Top view (top) and side view (bottom) of penta-graphane. Yellow and blue spheres show two types of carbon atoms, while red balls correspond to hydrogens.
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Penta-graphene is a hypothetical carbon allotrope composed entirely of carbon pentagons and resembling the Cairo pentagonal tiling. 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.
Penta-graphene contains both sp2 and sp3 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 of 4.1–4.3 eV. Its hydrogenated form is called penta-graphane. 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.
- Einollahzadeh, Hamideh; Fazeli, Seyed Mahdi; Dariani, Reza Sabet (2016). "Studying the electronic and phononic structure of penta-graphane". Science and Technology of Advanced Materials. 17 (1): 610–617. arXiv:1511.06850. Bibcode:2016STAdM..17..610E. doi:10.1080/14686996.2016.1219970. PMC 5102001. PMID 27877907.
- Zhang, S.; Zhou, J.; Wang, Q.; Chen, X.; Kawazoe, Y.; Jena, P. (2015). "Penta-graphene: A new carbon allotrope". Proceedings of the National Academy of Sciences. 112 (8): 2372–2377. Bibcode:2015PNAS..112.2372Z. doi:10.1073/pnas.1416591112. PMC 4345574. PMID 25646451.
- Ewels, Christopher P.; Rocquefelte, Xavier; Kroto, Harold W.; Rayson, Mark J.; Briddon, Patrick R.; Heggie, Malcolm I. (2015). "Predicting experimentally stable allotropes: Instability of penta-graphene". Proceedings of the National Academy of Sciences. 112 (51): 15609–12. Bibcode:2015PNAS..11215609E. doi:10.1073/pnas.1520402112. PMC 4697406. PMID 26644554.
- Quijano-Briones, JJ.; Fernandez_escamilla, HN; Tlahuice-Flores, Alfredo. (2017). "Chiral penta-graphene nanotubes: Structure, bonding and electronic properties". Computational and Theoretical Chemistry. 1108: 70–75. doi:10.1016/j.comptc.2017.03.019.
- Avramov, P; Demin, V; Luo, M (2015). "Translation Symmetry Breakdown in Low-Dimensional Lattices of Pentagonal Rings". J. Phys. Chem. Lett. 6 (22): 4525–4531. doi:10.1021/acs.jpclett.5b02309. PMID 26582476.
- Nazir, Muhammad Azhar; Hassan, Arzoo; Shen, Yiheng; Wang, Qian (2022). "Research progress on penta-graphene and its related materials: Properties and applications". Nano Today. 44: 101501. doi:10.1016/j.nantod.2022.101501. S2CID 248767647.