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We constructed α-graphyne nanotubes (αGyNTs) and performed density functional theory calculations to investigate the electronic properties of zigzag and armchair αGyNTs. We found that all zigzag graphyne nanotubes (Z-αGyNTs) were semiconductors. In particular, the band gap of Z-αGyNTs showed an oscillatory dependence on tube size which could be further classified into three families with N z = 3 m − 1, 3 m and 3 m + 1 where m is a positive integer. This resulted in band gap magnitudes in the following rank order: 3 m − 1 > 3 m + 1 > 3 m. Armchair αGyNTs were also calculated to be semiconductor with very small band gaps when tube size is small, though they become metallic as the tube size increases. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were carried out to investigate how single-atom vacancies affect the electronic and magnetic properties of three types of graphyne model systems. Our simulations demonstrate that a single-atom vacancy can lead to an in-plane structural rearrangement, which plays an important role in tuning the electronic structures. A dispersionless spin-polarized band was observed around the fermi level, inducing strong magnetism in the three graphyne models. The single-atom vacancy can induce a 1.1–1.3 μ B magnetic moment into αGy and βGy, while this value increases significantly to about 1.8μ B for γGy. This single-atom vacancy technique is a promising method of manipulating the electronic and magnetic properties of graphyne. [ABSTRACT FROM AUTHOR]

In the present paper, density functional theory calculations were carried out on a detailed oxygen reduction reaction (ORR) process catalysed by nitrogen-doped β-graphyne (βGy). Nitrogen-doping can increase the positive charge of the adjacent carbon atom and the graphyne work function, promoting O 2 decomposition. Our calculations revealed that N-doped βGy can efficiently facilitate the ORR process via a four-electron mechanism, regardless of doping position. Additionally, our results revealed that the N doping site was essential for tuning the ORR catalytic activity. N1 doping was shown to more effectively promote the ORR than N2 doping. In addition, our research enhances the current understanding of catalytic activity at the molecular level. [ABSTRACT FROM AUTHOR]

Transition Metal ( TM ) atoms adsorption on γ-graphyne is here studied to unravel the electronic and magnetic properties tuning of this 2D carbon allotrope, with possible repercussions on molecular storage, sensing, and catalytic properties. A thorough density functional theory study, including dispersion, of the structural, energetic, diffusivity, magnetic, and doping properties for all 3 d , 4 d , and 5 d TM adatoms adsorbed on γ-graphyne is provided. Overall, TMs strongly chemisorb on γ-graphyne acetylenic rings, except d 10 group XII TMs which physisorb. Diffusion energy barriers span the 0.5–3.5 eV and adatom height with respect the γ-graphyne sheet seems to be governed by the TM atomic radius. All TMs are found to give n -doped γ-graphyne, where charge transfer decays along d series due to the increasing electronegativity of TMs. Middle TMs infer noticeable magnetism to γ-graphyne, yet magnetism is heavily quenched for early and late TMs. The large adsorption energies close to parent TM bulk cohesive energies, the high diffusion energy barriers, and the coulombic repulsion between positively charged TM adatoms provide a good environment for TMs to disperse over the γ-graphyne. [ABSTRACT FROM AUTHOR]

Density functional theory calculations were carried out to study how the position of single-atom doping affects the electronic properties of three graphyne models. We found that the position of the dopant (B, N, or O) plays an important role in tuning the electronic structure of graphynes. For α-graphyne, the electronic structure is significantly different for different positions of B and O doping. For β-graphyne, the electronic structure depends remarkably on the doping position for O doping, but not much for B and N doping, whereas for γ-graphyne, it depends on the position for B and O doping, but not for N doping. [ABSTRACT FROM AUTHOR]