dft calculations

The study of oxidation potential and electronic properties of conducting polymers are very important for designing new material with improved properties. The current study focused on the electrochemical information about potential electrode of pyrrole (Py) oligomers, nPy: n = 2-8, as well as their structural and electronic properties. Computational chemistry based on DFT calculations were used to determine an accurate standard oxidation potential (E_ox^°) for the nPy with respect to the calomel reference electrode in the aqueous and non-aqueous solutions. A nice agreement between the predicted and available experimental redox potential was obtained with an average absolute deviation of 0.016 V. A good linear correlation with both the HOMO level and the ionization potential were obtained for the E_ox^° values. Additionally, an estimated E_ox^° value of 0.21 V vs. SCE was obtained for poly(Py) in THF. The simulated current-voltage (IV) curves revealed an increase in the conductivity of nPy chains as the length of oligomer increasing. Based on the analysis of the band gap from the TD-DFT spectral results, a high ease of charge transport was observed for long oligomer chains. Poly(Py) films were synthesized electro-chemically by the direct anodic oxidation of pyrrole in an aqueous solution via cyclic voltammetry (CV) technique. It was found that the oxidation potential for oligo(Py) chains decreases through the growing polymer during the electro-polymerization.

The present work aims to examine the susceptibility to soil corrosion of base metal (BM) and heat affected zone (HAZ) of API L5 X60 steel pipeline, and to assess the ability of Di-(2-ethylhexyl) phosphoric acid (D2EHPA) to inhibit the corrosion of the two samples. An overview of the literature reported almost no studies related to the corrosion inhibition of pipeline in soil solutions. The experiments were carried out in a simulated soil solution (NS3) using electrochemical methods, a thermodynamic approach, and surface analysis. The results demonstrated that D2EHPA is a potent inhibitor for both steels in the soil solution. Indeed, its efficiency increased with the increase of its concentration, exceeding 98 % at the optimal concentration, even for HAZ which is less resistant to corrosion than BM, due to the coarsening  of α-ferrite grains. Polarization curves showed that D2EHPA acts as an anodic-type inhibitor, and the calculated standard free adsorption energy values deduced by Langmuir isotherm indicated that the phosphoric compound adsorbs via electrostatic and chemical bindings. The stability of the adsorbed D2EHPA layer, on both the surfaces of BM and HAZ that were immersed in the inhibitive solution for 168 h, has been proven by EIS studies. Moreover, the effective adsorption of D2EHPA at the steel/SN3 interface is clearly highlighted by Scanning Electron Microscopy (SEM) and FT-IR spectra. Theoretical DFT calculations were also performed to determine some electronic properties of the studied molecule and to find a correlation between the inhibitive effect and the electronic structure of the neutral form and the deprotonated form of D2EHPA.

This study deals with the interaction between the Amantadine drug (Ad) and the Boron Nitride NanoSheet (BNNSh). The interactions between the Ad molecule and BNNSh, doped Si-BNNSh, Ge-BNNSh, and Ga-BNNSh were carried out at the RCAM-B3LYP method with 6-31G(d) basis set using the Gaussian 09 program. The DFT calculations clarified a weak interaction between the Ad drug and BNNSh. The doped Si, Ge, and Ga-BNNSh were examined to obtain a suitable interaction between the Ad drug and BNNSh to make a suitable sensing device. The adsorption energy (Ead), as well as the gap energy between HOMO and LUMO (Eg), were calculated for the Ad drug and BNNSh and its doped Si-, Ge-, and Ga-BNNSh. The DFT calculations indicated that the Ead of the Ge-BNNSh/Ad complex is -19.67 which was suitable adsorption energy for the sensing ability with low recovery time. Also, the change of % ΔEg for the Ge-BNNSh/Ad is -21.50% which shows a high sensitivity of Ge-BNNSh to the Ad drug. This study showed that Ge-BNNSh is a promising candidate for being a possible sensor of the Ad drug.

Protecting the hair, skin, or products of itself are utilized by sunscreen filters which were frequently blocked hazardous UV-Vis radiation. Considering its photoprotective impact on the skin facing the radiation of ultraviolet and visible, TiO2 is a common and cost-efficient photocatalytic structure utilized in sunscreens. In this research, the continual process was done to optimize the green synthesis of TiO2 nanoparticles and nanocomposites through a new, easy, cost-efficient, and quick approach to making nanostructures utilizing a sonochemistry method. SiO2, Al2O3, ZnO, and MnO were utilized to compose green synthesized TiO2 nanoparticles for this purpose. The samples were recognized by XRD, FT-IR, DLS, and SEM. Also, the cytotoxicity and antibacterial activity were assessed. DFT computation was performed to identify the connected energy and band gap energy of nanocomposites by B3LYP/Lan2DZ quantum approach. TiO2/Al2O3 showed a lower size and the lowest agglomeration than synthesized TiO2 and other nanocomposites. Furthermore, all samples indicated strong antibacterial activity against investigated bacteria due to cell death caused by membrane permeability increase and bacterial wall integrity disruption. Nanostructures have cytotoxicity with a low level on A172 cells. The only exception is TiO2/ZnO which indicated a potent index of cytotoxicity on the cancerous cell lines as demonstrated by a low IC50 value of 50 ppm. The relative energy and band gap of nanocomposites indicated that TiO2/Al2O3 has the best stability in chemical and biochemical mediums among other nanocomposites. These green synthesized TiO2/Al2O3 nanostructures may have promising applications in nanoformulation to combat bacterial infections in the future.

In this study, the molecular and atomic adsorption energies, and total density of states (DOS) of the hydrogen on the on-top, bridge, and hollow positions of FCC (100), and FCC (111) surfaces of the metallic platinum were investigated using the DFT calculations. The total DOS result shows higher interaction between hydrogen molecule and metallic surface for the FCC (111) than the FCC (100) surface. Also, the intensity of the anti-bonding orbital for the bridge position is higher than two other positions on the FCC (100) surface, which shows that the hydrogen molecule in this position is ready to be dissociated into hydrogen atoms. In addition, the intensity of the anti-bonding orbital for hollow and bridge positions are higher than the on-top position on FCC (111) surface, which shows the hydrogen molecule in these positions are dissociated into hydrogen atoms. The results show that the comparison between the activation barrier energy (ΔEads) calculated from Lennard-Jones potential curves, and molecular adsorption energy determines whether the hydrogen molecule is dissociated on the surface. If the activation barrier energy (ΔEads) is higher than molecular adsorption energy, the probability that the hydrogen molecule will dissociate on the surface is very low.

In this research, the adsorption behavior of pristine, Si- and Ga- and Al-doped graphene is investigated toward ethionamide (EA) using Density Functional Theory (DFT) calculations. Total energies and geometry optimizations were obtained and Density of State (DOS) analysis was performed at B3lyp level of theory with the 6-31G* basis set. The adsorption energy (Ead) between EA and the pristine, Si-, Ga- and Al-doped graphene is changed in the following order: Ga-Complex-N(ring) > Al- Complex-N(ring) > Si-Complex-N(ring) > Complex-S. The Ead of the Graphene-EA complex is -2.552 kcal/mol, which is low and shows that the adsorption is physical. The % ΔEg= -59.61% for Si-doped graphene EA shows the high sensitivity of the Si-doped graphene to the adsorption of EA. The Eg for Ga-doped graphene-EA decreases significantly from 2.35 to 1.11 eV and the rate of change is %ΔEg = -52.75%, showing the high sensitivity of Ga-doped graphene to the adsorption of EA. However, the high Ead of -36.66 kcal/mol shows that the Ga-doped graphene can be used as a suitable sensing device only at higher temperatures. The % ΔEg= -58.98 % for Al-doped graphene-EA indicates the high sensitivity of the Al-doped graphene to the adsorption of EA. The Ead of -34.53 kcal/mol can be used as a suitable sensing device only at higher temperatures.

In this study, phosphorus trichloride (PCl3) and phosphorus triiodide (PI3) as the condensed inorganic materials were investigated based on the molecular dynamics simulation. To this purpose, molecular dynamics simulations were performed by applying force field parameters derived from the quantum chemistry approach. The potential energy data were computed at the B3LYP/6-31+G (d) and B3LYP/dgdzvpd levels of theory for different configurations of PCl3 and PI3, respectively. To determine force field parameters, a four-site all-atom force field model was used to correlate the potential energy data. Therefore, the force field parameters were applied to perform the molecular dynamics simulations. The MD simulations were performed to obtain the atomic number density, enthalpy, heat capacity, and radial distribution function in the NPT and NVT ensembles for PCl3 and PI3 dimers. There is a good consistency between the experimental data and simulation results over a wide range of experimental conditions.

One new azo Schiff-base derivative: 4-bromo-1,2-bis[2-hydroxy-5-(phenylazo) benzylideneamino]benzene (H2L) was synthesized and characterized by common spectroscopic techniques and elemental analysis. The ability of the new chemosensor for detection of some main and transition metal ions was studied by UV-Vis spectroscopy in the mixture of DMSO: water (9:1). Upon addition of Ca2+ and Cd2+ ions, dramatic changes were observed in the UV-Vis spectrum of ligand (one new absorbance band appeared in the range of 430- 450 nm, while the absorbance band at 351 nm disappeared). The stoichiometry of the complexes was determined using the Job method. The binding constants of Ca2+ and Cd2+ with receptor by Benesi-Hildebrand plots were found to be 2.874×104 M-1 and 6.445×104 M-1, respectively. The results indicated the receptor can recognize Ca2+ and Cd2+ ions from other cations in aqueous solution. Finally, the structure and electronic properties of the ligand and its complexes with Ca2+ and Cd2+ ions were analyzed by DFT and TD-DFT calculations.

Density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations were employed to investigate the electronic and nonlinear optical properties of some substituted C2Bn −2Hn (n = 14 −17) carboranes. Li, Na, K, F, Cl, Br are used as substituents. The carboranes substituted with alkali metal show considerably large first hyperpolarizability values than those of un-substituted ones. NLO response of the halogen-substituted systems is slightly enhanced. The well-known two-level model theory is investigated through TD-DFT approach to understand the origin of NLO response. This study indicates that alkali-metal substituted carboranes may be appropriate for nonlinear optical (NLO) applications.