Catalan solid

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The solids above (dark) shown together with their duals (light). The visible parts of the Catalan solids are regular pyramids.

In mathematics, a Catalan solid, or Archimedean dual, is a dual polyhedron to an Archimedean solid. There are 13 Catalan solids. They are named for the Belgian mathematician, Eugène Catalan, who first described them in 1865.

The Catalan solids are all convex. They are face-transitive but not vertex-transitive. This is because the dual Archimedean solids are vertex-transitive and not face-transitive. Note that unlike Platonic solids and Archimedean solids, the faces of Catalan solids are not regular polygons. However, the vertex figures of Catalan solids are regular, and they have constant dihedral angles. Being face-transitive, Catalan solids are isohedra.

Additionally, two of the Catalan solids are edge-transitive: the rhombic dodecahedron and the rhombic triacontahedron. These are the duals of the two quasi-regular Archimedean solids.

Just as prisms and antiprisms are generally not considered Archimedean solids, so bipyramids and trapezohedra are generally not considered Catalan solids, despite being face-transitive.

Two of the Catalan solids are chiral: the pentagonal icositetrahedron and the pentagonal hexecontahedron, dual to the chiral snub cube and snub dodecahedron. These each come in two enantiomorphs. Not counting the enantiomorphs, bipyramids, and trapezohedra, there are a total of 13 Catalan solids.

List of Catalan solids and their duals[edit]

Conway name
Archimedean Dual Face
Pictures Face angles (°) Dihedral angle (°) Midradius[1] Faces Edges Vert Sym.
triakis tetrahedron
truncated tetrahedron Isosceles
DU02 facets.png
Dual tetrahedron t01 ae.pngDual tetrahedron t01 A2.pngDual tetrahedron t01.png Triakis tetrahedronTriakis tetrahedron 112.885
129.521 1.0607 12 18 8 Td
rhombic dodecahedron
cuboctahedron Rhombus
DU07 facets.png
Dual cube t1 v.png Dual cube t1.pngDual cube t1 B2.png Rhombic dodecahedronRhombic dodecahedron 70.529
120 0.8660 12 24 14 Oh
triakis octahedron
truncated cube Isosceles
DU09 facets.png
Dual truncated cube t01 e88.pngDual truncated cube t01.pngDual truncated cube t01 B2.png Triakis octahedronTriakis octahedron 117.201
147.350 1.7071 24 36 14 Oh
tetrakis hexahedron
truncated octahedron Isosceles
DU08 facets.png
Dual cube t12 e66.pngDual cube t12.pngDual cube t12 B2.png Tetrakis hexahedronTetrakis hexahedron 83.621
143.130 1.5000 24 36 14 Oh
deltoidal icositetrahedron
rhombicuboctahedron Kite
DU10 facets.png
Dual cube t02 f4b.pngDual cube t02.pngDual cube t02 B2.png Deltoidal icositetrahedronDeltoidal icositetrahedron 81.579
138.118 1.3066 24 48 26 Oh
disdyakis dodecahedron
truncated cuboctahedron Scalene
DU11 facets.png
Dual cube t012 f4.pngDual cube t012.pngDual cube t012 B2.png Disdyakis dodecahedronDisdyakis dodecahedron 87.202
155.082 2.2630 48 72 26 Oh
pentagonal icositetrahedron
snub cube Pentagon
DU12 facets.png
Dual snub cube e1.pngDual snub cube A2.pngDual snub cube B2.png Pentagonal icositetrahedronPentagonal icositetrahedron (Ccw) 114.812
136.309 1.2472 24 60 38 O
rhombic triacontahedron
icosidodecahedron Rhombus
DU24 facets.png
Dual dodecahedron t1 e.pngDual dodecahedron t1 A2.pngDual dodecahedron t1 H3.png Rhombic triacontahedronRhombic triacontahedron 63.435
144 1.5388 30 60 32 Ih
triakis icosahedron
truncated dodecahedron Isosceles
DU26 facets.png
Dual dodecahedron t12 exx.pngDual dodecahedron t12 A2.pngDual dodecahedron t12 H3.png Triakis icosahedronTriakis icosahedron 119.039
160.613 2.9271 60 90 32 Ih
pentakis dodecahedron
truncated icosahedron Isosceles
DU25 facets.png
Dual dodecahedron t01 e66.pngDual dodecahedron t01 A2.pngDual dodecahedron t01 H3.png Pentakis dodecahedronPentakis dodecahedron 68.619
156.719 2.4271 60 90 32 Ih
deltoidal hexecontahedron
rhombicosidodecahedron Kite
DU27 facets.png
Dual dodecahedron t02 f4.pngDual dodecahedron t02 A2.pngDual dodecahedron t02 H3.png Deltoidal hexecontahedronDeltoidal hexecontahedron 86.974
154.121 2.1763 60 120 62 Ih
disdyakis triacontahedron
truncated icosidodecahedron Scalene
DU28 facets.png
Dual dodecahedron t012 f4.pngDual dodecahedron t012 A2.pngDual dodecahedron t012 H3.png Disdyakis triacontahedronDisdyakis triacontahedron 88.992
164.888 3.7694 120 180 62 Ih
pentagonal hexecontahedron
snub dodecahedron Pentagon
DU29 facets.png
Dual snub dodecahedron e1.pngDual snub dodecahedron A2.pngDual snub dodecahedron H2.png Pentagonal hexecontahedronPentagonal hexecontahedron (Ccw) 118.137
153.179 2.0971 60 150 92 I

All Catalan solids to scale with Archimedean solid edges superimposed. Sorted by midradius in descending order:

Catalan Solids to Scale.svg

All facets of Catalan solids, same scale as above:

Catalan Facets.svg


The Catalan solids, along with their dual Archimedean solids, can be grouped in those with tetrahedral, octahedral and icosahedral symmetry. For both octahedral and icosahedral symmetry there are six forms. The only Catalan solid with genuine tetrahedral symmetry is the triakis tetrahedron (dual of the truncated tetrahedron). The rhombic dodecahedron and tetrakis hexahedron have octahedral symmetry, but they can be colored to have only tetrahedral symmetry. Rectification and snub also exist with tetrahedral symmetry, but they are Platonic instead of Archimedean, so their duals are Platonic instead of Catalan. (They are shown with brown background in the table below.)

Tetrahedral symmetry
Polyhedron 4-4.png Polyhedron truncated 4a max.png Polyhedron truncated 4b max.png Polyhedron small rhombi 4-4 max.png Polyhedron great rhombi 4-4 max.png Polyhedron snub 4-4 left max.png
Polyhedron 4-4 dual blue.png Polyhedron truncated 4a dual max.png Polyhedron truncated 4b dual max.png Polyhedron small rhombi 4-4 dual max.png Polyhedron great rhombi 4-4 dual max.png Polyhedron snub 4-4 left dual max.png
Octahedral symmetry
Archimedean Polyhedron 6-8 max.png Polyhedron truncated 6 max.png Polyhedron truncated 8 max.png Polyhedron small rhombi 6-8 max.png Polyhedron great rhombi 6-8 max.png Polyhedron snub 6-8 left max.png
Catalan Polyhedron 6-8 dual blue.png Polyhedron truncated 6 dual.png Polyhedron truncated 8 dual max.png Polyhedron small rhombi 6-8 dual max.png Polyhedron great rhombi 6-8 dual max.png Polyhedron snub 6-8 left dual max.png
Icosahedral symmetry
Archimedean Polyhedron 12-20 max.png Polyhedron truncated 12 max.png Polyhedron truncated 20 max.png Polyhedron small rhombi 12-20 max.png Polyhedron great rhombi 12-20 max.png Polyhedron snub 12-20 left max.png
Catalan Polyhedron 12-20 dual max.png Polyhedron truncated 12 dual max.png Polyhedron truncated 20 dual max.png Polyhedron small rhombi 12-20 dual max.png Polyhedron great rhombi 12-20 dual max.png Polyhedron snub 12-20 left dual max.png


All dihedral angles of a Catalan solid are equal. Denoting their value by , and denoting the face angle at the vertices where faces meet by , we have


This can be used to compute and , , ... , from , ... only.

Triangular faces[edit]

Of the 13 Catalan solids, 7 have triangular faces. These are of the form Vp.q.r, where p, q and r take their values among 3, 4, 5, 6, 8 and 10. The angles , and can be computed in the following way. Put , , and put




For and the expressions are similar of course. The dihedral angle can be computed from


Applying this, for example, to the disdyakis triacontahedron (, and , hence , and , where is the golden ratio) gives and .

Quadrilateral faces[edit]

Of the 13 Catalan solids, 4 have quadrilateral faces. These are of the form Vp.q.p.r, where p, q and r take their values among 3, 4, and 5. The angle can be computed by the following formula:


From this, , and the dihedral angle can be easily computed. Alternatively, put , , . Then and can be found by applying the formulas for the triangular case. The angle can be computed similarly of course. The faces are kites, or, if , rhombi. Applying this, for example, to the deltoidal icositetrahedron (, and ), we get .

Pentagonal faces[edit]

Of the 13 Catalan solids, 2 have pentagonal faces. These are of the form Vp.p.p.p.q, where p=3, and q=4 or 5. The angle can be computed by solving a degree three equation:


Metric properties[edit]

For a Catalan solid let be the dual with respect to the midsphere of . Then is an Archimedean solid with the same midsphere. Denote the length of the edges of by . Let be the inradius of the faces of , the midradius of and , the inradius of , and the circumradius of . Then these quantities can be expressed in and the dihedral angle as follows:


These quantities are related by , and .

As an example, let be a cuboctahedron with edge length . Then is a rhombic dodecahedron. Applying the formula for quadrilateral faces with and gives , hence , , , .

All vertices of of type lie on a sphere with radius given by


and similarly for .

Dually, there is a sphere which touches all faces of which are regular -gons (and similarly for ) in their center. The radius of this sphere is given by


These two radii are related by . Continuing the above example: and , which gives , , and .

If is a vertex of of type , an edge of starting at , and the point where the edge touches the midsphere of , denote the distance by . Then the edges of joining vertices of type and type have length . These quantities can be computed by


and similarly for . Continuing the above example: , , , , so the edges of the rhombic dodecahedron have length .

The dihedral angles between -gonal and -gonal faces of satisfy


Finishing the rhombic dodecahedron example, the dihedral angle of the cuboctahedron is given by .


The face of any Catalan polyhedron may be obtained from the vertex figure of the dual Archimedean solid using the Dorman Luke construction.[2]

Application to other solids[edit]

All of the formulae of this section apply to the Platonic solids, and bipyramids and trapezohedra with equal dihedral angles as well, because they can be derived from the constant dihedral angle property only. For the pentagonal trapezohedron, for example, with faces V3.3.5.3, we get , or . This is not surprising: it is possible to cut off both apexes in such a way as to obtain a regular dodecahedron.

See also[edit]


  1. ^ Weisstein, Eric W. "Archimedean Solid". Retrieved 2022-07-02.
  2. ^ Cundy & Rollett (1961), p.  117; Wenninger (1983), p. 30.


External links[edit]