scholarly journals Theoretical Study of Solvent Effects on the Electronic and Thermodynamic Properties of Tetrathiafulvalene (TTF) Molecule Based on DFT

2021 ◽  
pp. 42-54
Author(s):  
Rabiu Nuhu Muhammad ◽  
N. M. Mahraz ◽  
A. S Gidado ◽  
A. Musa
Keyword(s):  
Thermodynamic Properties ◽  
Bond Length ◽  
Density Functional ◽  
Theoretical Study ◽  
Energy Gap ◽  
Basis Set ◽  
Basis Sets ◽  
Frontier Molecular Orbital ◽  
Orbital Energy ◽  
Chemical Hardness

Tetrathiafulvalene () is an organosulfur compound used in the production of molecular devices such as switches, sensors, nonlinear optical devices and rectifiers. In this work, a theoretical study on the effects of solvent on TTF molecule was investigated and reported based on Density Functional Theory (DFT) as implemented in Gaussian 03 package using B3LYP/6-31++G(d,p) basis set. Different solvents were introduced as a bridge to investigate their effects on the electronic structure. The HUMO, LUMO, energy gap, global chemical index, thermodynamic properties, NLO and DOS analysis of the TTF molecule in order to determine the reactivity and stability of the molecule were obtained. The results obtained showed that the solvents have effects on the electronic and non-linear-optical properties of the molecule. The optimized bond length revealed that the molecule has strong bond in gas phase with smallest bond length of about 1.0834Å than in the rest of the solvents. It was observed that the molecule is more stable in acetonitrile with HOMO-LUMO gap and chemical hardness of 3.6373eV and 1.8187eV respectively. This indicates that the energy gap and chemical hardness of TTF molecule increases with the increase in polarity and dielectric constant of the solvents. The computed results agreed with the results in the literature. The thermodynamics and NLO properties calculation also indicated that TTF molecule has highest value of specific heat capacity (Cv), total dipole moment () and first order hyperpolarizability () in acetonitrile, while acetone has the highest value of entropy and toluene has a slightly higher value of zero point vibrational energy (ZPVE) than the rest of the solvents. The results show that careful selection of the solvents and basis sets can tune the frontier molecular orbital energy gap of the molecule and can be used for molecular device applications.

Spectroscopic investigations and DFT studies of synthesized 4-acetamidophenyl 3,4,5-trimethoxybenzoate and 4-acetyl phenyl 3,4,5-trimethoxybenzoate a novel conjugate of gallic acid

2020 ◽  
Vol 17 ◽  
Author(s):  
Sangeeta Srivastava ◽  
Nadeem Ahmad Ansari ◽  
Sadaf Aleem
Keyword(s):  
Gallic Acid ◽  
Density Functional ◽  
Energy Gap ◽  
Basis Set ◽  
Major Constituent ◽  
Orbital Energy ◽  
Reactivity Descriptors ◽  
Homo And Lumo ◽  
Electrophilic Reactivity ◽  
Global And Local

: Gallic acid is abundantly found in amla (Phyllanthus emblica), a deciduous of the family phyllanthaceae. Gallic acid, the major constituent of the plant was methylated to 3,4,5 trimethoxy gallic acid, which then underwent steglich esterification first with paracetamol and then with 4-hydroxy acetophenone to yield 4-acetamidophenyl 3,4,5-trimethoxybenzoate and 4-acetyl phenyl 3,4,5-trimethoxybenzoate “respectively”. 1H NMR, 13C NMR, UV, FT-IR and mass spectroscopy were used to characterize the synthesized compounds. Density functional theory (B3YLP) using 6-31G (d,p) basis set have been used for quantum chemical calculations. AIM (Atom in molecule) approach depicted weak molecular interactions within the molecules whereas the reactive site and reactivity within the molecule were examined by global and local reactivity descriptors. The HOMO and LUMO energies and frontier orbital energy gap were calculated by time dependant DFT approach using IEFPCM model. Small value for HOMO–LUMO energy gap indicated that easier charge transfer occurs within compound 4. The nucleophilic and electrophilic reactivity were determined by MEP (molecular electrostatic potential) experiment. Polarizability, dipole moment, and first hyperpolarizability values were calculated to depict the NLO (nonlinear optical) property of both the synthesized compounds. The antimicrobial activity was also carried out and broad spectrum antibacterial activity against several strains of bacteria and certain unicellular fungi were exhibited by synthesized compound 3.

Theoretical investigation on tautomerism and NLO properties of Salicylideneaniline derivatives

2021 ◽  
Author(s):  
N. Daho ◽  
N. Benhalima ◽  
F. KHELFAOUI ◽  
O. SADOUKI ◽  
M. Elkeurti ◽  
...  
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Energy Gap ◽  
Intramolecular Proton Transfer ◽  
Basis Set ◽  
Frontier Molecular Orbital ◽  
Molecular Orbital Calculations ◽  
Visible Absorption ◽  
Charge Delocalization ◽  
Intramolecular Hydrogen

In this work, a comprehensive investigation of the salicylideneaniline derivatives is carried out using density functional theory to determine their linear and non-linear optical properties. Geometry optimizations, for gas and solvent phases, of the tautomers (enol and keto forms) are calculated using B3LYP levels with 6–31G (d,p) basis set . An intramolecular proton transfer, for 1SA-E and 2SA-E, is performed by a PES scan process at the B3LYP/6-31G (d,p) level. The optical properties are determined and show that they have extremely high nonlinear optical properties. In addition, the RDG analysis, MEP, and gap energy are calculated. The low energy gap value indicates the possibility of intramolecular charge transfer. The frontier molecular orbital calculations clearly show the inverse relationship of HOMO–LUMO gap with the first-order hyperpolarizability (β = 59.6471 × 10-30 esu), confirming that the salicylideneaniline derivatives can be used as attractive future NLO materials. Therefore, the reactive sites are predicted using MEP and the visible absorption maxima are analyzed using a theoretical UV–Vis spectrum. Natural bond orbitals are used to investigate the stability, charge delocalization, and intramolecular hydrogen bond.

scholarly journals Computational studies of the thermodynamic properties, and global and reactivity descriptors of fluorescein dye derivatives in acetonitrile using density functional theory

2021 ◽  
pp. 174751982199451
Author(s):  
Juma Mzume Juma ◽  
Said AH Vuai
Keyword(s):  
Density Functional Theory ◽  
Thermodynamic Properties ◽  
Ionization Potential ◽  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Basis Sets ◽  
Hybrid Functional ◽  
Functional Theory ◽  
Reactivity Descriptors

This work reports density functional theory calculations of the optimized geometries, molecular reactivity, energy gap, and thermodynamic properties of molecular dyes fluorescein (FS), fluorescein attached with methoxy (FSO), fluorescein attached with amine (FSA), fluorescein attached with methane (FSM), fluorescein attached with ethene (FSE), and fluorescein attached with thiophene (FST) using the hybrid functional B3LYP and 6-311G basis sets. When donating groups are attached to the molecular dye, the bond lengths are slightly decreased which is important for easy transfer of electron from donating to the accepting group. For all dyes, highest occupied molecular orbital/lowest occupied molecular orbital analysis results in positive outcomes upon electron injection to semiconductors and subsequent dye regeneration by the electrolyte. The ionization potential increases with increasing conjugation; therefore, the molecular dye attached to thiophene has the highest ionization potential. Meanwhile, a donating group with increased conjugation results in low electron affinity.

scholarly journals On the Use of DFT+U to Describe the Electronic Structure of TiO2 Nanoparticles: (TiO2)35 as a Case Study

2020 ◽  
Author(s):  
Angel Morales ◽  
Stephen Rhatigan ◽  
Michael Nolan ◽  
Frances Illas
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Plane Waves ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Rotationally Invariant

One of the main drawbacks in the density functional theory (DFT) formalism is the underestimation of the energy gaps in semiconducting materials. The combination of DFT with an explicit treatment of electronic correlation with a Hubbard-like model, known as DFT+<i>U</i> method, has been extensively applied to open up the energy gap in materials. Here, we introduce a systematic study where the selection of <i>U</i> parameter is analyzed considering two different basis sets: plane-waves (PWs) and numerical atomic orbitals (NAOs), together with different implementations for including <i>U</i>, to investigate the structural and electronic properties of a well-defined bipyramidal (TiO<sub>2</sub>)<sub>35 </sub>nanoparticle (NP). This study reveals, as expected, that a certain <i>U</i> value can reproduce the experimental value for the energy gap. However, there is a high dependence on the choice of basis set and, and on the +<i>U</i> parameter employed. The present study shows that the linear combination of the NAO basis functions, as implemented in FHI-aims, requires a lower <i>U</i> value than the simplified rotationally invariant approaches as implemented in VASP. Therefore, the transferability of <i>U</i> values between codes is unfeasible and not recommended, demanding initial benchmark studies for the property of interest as a reference to determine the appropriate value of <i>U</i>.

Revealing the Inhibition Efficiencies of Artesunate and Rutin for Corrosion of Steel: A Theoretical Study

2018 ◽  
Vol 762 ◽  
pp. 325-329 ◽  
Author(s):  
Gökhan Gece
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Theoretical Calculations ◽  
Aqueous Media ◽  
Basis Set ◽  
Orbital Energy ◽  
Molecular Orbital Energy ◽  
Experimental Findings ◽  
Corrosion Of Steel

Corrosion inhibition characteristics of artesunate and rutin on carbon steel in water has been studied using density functional theory (DFT). Quantum chemical parameters such as highest occupied molecular orbital energy (EHOMO), lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), and global reactivity properties have been calculated at the B3LYP/6-311G(d,p) basis set. The results of theoretical calculations confirm the experimental findings on the superiority of rutin to protect the corrosion of steel in aqueous media compared to artesunate.

scholarly journals Comparative experimental and theoretical study on the molecular structure and spectroscopic properties of sideroxol isolated from Sideritis stricta and its electronic properties

2021 ◽  
Vol 9 (2) ◽  
pp. 94-107
Author(s):  
Akin Azizoglu ◽  
◽  
Zuleyha Ozer ◽  
Carikci Sema ◽  
Turgut Kilic ◽  
...  
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Chemical Shifts ◽  
Molecular Geometry ◽  
Spectroscopic Properties ◽  
Basis Set ◽  
Basis Sets ◽  
Polarization Functions ◽  
Nmr Properties ◽  
Theory And Experiments

Sideroxol, a kaurene diterpene, was obtained from the acetone extract of Sideritis stricta plant. The ground-state molecular geometry, vibrational frequencies, and NMR chemical shifts were also investigated by using various density functional theories and Pople basis sets. The computed geometries are in good conformity with the experimental data. The comparison between theory and experiments indicates that B3LYP and M06 methods with the 6-31G(d) basis set are able to provide satisfactory results for predicting vibrational and NMR properties. There seems to be no significant effect of addition of diffuse and polarization functions in the basis set used herein.

scholarly journals Predictive calculation of structural, nonlinear optical, electronic and thermodynamic properties of andirobin molecule from ab initio and DFT methods

2021 ◽  
Vol 3 (9) ◽  
Author(s):  
M. T. Ottou Abe ◽  
C. L. Nzia ◽  
L. Sidjui Sidjui ◽  
R. A. Yossa Kamsi ◽  
C. D. D. Mveme ◽  
...  
Keyword(s):  
Thermodynamic Properties ◽  
Density Functional ◽  
Nonlinear Optical ◽  
Energy Gap ◽  
Basis Set ◽  
Dft Methods ◽  
Functional Theory ◽  
Hartree Fock ◽  
H Nmr ◽  
Experimental Values

AbstractThe structural, nonlinear optical, electronic and thermodynamic properties of andirobin molecule were carried out by density functional theory at the B3LYP, WB97XD level and at the Restricted Hartree–Fock level by employing 6–311G(d,p) basis set. The obtained values of bond lengths, bond angles, 1H NMR and 13C NMR are in good agreement with experimental values. The dipole moment and first static hyperpolarizability show that andirobin can be applied in nonlinear optical devices. HOMO–LUMO energy gap values were found to be greater than 4 eV and lead us to the conclusion that this molecule can be used as insulator in many electronic devices. The thermal energy (E), molar heat capacity at constant volume $$(C_{v}$$ ( C v ) and entropy (S) were also calculated.

scholarly journals Exchange Functionals and Basis Set Comparisons for Theoretical Studies of ZnO Nonoclusters

2021 ◽  
Author(s):  
Duwage Perera ◽  
jayendran Rasaiah
Keyword(s):  
Water Splitting ◽  
Density Functional ◽  
Energy Gap ◽  
Wide Band ◽  
Theoretical Method ◽  
Basis Set ◽  
Basis Sets ◽  
Triplet Energy ◽  
Energy Gaps ◽  
Zno Clusters

Catalysts made of nano-scaled metal oxide clusters can push the limits of chemical reactions in the manufacture of paints, cosmetics, and pharmaceuticals. The ZnO clusters can also act as semiconductors with a wide band gap of 3.4 eV at 300 K, and are prospective phoocatalysts in many reactions including H2 production in water splitting reactions. In this project, we studied the structural (geometry) and electronic properties (vertical detachment energy and electron affinity) of ZnO monomers and dimers that form model ZnO clusters, using density functional theory (DFT) with many different exchange functionals and 29 basis sets to optimize their choice. We compared the singlet-triplet energy gaps of small ZnO clusters to find the optimal ZnO cluster size and the best theoretical method to investigate their photocatalytic water splitting activity. Our results show that B3LYP/DGDZVP2 level of exchange functional/basis set theory is the most efficient and fastest of the ones considered. Comparison of the singlet-triplet energy gaps shows that the trimer (ZnO)3, with an energy gap of 58.66 k cal/mol, is approximately equal to the energy of a visible photon at 555 nm and a HOMO-LUMO gap of 4.4 eV, and is the best choice amongst the (ZnO)n clusters of different sizes when the number of monomers n in the clusters ranges from 1 to 6. We used the Gaussian16 software package for all the calculations.

scholarly journals On the Use of DFT+U to Describe the Electronic Structure of TiO2 Nanoparticles: (TiO2)35 as a Case Study

2020 ◽  
Author(s):  
Angel Morales ◽  
Stephen Rhatigan ◽  
Michael Nolan ◽  
Frances Illas
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Plane Waves ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Rotationally Invariant

One of the main drawbacks in the density functional theory (DFT) formalism is the underestimation of the energy gaps in semiconducting materials. The combination of DFT with an explicit treatment of electronic correlation with a Hubbard-like model, known as DFT+<i>U</i> method, has been extensively applied to open up the energy gap in materials. Here, we introduce a systematic study where the selection of <i>U</i> parameter is analyzed considering two different basis sets: plane-waves (PWs) and numerical atomic orbitals (NAOs), together with different implementations for including <i>U</i>, to investigate the structural and electronic properties of a well-defined bipyramidal (TiO<sub>2</sub>)<sub>35 </sub>nanoparticle (NP). This study reveals, as expected, that a certain <i>U</i> value can reproduce the experimental value for the energy gap. However, there is a high dependence on the choice of basis set and, and on the +<i>U</i> parameter employed. The present study shows that the linear combination of the NAO basis functions, as implemented in FHI-aims, requires a lower <i>U</i> value than the simplified rotationally invariant approaches as implemented in VASP. Therefore, the transferability of <i>U</i> values between codes is unfeasible and not recommended, demanding initial benchmark studies for the property of interest as a reference to determine the appropriate value of <i>U</i>.

scholarly journals Quantum chemical modeling of the structure and properties of SnO2 nanoclusters

2021 ◽  
Vol 12 (4) ◽  
pp. 283-290
Author(s):  
O. V. Filonenko ◽  
◽  
A. G. Grebenyuk ◽  
V. V. Lobanov ◽  
◽  
...  
Keyword(s):  
Bond Length ◽  
Cluster Size ◽  
Density Functional ◽  
Tin Dioxide ◽  
Energy Gap ◽  
Molecular Model ◽  
Basis Set ◽  
Atomization Energy ◽  
Hydroxyl Groups ◽  
Energy Characteristics

By the method of density functional theory with exchange-correlation functional B3LYP and basis set 3‑21G (d), the structural and energy characteristics have been considered of the molecular models of SnO2 nanoclusters of different size and composition with the number of Sn atoms from 1 to 10. Incompletely coordinated surface tin atoms were terminated by hydroxyl groups. It has been shown that the Sn–O bond length in nanoclusters does not depend on the cluster size and on the coordination number of Sn atoms, but is determined by the coordination type of neighboring oxygen atoms. Namely, the bond length Sn–O(3) (@ 2.10 Å) is greater than that of Sn–O (2) (@ 1.98 Å). The calculated values of Sn–O (3) bond lengths agree well with the experimental ones for crystalline SnO 2 samples (2.05 Å). The theoretically calculated width of the energy gap decreases naturally with increasing cluster size (from 6.14 to 3.46 eV) and approaches the experimental value of the band gap of the SnO 2 crystal (3.6 eV). The principle of additivity was used to analyze the energy characteristics of the considered models and to estimate the corresponding values for a cassiterite crystal. According to this principle, a molecular model can be represented as a set of atoms or atomic groups of several types that differ in the coordination environment and, therefore, make different contributions to the total energy of the system. The calculated value of the atomization energy for SnO2 is 1661 kJ/mol and corresponds satisfactorily to the experimentally measured specific atomization energy of crystalline SnO2 (1381 kJ/mol). It has been shown that a satisfactory reproduction of the experimental characteristics of crystalline tin dioxide is possible when using clusters containing at least 10 state atoms, for example, (SnO2)10×14H2O.

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