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In this paper, we study the effect of the axial deformation of carbon nanotubes in the zigzag and armchair directions on the stability of the interface between hydrogenated and non-hydrogenated regions. We analyze the specific energy of this interface as a function of the axial strain. We found that the clear interface can be obtained at a wider temperature range due to tube stretching. The energy barriers characterizing the process of hydrogen migration from the hydrogenated region of the nanotube to the pristine tube are calculated. It is concluded that the tube deformation significantly affects the stability of the system. For some tubes applied strain can qualitatively change the regularity of hydrogenation, changing the sign of the interface energy.

By performing density functional theory (DFT) calculations, we demonstrate that periodically repeating heterostructures of zigzag borophene nanoribbons (BNR) of different widths can form stable borophene superlattice (BSL). The energy band structures of BSL can be modulated through modifying the width and length of the segments. A metal-semiconductor transition can be obtained when the length of each segment is lengthened, whereas, the magnetism of BSL is influenced by the width of the segments. In those magnetic systems, the magnetic moments are mainly localized on protruding B atoms located at the edge, while no magnetic moments occur in the center B atoms. The hydrogenated BNR and BSL are further investigated. The hydrogenation can modify the electronic properties of BNR and BSL as well as quench the magnetism. All hydrogenated BNR and BSL are non-magnetic. Our results indicate that great potential exists in these systems for borophene utilization in nanoelectronics and spintronics.

A planar metamaterial (MM) mimicking electromagnetically-induced transparency (EIT) effect is demonstrated numerically and experimentally in the microwave region. The structure of MM is a periodicity of ring and zigzag spiral resonators, in which each resonator can be excited directly by the external field. By matching the characteristic resonance frequencies of two resonators, the coupling of two bright modes appears, leading to an EIT effect with a transparency peak at 4.86 GHz. Although the geometry of the structure is not perfectly symmetric, the proposed electromagnetically-induced transparency metamaterial (EIT-MM) is insensitive to the polarization of incoming wave. Furthermore, the EIT-MM exhibits a strong dispersion behavior, which leads to a high group index of 2785 and a group delay of 0.83 ns. Our work might be useful to potential applications using EIT-MM such as modulators, filters and sensors.

We investigate the effect of vacancy defect reconstruction on electron transport properties in a (4, 0) zigzag and (5, 5) armchair silicon-carbide nanotubes ( SiCNTs ) by applying self consistent non-equilibrium Green's function formalism in combination with the density-functional theory to a two probe molecular junction constructed from SiCNTs . The geometry optimization results show that single vacancies and di-vacancies in SiCNTs have different reconstructions. A single vacancy when optimized, reconstructs into a 5-1DB configuration in both zigzag and armchair SiCNTs , and a di-vacancy reconstructs into a 5-8-5 configuration in zigzag and into a 5-2DB configuration in armchair SiCNTs . Analysis of frontier molecular orbitals (FMO) and transmission spectrum show that the vacancy defect increases the band gap of (4, 0) metallic SiCNT and decreases the band gap of (5, 5) semiconducting SiCNT . Bias voltage dependent current characteristic show reduction in overall current in metallic SiCNT and an increase in overall current in semiconducting SiCNT .

Single-crystalline SnO2zigzag nanobelts and straight nanobelts with triangular tip were synthesized by a simple Tin–water reaction method. The product was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman scattering and micro-photoluminescence spectroscopy to obtain the structural and optical information. Why zigzag nanobelts and straight nanobelts can be formed respectively under the same experimental conditions? On the basis of TEM characterization and thermodynamic analysis, the formation mechanism of zigzag nanobelts and straight nanobelts were proposed respectively.

By using ab initio density functional theory we investigated the structural and electronic properties of semiconducting (9, 0), zinc oxide zigzag nanotube ( ZnOZNT ) bundle. The energetic and electronic evolutions of nanotubes in the bundling process are also studied. The effects of inter-tube coupling on the electronic dispersions of ZnONT bundle are demonstrated. Our results show that the inter-tube coupling leads to disappearance of the energy gap in semiconducting nanotube. We found that (9, 0) zigzag nanotube bundle has a metallic behavior.

We investigate the effect of changed BN nanoribbon on the rectifying behavior in zigzag graphene/BN nanoribbon heterojunction using first principles based on non-equilibrium Green’s function and density functional theory. The increased BN length in the scattering region reduces the rectifying performance of the device, and the maximum rectifying ratio is [Formula: see text] in the heterojunction. We discuss the different rectifying characteristics for the designed models by calculating the transmission spectra at different biases. The rectifying phenomenon is further investigated by the projected density of state of device. Furthermore, we explain the observed negative differential resistance effect by the transmission spectra and transmission eigenstates. The results suggest that the zigzag graphene/BN nanoribbon heterojunction leads to the asymmetric current, causing the rectifying phenomenon, and the BN length in the scattering region can modulate the rectifying performance of zigzag graphene/BN nanoribbon heterojunction.

Using non-equilibrium Green’s function method and maintaining the zigzag carbon chains unchanged, we investigate the transmission rate of acoustic phonon and the reduced thermal conductance through multi-frame graphene nanoribbons (GNRs). The results show that the reduced thermal conductance approaches [Formula: see text] in the limit [Formula: see text]. Due to the fact that only long wavelength acoustic phonons with zero cutoff frequency are excited at such low temperatures, the scattering influence on the long wavelength acoustic phonons by the multi-frame in GNRs can be ignored and these phonons can go through the scattering region perfectly. As the temperature goes up, the reduced thermal conductance decreases. This is because the high-frequency phonons are excited and these high-frequency phonons are scattered easily by the scattering structures. With the further rise in temperature, acoustic phonon modes with the cutoff frequency greater than zero are excited, which leads to a rapid increase of the reduced thermal conductance. This study shows that changing the frame structure by a small length can lead to a significant change of transmission probability. In the higher frequency region, the transmission spectra display complex peak-dip structures, which results from the fact that in higher frequency region more phonon modes are excited and scattered in the middle scattering region with multi-frames, and the scattering phonons are coupled with the incident phonons, with the increase of the length of frame structure, the scattering of the phonon is also enhanced, which leads to the decrease in the phonon transmission; by changing the frame structure, the parameters can effectively adjust the position of low-frequency phonon transmission valley. The frame structure can induce high-frequency phonon blocking effect and the blocking effect depending on the structure parameter of the frame. When the single frame and double frame GNRs are narrowest, the scattering from low-frequency phonons by the scattering structure is largest, which leads to the fact that the reduced thermal conductance is smallest at low temperatures; however, at high temperature, the reduced thermal conductance is biggest when the single frame and double frame GNRs are narrowest. This is because the scattering from high-frequency phonons by the scattering structure is the smallest. When the length of the frame structure is unchanged, a graphite chain is inserted in which the reduced thermal conductance is always reduced. These results provide an effective theoretical basis for designing the thermal transport quantum devices based on GNRs.

We have analyzed the spatio-temporal patterns of current self-oscillation under DC bias and terahertz frequency-dependent nonlinear dynamics in semiconducting single-walled zigzag carbon nanotubes (CNTs). It is found that different transport states, including periodic and chaotic, appear with the influence of an external AC signal. The global transitions between periodic and chaotic states are clearly resolved from Poincaré bifurcation diagram. When the driving frequency is fixed at inverse golden mean ratio times natural frequency, the nonlinear CNT system exhibits a more complex transition behavior than at other driving frequencies.

The quantum conductance of the electron interferometers composed of the armchair and metallic zigzag single-walled carbon nanotubes (SWNTs) in an axial magnetic field lower than 100 T has been studied by using the tight-binding approximation and Landauer–Buttiker formula. Quantum conductance oscillation as a function of gate voltage due to Fabry–Perot like electron interference was found. The analytical expressions of the rapid and slow conductance oscillation periods for the armchair SWNTs have been derived. It is shown that they depend on the magnetic field, gate voltage, and tube length. For the case of the metallic zigzag SWNTs, except rapid conductance oscillation, slow conductance oscillation was also found, which should not exist without the axial magnetic field.

Using a non-equilibrium Green’s function framework in combination with the complex energy-band method, an atomistic full-quantum model for solving quantum transport problems for a zigzag-edge graphene nanoribbon (zGNR) structure is proposed. For transport calculations, the mathematical expressions from the theory for zGNR-based device structures are derived in detail. The transport properties of zGNR-based devices are calculated and studied in detail using the proposed method.

In this work, we use first-principles methods to study the strain effects on the band structures of the armchair and zigzag arsenene nanoribbons (A-AsNRs and Z-AsNRs), as well as considering different ribbon widths. The results show that the band gap for each considered arsenene nanoribbons can be decreased when the size is increased. Moreover, strain can also reduce effectively the band gap of AsNRs. Interestingly, for A-AsNRs case, the indirect to direct band transition can be obtained under the tensile strain. In comparision, the direct–indirect transition only occurs under some strain ranges for zigzag AsNRs (Z-AsNRs).

We have investigated Al adsorption on the W (100) surface using LEED and low energy Ion Scattering Spectroscopy (ISS). We observe a p(2 × 1) double domain LEED image for the 1.0 ML Al/W (100) surface at annealing temperature 850°C. We also measured the Al adsorption site at the Al/W (100) — p(2 × 1) surface using ISS. It is found that Al atoms adsorbed at 0.7±0.1 Å aside from the center of the bridge sites with a zigzag structure — one atom adsorbs at the right-hand side and next atom at the left-hand side along the [100] direction. The height of the adsorbed Al atoms is determined to be 1.75±0.15 Å above the W surface layer.

The method to obtain phonon dispersion of achiral single-wall carbon nanotubes (SWNTs) from 6×6 matrix proposed by Mahan and Jeon7 has been extended to chiral SWNTs. The number of calculated phonon modes of a chiral SWNT (10, 1) is much larger than that of a zigzag one (10, 0) because the number of atoms in the translational unit cell of chiral SWNT is larger than that of an achiral one even though they have relative similar radius. The possible application of our approach to other models with more phonon potential terms beyond Mahan and Jeon's model is discussed.

Based upon the Slater–Koster tight-binding calculations, we investigated electronic properties of the "metallic" single-walled carbon nanotubes (SWNTs) in detail. Our results show that tube curvature may produce an energy gap at the Fermi level for zigzag and chiral "metallic" SWNTs, and this effect decreases with the increasing of either the radius or the chiral angle. Our calculated results are in good agreement with experiments.

The transport properties in ultrasmall single-wall carbon nanotubes (SWCNTs) under tensile strain have been theoretically investigated. The regular negative differential resistance (NDR) induced by the strain undergoes a process from enhancement to weakening in the zigzag (3,[Formula: see text]0) SWCNT. The NDR achieves maximum with applying 4% tensile strain. Compared to the case of (3,[Formula: see text]0) SWCNT, that NDR cannot be manipulated by applying strain clearly in (4,[Formula: see text]0) and (5,[Formula: see text]0) ultrasmall SWCNTs with tensile strain lower than 10%. It proposes this strain-induced NDR effect to demonstrate the possibility of finding potential applications in SWCNT-based NDR nanodevices such as in memory devices, oscillators and fast switching devices.

The finite element method is used here to investigate the vibrational behavior of single-walled boron nitride nanotube/polymer nanocomposites. The polymer matrix is modeled as a continuous media. Besides, nanotubes are modeled as a space-frame structure. It is shown that increasing the length of nanotubes at a constant volume fraction leads to decreasing of the nanocomposite frequency. By investigating the effect of volume percentage on the frequencies of the boron nitride nanotube-reinforced polymer nanocomposites, it is observed that for short nanotubes, the nanocomposites with larger nanotube volume fractions have larger frequencies. Also, through studying the first 10 frequencies of nanocomposites reinforced by armchair and zigzag nanotubes, it is shown that the effect of chirality on the vibrational behavior of nanocomposite is insignificant.

First-principles study based on density functional theory has been employed to investigate width-dependent structural stability and magnetic properties of monolayer zigzag MoS2 nanoribbons (ZZ-MoS2 NRs). The width N = 4–6 (the numbers of zigzag Mo–S chains along the ribbon length) are considered. The results show that all studied ZZ-MoS2 NRs are less stable than two-dimensional MoS2 monolayer, exhibiting that a broader width ribbon behaves better structural stability and an inversely proportional relationship between the structural stability (or the ribbon with) and boundary S–Mo interaction. Electronic states imply that all ZZ-MoS2 NRs exhibit magnetic properties, regardless of their widths. Total magnetic moment increases with the increasing width N, which is mainly ascribed to the decreasing S–Mo interaction of the two zigzag edges. In order to confirm this reason, a uniaxial tension strain is applied to ZZ-MoS2 NRs. It has been found that, with the increasing tension strain, the bond length of boundary S–Mo increases, at the same time, the magnetic moment increases also. Our results suggest the rational applications of ZZ-MoS2 NRs in nanoelectronics and spintronics.

New insight into the nature and formation of the multiphase ordering of oxygen onto threefold sites of fcc(110) (Rh, Pd and [Formula: see text] analogue) is presented. By including bond-to-band model and the potential-barrier for oxygen-metal chemisorption with theoretical and experimental observations, it is shown that the multiphase ordering, composed of (2×1)pmg, (2×1)p2mg and (2×2)p2mg structures, originates from the hybridized- O -2 forming at different oxygen coverages with a specific bonding environment. Unlike the long-bridge sited O -2 ions on the Cu(Ni, Ag)(110) which give the missing-row type reconstruction, the threefold-coordinated O -2 ions on the Rh(Pd)(110) form a tetrahedron through one bond to the metal atom underneath and two nonbonding lone pairs acting on its two neighbors in the first layer. In the (2×1)p2mg structure, the lack of one metal atom for the tetrahedron is compensated by a virtual bond pulling the electron-cloud of the dipoles that are induced by the lone pairs of other O -2 ions. The tetrahedron in the (2×2)pg structure requires an electron from a metal atom in the next nearest row at the surface. Therefore, the bond network interlocks all the surface atoms; and thereby, no atoms are missing. The zigzag protrusions in the STM images are recognized as metal dipoles deformed by the lone pairs of O -2 ions. The depressions correspond to rows of M + metal ions other than missing-row vacancies as had been expected previously.

The optical absorption spectra of zigzag fullerene tubes have been studied by using the extended Su–Schrieffer–Heeger model with the Coulomb interaction included. The numerical results indicate that the carbon number and the Coulomb interaction have great effects on the optical absorption spectra.

Spin-polarized electron transport through a zigzag zinc oxide nanoribbon (ZnONR) has been studied using first-principles transport simulations. Ribbons without edges passivated show 100% spin polarization at small bias voltage independently of width. The ribbons with edge zinc atoms passivated maintain absolute spin-filtering effect in much larger bias region. The results demonstrate that zigzag ZnONRs act as perfect spin-filters in the absence of magnetic electrodes and external fields.

In this paper, elastic properties of stanene under equiaxial or uniaxial tensions along armchair and zigzag directions are investigated by first-principles calculations. The stress–strain relation is calculated and the relaxation of the internal atom positions is analyzed. The high-order elastic constants are calculated by fitting the polynomial expressions. The Young’s modulus and Poisson ratio of the stanene is calculated to be 24.14 N/m and 0.39 N/m, respectively. The stanene exhibits lower Young’s modulus than those of the proceeding group IV elements, which is attributed to the smaller [Formula: see text]–[Formula: see text] bond energy in stanene than those of silicene and germanene. Calculated values of ultimate stresses and strains, second-order elastic constants (SOCEs) and the in-plane Young’s modulus are all positive. It proves that stanene is mechanically stable.

[Formula: see text] is a hcp metal surface with a rectangular geometry analogous to fcc(110), consisting of close-packed rows separated by the c-axis distance. Oxygen adsorption on [Formula: see text] leads to three ordered superstructures: (i) a c (2 × 4) O phase at an oxygen coverage θ = 0.5, with oxygen forming alternating zigzag and zagzig chains in the troughs of the [Formula: see text] lattice, (ii) a p (2 × 1) O — the more stable phase at θ = 0.5 — which represents a novel type of surface reconstruction characterized by a double-layer missing-row configuration of the Co lattice, and (iii) a p (2 × 1) 2O — the stable phase at θ = 1.0 — which analogous to the c (2 × 4) O phase contains oxygen zigzag chains in the [Formula: see text] troughs. Recent scanning tunneling microscopy and low energy electron diffraction results are reviewed, which revealed the substantial differences between [Formula: see text] and the fcc(110) metal surfaces with their pronounced tendency to missing-row type reconstructions.

The atomic structure and edge state of zigzag carbon nanoscrolls (ZCNSs) are investigated using first-principles calculations based on density functional theory. The results show a non-monotonic dependence of the total energy of ZCNS on the surface curvature due to a competition between the elasticity and the van der Waals interactions in a scroll. The edge states can be tuned by using different forms of edge hydrogenation and inner radius. It is found that the edge state range of monohydrogenated ZCNSs is smaller than that of monohydrogenated zigzag-edged graphene nanoribbons (ZGNRs), which is also verified using the tight-binding approximation. With the different edge hydrogenations, ZCNSs prefer the [Formula: see text] hybridization more than the [Formula: see text] one. Our present study could suggest the possibility of adjusting the electronic properties of ZCNSs and may provide potential applications in the electronic devices.

The mechanical stabilities and nonlinear properties of monolayer Gallium selenide ( GaSe ) under tension are investigated by using density functional theory (DFT). The ultimate stresses and ultimate strains and the structure evolutions of monolayer GaSe under armchair (AC), zigzag (ZZ) and equiaxial (EQ) tensions are predicted. A thermodynamically rigorous continuum description of nonlinear elastic response is given by expanding the elastic strain energy density in a Taylor series in Lagrangian strain truncated after the fifth-order term. Fourteen nonzero independent elastic constants are determined by least-square fit to the DFT calculations. Pressure-dependent elastic constants (Cij(P)) and pressure derivatives of [Formula: see text] are also calculated. Calculated values of ultimate stresses and strains and the in-plane Young's modulus are all positive. It proves that monolayer GaSe is mechanically stable.

Thermal conductivity of single-walled carbon nanotubes has been calculated considering the three-phonon and four-phonon processes. The contribution of the acoustic modes and optical modes in the relaxation rate of the phonon–phonon interaction and hence to the thermal conductivity have been considered. The thermal conductivity has been calculated for the (8, 0), (10, 0), (11, 0) and (13, 0) zigzag semiconducting nanotubes having different radii. It is found that the thermal conductivity increases linearly at low temperatures which is nearly T2 below 30 K and after reaching a peak, it decreases as aT-1 - bT-2 where a and b are constants and b > a at higher temperatures. It is also found that the thermal conductivity increases with increasing radius of the tube due to the independent effect of three-phonon process and four-phonon process. The thermal conductivity is also found to decrease with increasing tube length due to four-phonon process.

By using the first-principles methods based on density function theory (DFT), the effects of boron(B)/phosphorus(P) pair co-doping on the electrical properties of zigzag single-walled carbon nanotubes (SWNTs) have been investigated. We calculated the formation energies and band structures of (6, 0) metallic and (8, 0) semiconducting SWNTs with different B/P co-doping sites and concentrations. The obtained formation energies suggest that the B/P co-doping configurations are energetically stable structures and the B and P tend to form a B–P bond. It shows that an energy gap is opened by B/P co-doping in (6, 0) metallic SWNTs and the metallic carbon nanotubes are converted into semiconductors. For the (8, 0) semiconducting SWNTs, B/P co-doping influences the band structure, but it does not change the attributes essentially and the SWNTs are still semiconducting. It was also found that the band structures depend on the doping concentration as well as the doping site of B/P pair.

In this work, using the single-band Hubbard model, we numerically study the magnetic ordering in zigzag graphene nanoribbons (ZGNRs). We calculate density of states and charge density distribution in the ZGNR, and show the nontrivial behavior of its electronic band structure in the presence of an external transverse electric field. Then, the robustness of such edge magnetic ordering and consequent half-metallicity is investigated for nanoribbons defected with single-atom vacancies. Our results show that the nontrivial magnetic properties of ZGNRs are robust to an acceptable percentage of single atom vacancies.

Impact of induced strain on charge carrier mobility is investigated for a monolayer graphene sheet. The unsymmetrical hopping parameters between nearest neighbor atoms which emanate from induced strain are included in the density of states description. Mobility is then computed within the Born approximation by including three scattering mechanisms; charged impurity, surface roughness and lattice phonons interaction. Unlike its strained silicon counterpart, simulations reveal a significant drop in mobility for graphene with increasing strain. Additionally, mobility anisotropy is observed along the zigzag and armchair orientations. The prime reason for the drop in mobility can be attributed to the change in Fermi velocity due to strain induced distortions in the graphene honeycomb lattice.

Miniaturization of electronic devices carries them to the quantum limits which mean quantum effect will be dominant in nano-size device characterization. A first band analytical model of the quantum capacitance for (16, 0) zig-zag graphene nanoscroll (ZGNS) is presented. The behavior of the quantum capacitance within the degeneracy limits is approximated using the Maxwell–Boltzmann approximation within a range of E - EF > 3KBT. The quantum capacitance is subsequently derived from the carrier density of the ZGNS due to its significance within one-dimensional (1D) devices by employing the Taylor's series expansion for parabolic energy band structure approximation. Additionally, the quantum capacitance analytical derivation in term of ZGNS physical form considering the Archimedean spiral-type structure is modeled. Because of its unique geometry structure which provides high area for intercalation, it is expected that ZGNS structure (length and interlayer distances) will alter the quantum capacitance. We also report that at first sub-band of (16, 0) ZGNS the quantum capacitance reach degenerate limit at approximately of ≅ 0.49 × 10-10 F/m @ 49 pF/m .

We present two compact analytic formulae for calculating the channel number in graphene nanoribbons (GNRs), in terms of GNRs' width and Fermi energy. Numerical data obtained from these analytic formulae fit those obtained numerically from the exact formula, with accuracies within 1%. Using appropriate fit parameters, the compact formulae are valid for zigzag, armchair-metallic, and armchair-semiconducting GNRs, at room, liquid nitrogen, and liquid helium temperatures (i.e. 300, 77 and 4.2 K)