Tetrahedral-octahedral honeycomb
{{Short description|Quasiregular space-filling tesselation}}
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!bgcolor=#e7dcc3 colspan=2|Alternated cubic honeycomb | |
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bgcolor=#e7dcc3|Type | Uniform honeycomb |
bgcolor=#e7dcc3|Family | Alternated hypercubic honeycomb Simplectic honeycomb |
bgcolor=#e7dcc3|IndexingFor cross-referencing, they are given with list indices from Andreini (1-22), Williams(1-2,9-19), Johnson (11-19, 21-25, 31-34, 41-49, 51-52, 61-65), and Grünbaum(1-28).
|J21,31,51, A2 | |
bgcolor=#e7dcc3|Schläfli symbols | h{4,3,4} {3[4]} ht0,3{4,3,4} h{4,4}h{∞} ht0,2{4,4}h{∞} h{∞}h{∞}h{∞} s{∞}s{∞}s{∞} |
bgcolor=#e7dcc3|Coxeter diagrams | {{CDD|nodes_10ru|split2|node|4|node}} = {{CDD|node_h1|4|node|3|node|4|node}} {{CDD|node_1|split1|nodes|split2|node}} = {{CDD|node_h1|4|node|split1|nodes}} {{CDD|node_h|4|node|3|node|4|node_h}} {{CDD|node_h|4|node|4|node|2|node_h|infin|node}} {{CDD|node_h|4|node|4|node_h|2|node_h|infin|node}} {{CDD|node_h|infin|node|2|node_h|infin|node|2|node_h|infin|node}} = {{CDD|node_h|4|node_g|3sg|node_g|4|node}} {{CDD|node_h|infin|node_h|2|node_h|infin|node_h|2|node_h|infin|node_h}} = {{CDD|node_h|4|node_g|3sg|node_g|4g|node_g}} |
bgcolor=#e7dcc3|Cells | {3,3} 40px {3,4} 40px |
bgcolor=#e7dcc3|Faces | triangle {3} |
bgcolor=#e7dcc3|Edge figure | [{3,3}.{3,4}]2 (rectangle) |
bgcolor=#e7dcc3|Vertex figure | 80px80px 80px80px (cuboctahedron) |
bgcolor=#e7dcc3|Symmetry group | Fm{{overline|3}}m (225) |
bgcolor=#e7dcc3|Coxeter group | , [4,31,1] |
bgcolor=#e7dcc3|Dual | Dodecahedrille rhombic dodecahedral honeycomb Cell: 80px |
bgcolor=#e7dcc3|Properties | vertex-transitive, edge-transitive, quasiregular honeycomb |
The tetrahedral-octahedral honeycomb, alternated cubic honeycomb is a quasiregular space-filling tessellation (or honeycomb) in Euclidean 3-space. It is composed of alternating regular octahedra and tetrahedra in a ratio of 1:2.
Other names include half cubic honeycomb, half cubic cellulation, or tetragonal disphenoidal cellulation. John Horton Conway calls this honeycomb a tetroctahedrille, and its dual a dodecahedrille.
R. Buckminster Fuller combines the two words octahedron and tetrahedron into octet truss, a rhombohedron consisting of one octahedron (or two square pyramids) and two opposite tetrahedra.
It is vertex-transitive with 8 tetrahedra and 6 octahedra around each vertex. It is edge-transitive with 2 tetrahedra and 2 octahedra alternating on each edge.
{{Honeycomb}}
It is part of an infinite family of uniform honeycombs called alternated hypercubic honeycombs, formed as an alternation of a hypercubic honeycomb and being composed of demihypercube and cross-polytope facets. It is also part of another infinite family of uniform honeycombs called simplectic honeycombs.
In this case of 3-space, the cubic honeycomb is alternated, reducing the cubic cells to tetrahedra, and the deleted vertices create octahedral voids. As such it can be represented by an extended Schläfli symbol h{4,3,4} as containing half the vertices of the {4,3,4} cubic honeycomb.
There is a similar honeycomb called gyrated tetrahedral-octahedral honeycomb which has layers rotated 60 degrees so half the edges have neighboring rather than alternating tetrahedra and octahedra.
The tetrahedral-octahedral honeycomb can have its symmetry doubled by placing tetrahedra on the octahedral cells, creating a nonuniform honeycomb consisting of tetrahedra and octahedra (as triangular antiprisms). Its vertex figure is an order-3 truncated triakis tetrahedron. This honeycomb is the dual of the triakis truncated tetrahedral honeycomb, with triakis truncated tetrahedral cells.
Cartesian coordinates
For an alternated cubic honeycomb, with edges parallel to the axes and with an edge length of 1, the Cartesian coordinates of the vertices are: (For all integral values: i,j,k with i+j+k even)
:(i, j, k)
Image:TetraOctaHoneycomb-VertexConfig.svg of the cells surrounding each vertex.]]
Symmetry
There are two reflective constructions and many alternated cubic honeycomb ones; examples:
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!Symmetry !, [4,31,1] !, [3[4]] ![(4,3,4,2+)] |
Space group
!Fm{{overline|3}}m (225) !F{{overline|4}}3m (216) !I{{overline|4}}3m (217) !P{{overline|4}}3m (215) |
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Image
| | |
Types of tetrahedra
!1 !2 !3 !4 |
Coxeter diagram !{{CDD|nodes_10ru|split2|node|4|node}} = {{CDD|node_h1|4|node|3|node|4|node}} ! {{CDD|node_1|split1|nodes|split2|node}} = {{CDD|nodes|split2|node|4|node_h1}} = {{CDD|node_h0|4|node|3|node|4|node_h1}} !{{CDD|branch|4a4b|branch_hh|label2}} !{{CDD|node_h|4|node|3|node|4|node_h}} |
= Alternated cubic honeycomb slices =
The alternated cubic honeycomb can be sliced into sections, where new square faces are created from inside of the octahedron. Each slice will contain up and downward facing square pyramids and tetrahedra sitting on their edges. A second slice direction needs no new faces and includes alternating tetrahedral and octahedral. This slab honeycomb is a scaliform honeycomb rather than uniform because it has nonuniform cells.
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!{{CDD|node_h|2x|node_h|4|node|4|node}} !{{CDD|node_h|2x|node_h|6|node|3|node}} |
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= Projection by folding =
The alternated cubic honeycomb can be orthogonally projected into the planar square tiling by a geometric folding operation that maps one pairs of mirrors into each other. The projection of the alternated cubic honeycomb creates two offset copies of the square tiling vertex arrangement of the plane:
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Coxeter group ! ! |
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|{{CDD|node_1|split1|nodes|split2|node}} |{{CDD|node_1|4|node|4|node}} |
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!Image |
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!Name |alternated cubic honeycomb |
A3/D3 lattice
Its vertex arrangement represents an A3 lattice or D3 lattice.{{Cite web|url=http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/D3.html|title = The Lattice D3}}{{Cite web|url=http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/A3.html|title = The Lattice A3}} This lattice is known as the face-centered cubic lattice in crystallography and is also referred to as the cubic close packed lattice as its vertices are the centers of a close-packing with equal spheres that achieves the highest possible average density. The tetrahedral-octahedral honeycomb is the 3-dimensional case of a simplectic honeycomb. Its Voronoi cell is a rhombic dodecahedron, the dual of the cuboctahedron vertex figure for the tet-oct honeycomb.
The D{{sup sub|+|3}} packing can be constructed by the union of two D3 (or A3) lattices. The D{{sup sub|+|n}} packing is only a lattice for even dimensions. The kissing number is 22=4, (2n−1 for n<8, 240 for n=8, and 2n(n−1) for n>8).Conway (1998), p. 119
:{{CDD|node_1|split1|nodes|split2|node}} ∪ {{CDD|node|split1|nodes|split2|node_1}}
The A{{sup sub|*|3}} or D{{sup sub|*|3}} lattice (also called A{{sup sub|4|3}} or D{{sup sub|4|3}}) can be constructed by the union of all four A3 lattices, and is identical to the vertex arrangement of the disphenoid tetrahedral honeycomb, dual honeycomb of the uniform bitruncated cubic honeycomb:{{Cite web|url=http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/Ds3.html|title=The Lattice D3}} It is also the body centered cubic, the union of two cubic honeycombs in dual positions.
:{{CDD|node_1|split1|nodes|split2|node}} ∪ {{CDD|node|split1|nodes_10luru|split2|node}} ∪ {{CDD|node|split1|nodes_01lr|split2|node}} ∪ {{CDD|node|split1|nodes|split2|node_1}} = dual of {{CDD|node_1|split1|nodes_11|split2|node_1}} = {{CDD|node_1|4|node|3|node|4|node}} ∪ {{CDD|node|4|node|3|node|4|node_1}}.
The kissing number of the D{{sup sub|*|3}} lattice is 8Conway (1998), p. 120 and its Voronoi tessellation is a bitruncated cubic honeycomb, {{CDD|branch_11|4a4b|nodes}}, containing all truncated octahedral Voronoi cells, {{CDD|node|4|node_1|3|node_1}}.Conway (1998), p. 466
Related honeycombs
= C3 honeycombs=
The [4,3,4], {{CDD|node|4|node|3|node|4|node}}, Coxeter group generates 15 permutations of uniform honeycombs, 9 with distinct geometry including the alternated cubic honeycomb. The expanded cubic honeycomb (also known as the runcinated tesseractic honeycomb) is geometrically identical to the cubic honeycomb.
{{C3 honeycombs}}
= B3 honeycombs=
The [4,31,1], {{CDD|node|4|node|split1|nodes}}, Coxeter group generates 9 permutations of uniform honeycombs, 4 with distinct geometry including the alternated cubic honeycomb.
{{B3 honeycombs}}
= A3 honeycombs =
This honeycomb is one of five distinct uniform honeycombs[http://mathworld.wolfram.com/Necklace.html], {{OEIS el|A000029}} 6-1 cases, skipping one with zero marks constructed by the Coxeter group. The symmetry can be multiplied by the symmetry of rings in the Coxeter–Dynkin diagrams:
{{A3 honeycombs}}
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= Quasiregular honeycombs=
{{Quasiregular polychora and honeycombs}}
= Cantic cubic honeycomb=
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!bgcolor=#e7dcc3 colspan=2|Cantic cubic honeycomb
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