The effect of STW defects on the mechanical properties and fracture toughness of pristine and hydrogenated graphene
21 Jun 2017-Physical Chemistry Chemical Physics (The Royal Society of Chemistry)-Vol. 19, Iss: 24, pp 16023-16037
TL;DR: An overall improvement in the fracture toughness of pristine graphene as well as graphene containing hydrogen at the crack edges was predicted in this work.
Abstract: Graphene is emerging as a versatile material with a diverse field of applications Synthesis techniques for graphene introduce several topological defects such as vacancies, dislocations and Stone–Thrower–Wales (STW) defects Among them STW defects are generated without deleting any atom from the lattice position, but are introduced by rotating single C–C bonds In this article, molecular dynamics based simulations have been performed to study the effect of STW defects on the fracture toughness of pristine graphene as well as graphene with crack edges passivated with hydrogen atoms STW defects help in generating out of plane displacement in conjunction with redistribution of stress around the crack edges that can be used to improve the fracture toughness of brittle graphene An overall improvement in the fracture toughness of pristine graphene as well as graphene containing hydrogen at the crack edges was predicted in this work
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TL;DR: A systematic classification and physicochemical description of approaches leading to equip graphene with magnetic properties, including introduction of point and line defects into graphene lattices, spatial confinement and edge engineering, doping of graphene lattice with foreign atoms, and sp3 functionalization are discussed.
Abstract: Graphene, a single two-dimensional sheet of carbon atoms with an arrangement mimicking the honeycomb hexagonal architecture, has captured immense interest of the scientific community since its isolation in 2004. Besides its extraordinarily high electrical conductivity and surface area, graphene shows a long spin lifetime and limited hyperfine interactions, which favors its potential exploitation in spintronic and biomedical applications, provided it can be made magnetic. However, pristine graphene is diamagnetic in nature due to solely sp2 hybridization. Thus, various attempts have been proposed to imprint magnetic features into graphene. The present review focuses on a systematic classification and physicochemical description of approaches leading to equip graphene with magnetic properties. These include introduction of point and line defects into graphene lattices, spatial confinement and edge engineering, doping of graphene lattice with foreign atoms, and sp3 functionalization. Each magnetism-imprinting strategy is discussed in detail including identification of roles of various internal and external parameters in the induced magnetic regimes, with assessment of their robustness. Moreover, emergence of magnetism in graphene analogues and related 2D materials such as transition metal dichalcogenides, metal halides, metal dinitrides, MXenes, hexagonal boron nitride, and other organic compounds is also reviewed. Since the magnetic features of graphene can be readily masked by the presence of magnetic residues from synthesis itself or sample handling, the issue of magnetic impurities and correct data interpretations is also addressed. Finally, current problems and challenges in magnetism of graphene and related 2D materials and future potential applications are also highlighted.
162 citations
TL;DR: In this article, different types of interatomic potentials can be used for the modeling of graphene, hexagonal boron nitride (h-BN) and corresponding nanocomposites, and further elaborates on developments and challenges associated with the classical mechanics-based approach along with synergic effects of these nano reinforcements on host polymer matrix.
Abstract: Due to their exceptional properties, graphene and hexagonal boron nitride (h-BN) nanofillers are emerging as potential candidates for reinforcing the polymer-based nanocomposites. Graphene and h-BN have comparable mechanical and thermal properties, whereas due to high band gap in h-BN (~5 eV), have contrasting electrical conductivities. Atomistic modeling techniques are viable alternatives to the costly and time-consuming experimental techniques, and are accurate enough to predict the mechanical properties, fracture toughness, and thermal conductivities of graphene and h-BN-based nanocomposites. Success of any atomistic model entirely depends on the type of interatomic potential used in simulations. This review article encompasses different types of interatomic potentials that can be used for the modeling of graphene, h-BN, and corresponding nanocomposites, and further elaborates on developments and challenges associated with the classical mechanics-based approach along with synergic effects of these nano reinforcements on host polymer matrix.
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93 citations
TL;DR: In this article, the effect of grain boundaries on the interfacial properties of bi-crystalline graphene/polyethylene based nanocomposites was investigated, where molecular dynamics based atomistic simulations were performed in conjunction with the reactive force field parameters to capture atomic interactions within graphene and polyethylene atoms.
69 citations
TL;DR: In this article, the influence of grain boundaries on the interfacial thermal conductance between bi-crystalline graphene and polyethylene in a nanocomposite was investigated.
Abstract: The objective of this investigation was to elaborate on the influence of grain boundaries on the interfacial thermal conductance between bi-crystalline graphene and polyethylene in a nanocomposite. Reverse non-equilibrium molecular dynamics simulations were implemented in combination with Lennard-Jones and reactive force field interatomic potential parameters. According to the simulation results, high-energy grain boundary atoms in bi-crystalline graphene played a substantial role in enhancing the interfacial thermal conductance values. To further illuminate the mechanisms of enhanced graphene-polyethylene interfacial thermal conductance in the presence of grain boundaries, a systematic study on the vibrational density of states and structural evolution was also performed. It was found that the vibrational coupling between bi-crystalline graphene and the polymer was enhanced; whereas a decline in the radial density profile and coordination number resulted in a shifting of the in-plane vibrational modes such that they amalgamated with those of the polyethylene matrix. Thus, bi-crystalline graphene can be considered to be a superior potential reinforcement for nanocomposites as compared to the pristine configuration for applications in thermoelectric and thermal interface materials.
63 citations
TL;DR: The molecular dynamics based simulations performed in this article help to conclude that the spatial distribution and concentration of functional groups significantly affects the fracture behavior of GO nanosheets.
Abstract: The aim of this article is to study the effects of functional groups such as hydroxyl, epoxide and carboxyl on the fracture toughness of graphene These functional groups form the backbone of the intrinsic atomic structure of graphene oxide (GO) Molecular dynamics based simulations were performed in conjunction with reactive force field parameters to capture the Mode-I fracture toughness of functionalised graphene Simulations were performed in stages, to study the effect of these functional groups, individually as well as all together on the fracture toughness of GO nanosheets The molecular dynamics based simulations performed in this article helps us to conclude that the spatial distribution and concentration of functional groups significantly affects the fracture behavior of GO nanosheets
60 citations
References
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TL;DR: The dynamical steady-state probability density is found in an extended phase space with variables x, p/sub x/, V, epsilon-dot, and zeta, where the x are reduced distances and the two variables epsilus-dot andZeta act as thermodynamic friction coefficients.
Abstract: Nos\'e has modified Newtonian dynamics so as to reproduce both the canonical and the isothermal-isobaric probability densities in the phase space of an N-body system. He did this by scaling time (with s) and distance (with ${V}^{1/D}$ in D dimensions) through Lagrangian equations of motion. The dynamical equations describe the evolution of these two scaling variables and their two conjugate momenta ${p}_{s}$ and ${p}_{v}$. Here we develop a slightly different set of equations, free of time scaling. We find the dynamical steady-state probability density in an extended phase space with variables x, ${p}_{x}$, V, \ensuremath{\epsilon}\ifmmode \dot{}\else \.{}\fi{}, and \ensuremath{\zeta}, where the x are reduced distances and the two variables \ensuremath{\epsilon}\ifmmode \dot{}\else \.{}\fi{} and \ensuremath{\zeta} act as thermodynamic friction coefficients. We find that these friction coefficients have Gaussian distributions. From the distributions the extent of small-system non-Newtonian behavior can be estimated. We illustrate the dynamical equations by considering their application to the simplest possible case, a one-dimensional classical harmonic oscillator.
17,939 citations
TL;DR: In this article, the authors compared the canonical distribution in both momentum and coordinate space with three recently proposed constant temperature molecular dynamics methods by: (i) Nose (Mol. Phys., to be published); (ii) Hoover et al. [Phys. Rev. Lett. 77, 63 (1983); and (iii) Haile and Gupta [J. Chem. Phys. 79, 3067 (1983).
Abstract: Three recently proposed constant temperature molecular dynamics methods by: (i) Nose (Mol. Phys., to be published); (ii) Hoover et al. [Phys. Rev. Lett. 48, 1818 (1982)], and Evans and Morriss [Chem. Phys. 77, 63 (1983)]; and (iii) Haile and Gupta [J. Chem. Phys. 79, 3067 (1983)] are examined analytically via calculating the equilibrium distribution functions and comparing them with that of the canonical ensemble. Except for effects due to momentum and angular momentum conservation, method (1) yields the rigorous canonical distribution in both momentum and coordinate space. Method (2) can be made rigorous in coordinate space, and can be derived from method (1) by imposing a specific constraint. Method (3) is not rigorous and gives a deviation of order N−1/2 from the canonical distribution (N the number of particles). The results for the constant temperature–constant pressure ensemble are similar to the canonical ensemble case.
13,921 citations
TL;DR: This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
Abstract: Graphene is a wonder material with many superlatives to its name. It is the thinnest known material in the universe and the strongest ever measured. Its charge carriers exhibit giant intrinsic mobility, have zero effective mass, and can travel for micrometers without scattering at room temperature. Graphene can sustain current densities six orders of magnitude higher than that of copper, shows record thermal conductivity and stiffness, is impermeable to gases, and reconciles such conflicting qualities as brittleness and ductility. Electron transport in graphene is described by a Dirac-like equation, which allows the investigation of relativistic quantum phenomena in a benchtop experiment. This review analyzes recent trends in graphene research and applications, and attempts to identify future directions in which the field is likely to develop.
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TL;DR: The Open Visualization Tool (OVITO) as discussed by the authors is a 3D visualization software designed for post-processing atomistic data obtained from molecular dynamics or Monte Carlo simulations, which is written in object-oriented C++, controllable via Python scripts and easily extendable through a plug-in interface.
Abstract: The Open Visualization Tool (OVITO) is a new 3D visualization software designed for post-processing atomistic data obtained from molecular dynamics or Monte Carlo simulations. Unique analysis, editing and animations functions are integrated into its easy-to-use graphical user interface. The software is written in object-oriented C++, controllable via Python scripts and easily extendable through a plug-in interface. It is distributed as open-source software and can be downloaded from the website http://ovito.sourceforge.net/.
8,956 citations
TL;DR: This work reviews recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.
Abstract: Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.
7,987 citations