The structure of the Mg-exchanged forms of three natural phillipsite samples with SU(Si+Al)=0.63, 0.72, and 0.76 arc described. In the more acidic samples, exchanged Mg concentration is lower than 2 a.f.u. and Mg is fully hosted in site II. In sample (1), Mg is 2.4 a.f.u. and occupies and intermediate position between II and II'. As a consequence residual K in site I migrates to the centre of the type I cage inducing a relaxation in the structure which changes from monoclinic P2(1)/m to orthorhombic B2mb. The structure solution was troublesome because some phillipsite crystals surprisingly did not exchange for Mg.
The structure of the Mg-exchanged forms of three natural phillipsite samples with Si/(Si+Al)=0.63, 0.72, and 0.76 are described. In the more acidic samples, exchanged Mg concentration is lower than 2 a.f.u. and Mg is fully hosted in site II. In sample (1), Mg is 2.4 a.f.u. and occupies and intermediate position between II and II'. As a consequence residual K in site I migrates to the centre of the type I cage inducing a relaxation in the structure which changes from monoclinic P21/m to orthorhombic B2mb. The structure solution was troublesome because some phillipsite crystals surprisingly did not exchange for Mg.
Structure of Mg-exchanged phillipsites / Gualtieri, A. F.. - 378-381:II(2001), pp. 677-682. (Intervento presentato al convegno 7th European Powder Diffraction Conference tenutosi a Barcelona, esp nel 2000) [10.4028/www.scientific.net/MSF.378-381.677].
Structure of Mg-exchanged phillipsites
Gualtieri A. F.
2001
Abstract
The structure of the Mg-exchanged forms of three natural phillipsite samples with Si/(Si+Al)=0.63, 0.72, and 0.76 are described. In the more acidic samples, exchanged Mg concentration is lower than 2 a.f.u. and Mg is fully hosted in site II. In sample (1), Mg is 2.4 a.f.u. and occupies and intermediate position between II and II'. As a consequence residual K in site I migrates to the centre of the type I cage inducing a relaxation in the structure which changes from monoclinic P21/m to orthorhombic B2mb. The structure solution was troublesome because some phillipsite crystals surprisingly did not exchange for Mg.
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