6533b86ffe1ef96bd12ce8a7
RESEARCH PRODUCT
Essential features of the polytypic charoite-96 structure compared to charoite-90
Ira V. RozhdestvenskayaIra V. RozhdestvenskayaWulf DepmeierMichael CzankEnrico MugnaioliStefano MerlinoUte Kolbsubject
010504 meteorology & atmospheric sciencesElectron crystallographyAb initiocrystal structure analysisengineering.material010502 geochemistry & geophysicscharoite polytypes01 natural sciencesSilicateNanocrystalline materialchemistry.chemical_compoundCrystallographyelectron crystallographychemistryOctahedronElectron diffractionGeochemistry and PetrologyGroup (periodic table)Charoitecharoite polytypes; crystal structure analysis; electron crystallography; electron diffraction; electron diffraction tomographyengineeringelectron diffractionelectron diffraction tomography0105 earth and related environmental sciencesdescription
AbstractCharoite, ideally (K,Sr,Ba,Mn)15–16(Ca,Na)32[(Si70(O,OH)180)](OH,F)4·nH20, is a rock-forming mineral from the Murun massif in Yakutia, Sakha Republic, Siberia, Russia, where it occurs in a unique alkaline intrusion. Charoite occurs as four different polytypes, which are commonly intergrown in nanocrystallme fibres. We report the structure of charoite-96(a =32.11(6),b =19.77(4),c =7.23(1) Å, β = 95.85(9)°,V =4565(24) Å3, space groupP21/m),which was solvedab initioby direct methods on the basis of 2676 unique electron diffraction reflections collected by automated diffraction tomography and refined toR1/wR2=0.34/0.37. The structure of charoite-96 is related to that of the charoite-90, which was also solved recently. Both structures are composed of three different types ofdreiersilicate chains running along [001] and separated by ribbons of edge-sharing Ca- and Na-centred octahedra. In the structure of charoite-96, adjacent blocks formed by three different silicate chains and stacked along thexaxis, are shifted by a translation of 1/2c. The shifts involve a hybriddreierquadruple chain, [Si17O43]18–and a doubledreierchain, [Si6O17]10–. In charoite-90 adjacent blocks are stacked without shifts.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2011-12-01 |