Fig. 2 Crystal
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Object of the Month: From Invalidenstrasse 110 to Adlershof. A house facade and the morphological model of an ideal crystal

Object of the Month 02/2024
Fig. 1 Crystal general view
Fig. 1 Crystal general view. Photo: Dr. Holm Kirmse
The model (see fig. 1) shows the ideal shape of a crystal. This is a combination of three crystal shapes that can be found in the cubic crystal system. The cube catches the eye first because of the size of the faces. In crystallography, it is called a hexahedron because it is bounded by six identical faces. The second form is a tetrahedron (bounded by 4 faces). The third shape is bounded by twelve identical faces and is called a rhombdodecahedron. The individual faces of the three shapes can be given indices. Miller’s indices correspond to the reciprocal values of the intersection points of a given face with the axes x, y and z: In the cubic crystal system these three axes are perpendicular to each other and are of equal length. In case of the rhombdodecahedron, an individual face always intersects two axes in the same ratio, while the third axis is not intersected. The axis intersections are therefore 1 : 1 : ∞. The reciprocal values are 1 : 1 : 0. If the axes are chosen accordingly, Miller indices (110) – say “one one oh” – are obtained for the face oriented towards the observer.
Miller_Indizes_Ebenen
Arrangement of lattice planes inside a hexahedron and corresponding Miller indices. Source: Wikipedia - File: Miller Indices Ebenen.png - Created: 27 March 2006 (The original uploader was Noamik in the German Wikipedia) CC BY-SA 3.0
The mathematical consideration of the symmetry properties of crystals can not only be expressed in formulas, some people also see these shapes in completely different contexts. And that brings us to Invalidenstrasse 110: Before the Institute of Physics at Humboldt-Universität zu Berlin moved to its current location at Campus Adlershof in 2003, it was housed as the Institute of Physics and Electronics in the building Invalidenstrasse 110 at the junction with Chausseestrasse (see photo below right). The Institute of Crystallography with its research focus on crystal growth and crystal characterization was also part of the institute. The crystallography course was supported by an extensive teaching collection. Today, crystallography is part of the specialization in solid state physics in the Master’s degree course in physics. The crystallography teaching collection does further exist.
Fig. 2 Crystal
Fig. 2 (left): Identical polyhedron model seen from a different perspective. For guiding the eyes, the (110) face is highlighted. The face above exhibits an irregular hexagon. It belongs to the tetrahedron and is assigned by the Miller indices (111). For better imagination see the schematic drawings shown above depicting the arrangement of faces (100), (110), and (111). Photo: Dr. Holm Kirmse
Fig. 3 House facade Inv. 110
Fig. 3 (right): Facade of the institute building Invalidenstrasse 110. Photo: Oliver Zauzig

The facade of the former institute building with its faces parallel to Invalidenstrasse and Chausseestrasse exhibits a 45° cut off at the junction, creating an additional third face in which the main entrance is located. Whether intentional or not: if you lay the axis system along the edges of the building, then the Miller indices of this third face correspond exactly to the house number of the building. What now reads like one of the countless conspiracy stories is probably pure coincidence. It is well known that “one one oh” is also the telephone number of the police, physicists and chemists recognize the element Darmstadtium in it and as a binary system it plays an important role in computer science. And if you do recognize a connection between the ideal shape of a crystal and the facade of the building, it should be noted not only that the building was built in 1981 according to information from the Technical Department, but also that there was an inn called “Zum Kuhstall” at this address before 1920, at least according to research conducted by Foto Marburg.

In December 2023, the HU’s Technical Department handed over the property at Invalidenstrasse 110 to the Senate Department for Urban Development, Building and Housing for the upcoming conversion and refurbishment measures. These are planned to be carried out over the next five years.

Author: Dr. Holm Kirmse

Head of Crystallographic Teaching Collection
Newtonstrasse 15
12489 Berlin

Links
Polyhedron model combination cube-tetrahedron-rhombic dodecahedron in “Sammlungen digital”: https://sammlungen-digital.hu-berlin.de/viewer/image/2949349a-7155-45e2-a88e-57126add8e1a/2/

Corner of Chausseestraße/Invalidenstraße in the Technical Department of the HU: https://www.ta.hu-berlin.de/gebaeude/no:2215 and https://www.hu-berlin.de/de/pr/30-jahre-deutsche-einheit/bildergalerie-damals-und-heute/D2_hu20mh_30Jahre_DSF1544-1.jpg/view

Restaurant “Zum Kuhstall” in photo archive Foto Marburg: https://www.bildindex.de/document/obj20555125