Redetermination of junitoite, CaZn2Si2O 7·H2O

Hexiong Yang, Neil G. Jenkins, Robert T Downs

Research output: Contribution to journalArticle

Abstract

The crystal structure of the mineral junitoite, ideally CaZn 2Si2O7·H2O (calcium dizinc disilicate monohydrate), was first determined by Hamilton & Finney [Mineral. Mag. (1985), 49, 91-95] based on the space group Ama2, yielding a reliability factor R of 0.10, with isotropic displacement parameters for all non-H atoms. The present study reports a structure redetermination of junitoite using single-crystal X-ray diffraction data from a natural sample, demonstrating that the space group of this mineral is actually Aea2, which can be attained simply by shifting the origin. Topologically, the structure models in the space groups Aea2 and Ama2 are analogous, consisting of chains of corner-sharing ZnO 4 tetrahedra parallel to the b axis, cross-linked by Si 2O7 tetrahedral dimers (the site symmetry of the bridging O atom is ..2) along a and c, forming a three-dimensional framework. The Ca 2+ cations (site symmetry ..2) are situated in cavities of the framework and are bonded to five O atoms and one H2O molecule (site symmetry ..2) in a distorted octahedral coordination environment. However, some bond lengths, especially for the SiO4 tetrahedron, are noticeably different between the two structure models. Hydrogen bonding in junitoite is found between the water molecule and a framework O atom.

Original languageEnglish (US)
JournalActa Crystallographica Section E: Structure Reports Online
Volume68
Issue number10
DOIs
StatePublished - Oct 2012

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Minerals
Atoms
minerals
Model structures
tetrahedrons
atoms
symmetry
Molecules
R Factors
Bond length
Dimers
Cations
molecules
calcium
Calcium
Hydrogen bonds
Crystal structure
Positive ions
dimers
Single crystals

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Science(all)
  • Chemistry(all)

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Redetermination of junitoite, CaZn2Si2O 7·H2O. / Yang, Hexiong; Jenkins, Neil G.; Downs, Robert T.

In: Acta Crystallographica Section E: Structure Reports Online, Vol. 68, No. 10, 10.2012.

Research output: Contribution to journalArticle

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