Abstract
Single-crystal X-ray data were collected from a natural fibrous mordenite crystal of composition K2.99Ca1.85Na1.06Al7.89Si40.15O96⋅28H2O and from a platy synthetic mordenite crystal of composition Na6Al6.02Si42.02O96⋅19H2O. Diffraction data were measured with a point detector using a sealed X-ray tube and an image plate using synchrotron radiation, respectively. Both structures exhibit the same defect features visible in difference-Fourier maps. Domains of the entire Cmcm framework structure are reproduced by a non-crystallographic (001) mirror plane at z = 0 and z = 1/2. An identical description is a shift of framework domains 1/2 along the c axis. The concentration of this defect domain is 2.7(2) and 3.1(1)% for the natural and synthetic mordenite crystals, respectively. Reproductions of reciprocal layers from synchrotron image-plate data reveal diffuse scattering for hkl layers with l = 2n + 1. The diffuseness of these layers is not homogeneous but concentrates in the form of halos around selected reflections allowed for C-centering. Diffuse features in electron diffraction patterns of natural and synthetic mordenite have been described before and were interpreted either as evidence of c/2 faults or intergrowth with different mordenite-related structure-types. We have modeled a (100) defect layer that is modified from the mordenite characteristic puckered sheet of six-membered rings and allows coherent intergrowth of identical structural subunits shifted by c/2. These defect domains do not influence or obstruct the 12-membered ring-channels characteristic of this zeolite. The major difference in Si,Al distribution between the two samples is that the natural crystal has Al strongly enriched at T3, which is part of the four-membered rings. We suggest that a synergetic effect between extraframework cations and Si, Al ordering during crystal growth is responsible for Al enrichment in natural mordenite with ca. 2 Ca p.f.u. close to T3.
© 2015 by Walter de Gruyter Berlin/Boston
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- Composition and I4/m-P42/n phase transition in scapolite solid solutions
- Synthesis and characterization of K2Ca5(SO4)6·H2O, the equivalent of görgeyite, a rare evaporite mineral
- Phase relations in the system Fe-FeSi at 21 GPa
- The speciation of dissolved H2O in dacitic melt
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- Experimental determination of siderite stability and application to Martian Meteorite ALH84001
- Determination of the molar absorption coefficient for the infrared absorption band of CO2in rhyolitic glasses
- Crystallographic properties of the calcium phosphate mineral, brushite, by means of First Principles calculations
- The crystal structure of jonesite, Ba2(K,Na)[Ti2(Si5Al)O18(H2O)](H2O)n: A first example of titanosilicate with porous double layers
- Crystal-chemistry of talc: A near infrared (NIR) spectroscopy study
- Synthesis of beryllian sapphirine in the system MgO-BeO-Al2O3-SiO2-H2O and comparison with naturally occurring beryllian sapphirine and khmaralite, Part 2: A chemographic study of Be content as a function of P, T, assemblage and FeMg–1exchange
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- Sieve-textured plagioclase in dacitic magma: Interference imaging results
- Single crystal raman spectroscopy of cerussite
- Sodalite: High-temperature structures obtained from synchrotron radiation and Rietveld refinements
- The structure of metahohmannite, Fe3+2[O(SO4)2]⋅4H2O, by in situ synchrotron powder diffraction
- High-pressure synchrotron X-ray diffraction study of spessartine and uvarovite: A comparison between different equation of state models
- Quantum calculations of the electronic structure and NMR quadrupolar interaction parameters for tugtupite
- Identification of pyrite valence band contributions using synchrotron-excited X-ray photoelectron spectroscopy
- Micro-Raman studies of gypsum in the temperature range between 9 K and 373 K
- A new rare earth disilicate (REE2Si2O7; REE = Dy, Tm, Lu; type-L): Evidence for nonquenchable 10 GPa polymorph with silicon in fivefold trigonal bipyramidal coordination?
- Structural variations in the brownmillerite series Ca2(Fe2–xAlx)O5: Single-crystal X-ray diffraction at 25 °C and high-temperature X-ray powder diffraction (25 °C ≤ T ≤ 1000 °C)
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