Phagraphene [fæ’græfiːn] is a proposed graphene allotrope composed of 5-6-7 carbon rings. Phagraphene was proposed in 2015 based on systematic evolutionary structure searching. Theoretical calculations showed that phagraphene is not only dynamically and thermally stable, but also has distorted Dirac cones. The direction-dependent cones are robust against external strain with tuneable Fermi velocities.
Higher-energy allotropes named Haeckelite contained penta- hexa- and hepta-carbon rings. Three types (rectangular, oblique and hexagonal) were proposed as early as 2000. These metastable allotropes have a trival intrinsic metallic behavior.
An unrelated material called PHA/graphene is a polyhydroxyalkanoate graphene composite.
- Wang, Zhenhai; Zhou, Xiang-Feng; Zhang, Xiaoming; Zhu, Qiang; Dong, Huafeng; Zhao, Mingwen; Oganov, Artem R. (9 September 2015). "Phagraphene: A Low-Energy Graphene Allotrope Composed of 5–6–7 Carbon Rings with Distorted Dirac Cones". Nano Letters. 15 (9): 6182–6186. arXiv: . Bibcode:2015NanoL..15.6182W. doi:10.1021/acs.nanolett.5b02512. PMID 26262429.
- Terrones, H.; Terrones, M.; Hernández, E.; Grobert, N.; Charlier, J-C.; Ajayan, P. M. (21 February 2000). "New Metallic Allotropes of Planar and Tubular Carbon". Physical Review Letters. 84 (8): 1716–1719. Bibcode:2000PhRvL..84.1716T. doi:10.1103/PhysRevLett.84.1716. PMID 11017608.
- Cranford, S.W. (January 2016). "When is 6 less than 5? Penta- to hexa-graphene transition". Carbon. 96: 421–428. doi:10.1016/j.carbon.2015.09.092.