Acta Crystallographica Section C

Crystal Structure Communications

Volume 69, Part 9 (September 2013)

inorganic compounds

Acta Cryst. (2013). C69, 995-1001    [ doi:10.1107/S0108270113020921 ]

The tetra­germanates A2Ge4O9 (A = Na, K and Rb)

G. J. Redhammer and G. Tippelt

Abstract: The crystal structures of three alkali tetra­germanates A2Ge4O9 (A = Na, K and Rb) [namely disodium tetra­germanate, Na2Ge4O9, dipotassium tetra­germanate, K2Ge4O9, and dirubidium tetra­germanate, Rb2Ge4O9] are trigonal (space group P\overline{3}c1). The main building units are a three-membered ring of tetra­hedra, oriented within the (001) plane and forming tetra­hedral sheets. These sheets are connected to each other by two different regular isolated GeO6 octa­hedra via corner-sharing to build up a tetra­hedral-octa­hedral framework. The alkali cations are located in cavities within this framework and are sevenfold coordinated. The increasing size of the A-site cation is accommodated by twist deformations of the tetra­hedral rings and alterations in the Ge-O-Ge angles. With increasing size of the A-site cation, both the tetra­hedral and octa­hedral sites become more regular, with slightly decreasing <Ge-O> distances from Na2Ge4O9 to Rb2Ge4O9. This goes hand-in-hand with a more uniform distribution of bonds around the A-site cation. All these observations make Rb2Ge4O9 the most regular member of this A2Ge4O9 octa­hedral-tetra­hedral framework structure series.

Formula: Na2Ge4O9, K2Ge4O9 and Rb2Ge4O9

Keywords: crystal structure; alkali tetra­germanates; redetermination.

hkldisplay filedownload file

Structure factor file (CIF format) (45.0 kbytes)
[ doi:10.1107/S0108270113020921/fn3142Na2Ge4O9sup2.hkl ]
Contains datablock Na2Ge4O9

hkldisplay filedownload file

Structure factor file (CIF format) (49.9 kbytes)
[ doi:10.1107/S0108270113020921/fn3142K2Ge4O9sup3.hkl ]
Contains datablock K2Ge4O9

hkldisplay filedownload file

Structure factor file (CIF format) (53.0 kbytes)
[ doi:10.1107/S0108270113020921/fn3142Rb2Ge4O9sup4.hkl ]
Contains datablock Rb2Ge4O9


To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.

 bibliographic record in  format

  Find reference:   Volume   Page   
  Search:     From   to      Advanced search

Copyright © International Union of Crystallography
IUCr Webmaster