Stone-Wales Research Articles

Quantum transport properties of hybrid BN–C nanotubes: Strong spin filtering effect robust against Stone–Wales defects

Quantum transport properties of hybrid BN–C nanotubes: Strong spin filtering effect robust against Stone–Wales defects

Tuning the electronic properties of armchair boron phosphide nanoribbons via H/O/F passivation and Stone–Wales defect

To explore the possibility of various edge-passivating elements for armchair boron phosphide nanoribbons (ABPNR), we performed first-principles computation under the flagship of density functional theory. The bare and H, O, F-passivated structures were considered for the present calculations. The possibility of probable edge-passivation using these elements was assured by the binding energy analysis. Moreover, O emerges as the most efficient passivating element which is stable by more than 400 meV over F-passivation for nanoribbons of smallest width. It is predicted that considered passivating elements affected structural as well as electronic properties of the ABPNR. It is observed that O-passivation leads to narrow band gap behavior while F-passivations yields a band gap of 1.07 eV to 1.55 eV. The Stone–Wales defects are also discussed, showcasing their potential to tune the electronic properties of ABPNR for future semiconductor devices.

Lanthanide Atoms Induce Strong Graphene Sheet Distortion When Adsorbed on Stone-Wales Defects.

Local curvature in graphene can enhance its reactivity and catalytic activity and can be induced by the adsorption of certain chemical species. By employing periodic density functional theory (DFT) calculations, we demonstrate that significant local curvature can be systematically observed when lanthanide atoms (the full series from La to Lu) are adsorbed on the Stone-Wales (SW) defect in graphene, contrary to that in defect-free graphene. Despite the typical high coordination numbers of lanthanide species, their hapticity is always η2 (and not η5, η6, or η7), where Ln atoms are adsorbed on the (7,7) junction, forming relatively short Ln···C separations. Contrary to the pristine graphene, the SW region undergoes considerable distortion and results in much stronger Ln bonding. The positive charge acquired by Ln atoms upon adsorption on SW is approximately 1.5 times larger than that on defect-free graphene. The high visibility of electron-rich lanthanide species in scanning tunneling microscopy images provides a means to locate SW defects in graphene samples experimentally.

Effect of Stone-Wales defects on the mechanical properties of TiAl/CNT core-shell nanowires

In this study, the effect of Stone-Wales (SW) defects on the mechanical properties of TiAl/CNT core-shell nanowire was studied using molecular dynamics simulations. Our study revealed that SW defects can reduce the ultimate tensile strength and the fracture strain of TiAl/CNT core-shell nanowires. Notably, the ultimate tensile strength of TiAl/CNT core-shell nanowires initially decreased and then increased with the increasing number of SW defects. Conversely, the effect of SW defects on the Young’s modulus of TiAl/CNT core-shell nanowires was less pronounced, with the Young’s modulus showing little dependence on the presence of SW defects. The effect on the mechanical properties is a result of the combined effect of lattice changes, Stair-rod and Hirth dislocations, laminar faults and voids brought by the SW defects. These results provide new insights for further design and fabrication of advanced materials.

Potential of graphene as an adsorbent for HSSS· radical – A DFT investigation

The sulfane sulfur molecules are known to regulate many biological processes for the normal functioning of cells. Herein, the interactions of pristine, B-doped, N-doped, BN-codoped, monovacancy defected, and Stone-Wales (SW) defected graphene with HSSS· radical have been investigated theoretically in the framework of density functional theory (DFT) with an aim to understand if pristine or modified graphene can be used as an adsorbent for HSSS· radical. The analysis based on the structural details, Wiberg bond, ZPE-corrected adsorption energies, reaction enthalpies, reaction free energies and density of states (DOS) reveal that the pristine, BN-codoped, monovacancy defected and SW defected graphene would serve as potential adsorbents for adsorption of HSSS· radicals; the monovacancy defected graphene could be the best choice for this job. It is found that the B-doped graphene would act as a weak adsorbent but the N-doped graphene would not at all be suitable for adsorption of HSSS· radicals.

Tribological behavior of graphene/h-BN vdW heterostructures: the role of defects at the BN layer

Molecular dynamics simulations and first principles calculations were performed to study the tribological behavior of graphene/h-BN (G/h-BN) heterostructures with vacancy and Stone–Wales (SW) defect under uniform normal load, revealing the mechanism of the effect of defect types on friction, and discussing the coupling effect of temperature and interfacial defects on the tribological behavior of G/h-BN heterostructures. Under the normal force of 0.2 nN/atom, the friction force of the four systems is 0.0057, 0.0096, 0.0077, and 0.26 nN, respectively. The friction force of SW defect heterostructure is 45 times that of perfect interface heterostructure. The influence of defect type on friction force is SW > SV > DV. By observing the dynamic change of the Z-direction coordinate position of the sliding layer atoms, the slip potential energy curves and the evolution law of the moiré pattern, the relationship between the structural morphology and the energy change of different defective heterostructures and the frictional behavior was investigated comprehensively and intuitively for the first time. From the perspective of atomic strain, the deformation of heterostructures at the atomic level was quantified. The results showed that at 300 K and 0 K, the maximum strain of atoms in the sliding layer was 11.25% and 9.85%, respectively. The thermal perturbation mainly occurs in the out-of-plane direction, which in turn affects the friction. Through density functional theory, it is found that under uniform load, it is difficult to form bonds between the graphene sliding layer and the substrate layer when the defects are in the h-BN substrate layer, which has less influence on the friction of the system, thus making the defective heterostructures also remainsuperlubricity state. These results provide a new understanding of the interfacial friction of G/h-BN defective heterostructure.

First-principles study of lithium behavior in the ABA-stacking trilayer graphene with defects

To investigate the effect of defects on the Li embedding in graphene, we have studied the embedding and migration of Li in graphene with single-vacancy (SV), double-vacancy (DV), and Stone-Wales (SW) defects using the first-principles calculations. The results show that Li atom prefers to embed in regions with defect, and the presence of defect enhances the Li embedding in graphene. From the perspective of solution energy, Li embedded in the defect region of SV is the most stable, followed by the defect region of DV and SW. Migration results reveal that defects lead to an increase in the energy barrier for Li atom migration between layers and that Li is likely to be trapped in the defect region during migration. Open-circuit voltage and theoretical capacity calculations demonstrate that the lithium capacity of the ABA-stacking trilayer perfect graphene is 248 mAh/g. The lithium capacity diminishes to 165 mAh/g when a SW defect is present in the ABA-stacking trilayer graphene. In contrast, the lithium capacity increases to 270 mAh/g and 292 mAh/g when SV or DV defect is present in the ABA-stacking trilayer graphene, respectively. It is sufficient to show that graphene with low-density SW defect is unsuitable for application as electrode materials. Conversely, the low density of SV and DV defects can increase the lithium capacity of the ABA-stacking trilayer graphene at the same time, which will also lead to lithium deposition to some extent.

Vacancies and Stone–Wales type defects in monolayer BeN[formula omitted]

The recent synthesis of monolayer BeN4 at high pressure has sparked significant scientific interest in this material owing to the Dirac nature of its quasi-particles and some exotic properties such as high mobility and high stiffness, which are similar to those of graphene. In this work, the influence of some intrinsic defects and their associated physical effects are explored. We systematically studied the structural stability and electronic behavior of Be and N vacancies in monolayer BeN4 using first-principles calculations. In addition, we thoroughly investigated the possible Stone–Wales (SW) type defects, another kind of intrinsic topological defect, in BeN4. Our investigation revealed that N vacancies are more energetically favorable than Be vacancies. In particular, N vacancies preferentially form divacancies rather than monovacancies. Moreover, Be vacancies have a greater influence on the electronic behavior than N vacancies or SW defects. In addition, the electronic behavior of this robust π electron system was minimally influenced by N vacancies or SW defects. Our research revealed that the presence of a single N monovacancy is sufficient to induce a magnetic state, which may have potential applications in quantum sensing as well as spintronics. The migration of monovacancies along different potential trajectories, which display intriguing patterns, was analyzed. Our findings indicate that vacancy migration is more favorable in the armchair direction than in the zigzag direction. Therefore, the results of this study will not only contribute to a comprehensive understanding of the nature of various defects in BeN4, but also offer valuable guidance for future research in several device applications.

First-principles study of Stone–Wales defects in monolayer and Bernal-stacked hexagonal boron nitride

Recently, Stone–Wales (SW) defects gradually attracted people’s research interest because of their unique properties. The theoretical research indicated that the SW defect in hexagonal boron nitride (h-BN) can lead to new defect levels in bandgap, making h-BN apply in ultraviolet emitters. However, the SW defect is always observed in graphene and rarely observed in h-BN in the experiments. Here, we confirmed the SW defects are not easily formed in h-BN under thermodynamic conditions by first-principles calculations. Specifically, the monolayer h-BN with SW defect (h-BN-SW) has the weak bond strength, dynamic stability and high-temperature thermal stability, facilitating the healing of SW defects under high-temperature conditions and the role of hydrogen. Additionally, we found the SW defect in AB stacked h-BN (AB-h-BN) have good mechanical stability, dynamic stability and thermodynamic stability than h-BN-SW, especially for AB-h-BN-2SW (2SW defects formed in upper and lower layer of AB-h-BN, respectively), which can meet the requirements for its application in electronic devices. Even under thermodynamic conditions, the formation of SW defects is extremely challenging. Electron beam irradiation technology provides a window for the generation of SW defects in h-BN. This offers opportunities for the introduction and control of SW defects, while also creating potential for their application in electronic devices. Moreover, we found that the absorption peak broadens, and a new absorption peak appears with the generation of SW defects, which is mainly induced by the decrease of bandgap and the generation of defect levels. Our research can provide theoretical guidance at atomic scale for designing and applying h-BN with SW defect in the experiments.

Cement based nanofiltration membrane of porous boron nitride and graphene oxide for effective oil/water separation

The development of effective filters for crude oil/water separation presents a critical environmental challenge in the face of oil spills. Porous membrane separation stands as a vital technique for removing organic solvents, oils, and dyes from water. In this study, we designed and fabricated a nanofiltration membrane composed of graphene oxide (GO) and boron nitride (BN) incorporated into a cement-based matrix to enhance the selectivity and efficiency of unidirectional flux transportation. The integration of GO, with its rich functional groups, and BN, known for its hydrophobic properties, within the cement matrix, resulted in an improved water permeation rate. Moreover, the inclusion of BN flakes in the cement matrix significantly enhances its mechanical strength, reaching up to 15.93 MPa (∼35 % greater than pristine cement), establishing it as a robust nanofiltration membrane for simultaneous flux enhancement and water purification. This innovative filter demonstrated remarkable separation efficiency, achieving up to 99 % oil removal while allowing the passage of water. To gain a deeper understanding of our experimental findings, we conducted ab initio investigations into the adsorption behavior of water and oil components, including ethanethiol, thiophene, and toluene molecules, on h-BN, GO, and their defective structures (Stone-Wales defect). Our results affirm that porous h-BN and GO nanosheets, characterized by their high specific surface areas, exhibit remarkable sorption capabilities. This nanoengineered membrane showcases substantial adsorption capacity alongside physisorption characteristics suitable for recycling, thereby holding significant potential for the development of functional porous structural materials in the realm of high-performance, cost-effective, and environmentally sustainable water treatment solutions.

Stone-Wales defective C60 fullerene for hydrogen storage

Hydrogen energy is one of promising non-polluting and renewable energy sources. In this paper, we present a first principal study of hydrogen storage in pure C60 fullerene cage and Stone-Wales (SW) defective C60 cages using density functional theory (DFT) with applying both the exchange functional B3LYP and the dispersion correction wb97xd at 6–31+g(d,2p) basis set. In addition, the counterpoise correction is applied, and the basis set superposition error is calculated. The calculations underscore that the hydrogenation binding energy of C60 cages occurs through an endothermal process for C60Hin with a hydrogen binding energy of 0.09 eV and through an exothermal process for C60Hout, C60SW66Hout, and C60SW65Hout, cages with hydrogen binding energies of −2.17 eV, −2.96 eV, and −2.20 eV, respectively. Remarkably, for the first time, the intermediate hydrogen binding energy is found inside C60SW66Hin fullerene, and C60SW65Hin fullerene cages with energies of −0.26 eV and −0.81 eV, respectively. The hydrogen adsorption inside the cavity of C60SW66 fullerene cage is thermodynamically possible below 289.8 K and entire pressure range considered. Our results highlight, for the first time, that the endohedral cavity of C60SW66 is a promising new medium for hydrogen storage due to its binding energies (−0.26 eV) and its hydrogen storage weight percentage (5.3%) that are close to the optimal conditions specified by DOE for commercial use. In addition, this study opens up a new discovery of Stone-Wales defective C60 fullerene for further endohedral cavity applications.

Irregular network of extended defects in graphene and a new criterion of the crystal lattice melting

Investigation of graphite defects has long and rich history. However, it turned out, that most point defects in graphene, such as vacancies or topological Stone-Wales defect, have high formation energies, preventing them from formation in large quantities. Recently, we have proposed a new type of extended defects in graphene, with formation energy per atom only slightly above the melting temperature. This means, that these planar defects may occur near the melting temperature in sufficient quantities to influence the thermodynamic properties of graphene. Still, there is discrepancy between thermodynamic properties of these defects and their topology, which can be successfully resolved by proposition of a new defects' type – irregular network of extended defects, which will be described in this paper. The study of network stability from these defects enables us to formulate a new criterion of crystal lattice melting, which supersedes the Lindemann/Born criteria.

Topological regulations of Stone-Wales graphene

Designed synthesis of graphene-based materials containing Stone-Wales defects represents a promising strategy for graphene modification, because of their highly diverse structures and tunable properties. In graphene-based materials, Stone-Wales defects are caused by the in-plane atomic rearrangement and re-linkage of graphene's honeycomb structure. The resultant Stone-Wales graphene's are topoisomers of graphene. Topology is naturally a major factor in regulating the structures and properties of Stone-Wales graphene, but the regulation rules are mostly unclear. In this study, 478 low-energy Stone-Wales graphene allotropes with diverse topology are predicted using topology-based global optimization, for which the thermodynamic, electronic, and elastic properties are evaluated using the first-principles calculations. The dependencies of the predicated physical properties on topological quantities and patterns are explicitly determined. The current study may lay the groundwork for design, synthesis, and property tuning of graphene-based materials.

Enhanced H2 storage in silicene through lithium decoration and single vacancy and Stone‐Wales defects: A density functional theory investigation

AbstractDefect engineering and metal decoration onto 2‐D materials have gained major attention as a means of creating viable hydrogen storage materials. This Density Functional Theory (DFT) based study presents lithium decorated single vacancy (SV) and Stone‐Wales (SW) defective silicene as a viable media for storing hydrogen via physisorption. Introducing defects increases the Li adatom's binding energy from −2.36 eV in pristine silicene to −3.44 and −2.73 eV in SV and SW silicene, respectively, preventing Li adatom clustering. The presence of defects and Li adatom further aid hydrogen adsorption onto the substrates with binding energies present between the US‐DOE set range of −0.2 to −0.7 eV/H2 with the highest binding energy measured to be −0.389 eV/H2. The enhanced H2 binding energies are a result of a combined contribution of the Li(p) and Li(s) orbitals with the H(s) orbital with an indirect electronic transfer from the silicene substrate to the Li adatom. Upon double side Li decoration, both the Li‐decorated defective systems were able to effectively store multiple H2 molecules up to 28 H2 with the highest gravimetric density being 5.97 wt%. Ab Initio molecular dynamic simulations conducted at 300 K and 310 K confirm the stability of the Li adatom as well as the adsorbed H2 molecules at room temperature and establish the viability of these systems as effective, high gravimetric density, physisorption‐based hydrogen storage media.

Role of the Carbon Nanotube Junction in the Mechanical Performance of Carbon Nanotube/Polyethylene Nanocomposites: A Molecular Dynamics Study.

Carbon nanotube (CNT)-based networks are promising reinforcements for polymer nanocomposites without the issue of CNT agglomeration. In this study, the CNT junction, a vital and representative structure of CNT-based networks, was applied as the reinforcement of the polyethylene (PE) matrix. The tensile properties of the CNT-junction/PE nanocomposite were investigated via molecular dynamics (MD) simulations and compared with those of pure PE matrix and conventional CNT/PE nanocomposites. The CNT junction was found to significantly increase the mechanical properties of the PE matrix. The Young's modulus, yield strength, and toughness rose by 500%, 100%, and 200%, respectively. This mechanism is related to the enhanced interfacial energy, which makes the polymer matrix denser and stimulates the bond and angle deformations of the polymer chains. Furthermore, the CNT junction demonstrated a more profitable reinforcement efficiency compared to conventional straight CNTs in the PE matrix. Compared to the ordinary CNT/PE model, the improvements in the Young's modulus and toughness induced by the CNT junction were up to 60% and 25%. This is attributed to the reduced mobility induced by the geometry of the CNT junction and stronger interfacial interactions provided by the Stone-Wales defects of the CNT junction, slowing down the void propagation of the nanocomposite. With the understanding of the beneficial reinforcing effect of the CNT junction, this study provides valuable insights for the design and application of CNT-based networks in polymer nanocomposites.

Structure and electrical properties of bilayer zigzag silicene nanoribbons depending on stone-wales and applied electric fields by SCC-DFTB method

The influence of geometry and electrical properties of Stone-Wales (SW) defects and an applied electric field on bilayer zigzag silicene nanoribbons (ZSiNRs) were investigated using the self-consistent charge density functional tight-binding (SCC-DFTB) method. The results show that concave deformation occurs at SW defects, leading to varying degrees of disruption in the original symmetrical structure. The overall stability of the marginal Stone-Wales (MSW) nanoribbons surpasses that of the central Stone-Wales (CSW) nanoribbons, SW-II type defects are prone to form in bilayer nanoribbons. The band gap of MSW defective nanoribbons expands significantly, realizing the transition from metallic to semi-metallic and semi-conductor properties. The electrons are transferred from the inner to the outer side of the nanoribbons, with a higher prevalence of defect nanoribbons compared to those that are perfect. The electric field intensity significantly alters the properties of both MSW-I and MSW-II defective nanoribbons.

Chemical reactivity of graphene doped with 3d transition metals: nothing compares to a single vacancy.

Finding catalysts that do not rely on the use of expensive metals is one of the requirements to achieve sustainable production. The reactivity of graphene doped with 3d transition metals was studied. All dopants enhanced the reactivity of graphene and performed better than Stone-Wales defects and divacancies, but were inferior to monovacancies. For hydrogenation of doped-monovacancies, Sc, Ti, Cr, Co, and Ni induced more prominent reactivity on the carbon atoms. However, the metals were the most reactive center for V, Mn, and Fe-doped graphene. Cu and Zn turned the four neighboring carbon atoms into the preferred sites for hydrogenation. The addition of oxygen to doped graphene with Ti, V, Cr, Mn, Fe, Co, and Ni on a monovacancy revealed a more uniform pattern since the metal, preferred to react with oxygen. However, Sc induced a larger reactivity on the carbon atoms. The affinity of the 3d metal-doped graphene systems towards oxygen was inferior to that observed for single-vacancies. Therefore, vacancy engineering is the most favorable and least expensive method to enhance the reactivity of graphene. We applied Truhlar's M06-L method accompanied by the 6-31G* basis sets to perform periodic boundary conditions calculations as implemented in Gaussian 09. The ultrafine grid was employed and the unit cells were sampled employing 100k-points. Results were visualized employing Gaussview 5.0.1.

Point defects in Dirac semimetal BeN[formula omitted] monolayer and their interaction with gas molecules

Point defects in materials may occur during the fabrication process of monolayer materials, or these defects can be created via electron beam irradiation to the perfect crystals. Recently, a triclinic phase of beryllium tetranitride BeN4 was synthesized from elements at ∼85 GPa pressure and can become a monolayer under ambient conditions. In this study, we have introduced various point defects into the BeN4 monolayer such as Be or N mono vacancy (Bevac, Nvac), BeN divacancy (BeNvac), antisite defect of BeN atomic positions and Stone–Wales (SW) defect, and investigated electronic and magnetic changes in the material. It is found that with the Be vacancy, the Dirac cone of the BeN4 monolayer disappears and the Bevac monolayer shows semi-metallic properties with overlapping valence and conduction bands. N vacancy induces local magnetic moment (0.797 μB) to the structure, and the Nvac monolayer has a direct band gap value of 0.172 eV. While the BeN divacancy turns the structure to metal, the antisite-defected BeN4 monolayer turns into a non-magnetic semiconductor with a band gap value of 0.256 eV. Furthermore, we have introduced bare and defected BeN4 monolayers with CO, CO2, H2, H2O and O2 gas molecules and found that these molecules give rise to crucial effects on the electronic and magnetic properties of the materials. While the considered molecules are physisorbed on the bare BeN4 monolayer, the H2O molecule dissociated to OH and H on the Nvac structure, and O2 molecule strongly binds on Nvac and antisite BeN4 monolayers. Furthermore, we have reported that the antisite BeN4 monolayer may be a good candidate material for hydrogen storage devices with an adsorption energy of 0.355 eV of the H2 molecule. We believe that our theoretical findings will be beneficial for further experimental and theoretical studies on BeN4 structure.

On-Surface Synthesis of Non-Benzenoid Nanographenes Embedding Azulene and Stone-Wales Topologies.

The incorporation of non-benzenoid motifs in graphene nanostructures significantly impacts their properties, making them attractive for applications in carbon-based electronics. However, understanding how specific non-benzenoid structures influence their properties remains limited, and further investigations are needed to fully comprehend their implications. Here, we report an on-surface synthetic strategy toward fabricating non-benzenoid nanographenes containing different combinations of pentagonal and heptagonal rings. Their structure and electronic properties were investigated via scanning tunneling microscopy and spectroscopy, complemented by computational investigations. After thermal activation of the precursor P on the Au(111) surface, we detected two major nanographene products. Nanographene Aa-a embeds two azulene units formed through oxidative ring-closure of methyl substituents, while Aa-s contains one azulene unit and one Stone-Wales defect, formed by the combination of oxidative ring-closure and skeletal ring-rearrangement reactions. Aa-a exhibits an antiferromagnetic ground state with the highest magnetic exchange coupling reported up to date for a non-benzenoid containing nanographene, coexisting with side-products with closed shell configurations resulted from the combination of ring-closure and ring-rearragement reactions (Ba-a , Ba-s , Bs-a and Bs-s ). Our results provide insights into the single gold atom assisted synthesis of novel NGs containing non-benzenoid motifs and their tailored electronic/magnetic properties.

The Special Activity of Stone–Wales Defect Graphene for the Oxygen Reduction Reaction: A Comparison Study between the Charge-Neutral Model and the Constant Potential Model Calculated by Density Functional Theory

The Special Activity of Stone–Wales Defect Graphene for the Oxygen Reduction Reaction: A Comparison Study between the Charge-Neutral Model and the Constant Potential Model Calculated by Density Functional Theory