials that are used as CO 2 adsorbents, drug carriers, or catalysts. Here, the unique magadiite structure, which has resisted elucidation despite many attempts and applications the material offers, is finally described. A materialspecific strategy allowed the use of 3D electron diffraction which led to the success of deciphering the atomic structure. In order to enable an ab initio structure solution of the electron beam sensitive material, a sodium-free dehydrated form of magadiite was synthetically isolated, and, from that, it was subsequently possible to derive a structure model for the sodium form of magadiite, later successfully refined against powder X-ray diffraction data. Furthermore, a geometry optimization and simulations of spectroscopic data with DFT methods confirm the obtained crystal structure of sodium magadiite. These results finally prompted a detailed description of the layers and of the chemically active interlayer region and provide a huge impact toward the design of new and more efficient materials based on functionalized magadiite and related structures.

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Structure and properties of Na‐magadiite dependent on temperature

Cited by 23 publications

References 2 publications

The crystal structure of mineral magadiite, Na2Si14O28(OH)2∙8H2O

The crystal structure of mineral magadiite, Na2Si14O28(OH)2∙8H2O

New silica-pillared material prepared from the layered silicic acid of ilerite

The Elusive Structure of Magadiite, Solved by 3D Electron Diffraction and Model Building

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