Grazynes: Carbon-Based Two-Dimensional Composites with Anisotropic Properties

Abstract

A new family of two-dimensional carbon allotropes is presented, based on graphene stripes linked to each other by acetylenic connections. The large amount of allowed connectivities demands for a family name to them: Grazynes. The present study reports the energetic, structural, elastic, and electronic physicochemical properties of a set of simple grazynes by means of density functional theory based calculations, suggesting also possible synthetic routes. The main results conclude that these are exotic yet stable materials, stiffer than graphene in the acetylenic direction, highly anisotropic, and with the presence of Dirac points in the reciprocal space along the graphene stripes direction resistant to strain, regardless of its direction. Thus, grazynes infer directionality in electron conductivity and resilience to the materials stretching/compression, quite important, for instance, in the nanoelectronics applicability point of view.

Acetylene-Mediated Electron Transport in Nanostructured Graphene and Hexagonal Boron Nitride

“…This arises from the well-known overdelocalization of generalized gradient approximation (GGA) functionals, such as the here employed PBE. 21 However, the qualitative features of our reported band structures match those obtained in previous studies using hybrid functionals, 30 where this overdelocalization is counter-acted. The parabolic p x p y bands appear in the valence band for both types of materials (Figure 2a,b) being pinned at E F for AcGrs, and appearing lower in energy for AcBNs, which display a finite band gap.…”

“…Previous work on AcGrs (also known as grazynes) demonstrated these are fully planar 2D nanostructured materials. 30 AcGrs and AcBNs nanostructures can be regarded as 2D parallel arrays of zigzag graphene or h-BN nanoribbons, covalently connected via acetylene units, thus displaying a similarity with the recently bottom-up synthesized nanoporous graphene. 31 In panels a and b of Figure 2 we plot the orbital-resolved band structures for AcGr_1 and AcBN_1, respectively, where one may see that the low-energy spectra for both types of materials are mainly composed by p z and p x p y bands, shown in green and blue, respectively.…”

Designing All Graphdiyne Materials as Graphene Derivatives: Topologically Driven Modulation of Electronic Properties

“…The structures of these groups have been investigated in a recent work with the name “grazynes”. 56 Our analysis underlines a clear trend in the energy that can be easily generalized for similar structures for predictive purposes.…”

“…Interestingly, these two parameters seem to have similar weight, in fact the same energy is obtained in 6-hL with the smallest graphene ribbon and single diacetylenic unit and in 6-h 2 L 2 in which the increase of energy given by doubling the diacetylenic units is counterbalanced by doubling the graphene ribbon width. The structures of these group have been investigated in a recent work with the name "grazyines " [49]. Our analysis underlines a clear trend in the energy that can be easily generalized for similar structures for predictive purposes.…”

“…Among the 26 structures here investigated, these ones are the only containing a T shaped unit (see Figure 1), suggesting that T units would induce electronic effects leading to the occurrence of a band gap. In DOS, as circled in red, we find evindences for the existence of a zero-gap with Dirac cones The second class is formed by metallic systems and include structures made by graphene ribbons interconnected by diacetylenic groups (here called hL), also described as graziynes [49]. All these crystals (i.e.…”