The truncated hexadecachoron, or thex, also commonly called the truncated 16-cell, is a convex uniform polychoron that consists of 8 regular octahedra and 16 truncated tetrahedra. 1 octahedron and four truncated tetrahedra join at each vertex. As the name suggests, it can be obtained as the truncation of a hexadecachoron.
|Bowers style acronym||Thex|
|Coxeter diagram||o4o3x3x ()|
|Cells||8 octahedra, 16 truncated tetrahedra|
|Faces||64 triangles, 32 hexagons|
|Vertex figure||Square pyramid, edge lengths 1 (base) and √3 (sides)|
|Measures (edge length 1)|
|Dichoral angles||Tut–3–oct: 120°|
|Number of external pieces||24|
|Level of complexity||4|
|Abstract & topological properties|
|Symmetry||B4, order 384|
The vertices of a truncated hexadecachoron of edge length 1 are given by all permutations of:
Alternatively under D4 symmetry it can be given by all permutations and even sign changes of:
A truncated hexadecachoron has the following Coxeter diagrams:
- (full symmetry)
- (D4 symmetry, as truncated demitesseract)
- (as cantic tesseract)
- xuxo3xoox3oxux&#xt (A3 axial, truncated tetrahedron-first)
- ooooo4ooxoo3xuxux&#xt (BC3 axial, octahedron-first)
- ooxoo3xuxux3ooxoo&#xt (A3 axial, octahedron-first)
- ooxxuuxd ooxxuudx QqQoqooo qQoQoqoo &#zx (A1×A1×A1×A1 symmetry)
- oxux4oqoo xoxu4qooo&#zx (BC2×BC2 symmetry)
- Qqo ooo4oxo3xux&#zx (BC3×A1 symmetry)
The truncated hexadecachoron has a semi-uniform variant of the form o4o3y3x that maintains its full symmetry. This variant uses 8 octahedra of size y and 16 semi-uniform truncated tetrahedra of form x3y3o as cells, with 2 edge lengths.
With edges of length a (surrounded by truncated tetrahedra only) and b (of octahedra), its circumradius is given by and its hypervolume is given by .
It has coordinates given by all permutations of:
Both the uniform and semi-uniform truncated hexadecachoron are also isogonal under D4 symmetry, where it can be called the truncated demitesseract or cantic tesseract, but this does not give rise to any additional variations. This can be seen by its alternative coordinates as all permutations and even sign changes of:
The truncated hexadecachoron is the colonel of a regiment that also includes the truncated tesseractihemioctachoron.
Uniform polychoron compounds composed of truncated hexadecachora include:
- Truncated demidistesseract (2)
- Truncated stellated icositetrachoron (3)
- Truncated small stellated tetracontoctachoron (6)
- Truncated stellated dodecahedronary hexacosichoron (75)
|Rectified hexadecachoron = Icositetrachoron||ico||o4o3x3o|
|Small rhombated tesseract||srit||x4o3x3o|
|Great rhombated tesseract||grit||x4x3x3o|
|Small rhombated hexadecachoron = Rectified icositetrachoron||rico||o4x3o3x|
|Great rhombated hexadecachoron = Truncated icositetrachoron||tico||o4x3x3x|
- Bowers, Jonathan. "Category 2: Truncates" (#20).
- Bowers, Jonathan. "Tessic Isogonals".
- Klitzing, Richard. "thex".
- Quickfur. "The Truncated 16-cell".
- Wikipedia Contributors. "Truncated 16-cell".