| Autor: |
Julia Sordyl, Bartosz Puzio, Maciej Manecki, Olaf Borkiewicz, Justyna Topolska, Sylwia Zelek-Pogudz |
| Jazyk: |
angličtina |
| Rok vydání: |
2020 |
| Předmět: |
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| Zdroj: |
Minerals, Vol 10, Iss 6, p 494 (2020) |
| Druh dokumentu: |
article |
| ISSN: |
2075-163X |
| DOI: |
10.3390/min10060494 |
| Popis: |
Five lead-arsenate apatites (mimetites)-Pb5(AsO4)3X—where X denotes fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and hydroxide (OH)—were synthesized via precipitation from aqueous solutions. The crystal structures were determined through Rietveld refinement of powder synchrotron X-ray data. All the compounds crystallized in the hexagonal class symmetry (space group P63/m). The Rietveld refinement indicated that mimetite-Cl, -Br, -I, and -OH had an anion deficiency at position X. Substitution of halogens in a mimetite structure brought about systematic changes in unit-cell parameters, interatomic distances, and metaprism twist angles φ, proportional to the substituted halogen’s ionic radius. Mimetite-OH did not follow the linear correlations determined within the series. Twist angle φ, a useful device for monitoring changes in apatite topology, ranged from 20.34° for mimetite-F to 11.42° for mimetite-I. The geometric method has been proposed for determining the diameter of hexagonal channels hosting halogens in apatites. A comparison of the results with halogenated pyromorphites showed similar systematic trends: the substitutions in mimetites have comparable effect on the interatomic distances as in their phosphorous analogues. |
| Databáze: |
Directory of Open Access Journals |
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