Penta-graphene is a hypothetical
carbon allotrope composed entirely of carbon pentagons and resembling the
Cairo pentagonal tiling
In geometry, a Cairo pentagonal tiling is a tessellation of the Euclidean plane by congruent convex pentagons, formed by overlaying two tessellations of the plane by hexagons and named for its use as a paving design in Cairo. It is also called Ma ...
.
Penta-graphene was proposed in 2014 on the basis of analyses and simulations.
Further calculations predicted that it is unstable in its pure form,
but can be stabilized by hydrogenation.
[ Due to its atomic configuration, penta-graphene has an unusually negative ]Poisson’s ratio
In materials science and solid mechanics, Poisson's ratio \nu ( nu) is a measure of the Poisson effect, the deformation (expansion or contraction) of a material in directions perpendicular to the specific direction of loading. The value of Pois ...
and very high ideal strength believed to exceed that of a similar material, graphene
Graphene () is an allotrope of carbon consisting of a single layer of atoms arranged in a hexagonal lattice nanostructure. .indirect band gap
In semiconductor physics, the band gap of a semiconductor can be of two basic types, a direct band gap or an indirect band gap. The minimal-energy state in the conduction band and the maximal-energy state in the valence band are each characteriz ...
of 4.1–4.3 eV. Its hydrogenated form is called penta-graphane
Graphane is a two-dimensional polymer of carbon and hydrogen with the formula unit (CH)n where ''n'' is large. Partial hydrogenation results in hydrogenated graphene, which was reported by Elias et al in 2009 by a TEM study to be "direct evidence ...
. It has a diamond-like structure with ''sp''3 and no ''sp''2 bonds, and therefore a wider band gap (ca. 5.8 eV) than penta-graphene.[ Chiral penta-graphene nanotubes have also been studied as metastable allotropes of carbon.]
References
External links
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Graphene
Allotropes of carbon
Hypothetical chemical compounds
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