Search

The adsorption of several aromatic molecules on a black phosphorene surface was studied using density functional theory.

A computational study is employed to provide an insight view of the behaviour and function of the complexing agents for environmental friendly silver electroplating. The electronic properties of th...

The retarding of metal corrosion due to the effect on economic and safety matters is a challenging research area. The theoretical study could be helpful to understand the mechanism of inhibition and design some new inhibitors. The electronic properties of some pyrimidine derivatives in the gas and aqueous phase were investigated using the m062x/6-311G(3df,3pd) level of theory and the plane wave pseudopotential method and PBE functional were used in the analysis on the Fe(111) surface. The volume and HLG gave the better results for isolated molecule study. Different groups substituted or replaced in thion 2-mercapto pyrimidine (S=Py) structure to enhance its inhibition efficiency. The replacement of Se instead of S revealed the best results in all parameters. The study of inhibitor interaction with the metal surface provides better correlation with the experimental inhibition efficiency and better insight. Keto tautomers represented more efficiency in both gas and solid phase. We predicted that halogenate compounds obey different mechanism to prevent corrosion. Bader analysis indicated that the charge flow occurs from Fe atoms toward inhibitor molecules. As thermodynamic studies confirm that Se=Py is a good inhibitor, the kinetic study of dehydrogenation by CI-NEB method showed lower activation energy for it. So it may be introduced as a new inhibition candidate.

Benzo (α) pyrene (Bap) is one of the well-known compounds which forming covalent DNA and leads to carcinogenic activity. The [2 + 2] cycloaddition reaction of the benzopyrene epoxide (BaPe) with fu...

The storage of H2 molecules was studied theoretically on charged and uncharged Mg decorated graphene surfaces using density-functional theory and by incorporating the van der Waals (vdW) interactions. We found that an increase in the number of Mg atoms and H2 molecule increases the net interaction of the hydrogen molecule with the surface. The Mg-Gr+ has the hydrogen storage capacity of up to nine H2 molecules, with the average adsorption energy of −0.134 eV/H2. Also, we found that hydrogen molecules play an important role in the interaction between the graphene surface and the Mg atom. The charge density difference analysis showed that electron transfer occurs from H2 molecules to Mg atom in uncharged system. However, the Bader charge analysis showed that the positive charges in the Mg-Gr+ and nH2-Mg-Gr+ systems are concentrated on the Mg atom. When the number of H2 molecules reaches more than 4, the charge transfer instead occurs from the Mg atom to H2 molecules as well as to the graphene surface. This results in better interaction between the Mg atom and the Gr+ surface.

Following the demands to find high sensitivity sensors for pollutant gases with compact size, we investigate the adsorption mechanism and detecting capability of χ3 borophene, based on the density functional theory (DFT) calculations. Except for HCN, the overall structure of adsorbed molecules is maintained during the adsorption on the χ3 borophene surface. The obtained adsorption energies vary from −0.20 to −2.45 eV. While the CO2 molecule has a weak interaction with the surface, other molecules, notably CO, NO, NO2, SO, SO2, and SO3 adsorb strongly to the surface. The minimum-energy path and energy barrier for dissociation of the HCN molecule on the surface were studied in detail through the CI-NEB method. Plots of charge density difference and electron localization function demonstrated the covalent character of the formed bonds between N or S-containing gases and the surface. Our investigations of surface and adsorbate band alignments clearly justify the amount of charge transfer in the gap between the Fermi level of χ3 borophene and the LUMO of gas molecules. Furthermore, the surface sensitivity to adsorption was confirmed by analyzing the changes in the transmission coefficient, calculated with the non-equilibrium Green’s function approach. In terms of recovery time, SO, SO3, and NO2 molecules diminish the surface sensing performance, but the χ3 borophene surface is suitable for their removal from the environment. Accordingly, the thermal stability and adsorption capacity of these gases was investigated by Car-Parrinello molecular dynamics simulations. Our study not only clarifies the mechanism of the adsorption of various gas molecules on the χ3 borophene surface, but also reveals the benefit of χ3 in the sensing and removal of these gas species.

Understanding the interaction of organic molecule on metal surfaces is essential for a wide range of technological applications. Adsorption of nitrobenzene (NB) on Pd (1 1 1) surface in different positions was investigated with the periodic density functional theory (DFT) calculation. The most favorable adsorption configuration energetically was a parallel configuration that nitrogen located on top of Pd atom with −0.303 eV. In these weakly adsorption, choice of proper exchange-correlation is critical. VdW-C09 functional with −2.46 eV had the most adsorption energy. Some bimetallic surfaces like V/Pd (1 1 1), Fe/Pd (1 1 1), Ni/Pd (1 1 1), Pt/Pd (1 1 1) and Zn/Pd (1 1 1) were investigated in magnetic property and d-band model as well as geometry and energy to find the appropriate surface. The position of d-band center in the vicinity of Fermi energy represented more active bimetallic surfaces. PDOS, work function and charge transfer of the system were studied before and after adsorption of NB on the most appropriate surface (Fe/Pd (1 1 1)). Adsorption of nitrobenzene causes a decrease in work function of the surface and an increment of charge in the interface region.

The functionalization of the boron nitride nanocone (BNNC) by pyrrole molecule was studied using B3LYP/6-311+G(d) level of theory. The reaction was studied in three methods in different layers of the nanocone: Diels-Alder cycloaddition, quartet cycloaddition and the reaction of the nitrogen atom of the pyrrole molecule with the boron or nitrogen atom of the BNNC. Thermodynamic quantities, Chemical hardness and potential and electrophilicity index of the functionalized BNNC were studied. The results show that the tip of nanocone has a higher tendency for participation in the reaction and the most favorable product of the reaction between BNNC and pyrrole molecule is produced from the reaction of N atom of pyrrole with the B atom of BNNC. The reaction decreases the energy gap value which leads to increasing the reactivity and conductivity of functionalized nanocone. The calculated NICS values confirm the aromaticity in the pristine nanocone as well as in the functionalized nanocone.

In this paper, we study the effects of the configuration of two Al atoms doped into the unit cell of (7, 0) BNNTs, on their structural and electronic properties in solid state using density functional theory methods. Also, all possible configurations for Al double doped (7, 0) BNNT were investigated. The results showed that with Al doping, band gap decreased. Furthermore, an impurity state appears near the Fermi level when two Al atoms replace two boron atoms of adjacent layers. Contour plots of charge density distribution showed a protuberance surrounding N and B atoms adjacent to the substitute Al atoms.

The gas sensing performance of graphene could be unusually improved by decoration of various atoms on its sheet based on experimental and theoretical calculations. Considering that, as yet, experimental development on boron decorated graphene (BG) is still very rare; in this investigation, we used first-principle calculations to study the electrochemical properties of pure graphene (PG) in addition to various coverages of BG upon adsorption of CO as a lethal gas. We observe stronger adsorption as well as higher charge transfer in terms of increasing the B-coverage (Θ) from CO to graphene. Moreover, adsorption energies are scaled substantially by the rate of coverage attributed to the role of co-adsorption. We also find that all adsorption sites for boron on the graphene substrate lead to the same values at high coverage limit. Our results confirm experimental data on the enhanced gas sensitivity of boron-doped graphene and show that B-decorated manipulation of the graphene layer is potentially very favorable for designing new sensors for toxic gas detection.

Lithium storage on γ-Graphyne-like boron nitride (γ-BNyne) was studied using density functional theory. Li atoms gradually were placed on the surface. At each step, in addition to the optimization of the structure with the size of the γ-BNyne unit cell, the effect of lithium concentration on the unit cell size was investigated. The results of the second method showed deviation from the planar form with increasing lithium concentration which was not observed in the first method. All of Li binding energies obtained by the second method are greater and demonstrate a stronger interaction with the surface. Also, the lowest adsorption energy was obtained for 2Li/BNyne structure. The band structure plots indicated that the adsorption of Li atoms on the surface causes converting the surface into an n-type semiconductor and improving its conductivity. Bader charges analysis and the charge density differences demonstrated the charge transfer from Li atom to the surface and a quasi-covalent bond between Li and sp-hybridized nitrogen atom. The energy barrier for the best Li diffusion pathway on the surface was found of 0.45 eV. Our calculations indicate that γ-BNyne can appropriate for application in the Li-ion batteries as an anode material.

χ3 borophene is a promising 2D anode material in Lithium-ion batteries, but its pristine structure needs to be improved for increasing its specific capacity and Li diffusivity. For this purpose, the decoration of χ3 with the Fluorine atom was investigated using the density functional theory. Two F-decorated χ3 configurations (Fχ3-A and Fχ3-B) with very close energy and good kinetic stability were identified for the Li storage. Li atoms were gradually loaded on both configurations and the results showed a maximum specific capacity of 1396 mAh/g for the Fχ3-B structure which thermodynamically is a slightly lower stable configuration. The interaction of the Li atom with the surface is stronger in this configuration and resulting in −1.75 eV adsorption energy. The PDOS and band structure analysis showed a good metallic characteristic of the surface during lithiation process. The Li diffusion barrier in this structure is extremely low, 0.21 eV, which enables very fast Li diffusion on the surface. Also, this study demonstrated the importance of considering the different configurations resulting from decorating a structure, with proper thermodynamic and kinetic stability, in the computational investigation. As in this study, for F-decorated χ3 borophene, the configuration with lower stability and symmetry showed better results in all storage parameters of Li atoms.

Boron nitride nanotubes (BNNTs) are semiconductors with a wide band gap. In comparison with carbon nanotubes (CNTs), BNNTs have higher chemical stability, excellent mechanical properties and higher thermal conductivity. In this paper, we study the effect of diameters and substituting B and N atoms of various zigzag BNNTs with Al, on structural and electronic properties of BNNTs in solid state using the density functional theory method. The results of calculations of density of states and band structure (band) showed that the band gap between the valence and conduction level increases as a result of the enhancement of tube diameter of BNNTs. Finally, the results showed that the electronic properties of the pristine BNNTs can be improved by doping Al atom in the zigzag configuration of tubes.

In this article, we reported the structural and conductive properties of benzene derivatives/carboxylated zigzag SWCNTs. It was noticed that the carboxylated carbon nanotubes were appropriate adsorbents for benzene derivatives. We presented novel density of states and band structures for modified SWCNTs by both carboxylic group and benzene derivatives. The result showed that nitrobenzene/COOH-SWCNT comprising superb electronic properties can be effectually applied for electronic devices and solar cells, instead of aniline/SWCNT combined system.

We have investigated the electronic and structural properties of (10, 0) zigzag single-walled carbon nanotubes (SWCNT) which have adsorbed different alkali metals (X: Li, Na, K, and Cs) and the hydrogen atom by using Density Functional Theory (DFT). It was discovered that among the alkali elements, Li atoms form the strongest bond with SWCNT. In addition, a significant shift was observed in the electronic state of alkali-adsorbed SWCNT compared to pristine SWCNT. Finally, it was proposed that due to showing excellent electronic structure, these modified nanotubes can be applied in new electronic devices, such as transistors, and field emission displays.

The adsorption of the potassium atom onto the surface of (n,0) zigzag nanotube (n = 5–10) and (n,n) armchair nanotubes (n = 3, 5) has been studied by density functional theory. The local density approximation calculation of adsorption energy (E ads) emphasized on the dependency of E ads to the diameter and chirality of the nanotube. E ads decreases when the diameter increases. So the (5,0)-K system has the highest adsorption energy among all structures. Furthermore, a significant change was observed in the electronic properties of potassium-adsorbed single-walled carbon nanotube (SWCNT) and the metallic behavior of the nanotube improved. Therefore, our results showed that such modified SWCNTs can be applied in nanodevices such as transistors.

In this letter, modifications of (10,0) functionalized zigzag Single-Wall Carbon Nanotubes in different sites by thiophene groups were studied using density functional theory. Geometric structures and electronic properties were investigated. After modification a significant change was observed in band structure and density of states and metallic properties were obtained. The best result for application in organic photovoltaic cells was achieved when two organic groups were placed on opposite sides of the wall of the SWCNT symmetrically.

Adsorption of carbon monoxide molecule (CO) on super cell Al-substituted (10, 0) single walled carbon nanotubes (Al-substituted SWCNTs) with different concentration of aluminum is investigated by using density functional computations to find out its sensing properties for the toxic CO gas. It is found that the sensing properties substantially depends on the Al concentrations, because of band structure modifications in comparison with the pristine (10, 0) SWCNT after the adsorption of CO molecule. Also, these properties are strongly dependent on the sites of the SWCNT that the CO molecule is attached. These modified nanotubes acceptable sensors for detecting the CO toxic gas.

A detailed study of the gas flow in carbon nanotubes (CNT) and carbon nanotube junctions (CNTJ) can open the way towards the study of the reaction mixture flow in prospective nano-reactors. In this work, flow of the pure and mixed CO/CO 2 gases through some selected CNTs and three types of CNT1- J -CNT2 CNTJs, ( 12 , 12 )- J -( 3 , 8 ), ( 12 , 8 )- J -( 8 , 12 ) and ( 8 , 8 )- J -( 13 , 0 ), are studied using molecular dynamic simulations. Results of this study show that regardless of the diameter and helicity type of the CNT1 and CNT2, when the flow starts with the molecules in the CNT1, the number density of molecules in the CNT2 is higher than that in the CNT1. Projected radial distribution of the molecules are calculated and analyzed in terms of the molecule–molecule and molecule-wall interactions. The well-structured projected radial distribution results show that the CNT radius and helicity as well as the type of molecules determine the lateral distribution of the gas molecules along the flow.

In this work, the adsorption of benzene molecule on (10,0) functionalized zigzag single-wall carbon nanotubes was studied using density functional theory. Geometric structures, adsorption energies and electronic properties of five supercells were investigated. It was found that the carboxylation causes a notable increment in the adsorption capability of SWCNT in uptaking benzene as a pollutant molecule. The highest absorbency was achieved when benzene molecule had interaction with both SWCNT and COOH functional group through π-π interaction and hydrogen bonding.

The pair-potential energy functions SF 6 -noble gases have been determined from a direct inversion of the experimentally reduced-viscosity collision integrals obtained from the corresponding states correlation. The resulting potentials are in an excellent agreement with the previously determined potentials. The collision integrals and thier ratios of these potentials which are necessary to calculate the theoretical values of transport coefficients are computed. The collision integrals have been used to predict the diffusion coefficients of the binary mixtures of hexafluoride with noble gases. The results indicate the agreement between theory and experiment is within the experimental uncertainties.

Bond order force field molecular dynamic simulation and also a complimentary density functional theory method are employed for lithiation of narrow carbon nanotubes (CNTs). Since interior region of the narrow tubes (diameters < 7 A) is strongly influenced by their walls' 'curvature effect', endo-lithiation occurs via formation of lithium chains. Whereas, in the case of exo-lithiation the absorbed lithium atoms form coaxial cylinders up to radiuses of 12 A. Meanwhile, although to some extent chirality of the CNTs has minor effects on endo-litiation's distribution, the main factor in the total lithium storage capacity is the diameter. In addition, to obtain more applicable results this study is extended also for a bundle of the CNTs and it is seen that the adsorption energy and also the storage capacity enhance about 1.5 times.