Elastic properties of graphyne-based nanotubes

Abstract

Graphyne nanotubes (GNTs) are nanostructures obtained from rolled up graphyne sheets, in the same way carbon nanotubes (CNTs) are obtained from graphene ones. Graphynes are 2D carbon-allotropes composed of atoms in sp and sp 2 hybridized states. Similarly to conventional CNTs, GNTs can present different chiralities and electronic properties. Because of the acetylenic groups (triple bonds), GNTs exhibit large sidewall pores that influence their mechanical properties. In this work, we studied the mechanical response of GNTs under tensile stress using fully atomistic molecular dynamics simulations and density functional theory (DFT) calculations. Our results show that GNTs mechanical failure (fracture) occurs at larger strain values in comparison to corresponding CNTs, but paradoxically with smaller ultimate strength and Young's modulus values. This is a consequence of the combined effects of the existence of triple bonds and increased porosity/flexibility due to the presence of acetylenic groups.

On the Mechanical Properties of Popgraphene‐Based Nanotubes: a Reactive Molecular Dynamics Study

“…The Y Mod (estimated up to 5 %) and σ US (measured at critical strain) values for (0,3)/(7,0) PopNTs are and / , respectively. Those Y mod and σ US values are similar to the ones reported for conventional armchair and zigzag CNTs, and also Phagraphene tubes (PhaNTs) using the same methodology, [18,34] being however significantly higher than values found for Graphyne tubes (GyNTs) [34] . For instance, the average of Y mod values found for α ‐GyNTs is ten times smaller while Y mod values found for γ ‐GyNTs are about half of the values found for PopNTs.…”

“…The Young's modulus ( Y Mod ) (750–900 GPa) and ultimate strength ( σ US ) (120–150 GPa) values are similar to the ones reported for conventional armchair and zigzag carbon nanotubes (CNT) using the same methodology [34] and they are not significantly dependent on the chirality and/or diameter. However, the values for the critical strain ( ϵ c ) for PopNTs are significantly chirality dependent, which is different from the corresponding CNT ones.…”

“…At this point, it is worth to mention that our results for (n,0) PopNTs suggest that they behave similarly to γ ‐GyNTs concerning the observed smaller resilience (low critical strain values). However, the (0,n) PopNTs have their flexibility compared with PhaNTs ( ), and even a slightly high resilience than conventional CNTs ( ) and (n,n) α ‐GyNTs ( ), but still low resilience when compared to (n,0) α ‐GyNTs ( ) [18,34] …”

“…In our recent contributions, [34,35] the values for the elastic properties of carbon‐based nanostructures obtained from MD simulations using the Reaxff potentials were contrasted with the ones obtained using density functional theory (DFT) calculations. The calculated elastic properties showed a good agreement between the MD and DFT frameworks.…”

“…The evolution of the average atomic stress distribution in the tubes under stretching is calculated using the von Mises stress tensor [31,34,47,48] which is defined as …”