Electronic Structure And Electromagnetic Properties Of Nanometer Graphene:First-principles Study

The magnetic properties of various finite-shaped graphene fragments were studied through the electronic structure first-principles calculations with the all-electron numerical orbital scheme based on density functional theory.It is proved that the spin magnetic order of GNF is derived from the Topological Frustration of the ? bond which can be determined by its shape.Graphene fragments with a certain topology can be made by etching technology to achieve the application of controllable spin electron nanomaterials and devices.Some special structures that can be used as basic logic gates are calculated and the first-principles electronic structure is calculated,which provides an effective scheme and theoretical basis for the design of high-density ultra-fast spin devices.The results show that the logic gate structure based on the finite graphene fragment can perform error correction operations with low error rate at room temperature.The size effect and topological resistance can form magnetic order in the finite graphene nanoscale.In this paper,the graphene finite fragment that can produce large spin or electron spin anti-ferromagnetic coupling is reasonably classified.Some special structures that can be used as basic logic gates are proposed and the first principle electronic structure is calculated,which provides an effective scheme and theoretical basis for the design of high-density ultra-fast spin devices.The results show that the logic gate structure based on finite graphene fragment can make error-correcting operation at room temperature.The electronic structure of monolayer graphene nanoplatelets and nanowires is theoretically studied though quantum mechanics calculations of tight binding atomicorbital combination scheme based on density functional theory.The quantum transport characteristics of system electrons are calculated by combining the the methods of the first-principles and non-equilibrium Green's function.The first-principles calculated electronic structures are also employed to study the electrical conductivity and band-gap mechanism of the ordered porous graphene nano-meshes.The electron transmission spectra of graphene nanowires shows an approximate step change and considerable ballistic conductivity peaks at the Fermilevel.The electronic band structures of graphene nanoplatelets open a substantial band-gap at Fermi level and exhibit more discrete high-density narrow bands and represent sharp peaks due to quantum confinement in electron transmission spectra.In graphene nanomeshes with magnetic porous arrays,anti-ferromagnetic coupling adds a quantum restriction by the inversion symmetry of the symmetric sublattices,resulting in the transition from binary degeneracy at K point into a band-gap in band structure.The band-gap width of graphene nanomeshes can be adjusted effectively by controlling the density of mesh holes,which provides theoretical basis for the application to graphene electronic nano-devices.