Mechanical and Thermal Stability of Graphyne and Graphdiyne Nanoscrolls
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Mechanical and Thermal Stability of Graphyne and Graphdiyne Nanoscrolls Daniel Solis1, Cristiano F. Woellner1,2, Daiane D. Borges1, and Douglas S. Galvao1 1 Applied Physics Department, University of Campinas - UNICAMP, Campinas-SP 13083-959, Campinas-SP, Brazil 2 Department of Materials Science and Nano Engineering, Rice University, Houston, Texas, USA
ABSTRACT Graphynes and graphdiynes are carbon 2D allotrope structures presenting both sp2 and sp hybridized atoms. These materials have been theoretically predicted but due to intrinsic difficulties in their synthesis, only recently some of these structures have been experimentally realized. Graphyne nanoscrolls are structures obtained by rolling up graphyne sheets into papyrus-like structures. In this work, we have investigated, through fully atomistic reactive molecular dynamics simulations, the dynamics of nanoscroll formation for a series of graphyne (α, β, and δ types) structures. We have also investigated their thermal stability for a temperature range of 200-1000K. Our results show that stable nanoscrolls can be formed for all structures considered here. Their stability depends on a critical value of the ratio between length and height of the graphyne sheets. Our findings also show that these structures are structurally less stable then graphene-based nanoscrolls. This can be explained by the graphyne higher structural porosity which results in a decreased pi-pi stacking interactions.
INTRODUCTION With the materials science revolution created by the advent of graphene, there is a renewed interest in other 2D carbon allotropes, such as graphynes and graphdiynes [1-5] (Figure 1). Graphynes and graphdiynes are carbon 2D allotrope forms presenting both sp2 and sp carbon hybridized atoms and many different structures can be generated form these motifs [1-5]. The main difference between graphynes and graphdiynes are the number of acetylenic (one and two, respectively) groups connecting benzene rings. These materials have been theoretically predicted in 1987 [1], but due to intrinsic difficulties in their synthesis, only recently some structures have been experimentally realized [6,7]. These successful syntheses renewed the interest in these structures and remarkable electronic properties have been predicted for some of them [1-8]. Graphyne-like nanotubes [2] have already been successfully produced [7], but other structures remain to be explored. Among these potential new structures is worth mention the possibility of the existence of graphyne/graphdiyne nanoscrolls. Nanoscrolls are structures obtained by rolling up nanosheeets into papyrus-like topology [9] (Figure 1). Nanoscrolls present high radial flexibility and large solvent accessible surface area, which opens the possibility of many applications. This kind of structure has been already experimentally realized with different materials, such as graphene, graphene oxide and hexagonal boron nitride, for a recent scroll review see ref. [10]. In this work, we have investigated, through fully atomistic reactive mol
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