Elongated dodecahedron

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Elongated dodecahedron
Rhombo-hexagonal dodecahedron.png
Type Parallelohedron
Faces 8 rhombi
4 hexagons
Edges 28
Vertices 18
Vertex configuration (8) 4.6.6
(8) 4.4.6
(2) 4.4.4.4
Symmetry group Dihedral (D4h), [4,2], (*422), order 16
Rotation group D4, [4,2]+, (422), order 8
Properties Convex
Net
Elongated dodecahedron net.png
3D model of a elongated dodecahedron Elongated Dodecahedron.stl
3D model of a elongated dodecahedron

In geometry, the elongated dodecahedron, [1] extended rhombic dodecahedron, rhombo-hexagonal dodecahedron [2] or hexarhombic dodecahedron [3] is a convex dodecahedron with 8 rhombic and 4 hexagonal faces. The hexagons can be made equilateral, or regular depending on the shape of the rhombi. It can be seen as constructed from a rhombic dodecahedron elongated by a square prism.

Contents

Parallelohedron

Along with the rhombic dodecahedron, it is a space-filling polyhedron, one of the five types of parallelohedron identified by Evgraf Fedorov that tile space face-to-face by translations. It has 5 sets of parallel edges, called zones or belts.

Parallelohedron edges elongated rhombic dodecahedron.png

Tessellation

Rhombo-hexagonal dodecahedron tessellation.png

This is related to the rhombic dodecahedral honeycomb with an elongation of zero. Projected normal to the elongation direction, the honeycomb looks like a square tiling with the rhombi projected into squares.

Variations

The expanded dodecahedra can be distorted into cubic volumes, with the honeycomb as a half-offset stacking of cubes. It can also be made concave by adjusting the 8 corners downward by the same amount as the centers are moved up.

Elongated dodecahedron flat.png
Coplanar polyhedron
Elongated dodecahedron flat net.png
Net
Elongated dodecahedron flat honeycomb.png
Honeycomb
Elongated dodecahedron concave.png
Concave
Elongated dodecahedron concave net.png
Net
Elongated dodecahedron concave honeycomb.png
Honeycomb

The elongated dodecahedron can be constructed as a contraction of a uniform truncated octahedron, where square faces are reduced to single edges and regular hexagonal faces are reduced to 60 degree rhombic faces (or pairs of equilateral triangles). This construction alternates square and rhombi on the 4-valence vertices, and has half the symmetry, D2h symmetry, order 8.

Contracted truncated octahedron.png
Contracted truncated octahedron
Contracted truncated octahedron net.png
Net
Contracted truncated octahedron honeycomb.png
Honeycomb

See also

Related Research Articles

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<span class="mw-page-title-main">Parallelohedron</span> Polyhedron that tiles space by translation

In geometry, a parallelohedron is a polyhedron that can be translated without rotations in 3-dimensional Euclidean space to fill space with a honeycomb in which all copies of the polyhedron meet face-to-face. There are five types of parallelohedron, first identified by Evgraf Fedorov in 1885 in his studies of crystallographic systems: the cube, hexagonal prism, rhombic dodecahedron, elongated dodecahedron, and truncated octahedron.

<span class="mw-page-title-main">Elongated octahedron</span> Convex polyhedron with 8 faces

In geometry, an elongated octahedron is a polyhedron with 8 faces, 14 edges, and 8 vertices.

<span class="mw-page-title-main">Elongated gyrobifastigium</span> Space-filling polyhedron with 8 faces

In geometry, the elongated gyrobifastigium or gabled rhombohedron is a space-filling octahedron with 4 rectangles and 4 right-angled pentagonal faces.

References

  1. Coxeter (1973) p.257
  2. Williamson (1979) p169
  3. Fedorov's five parallelohedra in R³