464747 Pore-Pore and Pore-Edge Interactions in Graphene Sheets and Nanoribbons

Monday, November 14, 2016: 2:35 PM
Carmel I (Hotel Nikko San Francisco)
Lin Du, Department of Chemical Engineering, University of Massachusetts, Amherst, Amherst, MA and Dimitrios Maroudas, Department of Chemical Engineering, University of Massachusetts Amherst, Amherst, MA

Defect engineering of graphene is a promising approach toward fabrication of carbon-based two-dimensional materials with unique properties and function. The assembly of nanopores, formed by irradiation or lithographically, is of particular interest for developing patterning strategies in graphene sheets and graphene nanoribbons (GNRs). Toward this end, a fundamental understanding is required of the interactions between such pores in graphene sheets and between pores in graphene nanoribbons and the nanoribbon edges and how these interactions mediate pore migration and coalescence processes.

In this presentation, we report a systematic analysis of pore-edge interactions in GNRs and pore-pore interactions in graphene sheets based on atomic-scale simulations according to reliable interatomic potentials. Based on molecular-statics (MS) computations, we have found that when two pore edges or a pore edge and a GNR edge are in close proximity (a few bond lengths), their interactions are strongly attractive and lead to pore coalescence or drive the pore to the GNR edge, thus changing the GNR edge morphology. At longer distances between pore edges or between pore and GNR edges, elastic interaction potentials based on elastic inclusion theory can describe the MS simulation results very well, and can be used for coarse-grained modeling of pore assembly in graphene and GNRs. We have characterized systematically the effects of pore size and GNR edge type on these interaction potentials. We have found that the GNR edge type has a very weak effect on the pore-edge interaction potential, while the pore size and, thus, curvature has a stronger effect on the interaction. With this understanding of pore-pore and pore-GNR edge interactions, we designed and conducted molecular-dynamics (MD) simulations of nanopore dynamics at high temperature in the vicinity of both GNR edges and other pores in graphene sheets. We found that the pore-edge and pore-pore interactions provide thermodynamic driving forces for nanopore migration toward the GNR edge or toward a larger pore through a sequence of carbon ring reconstructions and facilitate pore coalescence and GNR edge morphological evolution. Finally, we have conducted nudged elastic band calculations to construct the optimal pore migration paths and obtain a fundamental understanding of the mechanisms for driven pore migration and coalescence.

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