Mechanical Properties Of Graphene Nanoribbons Research Articles

A Study on Different Bandwidths and Rim Decorations’ Influence on the Mechanical Properties of Graphene Nanoribbon

This paper structured the Graphene Nanoribbon with different bandwidths and rim decorations and obtained the ideal strength and modulus of elasticity based on the calculation under the First Principle. It can be known that the mechanical properties of Graphene Nanoribbon are close to that of graphene, which have less changes with different bandwidth. However, the mechanical properties would be influenced by different decorations which may change the electronic connection state of edge carbon atoms. The results found in this paper can provide some reference for researchers to study the mechanical properties of graphene nanoribbons in the future.

The Effect of 555-777 Defect on Mechanical Properties of Graphene Nanoribbon

In this study, the effects of 555-777 defect on Young’s modulus, fracture strength and fracture strain of armchair graphene nanoribbons (AGNRs) and zigzag graphene nanoribbons (ZGNRs) were investigated by using Molecular Dynamics simulations under uniaxial tension. The simulation results show that 555-777 defect significantly reduces the fracture strength and fracture strain of AGNRs and ZGNRs, but has little effect on Young's modulus. The influence of 555-777 defect on the mechanical properties of AGNRs is greater than that of ZGNRs. This study provides a better understanding of mechanical properties of graphene nanoribbons.

Simulated mechanical properties of finite-size graphene nanoribbons

There are many simulation studies of mechanical properties of graphene nanoribbons (GNR), but there is a lack of agreement regarding elastic and plastic behavior. In this paper we aim to analyze mechanical properties of finite-size GNR, including elastic modulus and fracture, as a function of ribbon size. We present classical molecular dynamics simulations for three different empirical potentials which are often used for graphene simulations: AIREBO, REBO-scr and REAXFF. Ribbons with and without H-passivation at the borders are considered, and the effects of strain rate and different boundaries are also explored. We focus on zig-zag GNR, but also include some armchair GNR examples. Results are strongly dependent on the empirical potential employed. Elastic modulus under uniaxial tension can depend on ribbon size, unlike predictions from continuum-scale models and from some atomistic simulations, and fracture strain and progress vary significantly amongst the simulated potentials. Because of that, we have also carried out quasi-static ab-initio simulations for a selected size, and find that the fracture process is not sudden, instead the wave function changes from Blöch states to a strong interaction between localized waves, which decreases continuously with distance. All potentials show good agreement with DFT in the linear elastic regime, but only the REBO-scr potential shows reasonable agreement with DFT both in the nonlinear elastic and fracture regimes. This would allow more reliable simulations of GNRs and GNR-based nanostructures, to help interpreting experimental results and for future technological applications.

An analytic investigation for the edge effect on mechanical properties of graphene nanoribbons

We derive analytical expressions for the Young's modulus and the Poisson's ratio of the graphene nanoribbon, in which free edges are warped by the compressive edge stress. Our analytical formulas explicitly illustrate the reduction of the Young's modulus by the warped free edges, leading to the obvious width dependence for the Young's modulus of the graphene nanoribbon. The Poisson's ratio is also reduced by the warped free edges, and negative Poisson's ratio can be achieved in the graphene nanoribbon with an ultra-narrow width. These results are comparable with previous theoretical works.

Mechanical properties of graphene nanoribbons under uniaxial tensile strain

Based on the density functional theory with the generalized gradient approximation, we investigated the mechanical properties of graphene nanoribbons in terms of their edge shape under a uniaxial tensile strain. The nanoribbons with armchair and zigzag edges retain their structure under a large tensile strain, while the nanoribbons with chiral edges are fragile against the tensile strain compared with those with armchair and zigzag edges. The fracture started at the cove region, which corresponds to the border between the zigzag and armchair edges for the nanoribbons with chiral edges. For the nanoribbons with armchair edges, the fracture started at one of the cove regions at the edges. In contrast, the fracture started at the inner region of the nanoribbons with zigzag edges. The bond elongation under the tensile strain depends on the mutual arrangement of covalent bonds with respect to the strain direction.

Strain–displacement relations for strain engineering in single-layer 2d materials

We investigate the electromechanical coupling in single-layer 2d materials. For non-Bravais lattices, we find important corrections to the standard macroscopic strain-microscopic atomic-displacement theory. We put forward a general and systematic approach to calculate strain–displacement relations for several classes of 2d materials. We apply our findings to graphene as a study case, by combining a tight binding and a valence force-field model to calculate electronic and mechanical properties of graphene nanoribbons under strain. The results show good agreement with the predictions of the Dirac equation coupled to continuum mechanics. For this long wave-limit effective theory, we find that the strain–displacement relations lead to a renormalization correction to the strain-induced pseudo-magnetic fields. A similar renormalization is found for the strain-induced band-gap of black phosphorous. Implications for nanomechanical properties and electromechanical coupling in 2d materials are discussed.

Contact-dependent mechanical properties of graphene nanoribbons: an ab initio study

The mechanical properties of graphene nanoribbons on Ni(111) surfaces with different contact sizes are investigated by means of density functional theory. For finite contact sizes, the stress behavior of graphene nanoribbons on metal electrodes is likely to be similar to that of suspended graphene, however the critical strain is not reached due to the sliding friction at the interface. The competition between frictional and external forces is responsible for the nonmonotonic stress behavior. It is indicated that the stick-slip motions of graphene on Ni(111) are as a result of applied external forces on the GNR/metal contact. Moreover, the effect of vacancies and chemical doping on the sliding friction are addressed. Graphene starts to slide on the surface under a much lower external force in the case of defected graphene, due to the weaker binding to the surface. For infinite contact sizes, a linear relationship between stress and strain are found until structural failure occurs by 11% applied strain. The corresponding critical strain for the suspended GNR (without electrodes) has been found to be 13%.

Mechanical properties of graphene nanoribbons with disordered edges

Using density functional theory (DFT), we investigate mechanical properties and failure characteristics of chiral and achiral graphene nanoribbons. Specifically, we study the dependence of maximum strength, Young’s modulus and failure pattern of nanoribbons on their widths, edge chirality and passivation. Besides investigating nanoribbons with perfect edges, nanoribbons with defective edges are considered and the impacts of the presence of Klein or edge pentagonal defects on the properties of nanoribbons are studied. Our DFT results show that as the width of achiral ribbons are reduced, their strength increases. Moreover, significant size effects on the Poisson’s ratio of armchair ribbons and Young’s modulus of zigzag ribbons are observed. The DFT modeling predicts that the presence of defects reduce the strength of chiral nanoribbons while defects might counter intuitively increase the Young’s modulus of chiral nanoribbons. The first-principle simulations show that achiral nanoribbons always fail along a zigzag surface, however the failure pattern of chiral nanoribbons can be more complicated and be accompanied by the nucleation of other kind of defects such as pentagonal–heptagonal rings prior to failure.

Size Dependent Mechanical Properties of Graphene Nanoribbons: Molecular Dynamics Simulation

Strain engineering is an effective method to tune the band gap and electronic transport properties of graphene nanoribbons (GNRs). However, strain/stress field may promote the system deviating from the equilibrium state, and the mechanical stability will become one of the key issues for reliable services of relevant devices. In this paper, the size-dependent mechanical properties of GNRs under tensile loading were studied by Molecular Dynamics (MD) simulations. The results indicate that the yield stress of both zigzag and armchair GNRs decreases with the ribbon length changing from 240 Å to 30 Å. However, the ductility of armchair GNRs was significantly improved. Radial Distribution Function (RDF) was employed to analyze the evolution of atomic configurations. It showed that lattice shearing is the main mechanism for the ductility of armchair GNRs.

ELECTRONIC, MAGNETIC, AND MECHANICAL PROPERTIES OF LINE-DEFECT EMBEDDED GRAPHENE NANORIBBONS: A FIRST-PRINCIPLES STUDY

We use first-principles method to investigate the electronic, magnetic, and mechanical properties of graphene nanoribbons (GNRs) with extended line defect. Particular attention has been placed on zigzag GNR with 5-8-5 line defect and armchair GNR with 4-8 line defect. The results show that the band gaps of GNRs can be effectively tuned by line defect, which depend on both their widths and the position of defect. The line-defect embedded GNRs are either metals or semiconductor with markedly reduced band gap. The band-gap reduction is attributed to the defect-induced impurity states. In particular, the metallic line-defect embedded zigzag GNRs are ferromagnetic at ground state, while those semiconducting ones are antiferromagnetic. Upon the line-defect embedded armchair GNRs, the band gaps vary periodically with the increasing widths. Our results imply the potential applications of line-defect embedded GNRs at nanoscale electronics.

Mechanical failure of zigzag graphene nanoribbons under tensile strain induced by edge reconstruction

The structural and mechanical properties of graphene nanoribbons (GNRs) under uniaxial tensile strain are studied by density functional theory. The ideal strength of a zigzag GNR (120 GPa) is close to that of pristine graphene. However, for a GNR with both edges reconstructed to pentagon–heptagon pairs (from hexagon–hexagon pairs) it decreases to 94 GPa and the maximum tensile strain is reduced to 15%. Our results constitute a comprehensive picture of the edge structure effect on the mechanical properties of GNRs.

Parametric study of elastic mechanical properties of graphene nanoribbons by a new structural mechanics approach

The elastic mechanical behavior of different sized zigzag and armchair graphene nanoribbons is numerically investigated and predicted using a new structural mechanic approach. According to the proposed method three dimensional, two nodded spring elements of three degrees of freedom per node, which remain straight when deformed, are combined in order to simulate realistically the interatomic interactions appearing within the graphene nanostructure. The computed variations of mechanical elastic properties are fitted by appropriate size dependent non-linear functions of two independent variables i.e. length and width, in order to express the analytical rules governing the elastic behavior of graphene nanoribbons within specific dimension limits. The numerical results, which are compared with corresponding data given in the open literature, demonstrate thoroughly the important influence of size and chirality of a narrow graphene monolayer on its elastic behavior.

Size-dependent non-linear mechanical properties of graphene nanoribbons

An atomistic, spring-based, non-linear finite element method is implemented in order to predict the non-linear mechanical behavior of graphene nanoribbons. According this method, appropriate non-linear springs are utilized to simulate each interatomic interaction. Their force–displacement curve follows the relation between the first differentiation of the potential energy of the corresponding interaction-bond deformation. The potential which corresponds to the bond angle variation is simulated by a torsional spring, while the bond stretching is simulated by a uniaxial compression/extension spring. The linear approximation, commonly made in the literature for the bond angle bending interaction, is not followed here and thus the overall non-linear response of the specific interaction is accurately introduced into the model. Following the proposed formulation, the tensile uniaxial stress–strain behavior for various graphene nanoribbons, of zigzag as well as armchair orientation, arise. The results demonstrate that the linear and non-linear mechanical properties are strongly dependent on the structure as well as on the size of the graphene strip tested.

Nonlinear Mechanical Properties of Graphene Nanoribbons

ABSTRACTBased on atomistic simulations, the nonlinear elastic properties of monolayer graphene nanoribbons under quasistatic uniaxial tension are predicted, emphasizing the effect of edge structures (armchair and zigzag, without and with hydrogen passivation). The results of atomistic simulations are interpreted using a theoretical model of thermodynamics, which enables determination of the nonlinear functions for the strain-dependent edge energy and the hydrogen adsorption energy, for both zigzag and armchair edges. Due to the edge effects, the initial Young’s modulus of graphene nanoribbons under infinitesimal strain varies with the edge chirality and the ribbon width. Furthermore, it is found that the nominal strain to fracture is considerably lower for armchair graphene nanoribbons than for zigzag ribbons. Two distinct fracture mechanisms are identified, with homogeneous nucleation for zigzag ribbons and edge-controlled heterogeneous nucleation for armchair ribbons.

Atomistic simulations of mechanical properties of graphene nanoribbons

The mechanical behavior of graphene nanoribbons (GNRs) was investigated by molecular dynamics (MD) simulations. The simulation results showed that GNRs behave nonlinear elastically under tensile loads. When the strain exceeds 18%, the stress stiffening causes an increase in the Young's modulus. The width of a GNR has slight effects on the Young modulus and fracture strength. The maximum strain at which fracture occurs can reach 30.26% with an intrinsic strength of about 0.175 TPa. The excellent flexibility is attributed to the elongation of the C C bonds and the variations of the bond angles.

Mechanical properties of graphene nanoribbons

Herein, we investigate the structural, electronic and mechanical properties of zigzag graphenenanoribbons in the presence of stress by applying density functional theory within the GGA-PBE(generalized gradient approximation-Perdew–Burke–Ernzerhof) approximation. The uniaxialstress is applied along the periodic direction, allowing a unitary deformation in the range of ± 0.02%. The mechanical properties show a linear response within that range while a nonlineardependence is found for higher strain. The most relevant results indicate that Young’smodulus is considerable higher than those determined for graphene and carbon nanotubes.The geometrical reconstruction of the C–C bonds at the edges hardens the nanostructure.The features of the electronic structure are not sensitive to strain in this linear elasticregime, suggesting the potential for using carbon nanostructures in nano-electronic devicesin the near future.