# Hexagonal tiling

Hexagonal tiling
Hexagonal tiling
Type Regular tiling
Vertex configuration 6.6.6 (or 63)
Schläfli symbol(s) {6,3}
t{3,6}
Wythoff symbol(s) 3 | 6 2
2 6 | 3
3 3 3 |
Coxeter diagram(s)

Symmetry p6m, [6,3], (*632)
Rotation symmetry p6, [6,3]+, (632)
Dual Triangular tiling
Properties Vertex-transitive, edge-transitive, face-transitive

6.6.6 (or 63)

In geometry, the hexagonal tiling or hexagonal tessellation is a regular tiling of the Euclidean plane, in which three hexagons meet at each vertex. It has Schläfli symbol of {6,3} or t{3,6} (as a truncated triangular tiling).

Conway calls it a hextille.

The internal angle of the hexagon is 120 degrees so three hexagons at a point make a full 360 degrees. It is one of three regular tilings of the plane. The other two are the triangular tiling and the square tiling.

## Applications

The hexagonal tiling is the densest way to arrange circles in two dimensions. The Honeycomb conjecture states that the hexagonal tiling is the best way to divide a surface into regions of equal area with the least total perimeter. The optimal three-dimensional structure for making honeycomb (or rather, soap bubbles) was investigated by Lord Kelvin, who believed that the Kelvin structure (or body-centered cubic lattice) is optimal. However, the less regular Weaire-Phelan structure is slightly better.

This structure exists naturally in the form of graphite, where each sheet of graphene resembles chicken wire, with strong covalent carbon bonds. Tubular graphene sheets have been synthesised; these are known as carbon nanotubes. They have many potential applications, due to their high tensile strength and electrical properties. Silicene is similar.

Chicken wire consists of a hexagonal lattice (often not regular) of wires.

The hexagonal tiling appears in many crystals. In three dimensions, the face-centered cubic and hexagonal close packing are common crystal structures. They are the densest known sphere packings in three dimensions, and are believed to be optimal. Structurally, they comprise parallel layers of hexagonal tilings, similar to the structure of graphite. They differ in the way that the layers are staggered from each other, with the face-centered cubic being the more regular of the two. Pure copper, amongst other materials, forms a face-centered cubic lattice.

## Uniform colorings

There are 3 distinct uniform colorings of a hexagonal tiling, all generated from reflective symmetry of Wythoff constructions. The (h,k) represent the periodic repeat of one colored tile, counting hexagonal distances as h first, and k second.

k-uniform 1-uniform 2-uniform 3-uniform
Symmetry p6m, (*632) p3m1, (*333) p6m, (*632) p6, (632)
Picture 100px 100px 100px
Colors 1 2 3 2 4 2 7
(h,k) (1,0) (1,1) (2,0) (2,1)
Wythoff {6,3} t{3,6} t{3[3]}
Wythoff 3 | 6 2 2 6 | 3 3 3 3 |
Coxeter
Conway H cH

The 3-color tiling is a tessellation generated by the order-3 permutohedrons.

### Chamfered hexagonal tiling

A chamferred hexagonal tiling replacing edges with new hexagons and transforms into another hexagonal tiling. In the limit, the original faces disappear, and the new hexagons degenerate into rhombi, and it becomes a rhombic tiling.

Hexagons (H) Chamfered hexagons (cH) Rhombi (daH)

## Related tilings

The hexagons can be dissected into sets of 6 triangles. This process leads to two 2-uniform tilings, and the triangular tiling:

Regular tiling Dissection 2-uniform tilings Regular tiling
120px
Original

1/3 dissected
120px
2/3 dissected
120px
fully dissected

The hexagonal tiling can be considered an elongated rhombic tiling, where each vertex of the rhombic tiling is stretched into a new edge. This is similar to the relation of the rhombic dodecahedron and the rhombo-hexagonal dodecahedron tessellations in 3 dimensions.

 160px Rhombic tiling Hexagonal tiling 160px Fencing uses this relation

It is also possible to subdivide the prototiles of certain hexagonal tilings by two, three, four or nine equal pentagons:

 175px Pentagonal tiling type 1 with overlays of regular hexagons (each comprising 2 pentagons). 175px pentagonal tiling type 3 with overlays of regular hexagons (each comprising 3 pentagons). 175px Pentagonal tiling type 4 with overlays of semiregular hexagons (each comprising 4 pentagons). 175px Pentagonal tiling type 3 with overlays of two sizes of regular hexagons (comprising 3 and 9 pentagons respectively).

### Symmetry mutations

This tiling is topologically related as a part of sequence of regular tilings with hexagonal faces, starting with the hexagonal tiling, with Schläfli symbol {6,n}, and Coxeter diagram , progressing to infinity.

This tiling is topologically related to regular polyhedra with vertex figure n3, as a part of sequence that continues into the hyperbolic plane.

It is similarly related to the uniform truncated polyhedra with vertex figure n.6.6.

This tiling is also a part of a sequence of truncated rhombic polyhedra and tilings with [n,3] Coxeter group symmetry. The cube can be seen as a rhombic hexahedron where the rhombi are squares. The truncated forms have regular n-gons at the truncated vertices, and nonregular hexagonal faces.

## Wythoff constructions from hexagonal and triangular tilings

Like the uniform polyhedra there are eight uniform tilings that can be based from the regular hexagonal tiling (or the dual triangular tiling).

Drawing the tiles colored as red on the original faces, yellow at the original vertices, and blue along the original edges, there are 8 forms, 7 which are topologically distinct. (The truncated triangular tiling is topologically identical to the hexagonal tiling.)

## Monohedral convex hexagonal tilings

There are 3 types of monohedral convex hexagonal tilings.[1] They are all isohedral. Each has parametric variations within a fixed symmetry. Type 2 contains glide reflections, and is 2-isohedral keeping chiral pairs distinct.

3 types of monohedral convex hexagonal tilings
1 2 3
p2, 2222 pgg, 22× p2, 2222 p3, 333
120px 120px 120px 120px
120px
b=e
B+C+D=360°
120px
b=e, d=f
B+C+E=360°
120px
a=f, b=c, d=e
B=D=F=120°
120px
2-tile lattice
120px
4-tile lattice
120px
3-tile lattice

## Topologically equivalent tilings

Hexagonal tilings can be made with the identical {6,3} topology as the regular tiling (3 hexagons around every vertex). With isohedral faces, there are 13 variations. Symmetry given assumes all faces are the same color. Colors here represent the lattice positions.[2] Single-color (1-tile) lattices are parallelogon hexagons.

13 isohedrally-tiled hexagons
pg (××) p2 (2222) p3 (333) pmg (22*)
100px 100px 100px
pgg (22×) p31m (3*3) p2 (2222) cmm (2*22) p6m (*632)
100px 100px

Other isohedrally-tiled topological hexagonal tilings are seen as quadrilaterals and pentagons that are not edge-to-edge, but interpreted as colinear adjacent edges:

pmg (22*) pgg (22×) cmm (2*22) p2 (2222)
100px
Parallelogram
100px
Trapezoid

Parallelogram

Rectangle
100px
Parallelogram
100px
Rectangle
100px
Rectangle
Isohedrally-tiled pentagons
p2 (2222) pgg (22×) p3 (333)
120px 120px 120px

The 2-uniform and 3-uniform tessellations have a rotational degree of freedom which distorts 2/3 of the hexagons, including a colinear case that can also be seen as a non-edge-to-edge tiling of hexagons and larger triangles.[3]

It can also be distorted into a chiral 4-colored tri-directional weaved pattern, distorting some hexagons into parallelograms. The weaved pattern with 2 colored faces have rotational 632 (p6) symmetry.

Regular Gyrated Regular Weaved
p6m, (*632) p6, (632) p6m (*632) p6 (632)
150px 150px
p3m1, (*333) p3, (333) p6m (*632) p2 (2222)
150px 150px 150px

## Circle packing

The hexagonal tiling can be used as a circle packing, placing equal diameter circles at the center of every point. Every circle is in contact with 3 other circles in the packing (kissing number).[4] The lattice volume is filled by two circles, so the circles can be alternately colored. The gap inside each hexagon allows for one circle, creating the densest packing from the triangular tiling, with each circle contact with the maximum of 6 circles.