Transformation of a graphene nanoribbon into a hybrid 1D nanoobject with alternating double chains and polycyclic regions

Abstract

Molecular dynamics simulations show that a graphene nanoribbon with alternating regions which are one and three hexagons wide can transform into a hybrid 1D nanoobject with alternating double chains and...

Optimal model of semi-infinite graphene for ab initio calculations of reactions at graphene edges by the example of zigzag edge reconstruction

“…The latter result means that images of 57 pairs should be separated by at least 6 hexagons (about 15 Å). Such requirements on the model GNRs should be taken into account in further studies of generation of subsequent 57 pairs for consecutive zigzag edge reconstruction and simulations of other phenomena at graphene edges such as edge etching [42,44,54,55], formation of atomic chains [38,56,57], migration of atoms [22,37,53], graphene growth [58][59][60], chemical absorption [14,21,25,27,29,[31][32][33][34][35][36], etc.…”

“…There is, nevertheless, a considerable scatter in activation barriers and reaction energies reported. For formation of an isolated pentagon-heptagon (57) pair (see Fig. 2c), the values of 1.12 eV [12] and 1.61 eV [22], 1.80 eV [13] were obtained via DFT calculations for zigzag graphene nanoribbons (ZGNRs) and 2.41 eV for the zigzag edge of a graphene flake [48] (see also [5] for review).…”

“…2c) to come up with the adequate model for studies of reactions at graphene edges. This model can be later applied for DFT studies of formation of subsequent 57 pairs for complete zigzag edge reconstruction as well as other phenomena at graphene edges such as edge etching [42,44,54,55], formation of atomic chains [38,56,57], migration of atoms [22,37,53], graphene growth [58][59][60], chemical absorption [14,21,25,27,29,[31][32][33][34][35][36], etc. As a result, we also obtain the converged reaction energy and activation barrier for formation of an isolated 57 pair at the zigzag graphene edge.…”

Reconstruction of Zigzag Graphene Edges: Energetics, Kinetics, and Residual Defects

“…27,29 In the present Letter we consider pristine edges, which can be obtained by annealing at 600 • C 24,32 or irradiation by electrons with the kinetic energy insufficient to cause carbon bond rearrangements. 40 This is the case for typical transmission electron microscopy studies of the reconstruction. 24,[27][28][29][30][31] Previous calculations 14,19,23,24,36 for pristine graphene edges gave a significant barrier for the first reconstruction step, formation of the first 57 pair.…”

“…In spite of being more stable thermodynamically than other pristine graphene edges, reconstructed zigzag edges are not the most abundant ones in the experiments. ,− The reason can be a large barrier for the reconstruction, , edge contamination, or the effect of electron irradiation on edge stability. , In the present Letter, we consider pristine edges, which can be obtained by annealing at 600 °C , or irradiation by electrons with the kinetic energy insufficient to cause carbon bond rearrangements . This is the case for typical transmission electron microscopy studies of the reconstruction. ,− Previous calculations ,,,, for pristine graphene edges gave a significant barrier for the first reconstruction step, formation of the first 57 pair.…”