Armchair Single-walled Carbon Nanotubes Research Articles

N⁻₃ azide anion confined inside finite-size carbon nanotubes.

In this work, the confinement of an N[Formula: see text] azide anion inside finite-size single-wall zigzag and armchair carbon nanotubes of different diameters has been studied by wave function and density functional theory. Unrelaxed and relaxed interaction energies have been computed, resulting in a favorable interaction between the guest and host system. In particular, the largest interaction has been observed for the confinement in an armchair (5,5) carbon nanotube, for which a natural population analysis as well as an investigation based on the molecular electrostatic potential has been carried out. The nature of the interaction between the two fragments appears to be mainly electrostatic, favored by the enhanced polarizability of the nanotube wall treated as a finite system and passivated by hydrogen atoms. The results obtained are promising for possible applications of this complex as a starting point for the stabilization of larger polynitrogen compounds, suitable as a high-energy density material.

Molecular mechanics-based finite element analysis of graphene sheet and carbon nanotubes using the rebo potential

Molecular mechanics-based finite element (FE) models of graphene sheet and single-walled zigzag and armchair carbon nanotubes (CNTs) are developed on the basis of the assumption that the carbon nanostructures, when loaded, behave like frame structures. The behavior of carbon–carbon bonds, which are represented by beam elements, is simulated using the many-body second generation reactive empirical bond order (REBO) potential. By means of the FE models, the tensile behavior of carbon nanostructures is simulated. The FE models are verified against molecular dynamics simulations. The computed results in terms of tensile stress–strain curves and fracture patterns are compared with results obtained using the pairwise modified-Morse potential. Different tensile properties and fracture patterns are predicted using the two potentials. This is mainly attributed to the deviations in the force–bond length curves and to the contribution of bond angle variation which is present in REBO. The present work is the first attempt to implement the REBO potential into a continuum model of carbon nanostructures and paves the way for a more systematic incorporation of atomistic simulation methods into continuum models.

Structure and electronic properties of deformed single-walled carbon nanotubes: quantum calculations

The electronic properties of single-walled carbon nanotubes (SWCNTs) can be modified by deforming their structure under high pressure. The aim of this study was to use quantum calculations to investigate one such property, the energy band gap, in relation to molecular structures of armchair and zigzag SWCNTs of various sizes and shapes deformed by applied forces. To model the increase in pressure, the degree of flatness (η) of the SWCNTs was adjusted as the primary parameter. The calculations gave accurate C-C bond lengths of the SWCNTs in their distorted states; these distortions significantly affected the electronic properties, especially the energy band gap of the SWCNTs. These results may contribute to a more refined design of new nano-electronic devices.

Role of Interatomic Potentials in Simulation of Thermal Transport in Carbon Nanotubes

Interatomic potentials, which describe interactions between elements of nanosystems, are crucial in theoretical study of their physical properties. We focus on two well known empirical potentials, i.e. Tersoff's and Brenner's potentials, and compare their performance in calculation of thermal transport in carbon nanotubes. In this way, we study the temperature and diameter dependence of thermal conductivity of single walled armchair carbon nanotube by using the mentioned interatomic potentials. We take advantage of direct non-equilibrium molecular dynamics simulation, which well resembles the experimental set up for thermal conductivity measurement. The results show that increasing the temperature increases the conductivity in contrast with diameter growth which decreases the thermal conductivity. It is important to note that both interatomic potentials describe the system behavior very well, however they lead to different conductivity values. It is found that the difference between the performance of studied potentials can be seen more obviously in longer tubes. We also observe a peak in thermal conductivity by increasing system temperature. System is deformed at T≈1000 K, when Tersoff's potential is employed for description of interactions. While its instability occurs at higher temperature (T≈1600 K), when we try to simulate system by Brenner's potential.

Cover Picture: A Computational Study of a Single‐Walled Carbon‐Nanotube‐Based Ultrafast High‐Capacity Aluminum Battery (Chem. Asian J. 15/2017)

Armchair single-walled carbon nanotubes (SWNT) have been explored as a cathode material for aluminum batteries using density functional calculations. The stable system, in which AlCl4 is adsorbed on SWNT, exhibits an ultrafast charge/discharge rate with a more favorable diffusion on the inner surface than on the outer surface. Storage capacities as high as 275 mAh g−1 can be obtained in (25,25) SWNT as compared to previously studied graphite cathode (70 mAh g−1). This study provides a mean to further explore carbon nanotube materials for aluminum batteries. More information can be found in the Full Paper by Biswarup Pathak et al. on page 1944 in Issue 15, 2017 (DOI: 10.1002/asia.201700570).

Density of States of Single Walled Carbon Nanotubes in Long Energy Range: A Computational Comparative Study

This paper reports the density of states (DOS) of chiral (4, 1), armchair (4, 4), and zigzag ((4, 0) single walled carbon nanotubes (SWCNTs) in long energy range by using ab- initio Density Functional Theory (DFT). Our simulation results show the distinguishable features of three types of CNTs in terms density of states (DOS), so that they can be fully exploited in nano-devices. The results are helpful for studying the working principles of the CNT based electronic devices and to design new ones.

Theoretical Study on the Chemical Reactivity in the Armchair Single-walled Carbon Nanotube: Proton and Methyl Group Transfer

Proton transfer (PT) and methyl group transfer (MGT) occurring in small biomimetic systems, Formamide-Formamidic acid (FA-FI), and N-formyl-N-methylformamide-(E)-methyl N-formylformimidate (NMFA-NMFI) are investigated in the gas phase and in single-walled carbon nanotubes by using the density functional theory and the ONIOM approach. It is shown that PT reaction is disfavoured in single-walled CNT (5.5) because it increases the energy barrier, while confinement in CNT (6,6) decreases the energy barrier of MGT. In contrast, the MGT reaction is notably affected by the confinement CNT(6,6) in view of the geometries and energies. The confinement of CNT(6,6) has an influence on the structures and energy barriers, and the activation energies obviously decrease slightly.

A First-Principles Study on Interaction between Carbon Nanotubes (10,10) and Gallates Derivatives as Vehicles for Drug Delivery

First principles calculations were carried out for investigation the novel 7-hydroxycoumarinyl gallates derivatives in gas and liquid phases using density functional theory (DFT) method. Computational chemistry simulations were carried out to compare calculated quantum chemical parameters for gallates derivatives. All calculations were performed using DMol3 code which is based on DFT. The Double Numerical basis set with double numerical plus d-function (DND) was used. Calculations were carried out to study the interaction of covalently binding gallates derivatives to the armchair single-walled carbon nanotube (10, 10). The local reactivity was studied through the fukui indices in order to predict both the reactive centers and the practicable sites of nucleophilic and electrophilic attacks. The adsorption energies, the quantum molecular descriptors analysis and the structural changes at the adsorption site are indicative of chemisorption on the armchair single-walled carbon nanotube (10, 10) surface. The HOMO and LUMO are witness to the substantial changes in the electronic properties of the SWCNT systems. Adsorption energies indicate that 7-hydroxycoumarinyl gallates derivatives are physicosorbed on carbon nanotube (10, 10). This property enables the delivery of these derivatives with anti-cancer potential from the nanotube at the targeted sites. These results are extremely relevant in order to diagnosis the potential applications of carbon nanotubes as efficient boats for targeted drug delivery.

Extended theory of elastica for free torsional, longitudinal, and radial breathing vibrations of single-walled carbon nanotubes

Single-walled carbon nanotube (SWCNT) can be viewed as a two-dimensional elastica obtained from rolling up graphene into a cylinder. By extending the formulation of elastica to dynamic problems, the present study provides an analysis for free torsional, longitudinal, and radial breathing vibrations of SWCNTs. With incorporating the effects of both geometrical and material nonlinearities, the exact closed-form expressions are obtained for the deformation field and the natural angular frequency of the elastica corresponding to the freely vibrating SWCNT. It is shown that torsional, longitudinal, and radial breathing modes of deformation are coupled to each other in free vibration of SWCNTs. However, for the special cases of zigzag and armchair SWCNTs as well as the limiting case of large-radius SWCNTs, torsional mode of deformation is decoupled from the other two modes.

A comprehensive density functional theory study on molecular structures of (5, 5) carbon nanotube doped with B, N, Al, Si, P, Co, and Ni

Armchair single-walled carbon nanotubes (SWNTs), which were doped with B, N, Al, Si, P, Co, and Ni, have been studied using computational simulations based on density functional theory (DFT). The topological analysis and the electron localization function show that the nature of the interaction between carbon atoms and the dopant X atoms is not purely covalent or an ionic. In order to gain a deeper understanding of the interaction between X atoms and C atoms, calculations of natural bond orbital (NBO) analysis, bond order analysis, atomic charge analysis, and electrostatic potential (ESP) on the van der Waals (vdW) surfaces of molecules are required. The Natural population analysis (NPA), Hirshfeld and atomic dipole moment corrected Hirshfeld (ADCH) atomic charges and molecular electrostatic potential maps on vdW surfaces of C79H20Xs show that ESP values are in good agreement with ADCH values. The calculations of The Laplacian bond order (LBO), Mayer bond order (MBO) and Fuzzy bond order (FBO) illustrate that LBO has a strong correlation with the bond length. In addition, the calculations show that Fermi energies of the pristine C (5, 5) carbon nanotubes (CNTs) and all doped CNTs are equal to the energies of their highest occupied molecular orbital (HOMO). This work presents a comparison about the bonding characteristic between the doped atoms (X) and carbon atoms.

Solvation Enhances the Distinction between Carboxylated Armchair and Zigzag Single-Wall Carbon Nanotubes (SWNT-COOH)

The effect of various solvents on the structures and properties of carboxylated SWNTs has been explored using the same level different basis set approach (SLDB), where B3LYP functional of density functional theory (DFT) was applied. Armchair (4,4) and zigzag (8,0) and (9,0) tubes were considered as the testbed. In order to simulate varying concentration of −COOH groups, one to five acids groups were placed at one end of these tubes. These samples were placed in different solvents (namely, CS2, THF, and water) with varying polarity and results were compared with gas-phase properties. Similar to the gas-phase, zigzag tubes also exhibit both regular (r-COOH, ν(C═O) above 1700 cm–1) and low-frequency (lf-COOH, ν(C═O) below 1700 cm–1) acid groups. Characteristics of the r-COOH group are not affected much in solvents, but lf-COOH of the zigzag tube is the one that makes these tubes distinguishable from its armchair cousin. Stability and charge distribution of SWNT-COOH strongly depend on the number of acid groups in different solvents which may help controlling further functionalization. Vibrational analyses reveal certain features in the 1400–1600 cm–1 range that are characteristic of lf-COOH and in different solvents, which may help in the assignment of experimental spectra of oxidized SWNT in solvents.

Noncovalent interactions of free-base phthalocyanine with elongated fullerenes as carbon nanotube models

Noncovalent interactions of free-base phthalocyanine (H2Pc) with closed-cap armchair (5,5) and zigzag (10,0) single-walled carbon nanotubes (ANT and ZNT, respectively), as well as, for comparison, with C60 and C80(I h) fullerenes, whose hemispheres were used to close the ends of nanotube models, were studied theoretically by using one pure dispersion-corrected GGA functional (PBE with a long-range dispersion correction by Grimme, or PBE+D) and two hybrid meta exchange-correlation functionals (M05-2X and M06-2X). Strong complexation was observed in all four systems studied. The general trend found is that the interaction strength increases with the size (number of C atoms) of carbon nanocluster, that is, in the order of ZNT > ANT > C80 > C60. Depending on the DFT functional employed, the interaction strength decreased in the order of PBE+D > M06-2X > M05-2X. A common feature for the geometry of all four complexes considered, reproduced in all the calculations, is that H2Pc macrocycle undergoes strong distortion, which allows for increasing its contact surface with the nanotube sidewall or spherical fullerene, and therefore makes π-π interactions more efficient.

Quantum Chemical Study on the adsorption of metformin drug on the surface of pristine, Si- and Al-doped (5, 5) SWCNTs

Adsorption properties of metformin (MF) drug onto pristine, Si- and Al-doped (5, 5) armchair single-wall carbon nanotubes (SWCNTs) were studied using density functional theory (DFT) calculations at the B3LYP and ωB97XD methods with the standard 6–311G** basis set. The most stable geometries of the MF drug molecule onto pristine, Si- and Al-doped (5, 5) CNTs were selected and evaluated in the gaseous and aqueous environments. We calculated the natural bond orbitals (NBO), Frontier molecular orbital (FMO), density of states (DOS) and molecular electrostatic potential (MEP) of systems upon adsorption of MF drug. It was found that the reaction of MF drug with pure SWCNT is physisorption in nature, while high chemisorption can be achieved by using Al- and Si-doped SWCNTs. Despite Al-doped SWCNT provides stronger adsorption, however the change in the energy gap of Si-doped SWCNT is more pronounced. It is predicted that MF drug incorporating Si-doped SWCNT can be extended as drug delivery system.

Vibrational behavior of single-walled carbon nanotubes based on cylindrical shell model using wave propagation approach

The vibration analysis, based on the Donnell thin shell theory, of single-walled carbon nanotubes (SWCNTs) has been investigated. The wave propagation approach in standard eigenvalue form has been employed in order to derive the characteristic frequency equation describing the natural frequencies of vibration in SWCNTs. The complex exponential functions, with the axial modal numbers that depend on the boundary conditions stated at edges of a carbon nanotube, have been used to compute the axial modal dependence. In our new investigations, the vibration frequency spectra are obtained and calculated for various physical parameters like length-to-diameter ratios for armchair and zigzag SWCNTs for different modes and in-plane rigidity and mass density per unit lateral area for armchair and zigzag SWCNTs on the vibration frequencies. The computer software MATLAB is used in order to compute these frequencies of the SWCNTs. The results obtained from wave propagation method are found to be in satisfactory agreement with that obtained through the previously known numerical molecular dynamics simulations.

Molecular dynamics simulation of carbon nanotube pull-out from polyethylene matrix

The objective of this study is to examine the influence of carbon nanotube (CNT) pull-out from polyethylene (PE) matrix on the mechanical properties of CNT/PE composite. Materials Studio 8.0 has been used for carrying out the molecular dynamics (MD) simulation. The mechanical properties predicted are the Young's modulus and the interfacial shear stress (ISS). The effect of increase in strain on the Young's modulus of CNT has also been studied. A (5,5) armchair single walled carbon nanotube (SWCNT) of diameter 6.78 Å and length of 49.2 Å has been used. When the SWCNT was pulled out from the PE matrix by 10 Å, there was 14.30% reduction in the longitudinal modulus (E33). When the displacement was increased to 50 Å, E33 was reduced by 43.79% with respect to a fully embedded CNT. ISS was mainly distributed over the first and final 10 Å of pull-out, in the stage I and stage III where the energy increments see a large change.

Charge-induced electrochemical actuation of armchair carbon nanotube bundles

The effects of charge doping on the structural deformation and on the electronic structure of armchair single wall carbon nanotube (SWNT) bundles are investigated through first-principles calculations. In particular, we select a (6,6) SWNT as an example and we calculate a mechanical deformation in the SWNT bundles as a function of gate voltage, which could serve as a basis of the electromechanical actuators in an artificial muscle. We find that the magnitudes of the actuation responses such as strain and stress of the (6,6) SWNT bundle in the case of hole doping are substantially larger than those of electron doping. The (6,6) SWNT bundle also exhibits a low-symmetry and opens an energy band gap of about 0.41 eV around the charge neutral condition, which allows a semiconductor-to-metal transition in the electron-doping regime when the relative shift of the Fermi energy goes up to 0.60 eV, above which the Young modulus increases.

Magnetic Transport Properties of Fe-Phthalocyanine Dimer with Carbon Nanotube Electrodes* *Supported by the National Natural Science Foundation of China under Grant No 11104115, and the Natural Science Foundation of Shandong Province under Grant No ZR2016AM11.

Based on the non-equilibrium Green’s method and density functional theory, the magnetic transport of Fe-phthalocyanine dimers with two armchair single-walled carbon nanotube electrodes is investigated. The results show that the system can present high-performance spin filtering, magnetoresistance, and low-bias spin negative differential resistance effects by tuning the external magnetic field. These results show that the Fe-phthalocyanine dimer has the potential to design future molecular spintronic devices.

Length dependent stability of single-walled carbon nanotubes and how it affects their growth

Using density-functional theory the stability of armchair and zigzag single-walled carbon nanotubes and graphene nanoribbons was investigated. We found that the stability of armchair and zigzag nanotubes has different linear dependence with regard to their length, with switches in the most stable chirality occurring at specific lengths for each nanotube series. We explain these dependencies by competing edge and curvature effects. We have found that within each series armchair nanotubes are the most stable at short lengths, while zigzag nanotubes are the most stable at long lengths. These results shed new insights into why (near) armchair nanotubes are the dominant product from catalytic chemical vapor deposition growth, if templating is not used. Paradoxically, the stability of armchair nanotubes at short lengths favors their growth although zigzag nanotubes are more stable at long lengths, resulting in the production of the least stable nanotubes.

Migration of a carbon adatom on a charged single-walled carbon nanotube

We find that negative charges on an armchair single-walled carbon nanotube (SWCNT) can significantly enhance the migration of a carbon adatom on the external surfaces of SWCNTs, along the direction of the tube axis. Nanotube charging results in stronger binding of adatoms to SWCNTs and consequent longer lifetimes of adatoms before desorption, which in turn increases their migration distance several orders of magnitude. These results support the hypothesis of diffusion enhanced SWCNT growth in the volume of arc plasma. This process could enhance effective carbon flux to the metal catalyst.

A DFT study on the geometry, tautomerism and noncovalent interactions of the Mepivacaine drug with the pristine SWCNT and –COOH functionalized SWCNT

The Mepivacaine drug is used as a local anesthetic in dentistry, which could exist as three different tautomers. Herein, geometry, energy behavior as well as tautomerization of these tautomers have been investigated by employing density functional theory (DFT) and considering the solvent effects with the polarizable continuum model (PCM) model. The most stable tautomer of the Mepivacaine has a carbonyl and an –NH amine groups in its structure. The frontier orbitals and the energy gap of the molecule have been computed using the natural bond orbital analysis (NBO). Also, the armchair (5,5) single wall carbon nanotube (SWCNT) was used for investigation of the noncovalent interactions of the Mepivacaine molecule with the pristine SWCNT and the –COOH functionalized SWCNT in several forms. Geometries of the possible forms have been optimized. The most stable form for noncovalent interactions of the drug with each of the pristine and functionalized SWCNTs have been determined. The intermolecular H-bonds have essential role in energy behavior of the noncovalent interactions between the Mepivacaine drug and the investigated SWCNTs.