The size-dependent elastic mechanical properties of various γ-graphyne structures as graphyne, graphdiyne, graphyne-3, and graphyne−4 are studied in this work. The interatomic interactions between ...the carbon atoms in a nanostructure are simulated combining the molecular mechanics theory with appropriate spring-like finite elements. Specifically, the bond tension and bond angle bending interactions are simulated with suitable translational spring elements concerning three types of covalent bonds: single, aromatic, and triple. Considering the ideal geometry of every graphyne structure and regarding different nanostructure sizes, several finite element models are employed. Applying suitable boundary conditions to the models, the size-dependent mechanical properties as Young's and shear moduli, as well as Poisson's ratio of every nanostructure are finally calculated in each direction. Fitting the finite element analysis results, new empirical-analytical equations are derived for the prediction of graphyne structures elastic constants. The comparison of the obtained results with the results found in the open literature, where it is possible, establishes the reasonable accuracy of the proposed approach.
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•Graphyne structures present a strong size-dependent elastic behavior in nanoscale, especially for dimensions lower than 10 nm.•Graphyne is the stiffest structure of its family and the stiffness decreases as the acetylenic linkage becomes larger.•The proposed finite element approach presents high computational efficiency and reasonable accuracy.•The arisen analytical-empirical expressions can be used for a fast estimation of elastic constants in the design process.
Reverse degree-based topological indices (RDTIs) are applied to analyze the structural properties of molecules such as gamma graphyne and armchair graphyne nanoribbons. RDTIs provide valuable ...information about the connectivity patterns of atoms within a molecule, aiding in understanding its chemical and physical properties. For gamma graphyne and armchair graphyne nanoribbons, RDTIs would involve calculating the contributions from various atom pairs based on the degree differences between them. These indices consider the reverse order in which degrees are subtracted. RDTIs capture important aspects of molecular structure, including branching, degree distribution, and connectivity. Using RDTIs, one can assess the complexity, stability, and other characteristics of gamma graphyne and armchair graphyne nanoribbons. This paper focus on two structures made from hexagonal honeycomb graphite lattices, like gamma graphyne, and armchair graphyne nanoribbons. The methodology used in this study is First and second reverse Gourava indices, hyper first and second reverse Gourava indices, reverse multiplicative sum connectivity Gourava index, and reverse multiplicative product connectivity Gourava. Furthermore, these indices play a vital role in quantitative structure-property relationships and offer insights into the behaviour and reactivity of these unique molecular structures. Further research and computational analysis of RDTIs will deepen our understanding of these fascinating carbon-based materials.
The properties of radially collapsed armchair single-walled α-graphyne nanotubes (α-SWGNTs) are investigated using density functional theory with van der Waals (vdW) corrections. Here, our main goal ...is to study the structural properties of stable collapsed SWGNT forms and how the corresponding electronic structure are modified in comparison to the circular counterparts. The presence of carbon atoms with sp and sp2 hybridization makes the SWGNTs to present an intriguing geometry for their cross section in the collapsed form and, as a result, the electronic structure of these system is sensitivity to the stacking mode between layers. We find a threshold diameter (26 Å) for which the collapsed structure is more stable than the circular phase, indicating that the natural form of large SWGNTs is radially collapsed. Furthermore, we identified that the collapsed structure is semiconductor when the diameter of the circular phase is greater than 19 Å, with band gap values adjusted by the type of stacking between layers. We believe these results can open up possibilities of using such structures in the setups of nanoelectronic device, and provide a basis for future experimental and theoretical research about collapsed graphyne nanotubes.
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Graphyne is of great interest to researchers due to its unique electronic and mechanical properties, which make it a potentially valuable material for a wide range of applications. The importance of ...graphyne lies in its potential to enable new technologies and applications in a variety of fields, from electronics to materials science. In this paper, the density functional theory (DFT) calculation was used to investigate CO2 and N2 adsorption on pristine and oxidized γ-graphyne in both two horizontal and vertical directions at hollow and bridge sites. Based on the results, the highest stability was observed when the CO2 and N2 molecules approached the γ-graphyne sheet in a hollow space. Oxygenation of γ-graphyne led to increased CO2 adsorption capacity compared to pristine γ-graphyne. This can be attributed to the interaction between the Pπ electrons of the carbon in graphyne and carbonyl groups with the unbonded electron pair of the oxygen in CO2, leading to a more significant interaction of CO2 with the γ-graphyne surface. Furthermore, no significant N2 absorption was observed for oxygenated γ-graphyne.
Nitrogen-doped graphyne/BiOBr nanocomposites were developed by in-situ sonochemical synthesis and boosted photocatalytic activity as well as mechanism on N2 fixation and pollutants degradation were ...investigated.
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•Nitrogen-doped graphyne/BiOBr nanocomposites are obtained via sonochemical synthesis.•The wrinkle-like layers of N-graphyne enwind around BiOBr sheets closely.•Boosted visible-light photocatalytic degradation of pollutants and N2 fixation are confirmed.•The enhanced photocatalytic mechanism is detected by a collection of characterizations.
In this study, a facile in-situ sonochemical synthesis process is developed to construct nitrogen-doped graphyne/BiOBr composites. Multiple techniques are implemented to characterize the structures, morphologies, electronic and optical properties, and photocatalytic activity of the as-prepared samples, including X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, Raman, and X-ray photoelectron spectroscopy, etc. The results indicate that the wrinkle-like layer structure of N-graphyne enwinds around the sheet structure of BiOBr. Compared to pristine BiOBr, N-graphyne/BiOBr composites present superior visible-light response, higher specific surface area, and more significant separation of photoinduced charge carriers verified by Brunauer-Emmett-Teller, UV–vis absorption spectroscopy, instantaneous photocurrent, electrochemical impedance spectroscopy, and photoluminescence, thus presenting more pronounced visible-light photocatalytic properties on N2 fixation and decomposition of pollutants. The optimal ratio of N-graphyne in N-graphyne/BiOBr composites is screened out for the photocatalytic decomposition of rhodamine B, levofloxacin, methylene blue, and nitrogen fixation under visible light illumination. Furthermore, the main active species are demonstrated as hole and O2– during photocatalytic degradation and the stable performance of is also observed for N-graphyne/BiOBr composites. The present research demonstrates that N-graphyne embellishment is an effective strategy to enhance the photocatalytic efficiency of BiOBr, which can be broadened as an excellent co-catalyst for decoration of other semiconductors.
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•electronic properties of γ-graphyne cluster models converge rapidly.•electronic properties of γ-graphyne clusters have a low dependence on vacancy defects.•γ-graphyne is an efficient ...electron acceptor (low LUMO and ability to delocalize excess charge).•photoinduced electron transfer from electron donors to γ-graphyne is efficient and fast.
The search for new materials is constantly ongoing. Recently, a two-dimensional carbon allotrope , γ-graphyne, has been synthesized with a unified crystalline structure . Because of its low LUMO and excellent electron mobility, it appears to be a promising electron acceptor for photovoltaic applications. Here we report an analysis of the electronic properties of model van der Waals complexes of γ-graphyne with several partners of different electronic nature. We show that photoinduced electron transfer from electron-donating partners to γ-graphyne is favorable and occurs on nano to picosecond time scale. In contrast, electron transfer from γ-graphyne to strong electron acceptors is unlikely. Our results open perspectives for the future application of γ-graphyne in photovoltaic devices.
We have investigated the hydrogen storage capabilities of scandium decorated holey graphyne, a recently synthesized carbon allotrope, by applying density functional theory and molecular dynamics ...simulations. We have observed that one unit cell of holey graphyne can adsorb 6 Sc atoms, and each Sc atom can adsorb up to 5H2 molecules with an average binding energy and average desorption temperature of −0.36 eV/H2 and 464 K, respectively. The gravimetric weight percentage of hydrogen is 9.80%, which is considerably higher than the Department of Energy, United-States requirements of 6.5%. We have found that a total amount of 1.9e charge transfers from the 3d and 4s orbitals of Sc atom to the C-2p orbitals of holey graphyne by performing the Bader charge analysis. Hydrogen molecules are bonded with the scandium atom by Kubas interactions. The ab-initio molecular dynamics simulations confirm the structural integrity of scandium decorated holey graphyne system at the high desorption temperatures. The presence of sufficient diffusion energy barriers for the Sc atom ensure the avoidance of metal-metal clustering in the system.
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•Using DFT and AIMD, H2 storage in Sc decorated holey graphyne is reported.•Single Sc adsorbs 5H2 molecules leading 9.80 wt %.•Molecular dynamics simulations ensure solidity of structure.•Sufficient diffusion energy barrier prevents metal-metal clustering.•H2 molecules are attached on Sc by Kubas interactions with average BE of −0.36 eV/H2.
•First numerical simulation on the electronic property for zigzag-edgeδ-graphyne nanoribbons;•A proposed junction based onδ-graphyne nanoribbon symmetrically with good circuit performance;•The ...spin-filtering efficiency can be up to 99%, and the maximum of rectification ratio reaches up to 106%.
Many layered graphene and graphene-like two-dimensional carbon materials have been successively proposed in theory and experiment owing to their exceptional properties and potential applications. By employing the first-principles study, we find that a new graphene-like material, δ-graphyne, whose properties of the zigzag-edged nanoribbon are very similar to those ones of zigzag-edged graphene case. The band structure clearly exhibits a metallic property in non-magnetic state. And we can see a visible spin splitting within the ferromagnetic state, however, spin degeneracy within the antiferromagnetic state. To this end, here we propose a molecular junction based on the zigzag-δ-graphyne nanoribbon symmetrically with additional phenyl rings at both edges. The computational results imply that the device has many good electron transport performances, such as negative differential resistance, spin-filtering and rectification effects, and so on. In particular, the spin-filtering efficiency can be up to 99%, and the maximum of the rectification ratio reaches up to 106%. The mechanisms for these effects are revealed and discussed in terms of the band structure, spin-resolved electron transmission spectrum, the local density of state and the transmission pathway. Therefore, our research results can provide a basis for the experimental preparation of the δ-graphyne-based junction.
In this paper, molecular dynamics simulations are applied to study the mechanical properties of two types of graphyne nanotubes; including α-graphyne and α2-graphyne nanotubes. The effects of the ...geometrical properties of the nanotubes on the stress-train curve, Young's modulus, fracture strain and maximum stress are studied. It is observed that Young's modulus of the α-graphyne nanotubes are significantly smaller than Young's modulus of the α2-graphyne nanotubes with the same geometrical parameters. Similarly, the maximum stress tolerated by the armchair α2-graphyne nanotubes are larger than the armchair α-graphyne nanotubes. However, α-graphyne nanotubes tolerate larger fracture strains than the α2-graphyne nanotubes. It is shown that increasing the nanotube diameter leads to increase in Young's modulus of the α-graphyne nanotubes and α2-graphyne nanotubes. However, increasing the nanotube lengths has an inverse effect on Young's modulus of the considered nanostructures.
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•MD simulations are applied to study the mechanical properties α-GNTs and α2-GNTs.•The effects of the geometrical properties on the stress-strain curve are studied.•Young's modulus of the α-GNTs are significantly smaller than that of the α2-GNTs.•Maximum stress tolerated by the armchair α2-GNTs are larger than armchair α-GNTs.•α-GNTs tolerate larger fracture strains than the α-GNTs.
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