Absolute Electronegativity Research Articles

Theoretical approach for the performance of 4-mercapto-1-alkylpyridin-1-ium bromide as corrosion inhibitors using DFT

Density function theory (DFT) study on adsorptivity and corrosion inhibition performance of 4-mercapto-1-alkylpyridin-1-ium bromide (where R = C8, C10 and C12) on carbon steel in 1 M HCl solution was presented. Quantum chemical descriptors were investigated to explain the performance of these molecules as corrosion inhibitors. These descriptors were EHOMO; energy of the highest occupied molecular orbital, ELUMO; energy of the lowest unoccupied molecular orbital, ΔE; the energy gap, η; Global hardness, S; global softness, I: ionization potential, A: electron affinity, X: absolute electronegativity, ΔN; the fraction of electron transferred, ω; global electrophilicity index, ΔEBack-donation; the back donation, f+, f−; Fukui indices for local nucleophilic and electrophilic attacks and s+, s− local softness. The result of descriptors calculation pronounces that the theoretical approach complies with the reported experimental data.

Gold Polar Intermetallics: Structural Versatility through Exclusive Bonding Motifs.

The design of new materials with desired chemical and physical characteristics requires thorough understanding of the underlying composition-structure-property relationships and the experimental possibility of their modification through the controlled involvement of new components. From this point of view, intermetallic phases, a class of compounds formed by two or more metals, present an endless field of combinations that produce several chemical compound classes ranging from simple alloys to true ionic compounds. Polar intermetallics (PICs) belong to the class that is electronically situated in the middle, between Hume-Rothery phases and Zintl compounds and possessing e/a (valence electron per atom) values around 2. In contrast to the latter, where logical rules of formation and classification systems were developed decades ago, polar intermetallics remain a dark horse with a huge diversity of crystal structures but unclear mechanisms of their formation. Partial incorporation of structural and bonding features from both nonpolar and Zintl compounds is commonly observed here. A decent number of PICs can be described in terms of complex metallic alloys (CMAs) following the Hume-Rothery electron-counting schemes but exhibit electronic structure changes that cannot be explained by the latter. Our research is aimed at the discovery and synthesis of new polar intermetallic compounds, their structural characterization, and investigation of their properties in line with the analysis of the principles connecting all of these components. Understanding of the basic structural tendencies is one of the most anticipated outcomes of this analysis, and systematization of the available knowledge is the initial and most important step. In this Account, we focus on a well-represented but rather small section of PICs: ternary intermetallic compounds of gold with electropositive and post-transition metals of groups 12 to 15. The strong influence of relativistic effects in its chemical bonding results in special, frequently unique structural motifs, while at the same time gold participates in common structure types as an ordinary transition element. Enhanced bonding strength leads to the formation and stabilization of complex homo- and heteroatomic clusters and networks that are compositionally restricted to just a few options throughout the periodic table. Because it has the highest absolute electronegativity among metals, comparable to those of some halogens, gold usually plays the role of an anion, even being able to form true salts with the most electropositive metals. We discuss the occurrence of the structure types and show the place of gold intermetallics in the general picture. Among the structures considered are ones as common as AlB2 or BaAl4 types, in line with the recently discovered diamond-like homoatomic metal networks, formation of local fivefold symmetry, different types of tunneled structures, and more complex intergrown multicomponent structures.

Quantum Chemical Investigation of the Relationship Between Molecular Structure and Corrosion Inhibition Efficiency of Benzotriazole and its Alkyl-Derivatives on Iron

In this study, we have investigated possible role as iron corrosion inhibitor of four benzotriazole derivatives, BTA, BTA-C1, BTA-C4, BTA-C6, using DFT calculations at B3LYP/6-311G** level of theory. For this purpose, we have determined some structural and electronic parameters such as HOMO and LUMO orbital energies, energy gap, electron affinity, ionization potential, hardness, softness, absolute electronegativity, chemical potential, electrophilicity index, fractions of electrons transferred and back donation, logP, molecular surface area, polar surface area, molecular volume, molar refractivity and have compared with experimental literature results. We have also computed and discussed the interaction energy of the inhibitors with iron surface. The calculated parameters are closely related to the inhibition efficiencies, and have compared with experimental literature values using linear regression analysis to determine the most effective parameters on inhibition efficiency.

Luminescent properties of Tb doped gadolinium aluminate nanophosphors for display and forensic applications

Abstract A novel green light emitting GdAlO3:Tb3+ (1–11 mol%) nanophosphor has been synthesized by the solution combustion method and the final products were characterized. The energy band gap of the samples was estimated in the range of 5.13–5.88 eV from diffuse reflectance spectra. The effect of the added Tb3+ ions on the electronic structure was considered based on the absolute electronegativity. The characteristic photoluminescence emission corresponding to the transition 5D4→7Fj (j = 6, 5, 4, 3) of the Tb3+ ions was observed in the wavelength range of 500–650 nm, and assigned due to the f–f transitions upon the 378 nm excitation. The optimized nanophosphor was found suitable for applications in the latent fingerprint detection. The photometric characterization has revealed the excellent color chromaticity coordinates and the correlated color temperature levels. They are on the same level of commercial phosphors and quite useful for green WLEDs, solid state displays and forensic applications as well.

Comments on Electronegativity Equalization with Pauling Units

Objective: It is known that the electronegativities of functional groups can be significantly to used predict the reaction mechanisms and to explain inductive effects of chemical compounds. Method: Bratsch equation is one of the most important equations used to calculate the electronegativities of functional groups. Conclusion: In the present study, some important comments and contributions related to Bratsch's group electronegativity equation are presented. In addition, it is proposed that absolute electronegativity should be considered in comparison of inductive effects of functional groups. Keywords: Bratsch equation, chemical hardness, conceptual density functional theory, electronegativity, group electronegativity, sanderson's electronegativity equalization principle.

Schiff-base derivatives as corrosion inhibitors for carbon steel materials in acid media: quantum chemical calculations

ABSTRACTQuantum chemical calculations based on Hartree–Fock, AM1 and B3LYP functions were performed on the three Schiff-base compounds used as corrosion inhibitors for carbon steels in acid media. The quantum chemical calculations were conducted to determine the relationship between inhibition efficiency (IE) and the molecular structure of inhibitors. Several quantum chemical parameters, such as charge distribution, energy and distribution of the highest occupied molecular orbital (EHOMO) and lowest unoccupied molecular orbital (ELUMO), absolute electronegativity (χ) and the fraction of electrons (ΔN) transferred from inhibitors to the steel surface, were calculated and correlated with inhibition efficiencies. The results showed that the IE of Schiff-base compounds enhanced with increasing EHOMO or decreasing ELUMO; meanwhile, N atoms on Schiff-base molecules were the most probable sites for adsorption of inhibitor molecules on the metal surface. The inhibition mechanisms of three Schiff-base compounds were obtained from different calculation methods, and the results from each method are consistent.

Study on the interactions of Ag nanoparticles with low molecular weight organic matter using first principles calculations

Experimental studies on environmental processes such as aggregation, disaggregation, dissolution, surface transformation, and adsorption of engineered nanoparticles (ENPs) in the aquatic systems are reported to be influenced by their interactions with natural organic matter (NOMs) and ENPs inherent physicochemical properties. Herein, density functional theory (DFT), classical lattice dynamics (CLD), and quantum mechanical calculations based on frontier molecular orbital (FMO) theory were applied to elucidate the interactions of ENPs and NOMs. Results were derived for the adsorption energies of formic acid (CH2O2), acetic acid (C2H4O2), and ascorbic acid (C6H8O6) on silver (Ag) ENPs (111) surface – and its shapes, namely: spherical, cylindrical, and different tetrahedron positions (faces, vertices and edges) using the DFT and CLD. Results showed that the adsorption energies increased as the molecular weight of the adsorbate increased; thus C6H8O6 had the highest adsorption energies for surface, spherical- and cylindrical-shaped Ag ENPs. At different positions of tetrahedron Ag ENP (111) surface, results indicated faces exhibited higher adsorption energies compared to the edges; hence, likely to be the most preferred adsorption sites. Overall, results derived from both in silico techniques suggest that Ag ENPs are likely to be easily adsorbed by NOMs with larger molecular mass. In addition, calculations using FMO theory showed a direct relationship with each of the four parameters viz.: the dipole moment (μ), molecular surface area (MSA), absolute electronegativity (χ), and absolute hardness (η) to the molar mass of the adsorbate. Hence, from our theoretical results: μ, MSA, χ, and η properties, and the adsorption energies are likely quantum mechanical descriptors of ENMs adsorption to NOMs in the aquatic systems.

On the chemical bonding features in palladium containing compounds: A combined QTAIM/DFT topological analysis

Topological analyses of the electron density on N-benzoyl-L-pheylalanine and its palladium(II) complexes are carried out using the quantum theory of atoms in molecules (QTAIM) at the M06/6-31G(d) theoretical level. The topological parameters derived from the Bader theory are also analyzed; these are characteristics of Pd bond critical points and ring critical points. The calculated structural parameters are the highest occupied molecular orbital energy (E HOMO), the lowest unoccupied molecular orbital energy (E LUMO), the hardness (η), the softness (S), the absolute electronegativity (χ), the electrophilicity index (ω), and the fractions of electrons transferred (ΔN) from ethylenediamine, 2,2′-bipyridine and 1,10-phenanthroline complexes to N-benzoyl-L-pheylalanine. The numerous correlations and dependences between the energy terms of the symmetry adapted perturbation theory approach, geometrical, topological, and energy parameters are detected and described.

Synthesis, crystal structure, electrochemical and anti-corrosion studies of Schiff base derived from o-toluidine and o-chlorobenzaldehyde

In this report, a Schiff base, E-N-(2-chlorobenzylidiene)-2-methylaniline, has been synthesized and characterized using Elemental analysis, MS, FTIR, and NMR (1H and 13C) spectroscopic techniques. The structure of the compound was determined by single crystal X-ray diffraction studies. The structure showed a disorder, as if ‘inverted’, around a point between the carbon and nitrogen bridge atoms in a 0.68:0.32 ratio. The methyl and chloride swap positions of the opposite phenyl rings, as well as bridging carbon and nitrogen. The solid state molecular geometry has been compared with the theoretical data obtained using density functional theory (DFT). The ELUMO–HOMO, dipole moments, chemical potential, absolute electronegativity and hardness of the compound were studied by DFT. The corrosion inhibition study of the Schiff base was investigated for mild steel in 1 M HCl medium using electrochemical (potentiodynamic polarization and electrochemical impedance spectroscopy) methods. The results showed that the compound exhibited appreciable inhibition efficiency at higher concentration with potentiodynamic polarization studies revealing a mixed-type inhibitor of predominantly anodic type. Scanning electron micrographs (SEM) and EDX studies revealed the film-forming ability of the ligand on the mild steel surface. Some quantum chemical parameters calculated correlate well with the experimental results. Based on the theoretical and experimental results obtained, the enhanced corrosion inhibition efficiency could be ascribed to the presence of the azomethine and the aromatic rings characteristic of the Schiff base.

Revealing Germylene Compounds to Attain Superbasicity with Sigma Donor Substituents: A Density Functional Theory Study.

Compounds of GeII are shown for the first time to function as superbases. Two B(N=PiPr3 )2 groups attached to a germanium(II) center show a gas-phase proton affinity of 296.2 kcal mol-1 , which is close to the range of a hyperbase as revealed by B3LYP-D3/6-31G(2d,p) level of theory. These DFT calculations showed better agreement of geometrical parameters for the reported stable germylene compound 1 than previously reported calculations. A systematic study with different substitutions of GeII revealed that such a system can achieve basicity close to a hyperbase. The stabilities of these superbases were examined with dimerization energy and singlet-triplet state energy difference (ΔES-T ). Furthermore, the calculated gas-phase proton affinity values also show good correlation with the most negative valued point (Vmin ) in electron-rich regions from the molecular electrostatic potential. The high PA values of compounds were also supported by ionization potential, electron affinity, absolute electronegativity, and absolute hardness calculations. The energetics for the reaction with BH3 and AlMe3 further suggest that the lone pair of GeII can act as a Lewis base and display higher donor-acceptor bond strengths.

Study of Anti-Tarnishing Mechanism in Ag-In Binary System by Using Semi-Quantum-Mechanical Approach

Tarnishing of silver objects have been real issues throughout millennia of human civilization history due to the fact that silver is very susceptible to sulfur element and can easily get tarnished by sulfur-containing gases. Over the past several decades, researchers have been studying mechanisms of tarnishing phenomena and tried to formulate and develop anti-tarnishing engineering solutions for various fields of applications, including jewelry, catalysts, electronics and optics. Recently, our research group demonstrated that silver-indium solid solutions possessed excellent anti-tarnishing property by quantitative experimental studies. However, the anti-tarnishing mechanism in silver-indium binary system is still unknown. In this paper, anti-tarnishing mechanism in silver-indium binary system is studied by a semi-quantum-mechanical approach. Silver-indium thin film were systematically examined by several experimental approaches in order to study their crystallography and surface properties thermodynamically. An original semi-quantum-mechanical approach was introduced for calculating the Hard and Soft Acids and Bases quantifiable parameters based on conceptual DFT formalization and incorporated with the Hammer-Nørskov d-band model, namely, absolute electronegativity and chemical hardness. Finally, the discovery of increasing absolute electronegativity and chemical hardness can be used to theoretically interpret the most fundamental mechanism behind the mystery of anti-tarnishing phenomenon in the silver-indium binary system.

Synthesis and Conjoint Experimental-DFT Characterization of Some Pyrazolone Functionalized Dioxovanadium (V) Schiff Base Complexes

This paper is concerned with the synthesis and hyphenated DFT-experimental characterization of dioxovanadium(V) complexes of semicarbazones ONO-donor ligands, LH [where, LH=N-(4’-benzoylidene-3’- methyl-1’-phenyl-2’-pyrazolin-5’-one)-semicarbazone (bmphp-semH), N-(4’-butylidene-3’-methyl-1’-phenyl-2’- pyrazolin-5’-one)-semicarbazone (bumphp-semH), N-(4’-iso-butylidene-3’-methyl-1’-phenyl-2’-pyrazolin-5’-one)- semicarbazone (iso-bumphp-semH) or N-(3’-methyl-1’-phenyl-4’-propionylidene-2’-pyrazolin-5’-one)-semicarbazone (mphpp-semH)] and were prepared from ethanol-methanol mixed solvent (1/10) solutions of bis(acetylacetonato) oxovanadium(IV) complexes of the above ligands by oxidizing with atmospheric oxygen (bubbling air) for 2-3 days. The composition and formulae of complexes were confirmed by various physiochemical analysis, viz., percentage of different elements, magnetic susceptibility, conductance, FT-IR, UV-Visible and mass spectrometry. One of the representative complexes, cis-[VO2(bmphp-sem)(H2O)] was investigated at the convergence of DFT and experimental formulation interface. The standard B3LYP/LANL2DZ combinations were used to arrive at the approx of geometry optimization, charge distribution and molecular orbital descriptions. The global reactivity parameters like absolute electronegativity (χabs) and absolute hardness (η) have also been involved. From the overall studies it has been found that the compounds possess cis-octahedral structure.

Quantum-chemical substantiation of the properties of the bioreagent oxidizing non-ferrous metal sulfides

The paper determines the structural formula and quantum chemical characteristics of the most energetically probable, stable conformation of the bioreagent molecule formed during the oxidation of iron (II) ions by the autotrophic mesophilic iron-oxidizing bacteria Acidithiobacillus ferrooxidans in a solution of sulfuric acid consisting of iron (III) ion and three acid residues of glucuronic acid. The bioreagent oxidant is widely used in the industry for leaching metals from non-ferrous sulfide ores and enrichment concentrates. The quantum chemical characteristics of the bioreagent molecule are analyzed in comparison with the characteristics of anhydrous iron (III) sulphate, also used in hydrometallurgy as an oxidizer. The structure and quantum-chemical characteristics are studied using the method of molecular computer simulation, the theory of boundary molecular orbitals, and the Pearson principle. It has been established that the most energetically probable, stable conformation of the bioreagent molecule contains the acid residues of glucuronic acid of a non-cyclic structure. According to the research results, the bioreagent refers to the more rigid Lewis acid – electron acceptor – than iron (III) sulphate. The bioreagent molecule is less polarized, characterized by lower absolute electronegativity and 2 times larger volume. A theoretical substantiation of the greater persistence of primary sulphides – pyrite, pentlandite, chalcopyrite, relative to the secondary minerals – pyrrhotine, chalcocite and covellite is proposed based on the calculated values of the boundary molecular orbitals, absolute stiffness and electronegativity of iron, copper and nickel sulfides. The bioreagent characteristics that determine the interaction efficiency – volume, heat of formation, steric energy and its components, total energy, etc. are many times greater than for Fe2(SO4)3. The high oxidative activity of the bioreagent relative to Fe2(SO4)3 can be justified by the higher partial charge of the iron atom, the greater length of bonds between atoms, the lower energy of the lower free molecular orbitals and the greater degree of charge transfer during the interaction of the bioreagent with the sulfide minerals.

Quantum-mechanical parameters for the risk assessment of multi-walled carbon-nanotubes: A study using adsorption of probe compounds and its application to biomolecules

This work forwards new insights into the risk-assessment of multi-walled carbon-nanotubes (MWCNTs) while analysing the role of quantum-mechanical interactions between the electrons in the adsorption of probe compounds and biomolecules by MWCNTs. For this, the quantitative models are developed using quantum-chemical descriptors and their electron-correlation contribution. The major quantum-chemical factors contributing to the adsorption are found to be mean polarizability, electron-correlation energy, and electron-correlation contribution to the absolute electronegativity and LUMO energy. The proposed models, based on only three quantum-chemical factors, are found to be even more robust and predictive than the previously known five or four factors based linear free-energy and solvation-energy relationships. The proposed models are employed to predict the adsorption of biomolecules including steroid hormones and DNA bases. The steroid hormones are predicted to be strongly adsorbed by the MWCNTs, with the order: hydrocortisone > aldosterone > progesterone > ethinyl-oestradiol > testosterone > oestradiol, whereas the DNA bases are found to be relatively less adsorbed but follow the order as: guanine > adenine > thymine > cytosine > uracil. Besides these, the developed electron-correlation based models predict several insecticides, pesticides, herbicides, fungicides, plasticizers and antimicrobial agents in cosmetics, to be strongly adsorbed by the carbon-nanotubes. The present study proposes that the instantaneous inter-electronic interactions may be quite significant in various physico-chemical processes involving MWCNTs, and can be used as a reliable predictor for their risk assessment.

Visible photon excited photoluminescence; photometric characteristics of a green light emitting Zn2TiO4:Tb3+ nanophosphor for wLEDs

A novel green light emitting Zn2TiO4:Tb3+ nanophosphor was synthesized via solution combustion synthesis and the final product was well characterized. From diffused reflectance spectra the energy band gap of the sample was estimated to be in the range 3.16–3.19 eV and the effect of Tb3+ on the electronic structure was calculated based on absolute electronegativity. The characteristic photoluminescence emission peak observed at 493 nm in the blue region was due to 5D3 → 7F3 and peaks at 515, 541, 579 and 620 nm corresponding to 5D4 → 7Fj (j = 6, 5, 4, 3), respectively, were due to f–f transitions of Tb3+ cations in the given host lattice upon 415 nm high energy visible photon excitation. Photometric characteristics suggest that the phosphors have a long lifetime, excellent color purity, color chromaticity coordinates and correlated color temperature values, so it is clearly evident that the optimized phosphor is quite useful for the green region of wLEDs, a ceramic pigment and for solid state display applications.

Quantum chemical studies on some new bipyrazole derivatives as corrosion inhibitors for steel materials

Purpose The purpose of this study is to perform quantum chemical calculations based on the DFT method on four bipyrazoles used as corrosion inhibitors for the plain carbon (“mild”) steel in acid media to determine the relationship between inhibition efficiency and the molecular structure of inhibitors. Design/methodology/approach Several quantum chemical parameters, such as the charge distribution, energy and distribution of highest occupied molecular orbital and lowest unoccupied molecular orbital, the absolute electronegativity (χ) values and the fraction of electrons (△N) transferring from inhibitors to the steel surface, were calculated and correlated with inhibition efficiencies. Findings The results showed that the inhibition efficiency of bipyrazole increased with the increasing in EHOMO, and the areas containing N atoms were the most probable sites to donate electrons for adsorbing the inhibitor molecules onto the metal surface. Originality/value It is a useful method to investigate the mechanisms of reaction by calculating the structure and electronic parameters, which can be obtained by means of theoretical quantum theory. Thus, the behavior and mechanism of the organic inhibitors can be obtained. Quantum chemical method can also be used to guide the selection and molecular design of inhibitors.

Density Functional Theory (DFT) modeling and Monte Carlo simulation assessment of inhibition performance of some carbohydrazide Schiff bases for steel corrosion

DFT and Monte Carlo simulation were performed on three Schiff bases namely, 4-(4-bromophenyl)-N′-(4-methoxybenzylidene)thiazole-2-carbohydrazide (BMTC), 4-(4-bromophenyl)-N′-(2,4-dimethoxybenzylidene)thiazole-2-carbohydrazide (BDTC), 4-(4-bromophenyl)-N′-(4-hydroxybenzylidene)thiazole-2-carbohydrazide (BHTC) recently studied as corrosion inhibitor for steel in acid medium. Electronic parameters relevant to their inhibition activity such as EHOMO, ELUMO, Energy gap (ΔE), hardness (η), softness (σ), the absolute electronegativity (χ), proton affinity (PA) and nucleophilicity (ω) etc., were computed and discussed. Monte Carlo simulations were applied to search for the most stable configuration and adsorption energies for the interaction of the inhibitors with Fe (110) surface. The theoretical data obtained are in most cases in agreement with experimental results.

The experimental and quantum chemical investigation for two isomeric compounds as aminopyrazine and 2-amino-pyrimidine against mild steel corrosion

Purpose The purpose of this paper is to investigate the adsorption and corrosion inhibition of two isomeric compounds (C4H5N3) as aminopyrazine (AP) and 2-amino-pyrimidine (2AP) on mild steel (MS) in 0.5 M HCl. The study was a trial to combine experimental and modelling studies and research effect of molecular geometry on inhibition effect of inhibitor molecules. Design/methodology/approach The thermodynamic, kinetic and quantum parameters were determined. The electrochemical impedance spectroscopy and anodic polarisation measurements were obtained. The scanning electron microscope was used for monitoring electrode surface. The highest occupied molecular orbital, energy of the lowest unoccupied molecular orbital, Mulliken and natural bonding orbital charges on the backbone atoms, absolute electronegativity, absolute hardness were calculated by density functional theory (DFT)/B3LYP/6-311G (++ d,p). Findings Results showed that AP and 2AP suppressed the corrosion rate of MS. The corrosion current values were 0.530, 0.050 and 0.016 mA cm-2 in HCl, AP and 2AP containing HCl solutions, respectively. It was illustrated with the blocked fraction of the MS surface by adsorption of inhibitors which obeyed the Langmuir isotherm. The inhibition efficiency follows the order: 2AP > AP which is in agreement with experimental and quantum results. Originality/value This paper provides lay a bridge on the molecular geometry and inhibition efficiency by electrochemical tests and modelling study. The inhibition effect of AP and 2AP has not been compared with each other, neither experimentally nor theoretically. This study put forward possible application of 2AP as corrosion inhibitor especially for closed-circuit systems.

Computational Studies for Inhibitory Action of 2-Mercapto-1-Methylimidazole Tautomers on Steel Using of Density Functional Theory Method (DFT)

The inhibition activity of thione–thiol tautomers of 2-mercapto-1-methylimidazole (MMI), namely 1-methyl-1H-imidazole-2 (3H)-thione (M1) and 1-methyl-1H-imidazole-2-thiol (M2) has been performed using density functional theory (DFT) B3LYP/6-311G (d, P) basis set level in order to elucidate the different inhibition efficiencies of these compounds as corrosion inhibitors. The calculated structural parameters correlated to the inhibition efficiency are the frontier molecular orbital energies EHOMO (Highest occupied molecular orbital energy), ELUMO (Lowest unoccupied molecular orbital energy), energy gap (ΔE), dipole moment (μ), hardness (η), softness (S), the absolute electronegativity (χ), the electrophilicity index (ω) and the fractions of electrons transferred (ΔN) from thione–thiol tautomer molecules to iron. The highest value of EHOMO is -5.30241 (eV) of M1 indicates the better inhibition efficiency than the other inhibitor M2. In our study, the trend for the (ΔEg gap) values follows the order M1>M2, which suggests that inhibitor M1 has the highest reactivity in comparison to M2 and would therefore likely interact strongly with the metal surface. The parameters like hardness (η), Softness (S), dipole moment (μ), electron affinity (EA) ionization potential (IE), electronegativity (χ) and the fraction of electron transferred (ΔN) confirms the inhibition efficiency in the order of M1>M2.

Theoretical study of the binding energy of some gases on Al-doped carbon nanotube

Adsorption of a single molecule of the gases, H2O, NH3 and HF inside and on the surface of a tube of Al-doped (5,0) single-walled carbon nanotubes (Al-CNT) was investigated using Density Functional Theory (DFT) at the B3LYP/6-31G(d) level. The results showed that adsorption of Al-CNT is independent of special orientation, all guest molecules prefer to be adsorbed into the surface of Al-CNT rather than into the CNT tube, and that HF binds stronger than H2O, which binds stronger than NH3. Upon adsorption of the guest molecules, the energy gap of Al-CNT was considerably reduced, resulting in improved electrical conductivity. DOS and NBO analysis were performed to discover intermolecular interactions. Chemical reactivity was investigated in terms of chemical hardness, softness and absolute electronegativity.