Cyclic symmetry in three dimensions

Point groups in three dimensions

Involutional symmetry
Cs, (*)
[ ] =

Cyclic symmetry
Cnv, (*nn)
[n] =

Dihedral symmetry
Dnh, (*n22)
[n,2] =
Polyhedral group, [n,3], (*n32)

Tetrahedral symmetry
Td, (*332)
[3,3] =

Octahedral symmetry
Oh, (*432)
[4,3] =

Icosahedral symmetry
Ih, (*532)
[5,3] =

In three dimensional geometry, there are four infinite series of point groups in three dimensions (n≥1) with n-fold rotational or reflectional symmetry about one axis (by an angle of 360°/n) does not change the object.

They are the finite symmetry groups on a cone. For n = ∞ they correspond to four frieze groups. Schönflies notation is used. The terms horizontal (h) and vertical (v) imply the existence and direction of reflections with respect to a vertical axis of symmetry. Also shown are Coxeter notation in brackets, and, in parentheses, orbifold notation.

Example symmetry subgroup tree for dihedral symmetry: D4h, [4,2], (*224)

Types

Chiral
Achiral
Piece of loose-fill cushioning with C2h symmetry

C2h, [2,2+] (2*) and C2v, [2], (*22) of order 4 are two of the three 3D symmetry group types with the Klein four-group as abstract group. C2v applies e.g. for a rectangular tile with its top side different from its bottom side.

Frieze groups

In the limit these four groups represent Euclidean plane frieze groups as C, C∞h, C∞v, and S. Rotations become translations in the limit. Portions of the infinite plane can also be cut and connected into an infinite cylinder.

Frieze groups
Notations Examples
IUC Orbifold Coxeter Schönflies* Euclidean plane Cylindrical (n=6)
p1∞∞[∞]+C
p1m1*∞∞[∞]C∞v
p11m∞*[∞+,2]C∞h
p11g∞×[∞+,2+]S

Examples

S2/Ci (1x): C4v (*44): C5v (*55):

Parallelepiped

Square pyramid

Elongated square pyramid

Pentagonal pyramid

See also

References

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