| Autor: |
Rastsvetaeva, R. K., Aksenov, S. M., Gridchina, V. M., Chukanov, N. V. |
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| Zdroj: |
Crystallography Reports; Oct2024, Vol. 69 Issue 5, p660-667, 8p |
| Abstrakt: |
The crystal structure of a new mineral from the eudialyte group, amableite-(Ce) Na15[(Ce1.5Na1.5)Mn3]Mn2Zr3 Si[Si24O69(OH)3](OH)2 ⋅ H2O, was refined using X-ray diffraction analysis in the R3 space group. This mineral was discovered in a hyperagpaitic pegmatite in the Saint-Amable massif, Canada. Amableite-(Ce) is a representative of the eudialyte group with the lowest calcium content; it differs from other representatives of this group by the dominance of lanthanides in a part of edge-sharing octahedra of the six-membered ring. The structure of amableite-(Ce) has a unit cell with the following parameters: a = 14.1340(2) Å, c = 30.378(1) Å, and V = 5255.6(3) Å3. In this paper, we propose a model for the distribution of cations within the amableite-(Ce) crystal structure based on a low-symmetry P3 space group. We refined 162 independent atomic positions in the isotropic–anisotropic approximation using 3968 reflections with F > 3σ(F) and obtained R = 4.6% as the final result. Despite the close agreement between the two space groups, the transition from R3 to P3 allows us to obtain a more detailed information about the local distribution of a number of elements over different framework sites. The models of the crystal structure of amableite-(Ce) in the framework of R3 and P3 symmetries, as well as other low-calcium minerals from the eudialyte group that have been studied previously within several space groups, have been compared. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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