Structural characteristics of Na,Fe-decationated eudialyte with the symmetry <Emphasis Type="Italic">R</Emphasis>3 |
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| Authors: | R K Rastsvetaeva A P Khomyakov |
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| Institution: | (1) Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 59, Moscow, 117333, Russia;(2) Institute of Mineralogy, Geochemistry, and Crystal Chemistry of Rare Elements, ul. Veresaeva 15, Moscow, 121357, Russia |
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| Abstract: | The crystal structure of a new highly decationated representative of the eudialyte group has been established (R = 0.055, 1734 |F|). The mineral is described by the simplified formula (H3O)9Na2(K, Ba,Sr)2Ca6Zr3Si26O66(OH)6](OH)3Cl · H2O (Z = 3). The unit-cell parameters are a = 14.078(3) Å, c = 31.24(1) Å; V = 5362 Å3; sp. gr. R3. Being chemically and structurally related to the hydrated analogues studied previously (in particular, to potassium oxonium eudialyte), the new mineral differs from its analogues in that it has a higher degree of Na-and Fe-cation depletion. The replacement of 3/4 of Na cations by loose and mobile H3O groups results in structure destabilization, which is seen from the high values of the thermal parameters of the atoms and the loss of the symmetry plane. |
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