Rare-earth Metal Substitution in Calcium Germanides with the Tetragonal Cr5B3 Type Structure
Date
2022-07-20
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Journal of Inorganic and General Chemistry
Abstract
Calcium germanides with two mid-late rare-earth metals, Ca5−xGdxGe3 and Ca5−xTbxGe3 (x≈0.1−0.2), have been synthesized and structurally characterized. Additionally, a lanthanum-rich germanide with calcium substitutions, La5−xCaxGe3 (x≈0.5) has also been identified. The three structures have been established from single-crystal X-ray diffraction methods and confirmed to crystallize with the Cr5B3-type in the tetragonal space group I4/mcm (no. 140; Z=4; Pearson symbol tI32), where part of the germanium atoms are interconnected into Ge2-dimers, formally [Ge2]6−. Rare-earth metal and calcium atoms are arranged in distorted trigonal prisms, square-antiprisms and cubes, centered by Ge or rare-earth/calcium metal atoms. These studies show that the amount of trivalent rare-earth metal atoms substituting divalent calcium atoms is in direct correlation with the lengths of the Ge−Ge bond within the Ge2-dimers, with distance varying between 2.58 Å in Ca5−xGdxGe3 and 2.75 Å in La5−xCaxGe3. Such an elongation of the Ge−Ge bond is consistent with the notion that the parent Ca5Ge3 Zintl phase (e. g. (Ca2+)5[Ge2]6−[Ge4−]) is being driven out of the ideal valence electron count and further reduced. In this context, this work demonstrates the ability of the germanides with the Cr5B3 structure type to accommodate substitutions and wider valence electron count while maintaining their global structural integrity.
Description
This is the peer reviewed version of the following article: Suen, Nian‐Tzu, and Svilen Bobev. “Rare-Earth Metal Substitution in Calcium Germanides with the Tetragonal Cr5B3 Type Structure.” Zeitschrift Für Anorganische Und Allgemeine Chemie, July 20, 2022. https://doi.org/10.1002/zaac.202200183, which has been published in final form at https://doi.org/10.1002/zaac.202200183. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited. This article will be embargoed until 07/20/2023.
Keywords
Germanides, crystal structure, Zintl phases, Lanthanides
Citation
Suen, Nian‐Tzu, and Svilen Bobev. “Rare-Earth Metal Substitution in Calcium Germanides with the Tetragonal Cr5B3 Type Structure.” Zeitschrift Für Anorganische Und Allgemeine Chemie, July 20, 2022. https://doi.org/10.1002/zaac.202200183.