Abstract
Designing new 2D systems with tunable properties is an important subject for science and technology. Starting from graphene, we developed an algorithm to systematically generate 2D carbon crystals belonging to the family of graphdiynes (GDYs) and having different structures and sp/sp2 carbon ratios. We analyze how structural and topological effects can tune the relative stability and the electronic behavior, to propose a rationale for the development of new systems with tailored properties. A total of 26 structures have been generated, including the already known polymorphs such as α-, β-, and γ-GDY. Periodic density functional theory calculations have been employed to optimize the 2D crystal structures and to compute the total energy, the band structure, and the density of states. Relative energies with respect to graphene have been found to increase when the values of the carbon sp/sp2 ratio increase, following however different trends based on the peculiar topologies present in the crystals. These topologies also influence the band structure, giving rise to semiconductors with a finite band gap, zero-gap semiconductors displaying Dirac cones, or metallic systems. The different trends allow identifying some topological effects as possible guidelines in the design of new 2D carbon materials beyond graphene.
Highlights
Carbon materials and their nanostructures played a relevant role in the science and technology of the last two decades: from fullerenes to carbon nanotubes and from polyconjugated polymers to graphene, the so-called “era of carbon allotropes” has been enlightened by groundbreaking results and Nobel prizes, paving the way to many interesting research topics.[1]
Several papers report on the prediction of properties of γGDY mainly through density functional theory (DFT) calculations.[5,6,27−32] From the experimental side, synthetic bottom-up approaches have been successfully employed to produce sub-fragments of GDY of different topologies and dimensions, in particular, by Haley and co-workers.[33−40] Later, different papers reported the preparation and characterization of extended 2D GDY sheets prepared through organometallic synthesis techniques, showing promising routes to the production of these systems, even though significant efforts should still be put to further investigate and understand their properties.[41−43] Recent advances in on-surface synthesis allow
Based on the 2D crystal structures selected by ToposPro, periodic boundary condition (PBC) DFT simulations have been carried out by employing CRYSTAL1750,51 to optimize the geometry and compute the electronic band structure and density of states (DOS)
Summary
Carbon materials and their nanostructures played a relevant role in the science and technology of the last two decades: from fullerenes to carbon nanotubes and from polyconjugated polymers to graphene, the so-called “era of carbon allotropes” has been enlightened by groundbreaking results and Nobel prizes, paving the way to many interesting research topics.[1]. Several papers report on the prediction of properties of γGDY mainly through density functional theory (DFT) calculations.[5,6,27−32] From the experimental side, synthetic bottom-up approaches have been successfully employed to produce sub-fragments of GDY of different topologies and dimensions, in particular, by Haley and co-workers.[33−40] Later, different papers reported the preparation and characterization of extended 2D GDY sheets prepared through organometallic synthesis techniques, showing promising routes to the production of these systems, even though significant efforts should still be put to further investigate and understand their properties.[41−43] Recent advances in on-surface synthesis allow To answer these questions, we have developed an algorithm to systematically generate new hybrid sp−sp[2] carbon structures as modifications of graphene by introducing linear diacetylenic units. The identification of new 2D carbon structures and the topology-based electronic properties give further insights into the design and understanding of new hybrid sp−sp[2] carbon 2D materials
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