Structure of calcinaksite KNa[Ca(H₂O)][Si₄O_l0], the first hydrous member of the litidionite group of silicates with [Si₈O₂₀]₈- tubes

Autor(en)

Sergey M. Aksenov, Ramiza K. Rastsvetaeva, Nikita V. Chukanov, Uwe Kolitsch

Abstrakt

Calcinaksite, KNa[Ca(H2O)][Si4Ol0], a new natural memberof the litidionite group, was found in a calcic xenolith fromalkaline basalt of the Bellerberg volcano, Eastern Eifel region,Rhineland-Palatinate, Germany. The crystal structure hasbeen studied based on single-crystal X-ray diffraction data.Triclinic unit-cell parameters are: a = 7.021 (2), b = 8.250 (3),c = 10.145 (2) A ° , = 102.23 (2), = 100.34 (2), = 115.09 (3),space group P11. The structure model was determined by the‘charge-flipping’ method and refined to R = 0.0527 inanisotropic approximation using 3057 I > 3(I). Calcinaksiteis a hydrous calcium-dominant litidionite-group mineral. Thecrystal structure of calcinaksite (like other litidionite-groupminerals and related compounds) is based on a heteropolyhedralframework and is characterized by the presence ofseveral types of channels. Calcium forms distorted CaO5Ø (Ø= H2O) octahedra while Na forms NaO5 square pyramids.Nine-coordinated K atoms are located in a channel extendingalong [010]. Water molecules occupy a channel running alongthe [100] direction and are characterized by a rather highequivalent isotropic displacement parameter of 0.053 (2) A ° 2.In calcinaksite, there are three short distances between thewater molecule and oxygen atoms, Ow-3 [2.844 (5) A ° ],Ow O9 [2.736 (4) A ° ] and Ow Ow [2.843 (7) A ° ]. Thesedistances correspond to three hydrogen bonds detected by IRdata (the bands at 3340, 3170 and 3540 cm-1).

Organisation(en)

Institut für Mineralogie und Kristallographie

Externe Organisation(en)

Russian Academy of Sciences

Journal

Acta Crystallographica. Section B: Structural Science

Band

70

Seiten

768-775

Anzahl der Seiten

8

ISSN

0108-7681

DOI

https://doi.org/10.1107/S2052520614012992

Publikationsdatum

07-2014

Peer-reviewed

Ja

ÖFOS 2012

105116 Mineralogie, 104017 Physikalische Chemie, 105113 Kristallographie

Schlagwörter

ASJC Scopus Sachgebiete

Electronic, Optical and Magnetic Materials, Metals and Alloys, Materials Chemistry, Atomic and Molecular Physics, and Optics

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/c6f65c46-653b-47f7-9147-032f120ffa1f