# Weaire-Phelan structure

The

**Weaire-Phelan structure**is a complex 3-dimensional structure. In1993 ,Denis Weaire andRobert Phelan , two physicists based atTrinity College Dublin found that in computer simulations offoam , this structure was a better solution of the "Kelvin problem" than the previous best-known solution, the Kelvin structure. [*Weaire D and Phelan R, "A counterexample to Kelvin's conjecture on minimal surfaces", Phil. Mag. Lett. 69, 107-110 (1994)*]**Kelvin structure**In

1887 ,Lord Kelvin asked how space could be partitioned into cells of equal volume with the least area of surface between them, i.e., what was the most efficient soap bubble foam? [*[*] This problem has since been referred to as the*http://zapatopi.net/kelvin/papers/on_the_division_of_space.html "On the Division of Space with Minimum Partitional Area", By Lord Kelvin (Sir William Thomson),Philosophical Magazine, Vol. 24, No. 151, p. 503 (1887)*]**Kelvin problem.**He proposed the foam of

bitruncated cubic honeycomb , which is called the**Kelvin structure.**This is theconvex uniform honeycomb formed by thetruncated octahedron , which is a 14-sided space-fillingpolyhedron (atetrakaidecahedron ), with 6 square sides and 8 hexagonal sides. To conform toPlateau's laws governing the structures of foams, the hexagonal faces are slightly curved.The

**Kelvin conjecture**is that the Kelvin structure solves the Kelvin problem: that the foam of the bitruncated cubic honeycomb is the most efficient foam. The Kelvin conjecture was believed and no counter-examples were known for more than 100 years, until it was disproved by the discovery of the Weaire-Phelan structure.Compare with the

Kepler conjecture (on the densest packing of spheres), which is generally considered to have been proven in 1998.**Description of Weaire-Phelan structure**The Weaire-Phelan structure uses two kinds of cells of equal volume; an irregular pentagonal

dodecahedron and a tetrakaidecahedron with 2 hexagons and 12 pentagons, again with slightly curved faces. The surface area is 0.3% less than the Kelvin structure, quite a large difference in this context. It has not been proved that the Weaire-Phelan structure is optimal, but it is generally believed to be likely: the Kelvin problem is still open, but the Weaire-Phelan structure is conjectured to be the solution.**Clathrate structure**The honeycomb associated to the Weaire-Phelan structure (obtained by flattening the faces and straightening the edges) is also referred to loosely as the Weaire-Phelan structure, and it was known well before the Weaire-Phelan structure was discovered, but the application to the Kelvin problem was overlooked. [

*A diagram can be found incite book*]

last=Pauling

first=Linus

title=The Nature of the Chemical Bond

year=1960

publisher=Cornell University Press

edition=3rd

page=471, as shown on [*http://www.susqu.edu/brakke/kelvin/Pauling.htm Ken Brakke's page*] .It is found as a

crystal structure inchemistry where it is usually known as the 'Type Iclathrate structure'.Gas hydrate s formed by methane, propane and carbon dioxide at low temperatures have a structure in whichwater molecules lie at the nodes of the Weaire-Phelan structure and arehydrogen bond ed together, and the larger gas molecules are trapped in the polyhedral cages.Some

alkali metal silicides and germanides also form this structure (Si/Ge at nodes, alkali metals in cages), as does thesilica mineralmelanophlogite (silicon at nodes, linked by oxygen along edges). Melanophlogite is a metastable form of SiO_{2}that is stabilized in this structure because of gas molecules trapped in the cages. The InternationalZeolite Association uses the symbol MEP to indicate the framework topology of melanophlogite.**Applications**The Weaire-Phelan structure is the inspiration for the design of the aquatic centre for the

2008 Olympics inBeijing inChina . [*Henry Fountain: [*]*http://www.nytimes.com/2008/08/05/sports/olympics/05swim.html A Problem of Bubbles Frames an Olympic Design*] , "New York Times", August 5, 2008; retrieved 2008 October 9.**See also***

Kepler conjecture

*Minimal surface

*Soap bubble

*Beijing National Aquatics Centre **References****External links*** [

*http://www.vongirsewald.com/foam/ Weaire-Phelan structure unfolded dodecahedron and tetrakaidecahedron in .pdf / .dxf formats*]

* [*http://www.mathaware.org/mam/03/images/sullivan/phw00000.jpgAn image of the Weaire-Phelan structure*]

* [*http://www.steelpillow.com/polyhedra/wp/wp.htm Weaire-Phelan Bubbles*] page with illustrations and freely downloadable 'nets' for printing and making models.

*Wikimedia Foundation.
2010.*

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