Theoretical characterization of tolanene: A new 2D sp-sp2 hybridized carbon allotrope

The search for new carbon allotrope forms has been the focus of much experimental and theoretical research. Some nonbenzenoid sp2-hybridized carbon allotropes have been proposed and synthesized, revealing properties unlike those observed for graphene. In the present work, first-principles calculations were performed to investigate a new two-dimensional (2D) carbon sheet - named tolanene - which may hypothetically be obtained from diphenylacetylene molecules as building blocks. The nonbenzenoid tolanene sheet has a periodic arrangement of four-, six-, eight-, and twelve-membered rings of sp and sp2 hybridized carbon atoms. Our calculations reveal that tolanene is mechanically and dynamically stable, and can potentially withstand a temperature as high as 1500 K quite easily. The structure presents a strong anisotropy in its mechanical properties, in a similar fashion to biphenylene. Additionally, we verify that the structure presents a metallic behavior, and its low-energy electronic structure is fully determined by pz orbitals, as in most carbon-based 2D materials. The application of tolanene as a potential anode material in Li-ion batteries is also explored. We find that it offers a competitive Li storage capacity and fast Li mobility along with other interesting electronic properties.