Composition-dependent variations in displacement, occupational and density modulation waves in plagioclase feldspar [Na1−x Ca x (Si3−x Al1+x O8)] solid solution with incommensurately modulated structure
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چکیده
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Europium-IV: an incommensurately modulated crystal structure in the lanthanides.
High-resolution x-ray powder-diffraction experiments were performed on europium metal at high pressure up to 50 GPa. At variance with previous reports, the hcp phase of Eu was observed to be stable not only to 18 GPa, but to 31.5 GPa. At 31.5(5) GPa, europium transforms to a phase (Eu-IV) with an incommensurately modulated monoclinic crystal structure with superspace group C2/c(q(1)0q(3))00. Th...
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Electrostatic calculations estimated the energy of hypothetical ion clustering in intermediate plagioclase feldspars. The calculated energy appears too great to allow segregation of Ca and Na atoms into domains upon annealing without a corresponding movement of A1 and Si from an original disordered structure. The calculated energy may be sufficiently small that Ca and Na atoms can disorder part...
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15 صفحه اولTransition from the incommensurately modulated structure to the lock-in phase in Co-åkermanite.
The adaptation of the incommensurate structure modulation in Ca(2)CoSi(2)O(7) (dicalcium cobalt disilicate) single crystals to decreasing temperature has been examined using in situ high-resolution transmission electron microscopy and electron diffraction. The transition from the incommensurate to the commensurate lock-in phase of Co-åkermanite exhibits a pronounced hysteresis of a highly strai...
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ژورنال
عنوان ژورنال: Acta Crystallographica Section A Foundations and Advances
سال: 2017
ISSN: 2053-2733
DOI: 10.1107/s0108767317099925