Te recomiendo leer mi última contribución “Penta-graphene: to be or not to be,» Mapping Ignorance, 25 Jul 2016, sobre el pentagrafeno (propuesto a principios de 2015) y la posibilidad de que no sea un nuevo alótropo del carbono, sino una reorentación cristalográfica del grafeno. La idea no es mía, sino del genial Sir Harold W. Kroto (1939–2016). Te copio el primer párrafo para incentivarte a su lectura.
«Graphene is a two-dimensional allotrope of carbon made of hexagons. In February 2015, penta-graphene, only made of pentagons, was theoretically proposed as another two-dimensional allotrope of carbon . Apparently, it is dynamically, thermally, and mechanically stable, exhibiting a large band gap (graphene is gapless). However, an exhaustive experimental search has been inconclusive, resulting in doubts on its experimental attainability . Recent results suggest that penta-graphene and graphene can be considered as crystallographic reorientations of the same material, rather than distinct allotropes . In fact, this can be the case for other theoretically proposed carbon allotropes, like ph-graphene , having a penta-hexagonal structure.»
 Shunhong Zhang et al., “Penta-graphene: A new carbon allotrope,” PNAS 112: 2372–2377 (Feb 2015), doi: 10.1073/pnas.1416591112.
 Christopher P. Ewels et al., “Predicting experimentally stable allotropes: Instability of penta-graphene,” PANS 112: 15609–15612 (Dec 2015), doi:10.1073/pnas.1520402112.
 Steven W. Cranford, “When is 6 less than 5? Penta- to hexa-graphene transition,” Carbon 96: 421–428 (Jan 2016), doi: 10.1016/j.carbon.2015.09.092.
 Xiaoming Zhang et al., “Prediction of an ultrasoft graphene allotrope with Dirac cones,” Carbon 105: 323–329 (Aug 2016), doi: 10.1016/j.carbon.2016.04.058.