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Tight-binding molecular dynamics simulation study of carbon nanomaterials Gun-Do Lee a, Cai-Zhuang Wang b, Euijoon Yoon a, Nongmoon Hwang a, and Kai-Ming Ho b a Department of Materials Science and Engineering, Seoul National University, Seoul, Korea b Department of Physics and Astronomy, Iowa State University, Ames, IA, USA Carbon nanomaterials, such as carbon nanotubes (CNTs), fullerenes, graphene, nanoporous carbons, and nano-diamonds, have been objects attracting tremendous attention due to their applicability for energy storage, nano-electromechanic devices, gas sensing, and drug delivery materials for recent decades. Various simulation methods have been used to study structural and electronic properties of carbon nanomaterials. Among them, ab initio and classical molecular dynamics (MD) simulations have been continuously performed to investigate carbon nanomaterials. Even if ab initio method is very accurate, it is very expensive and takes long time. Classical MD simulation methods have been sometimes found to be insufficient in describing properties of nanoscale materials. In order to overcome weak points of both methods, tight-binding method has been attempted. Environment-dependent tight binding (EDTB) method gives accurate results on a level comparable to ab initio calculation about diamond and amorphous carbon materials. We modified the original EDTB carbon potential by incorporating an angle dependence factor into the repulsive energy to describe correctly native defects in CNTs and graphene layers. Recently, we performed tightbinding molecular dynamics (TBMD) simulation by using modified EDTB carbon potential to study vacancy reconstruction in CNTs and graphene and evaporation processes at graphene nanoribbon (GNR) edges. In this study, we found that a double vacancy in graphene is reconstructed into a 555-777 composed of triple pentagons and triple heptagons which has been confirmed by a recent experiment [1]. Pentagonheptagon (5-7) pairs are found to play an important role in the reconstruction of vacancy in CNTs. In the TBMD simulation of GNR, we found the evaporation of carbon atoms from both the zigzag and armchair edges is preceded by the formation of heptagon rings, which serve as a gateway for carbon atoms to escape. In the simulation for a GNR armchair-zigzag-armchair junction, carbon atoms are evaporated row-by-row from the outermost row of the zigzag edge, which is in excellent agreement with recent experiments [1,2]. These results can be applied to nano-electronic devices fabrication through the temperature-controlled edge structure of GNR. [1] C. O. Girit et al. Science 323, 1705 (2009) [2] X. Jia et al. Science 323, 1701 (2009)