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 and very high ideal strength believed to exceed that of a similar material,

graphene Graphene () is a carbon allotrope consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice, honeycomb planar nanostructure. The name "graphene" is derived from "graphite" and the suffix -ene, indicating ...

. Penta-graphene contains both ''sp''² and ''sp''³ hybridized carbon atoms. Contrary to graphene, which is a good conductor of electricity, penta-graphene is predicted to be an insulator with an

indirect band gap In semiconductors, 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 characterized by ...

of 4.1–4.3 eV. Its hydrogenated form is called penta- graphane. 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

* Graphene Allotropes of carbon Hypothetical chemical compounds {{hyp-chem-compound-stub