Thompson Tetrahedron – Dislocation Theory Teaching Model

A 3D-printable Thompson tetrahedron for visualizing crystallographic slip systems, Burgers vectors, and Shockley partial dislocations in face-centred cubic (FCC) crystals.

The Thompson tetrahedron is a useful tool in materials science for understanding dislocation reactions and the geometry of the four {111} slip planes.

I couldn't find a suitable printable model, so I designed one in OpenSCAD!

Features

• Six ⟨110⟩ directions along the tetrahedron edges, representing perfect dislocations

• Twelve ⟨112⟩ directions connecting the vertices to the face centres, representing Shockley partials

• All four {111} slip planes, with optional Miller-index labels

• Engraved vector notation with crystallographic overbars and directional symbols

• Engraved lines connecting the vertices to the centres of each face

• Parametric OpenSCAD design with adjustable dimensions, label positions, and engraving depths

The crystallographic orientation follows the conventional Thompson tetrahedron representation. This was used as a reference: https://www.researchgate.net/figure/Thompson-tetrahedron-notation-for-FCC-slip-systems_fig23_228676911

Printing recommendations

The default edge length is 150 mm, providing sufficient space for readable engraved labels.

I recommend printing the model with one triangular face directly on the build plate, using PLA.

A smaller version may also work, although the fine lettering and overbars become more difficult to reproduce. The OpenSCAD source allows you to adjust the text size and engraving parameters.

If you find this model useful for teaching or studying dislocation theory, I'd be happy to hear about it!