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'Topochemical Reaction' in keywords Facet   Publication Year 1998  [X]
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1Author    Francoanellite K^alschpo^cpo, Stefan Dicka, Thomas ZeiskebRequires cookie*
 Title    Francoanellit K3A15HP04)6(P04)2*12H20: Struktur und Synthese durch topochemische Entwässerung von Taranakit-I 2 H2O: Structure and Synthesis by Topochemical Dehydration of Taranakite  
 Abstract    Single crystals of synthetic francoanellite K3Al5(HP0 4)6(P0 4)2-12H20 could be obtained for the first time by topochemical dehydration of taranakite crystals. An X-ray structure de­ termination showed francoanellite to be the mineral with the second longest crystallographic axis described hitherto. Crystal data: space group R3c, a = 869.0(2), c = 8227(1)pm, Z = 6 , R g = 0.042. Francoanellite is a layer structure mineral having six layers of composition [K3Al5(HP04)6(P04)2(H2 0)i2], connected by hydrogen bonds. The rigid layer is formed by columns of corner sharing hydrogen phosphate tetrahedra and AIOö-octahedra which are inter­ connected by additional six-coordinated A1 ions. In trigonal holes of the layer orthophosphate ions are situated. The structure of francoanellite is very similar to the structure of taranakite K3H6Al5(P04)8-18H20 which has planar water interlayers between the Al-phosphate layers. A neutron scattering experiment with subsequent Rietveld refinement of the powder pattern gave the H-atom positions. Hydrogen bonds in francoanellite are formed within the rigid layers and between them. During the reaction taranakite —► francoanellite crystals in an intermediate stage of dehy­ dration could be obtained. From the c-axis of 8858 pm and one-dimensional electron density projections it can be proposed that in these crystals every second water interlayer was lost and a first order staging product of the deintercalation of water from taranakite was formed. 
  Reference    Z. Naturforsch. 53b, 711—719 (1998); eingegangen am 2. März 1998 
  Published    1998 
  Keywords    Crystal Structure, Neutron Scattering, Francoanellite, Taranakite, Topochemical Reaction 
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 TEI-XML for    default:Reihe_B/53/ZNB-1998-53b-0711.pdf 
 Identifier    ZNB-1998-53b-0711 
 Volume    53