Penta-graphene

Penta-graphene is a hypothetical <a href="/facts/Carbon_allotrope/GSetCyq6">carbon allotrope</a> composed entirely of carbon pentagons and resembling the <a href="/facts/Cairo_pentagonal_tiling/IYXIjHs0">Cairo pentagonal tiling</a>. 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 <a href="/facts/Poisson%E2%80%99s_ratio/ppIsaujA">Poisson’s ratio</a> and very high ideal strength believed to exceed that of a similar material, <a href="/facts/Graphene/QDGUBaPt">graphene</a>.

Penta-graphene contains both <a href="/facts/Orbital_hybridisation/Fl7sz8Jm">sp2</a> and sp3 hybridized carbon atoms. Contrary to graphene, which is a good conductor of electricity, penta-graphene is predicted to be an <a href="/facts/Insulator_(electricity)/SfSXkrh5">insulator</a> with an <a href="/facts/Direct_and_indirect_band_gaps/9T1kkc6y">indirect band gap</a> of 4.1–4.3 eV. Its hydrogenated form is called penta-<a href="/facts/Graphane/3QMVg24s">graphane</a>. It has a diamond-like structure with sp3 and no sp2 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.

Penta-graphene open-in-new

Penta-graphene