We present a tight-binding theory of the Dirac point resonances due to adsorbed atoms and molecules on an infinite two-dimensional graphene sheet based on the standard tight-binding model of the graphene π -band electronic structure and the extended Hückel model of the adsorbate and nearby graphene carbon atoms. The relaxed atomic geometries of the adsorbates and graphene are calculated using d...

We investigate the magnetic ordering in zigzag edged graphene nanoribbons under cross-ribbon electric fields by using the Hubbard model within the unrestricted Hatree-Fock approximation. In the absence of applied electric field, the ground state is an “edge-magnetized state” with magnetic moments mainly localized on the edges, where the moments on the two edges are mutually antiparallel. Under ...

A central result in the space geometry of closed twisted ribbons is Călugăreanu’s theorem (also known as White’s formula, or the Călugăreanu-White-Fuller theorem). This enables the integer linking number of the two edges of the ribbon to be written as the sum of the ribbon twist (the rate of rotation of the ribbon about its axis) and its writhe. We show that twice the twist is the average, over...

The spatial current distribution in H-terminated zigzag graphene nanoribbons (ZGNRs) under electrical bias is investigated using time-dependent density-functional theory solved on a real-space grid. A projected complex absorbing potential is used to minimize the effect of reflection at simulation cell boundary. The calculations show that the current flows mainly along the edge atoms in the hydr...

The state of vanishing friction known as superlubricity has important applications for energy saving and increasing the lifetime of devices. Superlubricity, as detected with atomic force microscopy, appears when sliding large graphite flakes or gold nanoclusters across surfaces, for example. However, the origin of the behavior is poorly understood because of the lack of a controllable nanoconta...

Using molecular dynamics simulations with semi-empirical potentials, we demonstrate a method to fabricate carbon nanotubes (CNTs) from graphene nanoribbons (GNRs), by periodically inserting appropriate structural defects into the GNR crystal structure. We have found that various defect types initiate the bending of GNRs and eventually lead to the formation of CNTs. All kinds of carbon nanotubes...

Using SMEAGOL, an ab initio computational method that combines the non-equilibrium Green's function formalism with density-functional theory, we calculated spin-specific electronic conduction in systems consisting of single Fen and Nin nanostructures (n = 1-4) adsorbed on a hydrogen-passivated zigzag graphene nanoribbon. For each cluster we considered both ferromagnetically and antiferromagneti...

Equilibrium molecular dynamics simulations show that graphene nanoribbons (GNRs) with zigzag edges have higher thermal conductivity (j) than armchair-edged ones, and the difference diminishes with increasing temperature or ribbon width. The dominant phonon wavelength for thermal transport can be much longer (by orders of magnitude) than the difference between the “roughness” of smooth zigzag an...

This paper introduces a new design of penternary inverter gate based on graphene nanoribbon field effect transistor (GNRFET). The penternary logic is one of Multiple-valued logic (MVL) circuits which are the best substitute for binary logic because of its low power-delay product (PDP) resulting from reduced complexity of interconnects and chip area. GNRFET is preferred over Si-MOSFET for circui...

We introduce the notion of a half-ribbon Hopf algebra, which is a Hopf algebra H along with a distinguished element t ∈ H such that (H, R,C) is a ribbon Hopf algebra, where R = (t ⊗ t)∆(t) and C = t. The element t is closely related to the topological ‘half-twist’, which twists a ribbon by 180 degrees. We construct a functor from a topological category of ribbons with half-twists to the categor...