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In the last twenty years, carbon-based materials and nanostructures have gained more and more popularity. Driven by the breakthrough-discovery and the synthesis of fullerenes, nanotubes, graphene and carbynes, also the search for new exotic carbon allotropes attracted increasing attention in the scientific community, also in view of applications. This thesis focuses on the construction and the investigation of three novel crystalline allotropes of carbon, all mixing different orbital hybridizations. We have employed state-of-the-art numerical simulations to investigate structural, electronic, and mechanical properties of the three structures. Two of these allotropes, novamene and protomene, combine sp2 and sp3 hybridizations and exhibit a semiconductor character in their lowest-energy Peierls-dimerized configuration. Both structures show transitions towards a metallic state at a relatively small energy cost. The third allotrope, zayedene, mixes sp, in the form of a linear chain, and sp3 providing an enclosing cage. This structure exhibits a clear metallic character due to the dangling bonds inside the cavity. We predict characteristic high-frequency vibrations associated with sp chain stretching modes. We also investigate the thermodynamic stability of zayedene at standard conditions. Finally we suggest how hundreds of different allotropes can be built from the simple ones investigated. |
