Stone-Wales Research Articles

A study on the effect of defects on the buckling of double-walled carbon nanotubes under compression based on a new atomic-continuum coupling method

An atomic-continuum coupling (ACC) method is developed for the nonlinear mechanical analysis of defective double-walled carbon nanotubes (DWCNTs). The moving least squares (MLS) approximation is resorted to bridge the fully atomic discrete structures of defective DWCNTs and the corresponding virtual continuum solids. The intrinsic mechanic laws implied in nanostructures can be accurately mapped into the mechanical governing equations of the continuum models. Based on ACC method, a numerical computational scheme is developed for predicting the buckling and contact behaviors of defective DWCNTs, which do not need any numerical integration method to calculate potential functional and its derivatives. The numerical tests show that this method can furnish good predictions even with a small number of nodes. It is found that Stone–Wales (SW) defects can lead to greatly decrease in the buckling properties of DWCNTs. In contrary, the complex interlayer van der Waals (vdW) interactions can enhance the buckling resistance of DWCNTs.

Deep Learning on Atomistic Physical Fields of Graphene for Strain and Defect Engineering

Strain and defect engineering have profound applications in two‐dimensional materials, where it is important to determine the equilibrated atomistic structures with defect conditions under mechanical deformations for computational materials design. Nevertheless, how to efficiently predict relaxed atomistic structures and the associated physical fields on each atom or bond under evolving mechanical deformations remains as an essential challenge. To address this issue, a deep neural network architecture is designed to embed the state of applied strains into the defect‐engineered atomistic geometry, so that deformation‐coupled physical fields of interests on atoms or bonds can be predicted or derived over continuous state of deformations. For demonstration, the combination of applied tensile strains and shear strain on monolayer graphene with random distribution of Stone–Wales defects and vacancy defects is considered. The unique advantage of this framework is the development of strain‐embedding concept combined with generative adversarial network, which can be feasibly extended to other material and other conditions. The computational approach sheds light on boosting the efficiency of evaluating physical properties of 2D materials under complex strain and defect states.

Prediction of mechanical properties of phagraphene nanosheets and nanotubes: A molecular dynamics study

Phagraphene (PhaG), a recently discovered carbon allotrope, deviates from graphene's honeycomb lattice by featuring a distinctive unit cell composed of 20 carbon atoms arranged in a pentagonal-hexagonal-heptagonal ring sequence. This unique structure imparts mechanical properties comparable to graphene. In this investigation, Molecular Dynamics simulations are employed to estimate the mechanical characteristics of both nanosheets and nanotubes in their pristine and defective states. The study delves into the impact of defects, by introducing two types of defects—vacancies and Stone-Wales defects—into these nanostructures. Among these, Type-1 vacancies and Type-2 and Type-3 Stone-Wales defects prove dominant. It is determined from the results that nanosheets exhibit an average elastic modulus of approximately 0.8 TPa and an ultimate strength of 95 GPa, demonstrating an anisotropic nature. Phagraphene nanotubes (PhaNT), modeled through the revolution of atomic Cartesian coordinates of nanosheets, display an elastic modulus close to 0.9 TPa and an ultimate strength of 250 GPa. Additionally, this study investigates the impact of temperature on the mechanical properties of Phagraphene nanostructures. The findings reveal that as the temperature increases, there is a decrease in the tensile strength of both nanosheets and nanotubes. This temperature-dependent behavior provides valuable insights into the thermal stability and performance of Phagraphene nanostructures, further contributing to our understanding of their mechanical response under varying environmental conditions. The precision of the results is observed when nanosheets, each comprising 2800 or more carbon atoms, and nanotubes, each composed of 4500 or more carbon atoms, undergo testing under a tensile strain rate of 109/s.

Structural stability and electronic properties of charged point defects in monolayer blue phosphorus

As a new two-dimensional material, blue phosphorus has attracted considerable research interest due to its high carrier mobility and large bandgap. Although the structural defects of blue phosphorus have been discussed recently, the charged properties of these defects have not been explored. In this paper, using first-principles calculations based on density functional theory, the six most stable point defects and their corresponding charged states in blue phosphorus are studied, including Stone Wales (SW), single vacancy (SV), two double-vacancy (DV-1 and DV-2) and two substitution defects (O<sub>P</sub> and C<sub>P</sub>). The converged ionization energy values of charged defects in blue phosphorus are obtained by extrapolating the asymptotic expression of the energy dependent on the cell size. Subsequently, the formation energy values for different charge states are modified to determine their structural stabilities. Finally, their electronic properties are analyzed through band structures. The results suggest that SV<sup>1–</sup> is easy to ionize, owing to its lowest ionization energy (1.08 eV). Furthermore, among the defects we are considering, O<sub>P</sub><sup>1–</sup> is the most stable charged defect in blue phosphorus, with the lowest formation energy (–9.33 eV) under O-rich chemical potential condition. The negative formation energy indicates that O atoms can exist stably in blue phosphorus, implying that blue phosphorus is easily oxidized. The introduction of defect states will affect the bandgap of blue phosphorus, and the ionization of defects will cause the defect energy levels to shift, leading defects to transition between shallow and deep levels. This study provides theoretical guidance for the application of defect engineering in two-dimensional materials.

Two-dimensional Cu-doped G/h-BN/G heterostructures for highly sensitive gas detection: an ab initio study.

Two-dimensional materials like graphene and h-BN have drawn significant interest for gas sensing applications due to their high surface-to-volume ratio and exceptional physical properties. This study introduces a novel approach involving a 2-D G/h-BN/G heterostructure doped with a Cu atom to develop a highly sensitive gas sensor. The intermediate h-BN layers support the Cu dopant and enhance the electrical sensitivity by constraining the offset current. Density functional theory and non-equilibrium Green's function formalisms are employed to investigate the geometry, stability, and electrical properties of the G/h-BN/G structure with the Cu dopant at various vacancy sites, alongside exploring the adsorption behavior of six different gas molecules (NO2, CO, NH3, PH3, HCN, and HO2). Results reveal that doping Cu in the B vacancy and the Stone-Wales defect yields highly stable structures with promising electrical characteristics for gas sensing applications. Gas molecules exhibit a higher tendency to adsorb onto the Cu-doped structure compared to the pristine G/h-BN/G, demonstrating a stronger impact on current flow. The Cu-doped structures display robust electrical sensitivity toward NO2, CO, NH3, and HCN molecules, and the significant gap in current modulation for each gas indicates the potential for distinguishing different gas molecules. Hence, incorporating the Cu dopant in the G/h-BN/G heterostructures emerges as a promising platform for gas sensing applications.

Thermal transport in a defective pillared graphene network: insights from equilibrium molecular dynamics simulation.

Graphene-based hybrid nanostructures have great potential to be ideal candidates for developing tailored thermal transport materials. In this study, we perform equilibrium molecular dynamics simulations employing the Green-Kubo method to investigate the influence of topological defects in three-dimensional pillared graphene networks. Similar to single-layer graphene and carbon nanotubes, the thermal conductivity (k) of pillared graphene systems exhibits a strong correlation with the system size (L), following a power-law relation k ∼ Lα, where α ranges from 0.12 to 0.15. Our results indicate that the vacancy defects significantly reduce thermal conductivity in pillared graphene systems compared to Stone-Wales defects. We observe that, beyond defect concentration, the location of the defects also plays a crucial role in determining thermal conductivity. We further analyze the phonon vibrational spectrum and the phonon participation ratio to obtain more insight into the thermal transport in the defective pillared graphene network. In most scenarios, longitudinal and flexural acoustic phonons experience significant localization within the 15-45 THz frequency range in the defective pillared graphene system.

Investigation on edge defect characteristics and electronic transport characteristics of graphene nano cutting

The effects of cutting crystal direction and speed on edge morphology, defects and electron transport characteristics were studied by molecular dynamics from the distribution state of defect atoms, the number of defect atoms, cutting force and radial distribution function. The edge defects of zigzag graphene nanoribbons were extracted, and the difficulty of forming different kinds of defects and the influence of different defects on band gap were studied by density functional theory. The results indicate that cutting graphene along the [010] (zigzag) direction has a smaller variance and smoother cutting. The obtained graphene nanoribbons have fewer defects and good edge quality. And the higher the cutting speed, the fewer defects of the graphene nanoribbons formed, resulting in smaller damage. The typical defects at the edges include 5–8–5 defect (double-vacancy defect), 5–9 SV defect (single-vacancy defect), stone wales (SW) defect, chain defect, crack defect and hole defect. The relationship between the magnitude of forming energy values produced by different defect types is as follows: crack defect > chain defect > SW defect > 5–9 SV defect > 5–8–5 defect > hole defect. Hole defect is the most difficult to form. The band gap width of the cut edge containing defects is smaller than that of the perfect graphene nanoribbon, resulting in the increase of the conductivity of the graphene nanoribbon in the direction of metal characteristics. The presence of defects can open the band gap with of intrinsic graphene.

Influence of Stone-Wales defects on the structural and electronic properties of single-walled silicon nanotubes by SCC-DFTB calculations

In this work, using the self-consistent charge density functional tight-binding (SCC-DFTB) approach, we explored the effects of Stone-Wales (SW) defects on the structure and electronic properties of perfect single-walled silicon nanotubes(SWSiNTs), including zigzag (n1,0) (8≤n1≤16), armchair (n2,n2) (5≤n2≤10), and chiral (2n3,n3) (3≤n3≤8). We found that the presence of SW defects leads to changes in bond length and bond angle, resulting in structural changes at the defect site. However, nanotubes still exhibit tubular and hexagonal structures. Also, the defect structure of zigzag and armchair SW-II defective tubes is symmetrical, which means that the bond length of the Si-Si bond is equivalent to that of its symmetric bond. Besides, after introducing the SW-II defect, zigzag and chiral tubes become more stable, but the stability of armchair tubes with small diameter is reduced. The introduction of SW-Ⅰ and SW-Ⅱ defects transforms armchair SiNTs from semiconductor into semi-metallic properties. Moreover, for a perfect structure, the charge moves from inside out along the radial direction of the tube and the amount of charge is distributed in an axisymmetric manner. After introducing SW defects, the range of charge transfer is expanded, SW-Ⅱ defective structures appear inward deviation, and the atoms near the defect change from regular arrangement to inward aggregation. This work may provide a new way to adjust the electronic properties of SWSiNTs and open up wider applications in nanoelectronic devices.

Fluid-solid coupling for microscale transport of nanoparticles in ultralong carbon nanotubes

Achieving microscale motion of nanoparticles is crucial for the development of various nanodevices. Here we propose a novel fluid-solid coupling device that leverages a thermally-induced water flow to enable long-range nanoparticle transport within carbon nanotubes (CNTs). Our device comprises an ultralong CNT composed of repeated units filled with water. Each unit experiences an asymmetrical thermal gradient induced by intentionally incorporating asymmetrical configurations of atomic vacancies on the CNT surface. Through molecular dynamics (MD) simulations, we demonstrate that these repeated units with periodic thermal fields effectively induce a steady water flow, enabling continuous transportation of a nanoparticle (e.g., a C60 fullerene) within the ultralong CNT over microscale distances. Moreover, we reveal that the device can be also designed with various alternative options (e.g., Stone–Wales defects or carbon/boron-nitride heterojunctions). Our proposed device holds promising potential for microscale nanoparticle transport applications.

Variation in properties of double-walled zigzag and armchair silicon nanotubes depending on SW defects and applied electric fields by SCC-DFTB method

The geometric structure and electrical properties of the zigzag DWSiNT (8,0)@(12,0) and armchair DWSiNT (5,5)@(7,7) perfect tubes with the same diameter are simulated by self-consistent charge density functional tight binding method (SCC-DFTB). We considered the defective tubes by introducing three types of Stone-Wales (SW) defects, and further investigated the impact of both strong and weak electric fields on these defective tubes. Calculations demonstrate that the atomic arrangement regularity, degree of buckling, stability, energy gap, and charge distribution strongly depend on the type of perfect tubes. Following the introduction of the SW defects, the symmetry of the tubes disappeared, and there is a obvious atomic aggregation occurring at the defects. The armchair tubes demonstrate a higher stability compared to zigzag tubes and all exhibit metallic properties. SWⅡ and SWⅢ defects in zigzag tubes result in a transition from semiconductor to semi-metallic properties. The number of charge transfer increases, and the degree of atomic aggregation is more dispersed. The effect of applied electric field strength on perfect zigzag tubes is more obvious. The weak field has minimally impacted on the stability, and the strong field makes the stability improved to some extent. The presence of a strong field caused the energy gap values of (8,0)@(12,0) tube decrease sharply, and all tubes are transformed into semi-metal or metal. The weak electric field has a more pronounced regulation of band gap within the range of 0 V/nm - 0.3 V/nm on the inner tube. The consequences of this investigation can certainly be helpful in future experimental studies.

Reactivity of Stone-Wales defect in graphene lattice – DFT study

Understanding the reactivity of carbon surfaces is crucial for the development of advanced functional materials. The SW defect is commonly present in carbon materials, but a comprehensive understanding of its effects on the reactivity of carbons is missing. In this study, we systematically investigate the reactivity of graphene surfaces with the Stone-Wales (SW) defect using Density Functional Theory calculations. We explore the atomic adsorption of various elements, including rows 1–3 of the Periodic Table, potassium, calcium, and selected transition metals. Our results demonstrate that the SW defect enhances binding with the studied adsorbates when compared to pristine graphene, with carbon and silicon showing the most significant differences. Additionally, we examine the effects of mechanical deformation on the lattice by constraining the system with the SW defect to the pristine graphene cell. Interestingly, these constraints lead to even stronger binding interactions. Furthermore, for carbon, nitrogen, and oxygen adsorbates, we observe that mechanical deformation triggers the incorporation of adatoms into the carbon bond network, leading to the reorganization of the SW defect structure. This work establishes a foundation for future studies in the defect and strain engineering of graphene, opening avenues for developing advanced materials and catalysts with enhanced reactivity and performance.

Computational Modeling, Simulation and Tight–Binding Analysis of Electronic Characteristics of Defective Germanene Nanoribbons for Future Applications of High Sensitivity Ge-Based Nanosensors

In this research, the electronic characteristics of germanene sheet and nanoribbons using the computational modeling, simulation and tight binding approximation are investigated. Our analysis is focused on the pristine sheet of germanene as well as defective monolayer. The obtained results show that applying the Stone–Wales defect into the germanene monolayer changes the energy band structure. The E-k curves around the Dirac point are no longer linear, in which a band gap is opened, and the Fermi velocity is reduced. Furthermore, the main parameters such as density of states, carrier concentration in degenerate and non-degenerate limits, carrier effective mass, conductance and AC conductivity of germanene are analytically modeled with the inclusion of the spin–orbit coupling effect, temperature and ribbon width. Obtained results demonstrate that the inclusion of the spin–orbit coupling makes a small splitting of the energy levels and creating a small band gap. Finally, the Tight binding and computational values are compared with our simulation results and available data, and a rational agreement is reported in terms of trend and value. The findings of this study provide theoretical reference for the design of germanene-based nanosensors and optoelectronic devices.

Effect of Defects and Oxidation on CNT-Copper Interface: First-Principles Calculation and Experiment.

In this paper, the effects of carbon nanotube defects and a copper surface oxide layer on a carbon nanotube-copper interface were studied via first-principles. A defect-free CNT-Cu interface, Stone-Wales defect CNT-Cu interface, single-hole and double-hole defect CNT-Cu interface, and Cu2O-Cu interface were simulated and calculated. By simulating the differential charge density, atomic population, bond population and density of states of the interface model, the effects of various defects on the interface bonding and electrical conductivity of the composites during the preparation of the CNT-reinforced copper matrix composites were analyzed, which provided theoretical guidance for the preparation of CNT/Cu composites. After that, copper matrix composites with different CNT defect contents were prepared via different rolling deformation processes. Their hardness and electrical conductivity were tested, and the results were consistent with the results obtained via the first-principles calculations.

Ultrafast transformation of natural graphite into self-supporting graphene as superior anode materials for lithium-ion batteries

Graphite possesses remarkable potential as an anode material for lithium-ion batteries, thanks to its superb electrical conductivity and eco-friendliness. Nevertheless, challenging issues persist, such as its low maximum theoretical lithium storage capacity and constraints associated with the regular layered structure, which impede its practical application and advancement. In this regard, we proposed a novel approach to enhance the energy storage performance of lithium-ion batteries, involving the modification of natural graphite through irradiation with a high-current pulsed electron beam (HCPEB). Microscopic observations revealed that during the in-situ transformation of graphite particles into self-supporting graphene nanosheets, the high temperature generated by HCPEB irradiation led to the formation of structural defects, including Stone Wales and double vacancy defects. Consequently, the modified natural graphite electrode (particle size 12 μm) exhibited a reversible capacity of 420.4 mAh/g at 0.2C and maintained 94.5% of its reversible capacity after 500 cycles. In comparison to unmodified graphite (particle size 12 μm), the SEI film displayed enhanced stability, significantly improving cycling performance. These findings demonstrated that the defective graphene nanosheet structure enhances lithium storage activity sites, enlarges layer spacing, and enhances lithium storage performance. This study presents an efficient and environmentally friendly method for producing superior anode materials for lithium-ion batteries.

Influence of the boron doping and Stone–Wales defects on the thermoelectric performance of graphene nanoribbons

Influence of the boron doping and Stone–Wales defects on the thermoelectric performance of graphene nanoribbons

The Controllable Mechanical Properties of Coiled Carbon Nanotubes with Stone-Wales and Vacancy Defects.

Coiled carbon nanotubes (CCNTs) as a promising nanometer scale spring are investigated for the effect of the defects on the tensile mechanical properties of CCNTs by using molecular dynamics (MD) simulations. Six samples of defective CCNTs are constructed by introducing the defects in the different positions. The results show an obvious decrease in the spring constant and elastic limit of defective CCNTs, which results in the lower energy storage ability during the elastic range compared with the perfect CCNTs. However, the defected CCNTs exhibit better ductility (138.9%) and higher energy absorbing ability (1539.93 J/g) during the fracture process since introduced defects change the deformation pattern. Furthermore, among the defected CCNTs, the stiffness (1.48~1.93 nN/nm), elastic limit (75.2~88.7%), ductility (108.5~138.9%), and deformation pattern can be adjusted by changing the position or the type of defects. This study firstly provides insight into the effects of Stone-Wales (SW) and vacancy defects on the mechanical properties of CCNTs, and the obtained results are meaningful for designing CCNTs with specified properties by introducing defects.

A functional M-BN monolayer for application of photocatalytic water splitting via first-principles calculations

A BN monolayer (M-BN) was designed by introducing the Stone-Wales defects to h-BN. Using first principles calculations, we verified the energetic, dynamical, thermal and mechanical stability of M-BN. M-BN has a high Young's modulus and an anisotropic mechanical response. Moreover, the calculations results of electronic properties show that M−N- is an indirect band gap semiconductor. The band edge positions of the M−N- monolayer span the redox potential of water, which suggest its great potential in the application of photocatalytic water splitting. Remarkably, the high optical absorption capability of M−N- in the ultraviolet range make it to be a potential candidate in optoelectronic device applications. The current results provide insights for further exploring the new 2D materials for nanoelectronic and optoelectronic applications.

The synergistic regulation effect on the structure and electronic properties of graphene by methane plasma, Stone-Wales defect and equibiaxial strain

The synergistic regulation effects on the structure and electronic properties of graphene by methane plasma, Stone-Wales defect and equibiaxial strain has been investigated. It is found that the graphene containing Stone-Wales defect (SWG77) has metallicity, when surface adsorbing a CH3+ion, CH3+@SWG77 is a semiconductor with 0.339 eV indirect band gap. The stress-strain curve results indicate that adsorbing different plasma fragments in methane may influence to varying degrees on the ultimate strain of the SWG77 system. The hole mobility has an enhanced tendency as the tensile strain increases for the CH3+@SWG77 system. In addition, the hole mobilities seem to reach saturation when applied equibiaxial strain increase to 2 % or larger. Applying equibiaxial strain on the system substrate, the band gaps of CH3+@ SWG77 and 2CH3+@ SWG77 systems are almost unaffected. In addition, the concentration of CH3+ ion has a certain effect on the light absorption coefficient, reflectivity, and energy loss of the SWG77 system in the visible light region (1.62 eV–3.11 eV) and ultraviolet regions (3.11 eV–5.50 eV). Therefore, defect graphene with appropriate carrier mobility and band gap may be designed by adjusting the equiaxial strain and methyl concentration, which provides useful theoretical support for the development of optical electrical multifunctional electronic devices based on graphene, and is conducive to promoting the application of graphene materials in the field of band gap engineering.

Atomic insights into the fluorinated pristine and defected graphene sheets for inducing the electronic and magnetic properties with the aid of scandium metal decoration- Acumen from density functional theory

To scrutinize the electronic and magnetic properties of fluorinated pristine, stone wales, di-vacancy, and two stone wales defected graphene sheets by scandium (Sc) metal decoration, the density functional theory is used. The obtained maximum binding and interaction energy values confirm that the two Sc metals decorated on the direct top and bottom of pentagonal rings of the two stone wales graphene sheet have stronger interactions than others. To validate the interactions, natural population analysis and electron density difference map are performed, revealing that Sc metal is the electron donor in all complexes. After the formation of defects in the pristine sheet, energy gap values are reduced in the defected sheets. The density of states infers the shift in the fermi level of all complexes after defect formation and metal decoration. The ultraviolet–visible spectral analysis exposes the highest absorption peaks of all bare sheets at the UV region and after Sc metal decoration, the peaks get red shifted. The results show that Sc metal decorated on two stone wales graphene sheet interacts better with Sc metals than other complexes. The decoration of single Sc metal in all four bare sheets transforms the sheet from a non-magnetic to a magnetic state but when two Sc metals are decorated it became non-magnetic. The highest degree of spin polarization, P = 4.15 is obtained while decorating a single Sc metal on the hexagonal ring of the pristine sheet. The outcome of this work suggests that Sc metal decoration on pristine and defected graphene sheets has great potential to improve the electronic and magnetic properties of graphene for designing spintronic and data storage devices.

Hydrogen production and storage through adsorption and dissociation of H2O on pristine and functionalized SWCNT: a DFT approach.

Adsorption of 1 and 2 H2O molecules for hydrogen production and storage on the surface of pristine, carbamic acid and 2-amino 3-acetylpyridine functionalized SWCNTs with the dimensionality of (2, 4), (5, 5), and (6, 0) at various positions, i.e., center and edges were investigated by using computational DFT calculations. Adsorption energies and structural and electronic parameters were determined for pristine and functionalized SWCNTs with four different H2O orientations. Functionalization of 2-amino 3-acetylpyridine resulted in more favorable adsorption energies for 1 and 2 H2O molecules splitting as compared to spitting on pristine and carbamic acid functionalized SWCNT. Calculated adsorption constant, Kad confirmed greater binding interactions of functionalized SWCNTs with 1 and 2 H2O molecules as compared to pristine SWCNT. Isosurface for the adsorption of 1 and 2 H2O molecules on pristine and functionalized SWCNTs elaborated altered electrophilic and nucleophilic character. Effect of H2O concentration was monitored to determine hydrogen storage capacity which was found to be 7.17 wt.% for thirty molecules. An important finding of study is production of Stone-Wales (SW) defect upon H2O adsorption leading to increase in hydrogen production and its storage capacity. The functionalization of topological defected SWCNTs provides distinctive applications of CNTs for gas storage purposes.t: METHODS: In the current study, First Principal Density Functional Theory (DFT) calculations were carried which provides greater computational efficiency as compared to many traditional quantum mechanical methods. SCME: ADF (2018) modeling suite software with in framework of DFT approach using exchange correlation (XC) LDA-GGA (Generalized Gradient Approximation) with PBE (Perdew, Burke and Ernzerhof) functional and DZ (Double beta) basis set was employed to investigate structural, energetic and electronic aspects of adsorption on the surface of pristine, carbamic acid and 2-amino 3-acetly pyridine functionalized SWCNTs. (2, 4), (5, 5) and (6, 0) SWCNTs were designed using Avogadro's software and were imported to SCM: ADF graphical interface and were optimized as adsorbent. Single point energy (SPE), geometry optimization and high accuracy frequency calculations were performed to determine energetic, electronic and thermodynamic characteristics and feasibility of adsorption using XC of GGA-PBE functional & DZ basis set.