Mechanical properties of γ-graphyne nanotubes

Abstract

a g-Graphyne nanotubes (g-GNTs), which are formed by rolling up a g-graphyne sheet in a similar way to carbon nanotubes, exhibit unique mechanical properties due to the carbon atoms in the sp and sp 2 hybridized states. In this study, the mechanical properties of g-GNTs were investigated using molecular dynamics simulations. The effects of the dimensions, temperature, strain rate and the presence of a vacancy on the mechanical properties, i.e., Young's modulus, fracture strength and fracture strain, were comprehensively studied. The results indicate that the mechanical properties of the g-GNTs are not sensitive to the length and strain rate, while the Young's modulus increases with increasing diameter.Meanwhile, an obvious temperature-dependent mechanical behavior was also found due to the stronger thermal vibration of the atoms at a higher temperature, especially in terms of the fracture strength and fracture strain. In addition, the mechanical properties of the g-GNTs would be degraded with the existence of a vacancy, and they are more sensitive to the vacancy in the benzene rings than that in the acetylenic linkages, especially for the double-vacancy. The underlying mechanisms were analyzed from the stress distribution and fracture structure during tensile deformation.

Elastic properties of graphyne-based nanotubes

“…As expected from the dynamics of the pore shape, γ-GNTs exhibit higher Young's modulus values when compared to α-GNTs ones. The average Young's modulus values of the (5, 5) γ-GNT calculated here was 465 GPa, which is in agreement with a recent study, developed with the use of (AIREBO) potential, in which the obtained Young's modulus value was 466 GPa [25,28].…”

“…The Young's modulus values of the nanotubes studied here are presented in Table 3. The obtained Young's modulus of the (25,25) and (25, 0) CNTs were 995 GPa and 821 GPa, respectively, in good agreement with the average value 1020 GPa of single-walled CNTs obtained by Krishnan et al [50]. As expected from the dynamics of the pore shape, γ-GNTs exhibit higher Young's modulus values when compared to α-GNTs ones.…”

“…1). GNTs exhibit different electronic properties in comparison to CNTs, for instance, γ-GNTs are predicted to have the same band gap for any diameter [25]. There is a renewed interest in their electronic properties [26].…”

“…For example, molecular dynamics (MD) simulations have shown that, under twisting deformations, GNTs would be superplastic and more flexible than CNTs, with fracture occurring at angles three times larger than those of CNTs [29]. In another recent MD work [25] carried out with AIREBO potential, the mechanical properties of graphynes-based nanotubes of γ type (γ-GNTs) were predicted to not be very sensitive to their length and to the strain rate, while the Young's modulus (Y ) values increase with larger diameters.…”

Mechanical and thermal properties of graphyne-coated carbon nanotubes: a molecular dynamics simulation on one-dimensional all-carbon van der Waals heterostructures

“…In MD simulations, the adaptive intermolecular reactive empirical bond order (AIREBO) potential 41 derived from the second-generation Brenner potential was used to describe the short-range C-C interactions in component CNT and GNT layers as well as the long-range van der Waals (vdW) interaction between CNT and GNT layers. The AIREBO potential has been employed in many previous MD simulations to successfully reveal the mechanical properties of various carbon nanoallotropes, such as individual CNT, 42 GNT, 25 graphene, 43 and graphyne. 26 According to a previous study, 44 the mechanical properties, especially fracture behaviors of carbon nanomaterials, are very sensitive to the inner cutoff radius in AIREBO potential, since the selection of an appropriate cutoff function parameter can avoid the unrealistic hardening behavior observed at high strains near the fracture and thus is crucial to obtain reliable results.…”