Mechanical Properties of Vacancy-containing Graphene and Graphite Estimated by Molecular Dynamics Simulations
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Mechanical Properties of Vacancy-containing Graphene and Graphite Estimated by Molecular Dynamics Simulations Akihiko Ito1,2 and Shingo Okamoto1 1 Mechanical Engineering Course, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan 2 Composite Materials Research Laboratories, Toray Industries, Inc., Masaki-cho 791-3193, Japan ABSTRACT Using molecular dynamics (MD) simulation, we investigated the mechanical properties of graphene and graphite, which contain cluster-type vacancies. We found that as the vacancy size increases, the tensile strength drastically decreases to at least 56% of that of pristine graphene, whereas Young's modulus hardly changes. In vacancy-containing graphene, we also found that slip deformation followed by fracture occurs under zigzag tension. In general, tensile strength decreases as the size of cluster-type vacancies increases. However, the tensile strength of graphene with a clustered sextuple vacancy increases as the vacancy disappears because slip deformation proceeds. Furthermore, we found that slip deformation by vacancies in graphite occurs less easily than in graphene. Our results suggest that the shape of vacancies affects the strengths of graphene and graphite. I#TRODUCTIO# Recently, carbon materials have attracted considerable attention because of their superior mechanical and electric properties. Carbon materials such as diamond, graphene, carbon nanotubes, and fullerene have various properties because of differences in the types of bonds and atomistic structures. In particular, graphene has a rigidity and strength that are nearly equal to those of diamond, as well as novel electronic properties including high electron mobility. Thus, studies on graphene and graphite composed of graphene layers have recently been increasing [15]. The applications of graphene to nano electro mechanical systems are expected. Then measurements of its physical properties such as elastic properties have been investigated [3, 4]. Defects often affect the mechanical and electronic properties of materials. Recently, there have been reports of experimental studies on defects (i.e., vacancies, dislocations, grain boundaries) in graphene layers [5-7]. It is important to clarify the influence of defects on the mechanical and electrical properties of graphene and graphite when producing carbon materials with high performance. In this study, we investigated the influence of vacancy size on the mechanical properties of graphene and graphite. In addition, we clarified the difference of atomistic structure during tensile loadings between graphene and graphite. METHOD In the present study, we used two types of interatomic potentials: the second-generation reactive empirical bond order (REBO) and Lennard-Jones potentials. The second-generation REBO potential for covalent bonds is shown in eq. (1) [8].
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EREBO = ∑∑ VR (rij ) − Bij*VA (rij ) i
j >i
(1)
The terms VR(rij) and VA(rij) represent pair-additive interactions that reflect interatomic repulsions and attractions, respe
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