Chapter 4

Unit 4.1 – Glide Planes in Crystals (I)

Slides Unit 4.1

Transcript of Unit 4.1

Further material/links:

VESTA file of orthoclase with embedded glide planes
Explore the the glideplanes in orthoclase – a feldspar mineral. Can you find out, what type of glide plane is present?

Unit 4.2 – Glide Planes in Crystals (II)

Slides Unit 4.2

Transcript of Unit 4.2

Unit 4.3 – Screw Axes

Slides Unit 4.3

Transcript of Unit 4.3

Further material/links:

Olafur Eliasson
Link to the homepage of the Danish-Islandic artist Olafur Eliasson

A musical helix
Tones can be represented as a helix as well. This helix makes one turn with each octave.
Clever arrangements of notes result in the so-called shephards tones. They appear to descend or ascend continuously in pitch. An illusion to our ears.

Visit the link for further information about this phenomenon.

Unit 4.4 – Screw Axes in Crystal Structures

Slides Unit 4.4

Transcript of Unit 4.4

Further material/links:

A different interpretation of the 3(2) screw_axis in order to emphasize the similarity to a 3(1) screw

CIF file of the element Tellurium

Unit 4.5 – Space Groups and Space Group Symbols

Slides Unit 4.5

Transcript of Unit 4.5

Unit 4.6 – International Tables and The Spacegroup Pmm2

Slides Unit 4.6

Transcript of Unit 4.6

Further material/links:

Crystallographic Space Group Diagrams and Tables

Space Group Visualizer
Eckhard Hitzer and Christian Perwass worked on visualising point and space groups using the visualisation tool CLUCalc. This software implements Geometric Algebra, which allows for a direct implementation of symmetry operators in the algebra – great tool!

Unit 4.7 – The Space Group Pmm2 (II)

Slides Unit 4.7

Transcript of Unit 4.7