Mechanical properties of graphynes under uniaxial tension

Abstract

Two-dimensional (2D) materials are of great interest to researchers due to their exceptional properties. Among these materials, graphynes is a relatively unexplored class of nanostructure consisting of sp- and sp²-hybridised carbon atoms. They exhibit high strength and attractive electronic properties. When designing nanodevices based on graphene-like materials, it is important to study their mechanical properties.
This study investigated the deformation behaviour and mechanical properties of β₁-, β₃-, γ₁- and γ₂-graphenes under uniaxial tension at 0 K using the molecular dynamics method. Deformation caused the 2D structure to wrinkle, which is a characteristic behaviour of graphene-like structures.
Two deformation mechanisms were identified for these materials - bond elongation and rotation, and wrinkling of the structure. The same stages of deformation can be distinguished for all the structures considered: (1) elastic deformation (up to ε = 0.04); (2) structural transformation from a flat to a wrinkled structure with simultaneous changes in covalent bonds and angles; (3) complete flattening of the structure (reduction of wrinkle amplitude) with a sharp elongation of covalent bonds for the armchair (zigzag) direction; and (4) the pre-critical regime, during which the structure experiences high stresses and subsequent fracture.
Covalent bonds were found to break more easily at higher structure densities because the change in valence angles is limited and the ultimate tensile strength is lower.
For all structures, tensile fracture strain in the zigzag direction is insensitive to the presence of acetylene bonds, in contrast to the armchair direction. This indicates a similar fracture mechanism.

Speaker

Akhunova A.Kh.
aInstitute for Metals Superplasticity Problems of the Russian Academy of Sciences
Russia

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