Redetermination and new description of the crystal structure of vanthoffite, Na(6)Mg(SO(4))(4)
The crystal structure of vanthoffite {hexasodium magnesium tetrakis[sulfate(VI)]}, Na(6)Mg(SO(4))(4), was solved in the year 1964 on a synthetic sample [Fischer & Hellner (1964 ▸). Acta Cryst. 17, 1613]. Here we report a redetermination of its crystal structure on a mineral sample with improv...
Published in: | Acta Crystallographica Section E Crystallographic Communications |
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Main Authors: | , , |
Format: | Text |
Language: | English |
Published: |
International Union of Crystallography
2020
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Subjects: | |
Online Access: | http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7274003/ http://www.ncbi.nlm.nih.gov/pubmed/32523739 https://doi.org/10.1107/S2056989020005873 |
Summary: | The crystal structure of vanthoffite {hexasodium magnesium tetrakis[sulfate(VI)]}, Na(6)Mg(SO(4))(4), was solved in the year 1964 on a synthetic sample [Fischer & Hellner (1964 ▸). Acta Cryst. 17, 1613]. Here we report a redetermination of its crystal structure on a mineral sample with improved precision. It was refined in the space group P2(1)/c from a crystal originating from Surtsey, Iceland. The unique Mg (site symmetry [Image: see text]) and the two S atoms are in usual, only slightly distorted octahedral and tetrahedral coordinations, respectively. The three independent Na atoms are in a distorted octahedral coordination (1×) and distorted 7-coordinations intermediate between a ‘split octahedron’ and a pentagonal bipyramid (2×). [MgO(6)] coordination polyhedra interchange with one half of the sulfate tetrahedra in <011> chains forming a (100) meshed layer, with dimers formed by edge-sharing [NaO(7)] polyhedra filling the interchain spaces. The other [NaO(7)] polyhedra are organized in a parallel layer formed by [010] and [001] chains united through edge sharing and bonds to the remaining half of sulfate groups and to [NaO(6)] octahedra. The two types of layers interconnect through tight bonding, which explains the lack of morphological characteristics typical of layered structures. |
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