Young's moduli of carbon materials investigated by various classical molecular dynamics schemes

Gayk, Florian; Ehrens, Julian; Heitmann, Tjark; Vorndamme, Patrick; Mrugalla, Andreas; Schnack, Jürgen

doi:10.1016/j.physe.2018.02.009

Cited by 13 publications

(7 citation statements)

References 40 publications

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“…In general, there is a large dispersion in both experimental and simulation values. Experimental results show Youngʼs modulus in the range 0.5-1.4 TPa, and simulations in the range 0.4-1.5 TPa [22][23][24][25]. Most experiments for pristine, nearly defect-free graphene, give values close to 1 TPa.…”

Section: Introductionmentioning

confidence: 95%

Simulated mechanical properties of finite-size graphene nanoribbons

et al. 2020

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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.

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Section: Introductionmentioning

confidence: 95%

Simulated mechanical properties of finite-size graphene nanoribbons

et al. 2020

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“…Measurements using atomic force microscope (AFM) nanoindentation [6][7][8] are supported or predicted by theoretical studies done by density functional theory (DFT) calculations [9][10][11] and molecular dynamics (MD) simulations [12][13][14][15][16][17][18][19][20][21][22][23][24] of graphene nanosystems. These studies confirm the high stiffness and strength of this two-dimensional (2D) material.…”

Section: Introductionmentioning

confidence: 85%

Role of defects in the mechanical properties of graphene-copper heterostructures

Felix¹,

Chávez-Castillo²,

Meza-Montes³

2022

Nanotechnology

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Through molecular dynamics simulations of tensile tests, the role that vacancies and Stone-Wales defects play in the mechanical properties of sandwich-like heterostructures, composed by graphene and two symmetric copper layers at nanoscale, is studied. The dependence on the armchair and zigzag chiralities of the graphene layer is also investigated. During elastic deformation, defects negatively affect the mechanical response. However, defective systems can show an improvement of the plastic properties. Vacancies have a stronger impact compared to Stone-Wales defects. Elasticity, toughness, and ductility are enhanced along the zigzag chirality, while stiffness is improved along the armchair direction. The Poisson’s ratio was calculated for all graphene-copper heterostructures. At a critical strain it becomes negative along the thickness direction, preserving the auxetic property at higher strains. In general, the behavior is governed by the graphene response. Our findings can be useful to understand the strengthening mechanism induced by this two-dimensional material in metals like copper and for the design of similar systems.

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“…As a side remark, it can be noted that other choices for the molecular dynamics potentials of the same family include Tersoff 1990 72 , Tersoff 1994 73 and the optimized Tersoff 69 . Previous studies 74 found that the Tersoff 1989 is able to produce the correct graphene structure e.g. carbon-carbon distance in graphene whereas the Tersoff 1990 and Tersoff 1994 models cannot.…”

Section: Methodsmentioning

confidence: 98%

Rheology of Water Flows Confined between Multilayer Graphene Walls

Korotkin

Karabasov

2020

Langmuir

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Water confined by hydrophilic materials shows unique transport properties compared to bulk water thereby offering new opportunities for development of nano-fluidic devices. Recent experimental and numerical studies showed that nano-confined water undergoes liquid-to-solid phase-like transitions depending on the degree of confinement. In the case of water confined by graphene layers, the Van der Waals forces are known to deform the graphene layers, whose bending leads to further non-uniform confinement effects. Despite the extensive studies of nano-confined water at equilibrium conditions, the interplay between the confinement and rheological water properties, such as viscosity, slip length and normal stress differences under shear flow conditions, is poorly understood. The current investigation uses a validated all-atom non-equilibrium molecular dynamics model to simultaneously analyse continuum transport and atomistic structure properties of water in a slit between two moving graphene walls under Couette flow conditions. A range of different slit widths and velocity strain rates are considered. It is shown that under the sub-nanometer confinement, water loses its rotational symmetry of a Newtonian fluid. In such conditions, water transforms into ice, where the atomistic structure is completely insensitive to the applied shear force and which behaves like a frozen slab sliding between the graphene walls. This leads to the shear viscosity increase, although not as dramatic as the normal force increase that contributes to the increased friction force reported in previous experimental studies. On the other end of the spectra, for flows at large velocity strain rates in moderate to large slits between the graphene walls, water is in the liquid state and reveals a shear thinning behavior.In this case, water exhibits a constant slip length on the wall, which is typical of liquids in the vicinity of hydrophobic surfaces.

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Young's moduli of carbon materials investigated by various classical molecular dynamics schemes

Cited by 13 publications

References 40 publications

Simulated mechanical properties of finite-size graphene nanoribbons

Simulated mechanical properties of finite-size graphene nanoribbons

Role of defects in the mechanical properties of graphene-copper heterostructures

Rheology of Water Flows Confined between Multilayer Graphene Walls

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