Monthly Archives: March 2021

Space Group Diagrams (not only) for Lecturers

I’ve started another ‘230 project’.

This time it is concerned with space group diagrams.

Of course, the No. 1 source for such diagrams, i.e. symmetry element and general position diagrams, is Volume A of the International Tables for Crystallography (ITA). As valuable as they are for the daily life of a crystallographer, they are unsuitable when it comes to teaching.

Hitherto, there is another extremely valuable online resource for these diagrams:

The Hypertext Book of Crystallographic Space Group Diagrams and Tables

However, one of the features I don’t like about these diagrams is that they decided to present both diagrams (symmetry elements and general positions) in a superimposed fashion.

For this reason I decided to draw all diagrams again and to make them publicly available (CC license) in various formats (as a PNG picture, a PDF, and a PPT file) – ready for use for teaching purposes.

However, there will be limitations. Different origin choices will be taken into account, but further different settings will be disregarded. And I do not know, if I will be able to manage the drawings of all diagrams for the cubic space groups. Lets see 🙂

Up to now, the first two space groups of the triclinic crystal system are ready. Until the end of the month the diagrams for all monoclinic space groups should be available. Then further diagrams will be added from time to time.

Have fun!

Kapellasite

Kapellasite

  • Named after Christo Kapellas (1938-2004), collector and mineral dealer of Kamariza, Lavrion, Greece
  • Kapellasite is isostructural with Haydeeite [Cu3Mg(OH)6Cl2]
  • Kapellasite is a metastable polymorph of Herbertsmithite
  • Formula: Cu3Zn(OH)6Cl2
  • Space group: P-3m1 (No. 164)
  • Crystal system: trigonal
  • Crystal class: -3m
  • Lattice parameters: a = b = 6.300(1) Å, c =  5.733(1) Å, α = β = 90°, γ = 120°

Crystal structure[1] (click on the pictures to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • CuO4 square-planar coordination polygons (blue)
  • ZnO6 distorted octahedra (gray)
  • Oxygen (red)
  • Chlorine (green)

For a 3D interactive version, see here:

https://skfb.ly/6ZNHM

References:

[1] W. Krause, H.-J. Bernhardt, R.S.W. Braithwaite, U. Kolitsch, R. Pritchard
Kapellasite, Cu3Zn(OH)6Cl2, a new mineral from Lavrion, Greece, and its crystal structure
Mineralogical Magazine, 2006, 70, 329-340
DOI: 10.1180/0026461067030336

Bloedite

Blödite (also Bloedite)

  • named after the German mineralogist and chemist Karl August Blöde (1773 – 1820)
  • fun fact: the German adjective “blöd(e)” means “stupid”
  • Formula: Na2Mg(SO4)2  · 4 H2O
  • Space group: P21/a
  • Crystal system: monoclinic
  • Crystal class: 2/m
  • Lattice parameters: a = 11.126(2), b =  8.242(1) Å, c = 5.539(1) Å, α = 90°, β = 100.84(1)°, γ  90°

Crystal structure (click on the pictures to download the VESTA file):

(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,” J. Appl. Crystallogr., 44, 1272-1276 (2011).)

  • SO4 tetrahedra (yellow)
  • (distorted) NaO6 octahedra (purple)
  • MgO6 octahedra (green)
  • Oxygen (red)
  • Hydrogen (white)

For a 3D interactive version, see here:

https://skfb.ly/6ZEPS

Refs:

[1] F. C. Hawthorne, The Canadian Mineralogist 1985, 23, 669-674.
(PDF)