Chiral-Dependent Tensile Mechanics of Graphene

TL;DR

This study uses molecular dynamics to explore how graphene's tensile strength and strain vary with chiral direction, revealing a nearly isotropic elastic response but anisotropic fracture behavior across all temperatures.

Contribution

It provides the first comprehensive analysis of graphene's tensile mechanics across the full range of chiral directions, introducing a unified fracture model.

Findings

Tensile strength and strain increase monotonically with chiral angle.

Elastic stress in graphene is nearly isotropic across directions.

Fracture behavior is highly anisotropic despite isotropic elasticity.

Abstract

We report a molecular dynamics study on the tensile mechanics of graphene as gradually rotating the tensile direction from armchair to zigzag direction, covering the complete range of chiral directions which has never been explored so far. We observed monotonic increases of tensile strength and strain as the chiral (rotational) angle increases. Key feature is their negligible changes up to chiral angle of ~12{\deg} and the subsequent rapid increases and this pattern holds for all temperatures examined here (100-700 K). Considering a topologically consistent (zigzag-lines) breaking of graphene, we presented a unified fracture model that successfully reproduced the simulation results as well as explaining their physical origin. Notably, we found that the elastic stress of graphene is quasi-isotropic for all chiral directions in contrast to its anisotropic fracture behavior. Through the indentation simulations of graphene, we demonstrated that our rationale established in uniaxial (1D) tensile systems is applicable to 2D tensile systems as well.