Rhombic dodecahedron  

(Click here for rotating model) 

Type  Catalan solid 
Coxeter diagram  
Conway notation  jC 
Face type  V3.4.3.4
rhombus 
Faces  12 
Edges  24 
Vertices  14 
Vertices by type  8{3}+6{4} 
Symmetry group  O_{h}, B_{3}, [4,3], (*432) 
Rotation group  O, [4,3]^{+}, (432) 
Dihedral angle  120° 
Properties  convex, facetransitive edgetransitive, parallelohedron 
Cuboctahedron (dual polyhedron) 
Net 
In geometry, the rhombic dodecahedron is a convex polyhedron with 12 congruent rhombic faces. It has 24 edges, and 14 vertices of two types. It is a Catalan solid, and the dual polyhedron of the cuboctahedron.
The rhombic dodecahedron is a zonohedron. Its polyhedral dual is the cuboctahedron. The long diagonal of each face is exactly √2 times the length of the short diagonal, so that the acute angles on each face measure arccos(1/3), or approximately 70.53°.
Being the dual of an Archimedean polyhedron, the rhombic dodecahedron is facetransitive, meaning the symmetry group of the solid acts transitively on the set of faces. In elementary terms, this means that for any two faces A and B there is a rotation or reflection of the solid that leaves it occupying the same region of space while moving face A to face B.
The rhombic dodecahedron is one of the nine edgetransitive convex polyhedra, the others being the five Platonic solids, the cuboctahedron, the icosidodecahedron and the rhombic triacontahedron.
The rhombic dodecahedron can be used to tessellate threedimensional space. It can be stacked to fill a space much like hexagons fill a plane.
This polyhedron in a spacefilling tessellation can be seen as the Voronoi tessellation of the facecentered cubic lattice. Some minerals such as garnet form a rhombic dodecahedral crystal habit. Honeybees use the geometry of rhombic dodecahedra to form honeycomb from a tessellation of cells each of which is a hexagonal prism capped with half a rhombic dodecahedron. The rhombic dodecahedron also appears in the unit cells of diamond and diamondoids. In these cases, four vertices (alternate threefold ones) are absent, but the chemical bonds lie on the remaining edges.^{[1]}
The graph of the rhombic dodecahedron is nonhamiltonian.
If the edge length of a rhombic dodecahedron is a, the radius of an inscribed sphere (tangent to each of the rhombic dodecahedron's faces) is
the radius of the midsphere is
and the radius of the circumscribed sphere is
The area A and the volume V of the rhombic dodecahedron of edge length a are:
The rhombic dodecahedron has four special orthogonal projections along its axes of symmetry, centered on a face, an edge, and the two types of vertex, threefold and fourfold. The last two correspond to the B_{2} and A_{2} Coxeter planes.
Projective symmetry 
[4]  [6]  [2]  [2] 

Rhombic dodecahedron 

Cuboctahedron (dual) 
The eight vertices where three faces meet at their obtuse angles have Cartesian coordinates:
The coordinates of the six vertices where four faces meet at their acute angles are the permutations of:
The rhombic dodecahedron can be seen as a degenerate limiting case of a pyritohedron, with permutation of coordinates (±1, ±1, ±1) and (0, 1+h, 1−h^{2}) with parameter h=1.
The rhombic dodecahedron is a parallelohedron, a spacefilling polyhedron. Other symmetry constructions of the rhombic dodecahedron are also spacefilling, and as parallelotopes they are similar to variations of spacefilling truncated octahedra.^{[2]}
For example, with 4 square faces, and 60degree rhombic faces.
Net 
This construction has D_{2h} symmetry, order 8. It can be seen as a cuboctahedron with square pyramids augmented on the top and bottom. It has coordinates:
Another topologically equivalent variation, sometimes called a trapezoidal dodecahedron, is isohedral with tetrahedral symmetry, distorting rhombic faces into kites. It has 8 vertices adjusted in or out in alternate sets of 4, with the limiting case a tetrahedral envelope. Variations can be parametrized by (a,b), where b is determined from a for planar faces. (1,1) is the rhombic solution. As (a) approaches 1/2, (b) approaches infinity.
(1,1)  (7/8,7/6)  (3/4,3/2)  (2/3,2)  (5/8,5/2)  (9/16,9/2) 

Symmetry: [4,3], (*432)  [4,3]^{+}, (432)  [3^{+},4], (3*2)  

{4,3}  t{4,3}  r{4,3}  t{3,4}  {3,4}  rr{4,3}  tr{4,3}  sr{4,3}  s{3,4}  
Duals to uniform polyhedra  
V4^{3}  V3.8^{2}  V(3.4)^{2}  V4.6^{2}  V3^{4}  V3.4^{3}  V4.6.8  V3^{4}.4  V3^{5} 
This polyhedron is a part of a sequence of rhombic polyhedra and tilings with [n,3] Coxeter group symmetry. The cube can be seen as a rhombic hexahedron where the rhombi are squares.
Spherical  Euclidean  Hyperbolic  

*n32  *332  *432  *532  *632  *732  *832...  *∞32 
Tiling  
Conf.  V(3.3)^{2}  V(3.4)^{2}  V(3.5)^{2}  V(3.6)^{2}  V(3.7)^{2}  V(3.8)^{2}  V(3.∞)^{2} 
Symmetry *4n2 [n,4] 
Spherical  Euclidean  Compact hyperbolic  Paracompact  Noncompact  

*342 [3,4] 
*442 [4,4] 
*542 [5,4] 
*642 [6,4] 
*742 [7,4] 
*842 [8,4]... 
*∞42 [∞,4] 
[iπ/λ,4] 

Tiling Conf. 
V4.3.4.3 
V4.4.4.4 
V4.5.4.5 
V4.6.4.6 
V4.7.4.7 
V4.8.4.8 
V4.∞.4.∞ 
V4.∞.4.∞ 
Similarly it relates to the infinite series of tilings with the face configurations V3.2n.3.2n, the first in the Euclidean plane, and the rest in the hyperbolic plane.
V3.4.3.4 (Drawn as a net) 
V3.6.3.6 Euclidean plane tiling Rhombille tiling 
V3.8.3.8 Hyperbolic plane tiling (Drawn in a Poincaré disk model) 
Like many convex polyhedra, the rhombic dodecahedron can be stellated by extending the faces or edges until they meet to form a new polyhedron. Several such stellations have been described by Dorman Luke.^{[3]}
The first stellation, often simply called the stellated rhombic dodecahedron, is well known. It can be seen as a rhombic dodecahedron with each face augmented by attaching a rhombicbased pyramid to it, with a pyramid height such that the sides lie in the face planes of the neighbouring faces:
Luke describes four more stellations: the second and third stellations (expanding outwards), one formed by removing the second from the third, and another by adding the original rhombic dodecahedron back to the previous one.
The rhombic dodecahedron can tessellate space by translational copies of itself. Interestingly, so can the stellated rhombic dodecahedron.
The rhombic dodecahedron forms the hull of the vertexfirst projection of a tesseract to three dimensions. There are exactly two ways of decomposing a rhombic dodecahedron into four congruent parallelepipeds, giving eight possible parallelepipeds. The eight cells of the tesseract under this projection map precisely to these eight parallelepipeds.
The rhombic dodecahedron forms the maximal crosssection of a 24cell, and also forms the hull of its vertexfirst parallel projection into three dimensions. The rhombic dodecahedron can be decomposed into six congruent (but nonregular) square dipyramids meeting at a single vertex in the center; these form the images of six pairs of the 24cell's octahedral cells. The remaining 12 octahedral cells project onto the faces of the rhombic dodecahedron. The nonregularity of these images are due to projective distortion; the facets of the 24cell are regular octahedra in 4space.
This decomposition gives an interesting method for constructing the rhombic dodecahedron: cut a cube into six congruent square pyramids, and attach them to the faces of a second cube. The triangular faces of each pair of adjacent pyramids lie on the same plane, and so merge into rhombuses. The 24cell may also be constructed in an analogous way using two tesseracts.
