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Open AccessArticle

The Na2−nHn[Zr(Si2O7)]∙mH2O Minerals and Related Compounds (n = 0–0.5; m = 0.1): Structure Refinement, Framework Topology, and Possible Na+-Ion Migration Paths

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Laboratory of Nature-Inspired Technologies and Environmental Safety of the Arctic, Kola Science Centre, Russian Academy of Sciences, Fersmana str. 14, 184209 Apatity, Russia
2
Samara Center for Theoretical Materials Science, Samara State Technical University, Molodogvardeyskaya Str. 244, 443100 Samara, Russia
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Crystallography Department, Institute of Earth Sciences, St. Petersburg State University, University emb. 7/9, 199034 Petersburg, Russia
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Geo Environmental Centre “Geomodel”, Saint–Petersburg State University, Ul’yanovskaya Str. 1, 198504 Petersburg, Russia
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Geological Institute, Kola Science Centre, Russian Academy of Sciences, Fersmana str. 14, 184209 Apatity, Russia
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Nanomaterials Research Centre, Kola Science Centre, Russian Academy of Sciences, Fersmana str. 14, 184209 Apatity, Russia
*
Author to whom correspondence should be addressed.
Crystals 2020, 10(11), 1016; https://doi.org/10.3390/cryst10111016
Received: 26 October 2020 / Revised: 5 November 2020 / Accepted: 6 November 2020 / Published: 9 November 2020
(This article belongs to the Special Issue Crystal Chemistry and Properties of Minerals)
The Na2−nHn[Zr(Si2O7)]∙mH2O family of minerals and related compounds (n = 0–0.5; m = 0.1) consist of keldyshite, Na3H[Zr2(Si2O7)2], and parakeldyshite, Na2[Zr(Si2O7)], and synthetic Na2[Zr(Si2O7)]∙H2O. The crystal structures of these materials are based upon microporous heteropolyhedral frameworks formed by linkage of Si2O7 groups and ZrO6 octahedra with internal channels occupied by Na+ cations and H2O molecules. The members of the family have been studied by the combination of theoretical (geometrical–topological analysis, Voronoi migration map calculation, structural complexity calculation), and empirical methods (single-crystal X-ray diffraction, microprobe analysis, and Raman spectroscopy for parakeldyshite). It was found that keldyshite and parakeldyshite have the same fsh topology, while Na2ZrSi2O7∙H2O is different and has the xat topology. The microporous heteropolyhedral frameworks in these materials have a 2-D system of channels suitable for the Na+-ion migration. The crystal structure of keldyshite can be derived from that of parakeldyshite by the Na+ + O2− ↔ OH + □ substitution mechanism, widespread in the postcrystallization processes in hyperagpaitic rocks. View Full-Text
Keywords: keldyshite; parakeldyshite; crystal structure; ion migration; transformation; Raman spectroscopy; Voronoi analysis; topology keldyshite; parakeldyshite; crystal structure; ion migration; transformation; Raman spectroscopy; Voronoi analysis; topology
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Kabanova, N.A.; Panikorovskii, T.L.; Shilovskikh, V.V.; Vlasenko, N.S.; Yakovenchuk, V.N.; Aksenov, S.M.; Bocharov, V.N.; Krivovichev, S.V. The Na2−nHn[Zr(Si2O7)]∙mH2O Minerals and Related Compounds (n = 0–0.5; m = 0.1): Structure Refinement, Framework Topology, and Possible Na+-Ion Migration Paths. Crystals 2020, 10, 1016.

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