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A Cesium Rare‐Earth Silicate Cs 3 RESi 6 O 15 (RE=Dy–Lu, Y, In): The Parent of an Unusual Structural Class Featuring a Remarkable 57 Å Unit Cell Axis
Author(s) -
Terry Rylan,
Vinton Daniel,
McMillen Colin D.,
Kolis Joseph W.
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201708798
Subject(s) - octahedron , crystallography , silicate , ion , hydrothermal circulation , alkali metal , chemistry , crystal structure , caesium , rare earth , hydrothermal synthesis , x ray crystallography , materials science , mineralogy , diffraction , inorganic chemistry , physics , geology , organic chemistry , seismology , optics
The structure of Cs 3 RESi 6 O 15 , where RE=Dy–Lu, Y, In, is unusual in that it contains octahedrally coordinated rare‐earth ions; their relative orientation dictates the structure, as they rotate about the c ‐axis supported by the cyclic Si 6 O 15 framework. The repeat unit of the rotation is eight units generating a very long (ca. 57 Å) unit cell axis. This unusual repeat unit is created by the structural flexibility of the hexasilicate ring, which is in turn affected by the size of the rare earth ion as well as the size of alkali ion residing within the silicate layers. Previous work showed for the smaller Sc 3+ ion, the rotation of the octahedra is not sufficient to achieve closure at an integral repeat unit and an incommensurate structure results. The products are prepared as large, high quality single crystals using a high‐temperature (650 °C) hydrothermal method with CsOH and F − mineralizers. The presence of fluoride is essential to the formation of the product.