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Rotor-step straight skewing is a common method to reduce electromagnetic vibration of permanent magnet synchronous motors (PMSMs). However, the difference of the radial electromagnetic forces received by different axial positions of the stator caused by the elastic-plastic material is generally ignored in the theoretical analysis to determine the skewing structure, which makes the vibration suppression effect of the structure far less than expected in practical applications. Take a 48-slot 8-pole interior PMSM as an example, this paper compares the suppression effects of rotor-step straight skewing and rotor-step zigzag skewing when the elastoplasticity of the stator material is considered. It is pointed out that the rotor-step zigzag skewing can overcome the limitation of the straight skewing in restraining electromagnetic vibration in practical application. Based on the theoretical formula and multi-physical field simulation, the selection rules of the rotor-step zigzag skewing angle and segment number are summarized. Finally, the rationality and effectiveness of the simulation method are verified by experiments on the prototype.

Using density functional theory with the generalized gradient approximation, we explored the geometric and electronic structure of polymerized spiro [4,4]nonatetraene (spiro-graphene) as a possible two-dimensional carbon allotrope comprising sp2 and sp3 C atoms. By reflecting a shape of the hydrocarbon molecule, this two-dimensional allotrope has a covalent network of fused pentagons with nanometer-scale structural rippling. The covalent network is thermally and dynamically stable with a relatively high total energy, higher than graphene by 0.6 eV/atom. The spiro-graphene is a metal where two linear dispersion bands cross each other at the Fermi level. In addition to these linear dispersion bands, the covalent network possesses the Dirac nodal line just above the Fermi level and along the Brillouin zone boundary. Accordingly, the ribbons with zigzag edges derived from spiro-graphene possess edge states like those of graphene nanoribbons with zigzag edges.

A microwave system in the form of a quasi-optical (QO) transmission line is proposed as an interaction circuit of an amplifier or an oscillator based on the cyclotron resonance maser (CRM) instability. The circuit consists of periodically spaced along the horizontal ${z}$ -axis focusing mirrors, which transport the Gaussian wave beam along a zigzag path with vertical and inclined segments. A beam of electrons having sufficiently high perpendicular velocities is guided by a static B-field along the ${z}$ -axis so that the e-beam periodically crosses the wave beam. The CRM instability occurs in regions where an electromagnetic wave having a Bz-component, as in a gyrotron, propagates strictly across the e-beam resulting in the interaction with minimal sensitivity to particle velocity spread. Three-dimensional Particle-In-Cell (3-D PIC) simulations demonstrate the attractiveness of this “zigzag” CRM for the implementation of relatively broadband amplifiers or oscillators with unique (more than an octave bandwidth) frequency tunability at wavelengths of 1–2 mm.

Transverse spin angular momentum of light is a key concept in recent nanophotonics to realize unidirectional light transport in waveguides by spin-momentum locking. Herein we theoretically propose subwavelength nanoparticle chain waveguides that efficiently sort optical spins with engineerable spin density distributions. By arranging high-refractive-index nanospheres of different sizes in a zigzag manner, directional optical spin propagation is realized. The origin of the efficient spin transport is revealed by analyzing the dispersion relation and spin angular momentum density distributions. In contrast to conventional waveguides, the proposed asymmetric waveguide can spatially separate up- and down-spins and locate one parity inside and the other outside the structure. Moreover, robustness against bending the waveguide and its application as an optical spin sorter are presented. Compared to previous reports on spatial engineering of local spins in photonic crystal waveguides, we achieved substantial miniaturization of the entire footprint down to subwavelength scale., 20 pages, 5 figures

We present theoretical framework investigations of the influence of temperature variation on the electrical conductivity of zigzag carbon nanotubes (CNTs) under the applied homogeneous axial dc field. This study was done semiclassically by solving Boltzmann transport equation to derive the current density of zigzag CNT as a function of homogenous axial dc field and temperature. Plots of the normalized current density versus homogeneous dc field applied along the axis of semiconducting zigzag CNTs as room temperature increases from 293 to 299 K revealed a significant increase in electrical conductivity, whereas in metallic zigzag CNTs, almost constant or a negligible decrease in electrical conductivity is observed. The study predicts semiconducting zigzag CNT as a potential material for temperature sensors since it exhibits a faster response and a substantially higher sensitivity to room temperature changes than the metallic counterpart. The electrical conductivity of metallic zigzag CNTs increases immensely as the temperature is reduced to a very low value which could probably lead to a potential superconductivity property that usually occurs at very low temperatures. These potential temperature sensors and superconductors of nanomaterial have vast applications in current-day science and technology.

Nanomotors are essential in nanorobots and nanoenergy. The critical issues include stability and efficiency. Here, we have investigated the influence of hydroxyl groups on the transmission behavior of carbon nanotube based nanomotors using molecular dynamic simulations. The results showed that 100% transmission efficiency occurred in kinetic energy transmission, irrespective to the diameters and chiral angles of carbon nanotubes. Such stable and efficient transmission was attributed to the hydrogen bonds formed between hydroxyl groups on motor and rotor. The fastened responses were observed in the systems with zigzag and armchair carbon nanotube motor. Our results provide atomic insights into improving stability and efficiency in nanomotors.

We consider the finite ribbons of graphene with two principal orientations, zigzag and armchair, of their edges to study in detail impurity effects on their edge states. An alternative to the known description of quasiparticle states in terms of transversal standing waves is proposed in the recurrence relations for their spectra vs discrete numbers of atomic chains in the ribbon, permitting to simplify the Green function approach to the disorder effects in these systems. The derived analysis shows the microscopic mechanisms of perturbation by different types of impurities on low energy states and clarifies how the stability of topological states in zigzag systems to disorder is related to the discrete amplitudes of these states across the ribbon. An opposite possibility for Mott localization under local impurity perturbations is found for armchair type nanoribbons but at special values of their width.

In the present study, the characteristics of graphene/polycrystalline copper nanolaminated (GPCuNL) composites under shear loading are investigated by molecular dynamics simulations. The effects of different temperatures, graphene chirality, repeat layer spacing, and grain size on the mechanical properties, such as failure mechanism, dislocation, and shear modulus, are observed. The results indicate that as the temperature increases, the content of Shockley dislocations will increase and the maximum shear stress of the zigzag and armchair directions also decreases. The mechanical strength of the zigzag direction is more dependent on the temperature than that of the armchair direction. Moreover, self-healing occurs in the armchair direction, which causes the shear stress to increase after failure. Furthermore, the maximum shear stress and the shear strength of the composites decrease with an increase of the repeat layer spacing. Also, the shear modulus increases by increasing the grain size of copper.

Static investigation of slim to tolerably thick composite plate built up by single-walled cabon nanotubes (CNT) is examined utilising the limited component technique dependent on higher order zigza...

Application of the zigzag (24, 0) single-walled carbon nanotube (SWCNT) in delivery of carbamate and imine tautomers of capecitabine is investigated via quantum mechanical geometry optimizations followed by chemical shielding calculations. Torsion angle between ribose and cytosine rings is very close to the experimental value in both tautomers. This suggests that relative orientation of these rings is independent of presence of SWCNT. Their carbon nuclei become closer to the tube’s internal surface by about 1Å, when going from cytosine ring to aliphatic tail. Their cytosine and ribose rings bend so that fluorine atoms and 2[Formula: see text]-OH group form ion-[Formula: see text] interaction with the surface. Calculated binding energies aside from observation of these sorts of interactions in these tautomers can propose SWCNT as their potent delivery tool. Most of the obtained conclusions are manifested in the observed trends for calculated chemical shielding values. They make connections among the reported experimental and computational distributions of chemical shielding values inside SWCNTs.

Accurate control of doping concentrations and their positions have difficulties that can be theoretically investigated. DFT-NEGF was used in order to investigate the influence of various electrode configurations on the electron transport properties of capped-SWCNT junction. Three systems were examined in which a benzene molecule is placed between two carbon nanotubes configured as an armchair (5,5) and a zigzag (5,0) as an electrode. Zigzag nanotubes were selected in two forms, namely non-neutralized with hydrogen (pure) and neutralized with hydrogen. A theoretical simulation in the Landauer formalism that combines both NEGF and DFT was used by the OpenMx package. Ab initio calculation was performed using a pseudopotential approach within DFT-D2. Two prominent peaks (Pa and Pb) were seen for pre-voltages of 0.01 V to 0.1 V. By increasing the pre-voltage from 0.01 to 0.1 V, there was no significant change in the location of the peaks; however, for biases above 0.1 V, changes in the peaks were significant. Unlike the zzCNT(5,0)-NP/Benzene/zzCNT(5,0)-NP system, the current intensity behavior in the zzCNT(5,0)-HP/Benzene/zzCNT(5,0)-HP system was almost linear. The results showed that the armchair carbon nanotube system had the lowest current intensity as compared to the other two systems.

Graphene nanoribbons with zigzag edges(ZGNRs) have attracted much attention for their spin-polarized edge states predicted more than 15 years ago. Since the ZGNRs are fabricated on metal substrates using molecular precursors, due to their strong coupling with metal substrates, experimental detection of the spin-polarized edge states is still difficult. Here, we design a partially hydrogenated graphene(PHGr), in which periodic hexagonal graphene nanoflakes(GNFs) with zigzag boundaries are embedded in a hydrogenated graphene layer. Using density functional theory(DFT) based first-principles calculations, we find that the hexagonal GNFs exhibit spin-polarized boundary states at their opposite zigzag boundaries, which is similar with the bow-tie-shaped GNFs and ZGNRs. DFT calculations demonstrate that the PHGr is a semiconductor with an antiferromagnetic ground state. Moreover, the antiferromagnetic boundary states and semiconducting properties keep unchanged when the size of GNF varies from 1.4 nm to 2.3 nm. The robustness of the spin-polarized boundary states enables this PHGr as a robust material for detecting spin-polarized boundary states coming from zigzag boundaries. In addition, we find that single Au atoms selectively adsorbed on boundaries catalyze H2 dissociation and therefore lower the barrier of graphene hydrogenation. Therefore, the PHGr can be used not only in carbon-based spintronic devices but also as a platform for single atom catalyst.

Determining atomic structure of intercalated metallic layer under graphene is a hot-topic due to the potential applications in electronic engineering. In this study, Pb-intercalated graphene (PbG) is fabricated on SiC substrate and the atomic structure and electronic properties of the intercalated Pb atoms underneath graphene are investigated by scanning tunneling microscopy/spectroscopy (STM/STS). As the crystal facet of intercalated Pb atoms can be arranged in (111) (unit cell, 0.35 nm × 0.35 nm) and (110) (unit cell, 0.61 nm × 0.35 nm), mottled moire pattern (period, 2.5 nm) and striated moire pattern (period, 2.1 nm) are formed. Atomic arrangement of the intercalated Pb is sensitive to tip scanning resulting in the conversion of the two moire patterns. Nevertheless, the crystal orientation of moire patterns is always aligned with zigzag direction of graphene. As revealed by STS, PbG performs the similar electronic states to those of free-standing graphene due to the shielding effects of Pb intercalation. The crystallographic relationship between graphene and Pb atoms is also confirmed by density functional theory (DFT) calculations. The study provides crucial for understanding the structure of intercalated Pb atoms underneath a graphene layer, which may enable the development of new 2D materials capped by graphene.

A three-dimensional finite element (FE) model for single-walled carbon nanotubes with armchair and zigzag shapes is proposed in this paper (SWCNTs). Nodes are positioned at the locations of carbon atoms to design the FE models. And three-dimensional elastic beam components are used to model the bonds between them. The effect of the diameter length/diameter ratio on the diameter length/diameter ratio, cross sectional aspect ratio and number of elements on the Young’s modulus of SWCNTs has been considered herein. From the conducted experiments it can be observed that, the larger tube diameter can lead to higher Young’s modulus for carbon nanotubes. Such that, maximum elastic modulus for the armchair and the zigzag models has been obtained to be 1.0285TPa and 1.0396TPa when the diameters for the armchair and the zigzag models were 2.034nm and 1.957nm respectively. Increasing the length/diameter ratio has led the Young’s modulus to be increased for armchair and zigzag models such that its values can reach 1.0451TPa and 1.0191TPa respectively. The cross sectional aspect ratio of SWCNTs showed an inversely proportional effect on the elastic modulus in this work. As a result of rising the cross sectional aspect ratio to be2, the Young's modulus for armchair and zigzag models has decreased to 0.7991TPa and 0.8873TPa, accordingly. The change in geometry has been observed to be a defect and it is in general can decrease the modulus of elasticity. The number of elements in the armchair model considered as prominent factor that increases the young’s modulus to be 1.0280TPa when the number of element is 10836. In zigzag model, the number of element has no effect on the elastic modulus since the number of nodes that exposed to the applied load is fixed in this case. The findings showed that the proposed FE model may be useful for studying carbon nanotube mechanical action in the future.

The transport properties of a molecular bio-electronic device based on the alanine amino-acid are investigated. The considered device consists of an alanine molecule as the central potential-dot coupled to two zigzag graphene nanoribbon (ZGNR) conducting electrodes. The current-voltage characteristics of this dual tunnelling molecular junction are studied at two different optimised compositions of the central molecule. The proposed amino-acid based structure utilises the tunnelling coupling similar to that of semiconducting single-electron transistors (SETs) to avoid complications due to the atomic interfaces. The current-voltage characteristics show polarity-dependent behaviour making the device feasible of being applied as a molecular rectifier. Negative differential resistance (NDR) along with tuneable peak-current position has been also observed in the current-voltage characteristics. The device is also capable of being applied as a switch controllable by the central molecule orientation.

Embedded resistors in printed circuit boards (PCBs) are fabricated to provide high integration, improved electrical performance, and reduced parasitic capacitance and inductance in the high-frequency and high-speed environment. At present, the embedded resistance errors caused by etching metal film accuracy are generally more than 20%. In this work, real-time monitoring technology is developed to precisely control the resistance of electroless-plated embedded resistors. During the deposition process, the resistances of embedded resistors are monitored until reaching the targeted resistance, realizing the very ideal resistance error lower than 10%. Arbitrary shapes including serpentine and zigzag structures of embedded resistors are attempted to validate the practical capability of this approach. Reliability Characterization experiments such as high-temperature and high-pressure lamination, thermal shock and thermal cycles confirm the thermal and mechanical stability. It is demonstrated that the embedded resistors through real-time monitored electroless plating have tremendous potential in the manufacture of high-frequency and high-speed PCBs.

Carbon nanotube (CNT) based fibers/films are envisioned as the building blocks for next generation high-performance composite materials. However, the mechanical performance of the as-synthesized or as-prepared CNT bundles are still well below their constituent CNTs. Here, we systematically assessed the influence from the stacking morphology on the tensile properties of double-walled CNTs (DWNTs)-based bundles through molecular dynamics simulations. We found that the bundles containing zigzag DWNTs exhibit higher Young’s modulus, but lower yielding strength (and yielding strain) compared with that of the pure armchair DWNT-based bundles. In particular, an initial off-axial angle perturbation in one of the constituent DWNTs induces evident misalignments in other constituent DWNTs, which remarkably degrades the yielding strength and yielding strain of the bundle structures. Following the Hooke’s law, the impacts from the stacking morphology on the overall tensile properties of DWNT bundles can be quantitatively predicted by approximating each DWNT as an elastic column approximation. Overall, this work establishes a comprehensive understanding of the influence from the stacking morphology, which not only provides a perspective explanation of the unexpected low performance of as-synthesized CNT bundles, but also shed light on the design of high-performance CNT based bundles.

n‐peri‐Acenes (n‐PAs) have gained interest as model systems of zigzag‐edged graphene nanoribbons for potential applications in nanoelectronics and spintronics. However, the synthesis of n‐PAs larger than peri‐tetracene remains challenging because of their intrinsic open‐shell character and high reactivity. Presented here is the synthesis of a hitherto unknown n‐PA, that is, peri‐heptacene (7‐PA), in which the reactive zigzag edges are kinetically protected with eight 4‐tBu‐C6H4 groups. The formation of 7‐PA is validated by high‐resolution mass spectrometry and in situ FT‐Raman spectroscopy. 7‐PA displays a narrow optical energy gap of 1.01 eV and exhibits persistent stability (t 1/2≈25 min) under inert conditions. Moreover, electron‐spin resonance measurements and theoretical studies reveal that 7‐PA exhibits an open‐shell feature and a significant tetraradical character. This strategy could be considered a modular approach for the construction of next‐generation (3 N+1)‐PAs (where N≥3)., The synthesis of the hitherto unknown peri‐heptacene 7‐PA is demonstrated by a rational molecular design strategy in which the reactive zigzag edges are kinetically protected. The formation of 7‐PA is validated by high‐resolution mass spectrometry and in situ FT‐Raman spectroscopy. The open‐shell 7‐PA displays a narrow optical energy gap of 1.01 eV and exhibits a persistent stability (half‐life ≈25 min) under inert conditions.

Molecular dynamics simulations with adaptive intermolecular reactive empirical bond order (AIREBO) potential were carried out to study the effect of temperature and orientation on the tensile strength of pristine and defective bilayer graphene (BLG) sheet. Results obtained reveal that the fall in tensile strength of pristine AA stacked BLG due to the presence of vacancy is significant at room temperature (300 K) but decreases at higher temperature (1073 K). Interestingly, this phenomenon reverses in case of AB stacked BLG, wherein the percentage fall in strength at higher temperature due to defect is more than that at room temperature. In order to understand these discrepancies in the results obtained, three case studies were conducted, and the results obtained suggested that when defects are present in armchair direction, this phenomenon occurs. The study also reveals that in case of AB stacked BLG, zigzag direction is more defect tolerant at room and high temperatures. Interestingly, variation of tensile strength due to the orientation is in good agreement with projections from potential energy concepts and theoretical calculations. We envisage that the study will provide useful information to the device engineers for the optimisation of the mechanical properties and convenient structural adaptation of bilayer graphene while working at wide range of temperatures.

We show that very narrow armchair graphene nanoribbons of length L and width of 2 zigzag-rings undergo a metal-insulator-like transition at a critical length L c ≈ 10 nm, where the energy gap drops rather abruptly and topological “end” states appear, linked to dramatically transformed aromaticity. At Lc the conductivity, estimated through an invoked computational scheme, also rises almost discontinuously to a value near the nominal minimum conductivity of graphene σ min = 4 e 2 h . The end states (at the zigzag edges) generate sharp peaks in the density of states around the Fermi level at the Dirac points, coinciding with charge-neutrality points, associated with σmin. This suggests metallic-like behaviour, which however is an uncommon combination of interrelated “short-long”, (or “bulk”-“edge”) topological-aromatic transition(s) due to strong quantum confinement, combined with inversion symmetry conflict. This “multi-transition” is rather universal occurring also for wider AGNRs but for a much smaller Lc and in a less sharp way. The assumed lower total energy of such open states is an artefact of the mean-field treatment of the electron-electron interaction. In contrast, the topological “end” states reported here are unique and not spin, but rather pseudospin polarized. Thus, any observed magnetism should be considered non-conventional or of questionable origin.

The formaldehyde gas sensing properties of transition metal-doped graphene have been systematically investigated by first-principles calculations. The optimized geometries of transition metal-doped graphene with and without HCHO adsorption, adsorption energies, charge transfers and magnetic moments are obtained for various doped graphene systems. The calculated results show that Co-, Ni-, Cu-, Zn-, Pd- and Ag-doped systems have moderate adsorption energies, implying their potential applications as HCHO sensors. The two-probe sensor devices consisting of the central scattering region and pristine graphene electrodes with the armchair or zigzag transport directions are built, and the spin-polarized current–voltage curves are calculated by the non-equilibrium Green’s function method within the framework of density functional theory. For the Cu-, Zn- and Ag-doped systems, the average sensor response is over 80%, 40% and 290%, respectively. In particular, the Cu- and Ag-doped graphene devices have the highest value of response over 200% and 900% at low voltages, indicating a short response time and high sensitivity of these devices. The present study provides a theoretical basis for exploring practical applications of the transition metal-functionalized graphene as superior HCHO gas sensors.

Very recently, a novel phase of hydrogenated borophene, namely $$\alpha '$$ α ′ -4H, has been synthesized in a free-standing form. Unlike pure borophenes, this phase shows very good stability in the air environment and possesses semiconducting characteristics. Because of the interesting stiffness and flexibility of borophenes, herein, we systematically studied the mechanical properties of this novel hydrogenated phase. Our results show that the monolayer is stiffer (Y$$_\text {xy}$$ xy = $$\sim $$ ∼ 195 N/m) than group IV and V 2D materials and even than MoS$$_2$$ 2 , while it is softer than graphene. Moreover, similar to other phases of borophene, the inherent anisotropy of the pure monolayer increases with hydrogenation. The monolayer can bear biaxial, armchair, and zigzag strains up to 16, 10, and 14% with ideal strengths of approximately 14, 9, and 12 N/m, respectively. More interestingly, it can remain semiconductor under this range of tension. These outstanding results suggest that the $$\alpha '$$ α ′ -4H is a promising candidate for flexible nanoelectronics.

The single walled carbon nanotube (SWCNT) cloning or its seeded growth with a catalyst particle docked on one of its ends was proposed as the ultimate solution for chirality-specific SWCNT synthesis and, therefore, revealing the effect of catalyst particle size on the robustness of the SWCNT cloning is crucial for experimental designs. Through systematic atomic simulations, we have clearly demonstrated that the robustness of SWCNT cloning depends on both the chiral angle of the SWCNT and the ratio of the diameters between the SWCNT and the docked catalyst particle. The zigzag (ZZ) or near ZZ SWCNTs are highly sensitive to the size of the docked catalyst particle. A small change of the catalyst particle size could lead to a variation of the SWCNT’s chirality. In contrast, armchair (AC) or near-AC SWCNTs are less sensitive to the size of the docked catalyst particle and able to maintain their original chiralities within ∼30% variation of the catalyst particle size. This study greatly deepens our understanding of SWCNT’s growth mechanism and provides a quantitative guidance for SWCNT cloning.

Zigzag carbon nanobelts are a long-sought-after target for organic synthesis. Herein we report new strategies for designing and synthesizing unprecedented zigzag carbon nanobelts, which present a wave-like arrangement of hexagons in the unrolled lattice of (n,0) single wall carbon nanotubes (n=16 or 24). The precursors of these zigzag carbon nanobelts are hybrid cyclic arylene oligomers consisting of meta-phenylene and 2,6-naphthalenylene as well as para-phenylene units. The Scholl reactions of these cyclic arylene oligomers form multiple carbon-carbon bonds selectively at the α-positions of naphthalene units resulting in the corresponding zigzag carbon nanobelts. As monitored with fluorescence spectroscopy, one of these nanobelts binds C60 with an association constant as high as (6.6±1.1)×106 M-1 in the solution in toluene. Computational studies combining linear regression analysis and hypothetical homodesmotic reactions reveal that these zigzag nanobelts have strain in the range of 67.5 to 69.6 kcal mol-1 , and the ladderization step through Scholl reactions is accompanied by increase of strain as large as 69.6 kcal mol-1 . The successful synthesis of these nanobelts demonstrates the powerfulness and efficiency of Scholl reactions in synthesizing strained polycyclic aromatics.

The rising demand for developed electronics has led researchers to explore new design approaches using new materials and processes. The current device scaling using these new nanomaterials in advanced fabrication processes greatly improves the overall efficiency and performance of various electronic designs. In this study, the electronic behavior of all types of silicon-doped carbon nanoscrolls including armchair, zigzag, and chiral carbon nanoscrolls is investigated. Although the electronic properties of silicon carbide-based nanostructures and methods of synthesis have garnered great research attention in recent years, to date there have been no studies investigating analytical models or numerical simulation for the energy band structures and electronic characteristics of silicon carbide nanoscrolls. This paper presents a detailed analytical model of the energy band structure for various chiralities of silicon-doped graphene nanoscrolls and silicon carbide nanoscrolls. Our numerical results reveal metallic behavior for most small-diameter armchair Si-doped carbon nanoscrolls. However, for a given (n,n) armchair nanoscroll, the nanoscroll is a semiconductor if n is a multiple of 3. This is due to the effect of the quantization line intersection at the Dirac points. For larger diameters of armchair Si-doped carbon nanoscrolls, there is a small band gap between the associated valence and the conduction band which translates to semiconducting behavior.ae Our numerical study illustrates zero band gap for small-diameter zigzag silicon carbide nanoscrolls, which leads to metallic properties, while in larger nanoscrolls a small energy gap is seen. It seems that the associated energy gap is changed according to the overlap of the first spiral turn with the other turns. Also, the presence of variable small band gaps between the associated valence and conduction bands in large-diameter chiral nanoscrolls reveals that chiral Si-doped carbon nanoscrolls mainly exhibit semiconducting behavior. In the end, all the numerical results are tabulated as a periodic table in which a symmetric arrangement with respect to the armchair nanoscrolls is observed, and as a table diagonal data for the chiral Si-doped carbon nanoscrolls. Moreover, the effects of length variations on the energy structure of silicon carbide nanoscrolls is highlighted in the study.

Carbon-based tubular materials have sparked a great interest in future electronics and optoelectronics device applications. In this work, we computationally studied the mechanical properties of nanotubes generated from popgraphene (PopNTs). Popgraphene is a 2D carbon allotrope composed of 5-8-5 rings. We carried out fully atomistic reactive (ReaxFF) molecular dynamics for PopNTs of different chiralities ( n,0 and 0,n ) and/or diameters and at different temperatures (from 300 up to 1200 K). Results showed that the tubes are thermally stable (at least up to 1200 K). All tubes presented stress/strain curves with a quasi-linear behavior followed by an abrupt drop of stress values. Interestingly, armchair-like PopNTs ( 0,n ) can stand a higher strain load before fracturing when contrasted to the zigzag-like ones ( n,0 ). Moreover, it was obtained that Young's modulus (YMod ) (750-900 GPa) and ultimate strength (σUS ) (120-150 GPa) values are similar to the ones reported for conventional armchair and zigzag carbon nanotubes. YMod values obtained for PopNTs are not significantly temperature-dependent. While the σUS values for the 0,n showed a quasi-linear dependence with the temperature, the n,0 exhibited no clear trends.

Considering the demand for long spin communication distance in spintronics, graphene presents micrometer spin relaxation length at room temperature, making it one of the most promising two dimensional spintronic materials. However, achieving efficient spin injection (including pure spin current and spin polarized current) by reducing the spin dependent scattering between graphene and other materials like contact is still a core challenge. Here, we propose a novel approach to generate spin current in zigzag graphene nanoribbon (ZGNR) via photogalvanic (or photovoltaic) effect (PGE) from atomic first principle calculations. By designing ZGNR based device with spatial inversion symmetry, we find that the PGE induced pure spin current can be hiddenly generated without accompanying charge current. Furthermore, through applying a dual gate in the system, the generated pure spin current can be controlled when dual gate voltages have the opposite signs. Interestingly, when the signs of dual gate voltages are the same, the pure spin current can turn into the fully spin polarized current. More importantly, the generated spin current via PGE is independent of photon polarization and incident angles. Our investigations demonstrate ZGNR’s great potential application in noninvasive spin injection of the graphene based spintronic device.

Zigzag hydrocarbon belts have been fascinating chemists and materials scientists for decades because of their aesthetically appealing molecular structures, outstanding physical properties and intri...

Summary The electronic properties of finite-sized graphene fragments are strongly dependent on their topological structures. The existence of two or more extended zigzag edges could lead to unique open-shell character and magnetic activity. In this review, various types of well-defined graphene nanoribbons, nanographenes, and graphene-like molecules with open-shell character are summarized. Particularly, chemistry and electronic properties of graphene fragments with one, two, and three pairs of parallel zigzag edges, zethrenes with quinoidal structures, and [n]triangulenes with three zigzag edges are discussed in detail. Synthesis of this kind of open-shell molecules is very challenging, and both solution-phase and on-surface chemistry have been used. Their radical characters can be simply predicted in terms of Clar’s sextets and quantitatively analyzed by spin-unrestricted density functional theory or multireference quantum mechanical calculations. Their unique magnetic activity and quantum properties would render them promising materials for all carbon-based spintronic and quantum devices.

It is well known that the laser-induced dynamics of a system is determined by three laser parameters, namely, wavelength, pulse width, and intensity. In this study, the laser polarization is presented as a new parameter that determines the dynamics of highly anisotropic materials. By performing first-principles electron-ion dynamics simulations assuming a laser wavelength of 800 nm, a full width at half-maximum of 10 fs, and a field intensity of 4 V/A, carbon nanotubes (CNTs) were found to be fragile or robust when the polarization was parallel or perpendicular, respectively, to the tube axis. This behavior was observed for both zigzag and armchair CNTs and is thus expected to be only weakly dependent on CNT chirality. The obtained results are anticipated to encourage experimental efforts to select CNTs of a particular orientation using pulsed lasers with controlled polarization.

A possible route is given to achieve enhanced thermoelectric (TE) performance in a spin-orbit (SO) coupled graphene nanoribbon (GNR). The GNR is irradiated with a suitable polarized light so that the transmission function can have asymmetry around the chemical potential, which is the key requirement to enhance the TE performance. The interplay between SO coupling and irradiation on the nature of transmission function is critically investigated. Astounding TE results are obtained in the presence of light irradiation without modifying the other physical parameters of the system. The thermopower is enhanced significantly and at the same time, a considerable suppression in the thermal conductance is observed which yields favorable energy conversion. We discuss thermoelectric properties for the unpassivated and passivated GNRs as well. Both zigzag and armchair GNRs are taken into account, and finally, the results are studied by varying their widths in a wide range. Enhancing the thermoelectric performance by means of irradiation in a SO coupled system is completely new and has not been explored so far to the best of our concern, and might be applicable as well in other such topological systems.

We demonstrate via micromagnetic simulations that a magnetic domain, which has two straight domain walls (DWs) and is formed in a perpendicularly magnetized ferromagnetic metal (FM), moves through a perpendicularly magnetized ferromagnetic insulator (FI) because of the spin-transfer torque arising from a spin-polarized current flowing in the FM. This phenomenon could be used for realizing racetrack memory with a continuous loop structure built from a nanowire comprising an FM/FI junction. We employ two nanowire structures in which two FMs are separated by a rectangular or a zigzag FI. In the system with a rectangular FI, the domain passes through the insulator when the length of the insulator is shorter than the DW length. However, the domain transforms into an unstable structure with current-induced domain motion after it passes through the insulator. In the system with a zigzag FI, the domain passes through the insulator irrespective of the length of the insulator. When passing through the zigzag FI, the velocity of the domain increases.

Hydrogen passivation is an important method used to stabilize a specific graphene edge. Although several hydrogen-terminated graphene edges have been proposed in theory, a comprehensive exploration of highly stable hydrogen-terminated graphene edges is still absent. According to the bare graphene-edge databases, a series of hydrogen-terminated graphene edges have been proposed. The energy stability of hydrogen-terminated zigzag and armchair graphene edges is fully investigated. The six most stable hydrogen-terminated zigzag edges and six armchair edges of graphene are determined. Hydrogen passivation makes hydrogen-terminated graphene edges energetically more stable than bare graphene edges. The additional hydrogen atoms balance the dangling bonds of carbon atoms at edges by forming hydrogen-carbon covalent bonds. Hydrogen-terminated graphene edges with six-membered carbon rings have better global stability than those composed of non-hexagonal structural units. The effects of the experimental temperatures and hydrogen partial pressures on the stability of hydrogen-terminated graphene edges are fully investigated. Furthermore, hydrogen passivation can open the band gap of graphene effectively. These results provide a deep understanding of hydrogen-terminated graphene nanostructures.

The existence of a new two dimensional CN2 structure was predicted using ab-initio molecular dynamics (AIMD) and density-functional theory calculations. It consists tetragonal and hexagonal rings with C-N and N-N bonds arranged in a buckling plane, isostructural to tetrahex-carbon allotrope. It is thermodynamically and kinetically stable suggested by its phonon spectrum and AIMD. This nanosheet has high concentration of N and contains N-N single bonds with an energy density of 6.3 kJ/g, indicating potential applications as high energy density materials. It possesses exotic mechanical properties with negative Poisson's ratio and an anisotropic Young's modulus. The modulus in the zigzag direction is predicted to be 340 N/m, stiffer than h-BN and penta-CN2 sheets and comparable to graphene. Its ideal strength of 28.8 N/m outperforms that of penta-graphene. The material maintains phonon stability upon the application of uniaxial strain up to 10% (13%) in the zigzag (armchair) direction or biaxial strain up to 5%. It possesses a wide indirect HSE band gap of 4.57 eV which is tunable between 3.37 - 4.57 eV through strain. Double-layer structures are also explored. Such unique properties may have potential applications in high energy density materials, nanomechanics and electronics., 24 pages, 10 figures, 2 tables. arXiv admin note: text overlap with arXiv:2012.07841

Single-atom catalysis has been of intense interest in recent years. Here, using first-principles simulations, we report a unique approach that obtains promising information about O2 activation and CO oxidation on active Pt-single-atom catalysts (Pt-SACs) on N-doped graphene (NGr). It is found that the activity of Pt-SACs can be tuned by changing the Pt-loading sites on Gr/NGr, with Pt on the zigzag edge of NGr having optimal performance. Employing charge analysis of various anchoring sites, we reveal that the catalytic performance has a strong dependence on the polarization charge on the Pt atoms. The correlations of these charges with binding energies and reaction barriers exhibit volcano-like trends. The polarization charge thus provides a parameter that allows predicting the catalytic properties for different active sites, providing insights into the electronic structure modulation of SACs on graphene-like supports.

A first principle study with the density functional theory method has carried for parallelogram graphene nanoflakes. In this work, we used ABINIT package to calculate the fundamental properties of parallelogram graphene nanoflakes in the armchair and zigzag types, due to the increase of the number of atoms. The effect of defect for these characters in each type is also presented. Depend on the calculation results, the bandgap of parallelogram graphene nanoflakes only exists in armchair types with the largest bandgap of 0.021 eV for 54 atoms, while the zigzag types have no bandgap. Based on these results, it can be said that the properties of parallelogram graphene nanoflakes were semimetal. In addition, the density of state results shows that the magnetic properties of parallelogram graphene nanoflakes were non-magnetic since the symmetrical properties between the density of states in spin up and spin down. Based on the results study of defect effect, it was found that the defect only affected the bandgap, but not the magnetic properties.

Based on the chiral indices, different structures like an arm chair, zigzag and chiral are formed and carbon nanotube (CNT) shows semiconducting and metallic properties. This is a very interesting phenomenon in the field of nanoelectronics research. Some fundamental parameters like diameter, bandgap, number of hexagons in a unit cell, and temperature affect the carbon nanotube properties. These parameters may also change the carrier mobility in the carbon nanotube based back-gated field effect transistor (FET). Diameter (directly proportional with mobility) and temperature (inversely proportional to the mobility) dependency is very much important on charge density.

The synchronously periodic re-melting of molten pool was firstly introduced in additive manufacturing to promote the epitaxial growth of columnar structure using a novel quasi-continuous-wave (QCW) laser. The epitaxial growth of columnar structure was intensified and the single-crystal-like sample with highly oriented “zigzag” columnar grains was produced. The modified molten-pool geometry and the synchronously high-frequency re-melting of the molten pool contribute to the formation of single-crystal-like structure. This work reports a new route to promote the continuously epitaxial growth of dendrites for fabrication of single-crystal-like sample.

A deployable log periodic dipole antenna (DLPDA) is proposed. The antenna consists of pairs of collapsible steel tape springs (as the dipoles), a novel stretchable zigzag double-sided parallel stripline (ZDPS) (as the boom), and a coplanar waveguide on one side of the parallel striplines to guide the electromagnetic wave from the backend to the frontend. As a result, the proposed antenna becomes foldable and can be stored in a small volume prior to deployment. A design guideline for the DLPDA is given based on the simplified circuit model. Furthermore, the ZDPS, which is found as a slow wave structure, has been studied. The empirical equations are derived to obtain its characteristic impedance and propagation constant, which are the key parameters for the design guideline. One prototype of the DLPDA has been fabricated and tested. The deployment mechanism of the prototype has been successfully demonstrated using compressed air in a lab. The prototype has a stowed volume of < 2000 cm3, which is only 2% of the volume in fully deployed state.

Zigzag carbon nanobelts are a long-sought-after yet unrealized target for organic synthesis. Herein, we report a study toward the synthesis of tetrabenzo[10]cyclacene, an undocumented zigzag carbon...

This article proposes an enhanced procedure for executing the standard variable load test that allows obtaining high correlation factors for indirectly measured stray-load loss during efficiency tests of induction motors. This helps to achieve the minimum values required by the international standards to consider the variable load test well executed, avoiding unwelcome test repetitions and leading to significant amount of time saved. With the machine at steady-state temperature, the enhanced procedure consists of alternatively applying load levels higher and lower than the rated load, so that the stator winding temperature zigzags around the rated value. Hence, multiple readings can be performed for each load point, having the machine in isothermal conditions. This allows averaging many measurements of the same load point to mitigate the impact of instrumentation and reading errors. The article includes load tests conducted on different induction motor sizes and pole counts, applying both the standard variable load test procedure and the proposed approach. The experimental results show that the proposed technique allows achieving higher correlation factors on the stray-load losses than the standard procedure.

The main agenda of the present research work is to evaluate the influence of FSW parameters and tool geometry on metallurgical properties during FSW of AA 6082-T6 aluminium alloy. Friction stir welding was performed on AA 6082-T6 using four different geometrical tool pin profiles namely Asymmetrical-Skew, Triangular concave threaded tool, Three flat threaded tool (TFT) and Tri-Flute concave threaded tool at three rotational speed’s (1000 rpm, 1200 rpm, 1400 rpm) and single traverse speed 25 mm/min. Microstructure of various regions on the weldments like Nugget Zone (NZ), Advancing side thermo-mechanically affected zone (AS-TMAZ),Advancing side heat affected zone (AS-HAZ), Advancing side boundary zone (AS-BZ), Retreating side thermo-mechanically affected zone (RS-TMAZ), Retreating side heat affected zone (RS-HAZ), Retreating side boundary zone (RS-BZ) were analysed using Labex FE PRO 900 metallurgical microscope. Defects like voids, cavities, zigzag lines and chunks were observed on most of the weldments. Occurrence of martensite and defects like voids, cavities, zigzag lines and chunks were observed at 1400 rpm near Nugget Zone (NZ), Advancing side thermo-mechanically affected zone (AS-TMAZ), Advancing side heat affected zone (AS-HAZ), Retreating side thermo-mechanically affected zone (RS-TMAZ), Retreating side heat affected zone (RS-HAZ).

A modified energy method is developed to investigate the elastic properties of single-walled carbon nanotubes. The energy of a system is expressed by the force field functions of the molecular mechanics. Under the assumption of a small deformation and the principle of minimum potential energy, the system function is established. In addition to consider the change of bond stretch and bond angle, the inversion energy is also proposed in this study. Based on the established model, the closed-form expressions of temperature-dependent Young's modulus, Poisson's ratio and strain energy of armchair and zigzag carbon nanotubes are obtained. The results show that the effect of tube diameter and inversion energy on the elastic constants of carbon nanotubes (CNTs) is significant when the tube diameter is small. Under different thermal expansion coefficients, the Young's modulus of carbon nanotubes varies nonlinearly with the temperature, whereas the Poisson's ratio is insensitive to the temperature. It is also found that the temperature has a greater effect on the tensile deformation of zigzag CNTs, which provides a more accurate theoretical foundation for the tensile fracture of CNTs in a thermal environment.

This article presents a circuit configuration to reduce the harmonic contents at the ac mains of a 12-pulse zigzag configured autotransformer-based diode bridge rectifier (DBR). The proposed circuit configuration employs a tapped interphase bridge rectifier at the dc side of 12-pulse DBR that results in higher pulses in the supply current, thus reducing the harmonic content and, thereby, improving the power quality of the system. Since the autotransformer employed is zigzag configured, the need for zero-sequence blocking transformer is eliminated. Moreover, the proposed circuit configuration at the dc side shapes the supply current near to a sine wave. Further, the proposed configuration is analyzed, simulated in MATLAB/Simulink, and the simulation results are presented, which confirms the improvement in power quality parameters in the input ac line current. Furthermore, the viability of the proposed configuration is verified by the experimental results that confirm the suitability of the proposed configuration in ac–dc applications.

The effect of heavy metal (HM) passivation on structural and electronic properties of monolayer zigzag graphene nanoribbon (ZGNR) is explored using the density functional theory (DFT) approach. The calculated bond lengths, binding energy (Eb), electronic band structure, and density of states (DOS) advocates that quantum properties of HM-passivated ZGNRs change as compared to H-ZGNR-H irrespective of their width. The HM-passivated ZGNRs exhibit n-type behavior via shifting their Fermi level towards the conduction band. Moreover, the additional electronic states are observed in HM-passivated ZGNR where energy levels are varying concerning Zn, Cd, and Hg passivation. The width-dependent quantum properties of HM-passivated ZGNR indicates their potentials in nanosensor devices for the heavy metal detector.

Stanene has revealed a new horizon in the field of quantum condensed matter and energy conversion devices but its significantly lower tensile strength limits its further applications and effective operation in these nanodevices. Van der Waals heterostructures have given substantial flexibility to integrate different two-dimensional (2D) layered materials over the past few years and have proven highly functional with exceptional features, appealing applications, and innovative physics. Considerable efforts have been made for the preparation, thorough understanding, and applications of van der Waals heterostructures in the fields of electronics and optoelectronics. In this paper, we have executed Molecular Dynamics (MD) simulations to predict the tensile strength of van der Waals heterostructures of stanene (Sn) adsorbed on graphene (Gr), hexagonal boron nitride (hBN), and silicon carbide (SiC) (Sn/Gr, Sn/hBN, and Sn/SiC, respectively) subjected to both armchair and zigzag directional loading at different strain rates for the first time, which has enticing applications in electronic, optoelectronic, energy storage and bio-engineered devices. Among all the van der Waals heterostructures, the Sn/SiC heterostructure exhibits the lowest tensile strength and tensile strain. Furthermore, it has been found that zigzag directional loading could endure more tensile strain before fracture. Besides, it has been disclosed that though the rule of mixtures may accurately reproduce the Young's modulus of these heterostructures, it has limitations to predict the tensile strength. Fracture analysis suggests that for the Sn/hBN heterostructure the fracture initiates from the stanene layer while for the Sn/Gr and Sn/SiC heterostructures the fracture initiates from the Gr and SiC layer, respectively, for both armchair and zigzag directional loading. Overall, this study would aid in the design and efficient operation of Sn/Gr, Sn/hBN, and Sn/SiC heterostructures when subjected to mechanical force.

Molecular compounds with zigzag carbon nanotube geometries are exceedingly rare. Here we report the synthesis and characterization of carbon-based nanotubes with zigzag geometry, best described as radially oriented [n]cyclo-meta-phenylenes, extending the tubularene family of compounds. By the incorporation of edge-sharing benzene rings into the tubularene's radial π-surface, we have uncovered the first step to give rise to the emergence of radial orbital distribution in zigzag nanorings.

The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum rings (TQRs) with tunable high-spin ground state, crucial for next-generation molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronene-like antidot in the center. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground state (S = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings for future quantum devices.