(361e) Edge Atomic Diffusion in Graphene Nanoribbons and Defect-Engineered Graphene

Edge atomic diffusion underlies numerous transport mechanisms in graphene nanoribbons (GNRs) and defect-engineered graphene, which can be exploited to develop patterning processes in graphene-based nanostructures and metamaterials. Toward this goal, in this presentation, we report the results of a systematic atomic-scale analysis of edge atomic diffusion in GNRs with different edge types at high temperature. The analysis is based on molecular-dynamics (MD) simulations according to a reliable interatomic interaction potential. We have analyzed MD trajectories in both zigzag- and armchair-edged GNRs, computed the respective edge atomic diffusivities as a function of temperature, and determined the activation energy barriers for edge atomic diffusion through the corresponding Arrhenius plots. From detailed analysis of the MD trajectories, we have identified the underlying atomic diffusion mechanisms, including adatom hopping and carbon ring reconstructions. Using climbing-image nudged elastic band (NEB) calculations, we have constructed the optimal kinetic pathways for these diffusion mechanisms and the corresponding activation barriers, which provide a comprehensive interpretation to the computed Arrhenius plots for edge diffusion. The identified diffusion mechanisms and predicted energy barriers have been validated through targeted first-principles density functional theory (DFT) calculations. Furthermore, we have studied systematically atomic diffusion on edges of nanopores in graphene sheets, examined its dependence on pore morphology and size, and used the results to analyze and interpret the dynamics of pore coalescence in graphene driven by an attractive pore-pore interaction. In addition to obtaining a fundamental understanding of edge atomic diffusion in graphene, our study sets the stage for further coarse-grained modeling of morphological dynamics in defect-engineered graphene and graphene nanoribbons.