Single-walled Aluminum Nitride Nanotubes Research Articles

The adsorption of bromomethane onto the exterior surface of aluminum nitride, boron nitride, carbon, and silicon carbide nanotubes: A PBC-DFT, NBO, and QTAIM study

The adsorption of bromomethane (CH3Br) onto the outer surface of the pristine armchair (5,5) single-walled aluminum nitride nanotube (AlNNT), boron nitride nanotube (BNNT), carbon nanotube (CNT), and silicon carbide nanotube (SiCNT) were investigated using density functional theory (DFT). The geometry optimization was performed by using the PBEPBE/6-31G(d) level of theory through 1D periodic boundary conditions (in which, each unit cell containing 40 atoms). Moreover, NBO and QTAIM analyses were also performed by using the same level of theory but using the complete nanotubes (each nanotube consists of 200 atoms). For further investigation, single point energy calculations were applied to each system using the CAM-B3LYP/DEF2-TZVP level of theory. The obtained adsorption energies indicate that among all of the aforementioned nanotubes, AlNNT exhibits the strongest affinity for the adsorption of the CH3Br molecule with the most negative adsorption energy. Based on the NBO and QTAIM results, it can be inferred that CH3Br tends to be chemisorbed onto the AlN and SiC nanotubes, whereas, in the case of CNT and BNNT, the adsorption is through weak van der Waals interactions and a physisorption process. Therefore, the results of this work may be useful in designing new types of nanosensor devices.

Investigation of the molecular structure, electronic properties, AIM, NBO, NMR and NQR parameters for the interaction of Sc, Ga and Mg-doped (6,0) aluminum nitride nanotubes with COCl2 gas by DFT study

In order to search for a novel sensor to detect and control exposure to phosgene (COCl2) molecule, the reactivities of pristine, Sc, Ga and Mg-doped (6,0) single-walled aluminum nitride nanotubes (AlNNTs) towards the COCl2 molecule are investigated by performing density functional theory calculations. It is found that the COCl2 molecule presents strong physisorption on the Mg and Sc-substituted Al defect sites, which is in contrast to its weak physisorption on pristine and Ga-doped AlNNTs. The AIM theory has been also used to examine the properties of the bond critical points: their electron densities and Laplacians. The nature of charge transfer between the oxygen atom of COCl2 and the impurity atoms is clarified. Natural bond orbital analysis reveals that the electronic configuration of the doped Mg metal represents a prominent change with respect to that of the Sc and Ga atoms. Also, the interaction of COCl2 gas and pristine/doped AlNNTs on the basis of four reactivity descriptors such as the overall stabilization energy (ΔESE), the individual energy change of acceptor (ΔEA(B)), the individual energy change of donor (ΔEB(A)) and charge transfer (ΔN) have been explained. We found that substituting an Al atom by Mg makes the electronic properties of the AlNNT strongly sensitive to the COCl2 molecule. Due to physisorption, NMR and NQR parameters of the adsorption sites are also altered. Density of the state investigation suggests that the Mg doping induces main changes in the electronic structure pattern of the interaction of phosgene gas with AlNNT.

O2 dissociation on the side wall of aluminum nitride nanotube: a DFT investigation

The probabilities of the singlet and triplet O2 dissociation on single-walled aluminum nitride nanotube (AlNNT) were explored here. The results suggest that the dissociation of singlet and triplet O2 on AlNNT go through intermediates on their pathways. Triplet O2 was found to be difficult to dissociate on (8, 0) AlNNT following the triplet dissociation pathways due to the high overall dissociation barriers that are greater than 1.48eV. The singlet O2 can dissociate on the nanotube following the singlet dissociation pathways with a lower dissociation barrier of 0.74eV. The effect of temperature was also considered and the results at room temperature indicated the unfavorable triplet dissociation barriers remained higher than 1.35eV. In contrast, a higher temperature helps facilitate the singlet pathway dissociation barrier to be decreased to 0.65eV at 298.15K. However, the overall dissociation of the triplet O2 on (8, 0) AlNNT decreases to 0.95eV at 0K and 0.86eV at 298.15K due to the spin–orbital coupling. With the decreasing of the overall dissociation barriers with increasing diameter of the nanotube, it can be further addressed that both singlet and triplet O2 can dissociate on AlNNT but more strict condition is needed for triplet O2 dissociation such as AlNNT with large diameter or high temperature. Moreover, the electronic structure of AlNNT would be modified and its conductivity increases when interacting with O2. The results presented here will be a guide for application of AlNNT in nanodevices such as detecting O2 and spintronics applications.

A quantum chemistry study on surface reactivity of pristine and carbon-substituted AlN nanotubes

A density functional theory investigation was performed to predict the surface reactivity of pristine and carbon-substituted (6,0) single-walled aluminum nitride nanotubes (AlNNTs). The properties determined include the electrostatic potentials VS(r) and average local ionization energies ĪS(r) on the surfaces of the investigated tubes. According to computed VS(r) results, the Al/N atoms in edge or cap regions show a different reactivity pattern than those at the middle portion of the tubes. Due to the carbon-substitution at the either Al or N sites of the tubes, the negative regions associated with nitrogen atoms are stronger than before. The prediction of surface reactivity and regioselectivity using average local ionization energies has been verified by atomic hydrogen chemisorption energies calculated for AlNNTs at the B3LYP/6–31G⁎ level. There is an acceptable correlation between the minima of ĪS(r) and the atomic hydrogen chemisorption energies, demonstrating that ĪS(r) provides an effective means for rapidly and economically assessing the relative reactivities of finite sized AlNNTs.

Adsorption of CO molecule on AlN nanotubes by parallel electric field

The behavior of the carbon monoxide (CO) adsorbed on the external surface of H-capped (6,0) zigzag single-walled aluminum nitride nanotube (AlNNT) was studied using parallel and transverse electric field (strengths 0-140 × 10(-4) a.u.) and density functional calculations. The calculated adsorption energies of the CO/AlNNT complex increased with increasing parallel electric field intensity, whereas the adsorption energy values at the applied transverse electric field show a significant reverse trend. The calculated adsorption energies of the complex at the applied parallel electric field strengths increased gradually from -0.42 eV at zero field strength to -0.80 eV at a field strength of 140 × 10(-4) a.u. The considerable changes in the adsorption energies and energy gap values generated by the applied parallel electric field strengths show the high sensitivity of the electronic properties of AlNNT towards the adsorption of CO on its surface. Analysis of structural parameters indicates that the nanotube is resistant to external electric field strengths. The dipole moment variations in the complex show a significant change in the presence of parallel and transverse electric fields, which results in much stronger interactions at higher electric field strengths. Additionally, the natural bond orbital charges, quantum molecular descriptors, and molecular orbital energies of the complex show that the nanotube can absorb CO molecule in its pristine form at a high applied parallel electric field, and that the nanotube can be used as a CO storage medium.

Electronic sensor for sulfide dioxide based on AlN nanotubes: a computational study

Single-walled aluminum nitride nanotubes (AlNNTs) are introduced as an electronic sensor for detection of sulfur dioxide (SO₂) molecules based on density functional theory calculations. The proposed sensor benefits from several advantages including high sensitivity: HOMO-LUMO energy gap of the AlNNT is appreciably sensitive toward the presence of SO₂ so that it decreases from 4.11 eV in the pristine tube to 1.01 eV in the SO₂-adsorbed form, pristine application: this nanotube can detect the SO₂ molecule in its pristine type without manipulating its structure through doping, chemical functionalization, making defect, etc., short recovery time: the adsorption energy of SO₂ molecule is not so large to hinder the recovery of AlNNTs and therefore the sensor will possess short recovery times, and good selectivity: the tube can selectively detect the SO₂ molecule in the presence of several molecules such as H₂O, CO, NH₃, HCOH, CO₂, N₂, and H₂.

Electric field effect on (6,0) zigzag single-walled aluminum nitride nanotube

Structural, electronic, and electrical responses of the H-capped (6,0) zigzag single-walled aluminum nitride nanotube was studied under the parallel and transverse electric fields with strengths 0-140 × 10(-4)a.u. by using density functional calculations. Geometry optimizations were carried out at the B3LYP/6-31G* level of theory using a locally modified version of the GAMESS electronic structure program. The dipole moments, atomic charge variations, and total energy of the (6,0) zigzag AlNNT show increases with increase in the applied external electric field strengths. The length, tip diameters, electronic spatial extent, and molecular volume of the nanotube do not significantly change with increasing electric field strength. The energy gap of the nanotube decreases with increases of the electric field strength and its reactivity is increased. Increase of the ionization potential, electron affinity, chemical potential, electrophilicity, and HOMO and LUMO in the nanotube with increase of the applied parallel electric field strengths shows that the parallel field has a much stronger interaction with the nanotube with respect to the transverse electric field strengths. Analysis of the parameters indicates that the properties of AlNNTs can be controlled by the proper external electric field.

NMR and NQR study of Si-doped (6,0) zigzag single-walled aluminum nitride nanotube as n or P –semiconductors

Density functional theory (DFT) calculations were performed to investigate the electronic structure properties of pristine and Si-doped aluminum nitride nanotubes as n or P-semiconductors at the B3LYP/6-31G* level of theory in order to evaluate the influence of Si-doped in the (6,0) zigzag AlNNTs. We extended the DFT calculation to predict the electronic structure properties of Si-doped aluminum nitride nanotubes, which are very important for production of solid-state devices and other applications. To this aim, pristine and Si-doped AlNNT structures in two models (Si(N) and Si(Al)) were optimized, and then the electronic properties, the isotropic (CS(I)) and anisotropic (CS(A)) chemical shielding parameters for the sites of various (27)Al and (14)N atoms, NQR parameters for the sites of various of (27)Al and (14)N atoms, and quantum molecular descriptors were calculated in the optimized structures. The optimized structures, the electronic properties, NMR and NQR parameters, and quantum molecular descriptors for the Si(N) and Si(Al) models show that the Si(N) model is a more reactive material than the pristine or Si(Al) model.

AlN nanotube as a potential electronic sensor for nitrogen dioxide

Equilibrium geometries, stabilities, and electronic properties of nitrogen dioxide (NO2) molecule adsorption on the exterior surface of single-walled aluminum nitride nanotubes (AlNNTs) have been investigated through density functional calculations for exploring their potential usage as nanosensors. The NO2 molecule is chemisorbed on the surface of AlNNTs with adsorption energies in the range −0.10 to −0.80eV. It has been revealed that electron transport through AlNNTs is significantly increased in the presence of the NO2 molecule due to the reduced HOMO–LUMO energy gap. Based on the obtained results, it is expected that AlNNTs can be a promising candidate in gas sensor devices for detecting the NO2 molecule. The results also show that the AlNNTs benefit from fairly short recovery time and high sensitivity.

DFT Studies on the Interaction of an Open-Ended Single-Walled Aluminum Nitride Nanotube (AlNNT) with Gas Molecules

The interaction of various gas molecules including H2, N2, O2 (in triplet and singlet), and H2O on the geometrical structures, energies, and electronic structures with open edges of zigzag (10, 0) ...

A theoretical study of CO adsorption on aluminum nitride nanotubes

Adsorption of toxic CO molecule on single-walled aluminum nitride nanotubes (AlNNTs) was investigated using density functional theory calculations. A detailed analysis of the energetic, geometry, and electronic structure of various CO adsorptions on the tube exterior surface was performed. In contrast to carbon and BN nanotubes, our results indicated that AlNNTs can strongly interact with CO molecules. The adsorption energy of the most stable configuration was calculated to be about −0.25 eV. The Morokuma–Kitaura decomposition for molecular interaction energies was used to investigate the nature of C–Al bond in the most stable CO–AlNNT complex, demonstrating that electrostatic forces and polarization term are basic factors of attractive interaction between CO and AlNNT. They provide 37.9 and 40.4% of attractive interaction and charge transfer energies make a little contribution to the adsorption energy of CO.

The effect of surface curvature of aluminum nitride nanotubes on the adsorption of NH3

Our main objectives are to address the following fundamental issues: (1) A density functional theory study on the structural and electronic properties of the zigzag single-walled aluminum nitride nanotubes (AlNNTs) with various diameters, using B3LYP/6-31G* level of theory. (2) An ONIOM study on the curvature effect of AlNNTs on the NH3 adsorption process using B3LYP/6-31G* and semiempirical AM1 approaches. Furthermore, a potential energy surface is calculated for NH3 moving toward AlNNT surface. In contrast to semiconducting carbon nanotubes (Louie, Top Appl Phys 80:113, 2001) our calculations confirmed that the HOMO–LUMO energy gap of AlNNTs increases with an increase of the tube diameter. Additionally, we showed that HOMO/LUMO interaction between NH3 and AlNNTs becomes stronger as the tube diameter decreases.

Stability and electronic properties of AlN nanotubes under the influence of external electric field

Zigzag and armchair single-walled aluminum nitride nanotubes, with diameters ranging from 5 A to 15 A, under the influence of perpendicular external electric fields, are studied using first-principle calculations. Through the analysis of the formation energy it is observed that tubes with larger diameters are energetically favored when compared to smaller ones. Also, it is shown that the electric fields up to 0.5 V/A have little influence on the stability of aluminum nitride nanotubes. Regarding the electronic structure, it was found that the larger the diameter of the tubes the greater the response to the electric field application, with a significant bandgap reduction up to 2.5 eV.

Density Functional Study of the Influence of Carbon Doping on the Aluminum-27 and Nitrogen-14 Electric Field Gradient Tensors in (10, 0) Single-Walled Aluminum Nitride Nanotube

Abstract Density functional theory (DFT) study was performed to investigate the influence of carbon doping (C-doping) on the electric field gradient (EFG) tensors at the sites of aluminum-27 (27Al) and nitrogen-14 (14N) nuclei in (10, 0) single-walled aluminum nitride nanotube (AlNNT). Two models of original and C-doped AlNNTs were optimized at first and then the EFG tensors were calculated in the optimized structures. The calculated EFG tensors were converted to measurable nuclear quadrupole resonance (NQR) spectroscopy parameters, quadrupole coupling constant (C Q ) and asymmetry parameter (η Q ). The calculated parameters in the original model reveal that the Al and N atoms located at the mouths of nanotube have the largest C Q values revealing their remarkable role in AlNNTs. When C-doping occurs, the C Q values of those nuclei directly bonding to C are significantly increased meaning that the active sites in the C-doped model are increased. The results also reveal that the Al and N play the basic and acidic agents roles, respectively, in AlNNT which is better observed in the C-doped model.

Carbon and silicon substitution in (4, 4) aluminum nitride nanotube — Density functional study of27Al and14N electric field gradient tensors

A computational study at the level of density functional theory (DFT) was performed to investigate the influence of Si and C substitution on the14N and27Al quadrupole coupling constants (CQ) in the armchair single-walled aluminum nitride nanotube (SWAlNNT). To this aim, a 1 nm AlNNT consisting of 28 Al and 28 N atoms was considered in which both mouths of the nanotube are capped by hydrogen atoms. Additionally, two other forms of this model of AlNNT were considered in which five Si and five C atoms were substituted in place of the five Al and five N atoms, with two rings in the length of nanotube, like a wire, in the first form; and three Si and three C atoms were substituted in place of three Al and three N atoms as a central ring on the surface of the AlNNT in the second form. The calculated CQvalues for three optimized AlNNT systems (raw and Si- and C-substituted) reveal diverse electronic environments in the above-mentioned systems. All the calculations were carried out using the Gaussian 98 software package.Key words: armchair nanotube, density functional theory, nuclear quadrupole resonance.

Density functional calculations Al-27 and N-14 quadrupole coupling constants in the H-capped (10, 0) and (4, 4) single-walled aluminum nitride nanotube

Density functional theory (DFT) calculations were performed to calculate nitrogen-14 and aluminum-27 quadrupole coupling constant in the representative considered models of zigzag and armchair aluminum nitride nanotubes (AlNNTs) for the first time. The considered models consisting of 1 nm length of H-capped (10, 0) and (4, 4) single-walled ANNT were first allowed to fully relax and then the C Q calculation were performed on the geometrically optimized models. The evaluated nuclear quadrupole coupling constant for the above-mentioned nuclei reveal that the considered models can be divided into four layers of nuclei with an equivalent electrostatic environment where those nuclei at the ends of tubes have a very strong electrostatic environment compared to the other nuclei along the length of tubes. Those nuclei at the center of the tube length also have an equivalent electrostatic environment. The calculations were performed based on the B3LYP DFT method and 6-31G ∗ and 6-31++G ∗∗ standard basis sets using the Gaussian 98 package of program.

First-Principles Calculations of AlN Nanowires and Nanotubes: Atomic Structures, Energetics, and Surface States

We explore the atomic and electronic structures of single-crystalline aluminum nitride nanowires (AlNNWs) and thick-walled aluminum nitride nanotubes (AlNNTs) with the diameters ranging from 0.7 to 2.2 nm by using first-principles calculations and molecular dynamics simulations based on density functional theory (DFT). We find that the preferable lateral facets of AlNNWs and thick-walled AlNNTs are {1010} surfaces, giving rise to hexagonal cross sections. Quite different from the cylindrical network of hexagons revealed in single-walled AlNNTs, the wall of thick-walled AlNNTs displays a wurtzite structure. The strain energies per atom in AlNNWs are proportional to the inverse of the wire diameter, whereas those in thick-walled AlNNTs are independent of tube diameter but proportional to the inverse of the wall thickness. Thick-walled AlNNTs are energetically comparable to AlNNWs of similar diameter, and both of them are energetically more favorable than single-walled AlNNTs. Both AlNNWs and AlNNTs are wide band gap semiconductors accompanied with surface states located in the band gap of bulk wurtzite AlN.

First-principles calculations on the open end of single-walled AlN nanotubes

Using density functional theory with the generalized gradient approximation, we have studied geometrical and electronic structures of open-ended armchair and zigzag single-walled Aluminum nitride (AlN) nanotubes. For small armchair AlN nanotubes, at least with the diameter less than that of the (8,8) nanotube, a self-closure behavior occurs due to the interaction between dangling bonds of Al and N atoms at the open end. Especially for the (4,4) AlN nanotube, a hemispherical cap with an octagon is formed, which is one half of a round Al 24 N 24 nanocage. The ionization potential of the Al-terminated zigzag AlN nanotube is smaller than that of the N-terminated one.

Strain energy and thermal stability of single-walled aluminum nitride nanotubes from first-principles calculations

We study the strain energy and stability of single-walled aluminum nitride nanotubes (SWAlNNTs) using density functional calculations. We find that SWAlNNTs have strain energy higher than 0.68 eV/atom relative to AlN cubic materials. The energy cost required in order to wrap up an AlN graphitic sheet in to a tube is lower than that required to form BN, GaN and carbon nanotubes with similar diameters from their corresponding graphitic sheets. Our simulations also reveal that SWAlNNTs once synthesized can stably exist at room temperature, and start to melt when temperature is higher than 600 K.