Modulated structure of a plagioclase An52: Theory and structure determination
Abstract
A modulated structure of an An52 (Labrador, Canada) was determined according to an extended theory of satellites. The theory explains the whole extinction rules of satellite reflections of plagioclase feldspars. The superstructure, which is interpreted as the periodic antiphase domains, consists of two centrosymmetric structure elements ϱ1 and ϱ2 with M2T8O16 (M: Ca, Na and T: Al, Si), c ∼ 7 Å. The structure-factors for main and satellite reflections are expressed as Fmain ∝ F1 + F2 and Fsat ∝ F1−F2, respectively, where F1 and F2 are the Fourier transforms of ϱ1 and ϱ2. Based on the model, ϱ1 and ϱ2 were refined. The R-factor attained 8% for 4910 reflections (Ra = 6.6% for 1640 a reflections and Re = 18.2% for 3270 e reflections), including unobserved reflections. Al/Si-distributions in the region of An100–An50 are discussed using the results of the refinement.
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Articles in the same Issue
- X-Ray and neutron diffraction study of alums
- Complex ion centres in heavily doped NaBr: Tl phosphors
- Distortions of octahedra and octahedral sheets in 1 M micas and the relation to their stability
- Structure of 2-hydroxybenzimidazole
- Structural investigations of synthetic fairchildite, K2Ca(CO3)2
- The crystal and molecular structure of [Co(PO4)(NH3)4] · 3 H2O
- The crystal structure of Benzoic Acid: a redetermination with X-rays at room temperature; a summary of neutron-diffraction work at temperatures down to 5 K
- Modulated structure of a plagioclase An52: Theory and structure determination
- Die Kristallstruktur des Dilithium tetrahydroxo-di-μ-peroxodiborats(Lithiumperoxoborats), Li2[B2(O2)2(OH)4]
- Über Wirkungsbereichsteilungen von kubischer Symmetrie II. Die Typen von Wirkungsbereichspolyedern in den symmorphen kubischen Raumgruppen
- Kristallstrukturen komplexer Alkali-Nickel-Azidhydrate
- Röntgentopographische Untersuchungen an CdTe-Einkristallen
- The crystal structure of synthetic Tl3SbS4
