Abstract
Seven natural analcime samples with atomic Si/Al ratios from 1.97 to 2.63 were investigated to explore the effects of intermediate range structure and Al for Si substitution up to the fourth nearest neighbor coordination shell on the 29Si NMR chemical shifts in the framework aluminosilicates. With increasing bulk Si/Al ratio, the 29Si chemical shifts of all Si(nAl) resonances become more negative (more shielded), consistent with previously reported trends for faujasite and LTA zeolite (Newsam 1985). For our analcimes, the total observed changes in chemical shift for the Si(3Al), Si(2Al), and Si(1Al) sites are ~0.5, 0.6, and 1.1 ppm, respectively, demonstrating that the effect of Si/Al ratio is more significant for the Si sites with a smaller number of next-nearest neighbor Al atoms. The mean value of the change in chemical shift per added Al on fourth nearest neighbor sites is ~2.8 ppm [2.3 ppm if Si(3Al) is excluded]. This value is similar to the results of recent QM/MM calculations and is somewhat larger than those previously reported for faujasite and LTA framework zeolite (~1.4 and 1.3 ppm). This difference correlates with the overall denser structure of analcime, including smaller cages and shorter Si-fourth neighbor distances. Combining these results with the known changes in 29Si chemical shifts for framework silicates due to changes in the first coordination shell, tetrahedral polymerization and second neighbor Al for Si substitution for tetrahedrally coordinated Si, we present an empirical relation between the changes in 29Si chemical shift and interatomic distance between Si and nearby atoms.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Characterization of cation environments in polycrystalline forsterite by 25Mg MAS, MQMAS, and QCPMG NMR
- Structure of nanocrystalline phyllomanganates produced by freshwater fungi
- First-principles study on variation of lattice parameters of mullite Al4+2xSi2–2xO10–x (x = 0.125, 0.250, 0.375)
- Natrolite may not be a “soda-stone” anymore: Structural study of fully K-, Rb-, and Cs-exchanged natrolite
- Metal retention, mineralogy, and design considerations of a mature permeable reactive barrier (PRB) for acidic mine water drainage in Northumberland, U.K.
- A relationship between d104 value and composition in the calcite-disordered dolomite solid-solution series
- XRD, micro-XANES, EMPA, and SIMS investigation on phlogopite single crystals from Mt. Vulture (Italy)
- Volume behavior of the 10 Å phase at high pressures and temperatures, with implications for H2O content
- Interfacial tension between immiscible liquids in the system K2O-FeO-Fe2O3-Al2O3-SiO2 and implications for the kinetics of silicate melt unmixing
- H2O and the dehydroxylation of phyllosilicates: An infrared spectroscopic study
- Effects of intermediate range structure on the 29Si NMR chemical shifts of framework silicates: Results for analcime
- High-temperature Mössbauer spectroscopy: A probe for the relaxation time of Fe species in silicate melts and glasses
- The thermal equation of state of FeTiO3 ilmenite based on in situ X-ray diffraction at high pressures and temperatures
- OH species, U ions, and CO/CO2 in thermally annealed metamict zircon (ZrSiO4)
- Crystallographic and chemical constraints on the nature of the proustite–pyrargyrite solid-solution series
- Accurate μRaman characterization of reaction products at the surface of (bio)oxidized pyrite
- Determination of manganese valence states in (Mn3+, Mn4+) minerals by electron energy-loss spectroscopy
- AFM study of the epitaxial growth of brushite (CaHPO4·2H2O) on gypsum cleavage surfaces
- Compressibility of protoamphibole: A high-pressure single-crystal diffraction study of protomangano-ferro-anthophyllite
- Crystal structure of hydrous wadsleyite with 2.8% H2O and compressibility to 60 GPa
- Dehydration and rehydration processes in gmelinite: An in situ X-ray single-crystal study
- Characteristics of emission centers in alkali feldspar: A new approach by using cathodoluminescence spectral deconvolution
- Mechanism of metamorphic zircon growth in a granulite-facies quartzite, Adirondack Highlands, Grenville Province, New York
- Speciation and mixing behavior of silica-saturated aqueous fluid at high temperature and pressure
- A critical comment on Thy et al. (2009b): Liquidus temperatures of the Skaergaard magma