A tricotage-like failure of nanographene

Abstract

The response of a nanographene sheet to external stresses was considered in terms of a mechanochemical reaction. The quantum chemical realization of the approach was based on the coordinate-of-reaction concept for the purpose of introducing a mechanochemical internal coordinate (MIC) that specifies a deformational mode. The related force of response is calculated as the energy gradient along the MIC, while the atomic configuration is optimized over all of the other coordinates under the MIC constant-pitch elongation. The approach is applied to the benzene molecule and (5,5) nanographene. A drastic anisotropy in the microscopic behavior of both objects under elongation along a MIC was observed when the MIC was oriented either along or normally to the C-C bond chain. Both the anisotropy and the high stiffness of the nanographene originate from the response of the benzenoid unit to stress.

Mechanochemical Reaction in Graphane under Uniaxial Tension

“…Molecular dynamic calculations applied to long armchair-edged graphene nanoribbon [8] have thrown light on a peculiarity of the ribbon deformation disclosing the formation of one-atom chain in due course of uniaxial tension, which was confirmed experimentally [9,10]. This peculiar behavior has been highlighted and given in detail later from the viewpoint of mechanochemical reaction that lays the foundation of the deformation-failurerupture process occurred in nanographenes [11,12]. The quantum-mechanochemicalreaction-coordinate (QMRC) approach used in the study has disclosed atomically matched peculiarities of the mechanical behavior, highlighted the origin of the mechanical anisotropy of graphene, and made allowance for tracing a deformationstimulated change in the chemical reactivity of both nanographene body and its individual atoms.…”

“…[23], respectively. The dependences of energy, force, stress and N D on either elongation or strain exhibit mechanical behaviour of the object at all the stages of the deformation considered at the atomic level [11,12]. The latter presents changing in the chemical activity of the body in due course of deformation.…”

“…The MICs related to graphane in the current study were aligned either along the C-C bonds or (5,5)nanographene normally to the latter as shown in Fig.1. The two sets distinguish two deformational modes that correspond to tensile deformation applied to zigzag and armchair edges of the sheets due to which they are nominated as zg and ach modes as was done previously in the case of graphene [11,12]. The right ends of the MICs in Fig.1 are clamped (the corresponding carbon atoms are immobilized) while the left ends move in a stepwise manner with increment δL=0.1Å at each step so that the current MIC length constitutes…”

“…We have used the (n a ,n z ) nomenclature of rectangular nanographenes suggested in [19]. subjected to uniaxial tensile deformation as well [11,12]. The identity of the carbon cores of both objects provides a perfect basis for a comparative study of the mechanical behavior of the pristine and chemically modified bodies.…”

“…The identity of the carbon cores of both pristine graphene [11,12] and graphane (5,5) nanosheets makes it possible to skip some details concerning the description of the sheet mechanical behavior presented in [11,12] and to mainly concentrate on this behavior difference under hydrogenation. A sketch of the main characteristics related to the ach mode of the graphene tensile deformation and failure is shown in Fig.2a.…”