Schematic depiction of the structures of (a) octagraphene, where a unit cell is indicated with the unit vectors a1 and a2; (b) single-wall sawtooth (10,0) and armchair (8,8) carbon nanotubes rolled from octagraphene; and (c) unconventional fullerenes of C36, C48, C80, and C96 obtained from octagraphene.
(a) Cohesive energy per atom as a function of lattice constant a for graphene, octagraphene, graphyne, and graphdiyne, respectively, where a 0 is the optimized lattice constant. (b) Phonon spectra of octagraphene.
(a) Stress-strain curves of graphene (GE), octagraphene (OGE), graphyne (GY), and graphdiyne (GDY) along armchair (AC) and zigzag (ZZ) or sawtooth (ST) directions. The experimental data of graphene are taken from Ref. 30. (b)Valence electron density of octagraphene.
(a) Electronic band structures and density of states (DOS) of octagraphene calculated by the density functional theory (DFT) and the tight-binding approximation (TBA) methods. (b) Fermi surface of octagraphene, where the hole packet (red) is at Γ point, and the electron pocket (blue) is at M point. (c) Energy bands of octagraphene nanotubes (3,3), (5,5), (12,12), (5,0), (8,0), and (16,0).
A schematic demonstration how to utilize the line defects in graphene to obtain octagraphene.
(a) Schematic structures of boron nitrogen pairs substitutionally doped octagraphene with different doping configurations, where carbon, boron, and nitrogen atoms are colored in blue, red, and green, respectively. (b)The corresponding band gaps (E g ) for different structures of (a), where the doping concentration is from small to large in sequence.
There are five possible adsorption sites of metal atoms on octagraphene, including one top site on C atoms (T), two bridge sites on top of intra-square (B) and inter-square (B′) C-C bond, respectively, and two hollow sites on top of square (H) and octagon (H′), respectively.
The configuration of four hydrogen molecules adsorbed on each Ti atom at H1 site. (a)-(d) reveal the single-side hydrogen storage configurations with one, two, three, and four hydrogen molecules adsorbed on each Ti atom, respectively; (e)-(h) show the double-side hydrogen storage configurations with one, two, three, and four H2 adsorbed on each Ti atom, respectively; where C, Ti and H atoms are colored in dark blue, bluish green, and brick red, respectively.
The symmetry, lattice constant (a 0), bond lengths lCC , plane density ρ, cohesive energy (Ec ), energy gap Eg between the bottom of conduction band and the top of valence band, Young's modulus E, breaking strength σ, and Poission's ratio ν for graphene, octagraphene, graphyne, and graphdiyne, respectively.
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