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.

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.

scholarly journals Oxane dendrimers of tetravalent elements as models for their dioxide polymorphs

Surface ◽  
2021 ◽  
Vol 13(28) ◽  
pp. 3-14
Author(s):  
A.G. Grebenyuk ◽  
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Tin Dioxide ◽  
Basis Set ◽  
Basis Sets ◽  
Hydroxyl Groups ◽  
High Symmetry ◽  
Molecular Models ◽  
Basis Set Superposition Error ◽  
Theoretical Approaches

Oxides of tetravalent elements are well known to have a lot of crystalline modifications. For example, most of silica polymorphs are characterized by tetrahedral coordination environment of silicon atoms. On the contrary, crystals of stishovite and of some silicate minerals have their silicon atoms in octahedral coordination spheres. It has been found experimentally that the phase transitions between silica polymorphs accompanied by a rearrangement of silica-oxygen tetrahedrons into octahedra require an energy income (preference energy) of 54 kJ/mol. When increasing the atomic mass of the oxide forming element, the former decreases extremely and for tin dioxide is equal to -59 kJ/mol. These values can be reproduced in a theoretical way, within the frameworks of modern quantum chemical methods and periodic models. High disperse silica nanoparticles (as well as those for other oxides) have only the nearest order of atomic stationing, so that theoretical approaches developed for crystals cannot be applied to small particles. These particles can be transformed into stishovite form under hydrothermal conditions. Such a process can be simulated within cluster approximation by use of molecular models. This work is devoted to quantum chemical simulation of formation of the fragments with hexa-coordinated atoms of silicon and of its analogs in the structure of oxane dendrimers. A row of high symmetry models was examined containing two, three, five, and seventeen atoms of silicon and of germanium, titanium and tin, terminated with hydroxyl groups. These structures can be rearranged into another ones including oxide forming atoms with elevated (equal to 5 or 6) coordination number, so mimicking the rutile-like structure. Such models let it possible to fulfill the procedure of transformation without rupturing siloxane bonds, so remaining within a deformation approach. Another advantage is the exclusion of the basis set superposition error due to use of molecular models of the same total formula for all the coordination states. All calculations were carried out by Hartree-Fock and density functional theory methods with the all-electron (3-21G*) and valent (SBKJC) basis sets by means of the GAMESS program. Models of various size have been examined, in particular, disiloxane (HO)3Si-O-Si(OH)3 witch can be transformed into a self-coordinated form where one of silicon atoms becomes a five-coordinated; trisiloxane (HO)3Si-O-Si(OH)2-O-Si(OH)3 can be rearranged into symmetric isomer with one hexa-coordinated silicon atom. Pentasiloxane with neo-structure of [(HO)3Si-O]4Si forms three coordination structures, the most stable of them mimicking the stishovite crystal; it contains one 6-coordinated and two 5-coordinated silicon atoms. Siloxane containing 17 silicon atoms has a super-neo-structure of {[(HO)3Si-O]3Si-O}4Si; it includes seven six-coordinated and four five-coordinated silicon atoms. Relative models for silicon analogs have been also examined. When analyzing a dependence of the energy differences between open and coordinated oxane structures on the number of atoms of the oxide forming element in the cluster, one can jump to the conclusion that the specific value of this characteristic monotonously decreases with the increase in the number of atoms of the molecular model, so becoming close to the experimental data.

A Computational Study of Catalytic Platinum Nanoparticles With and Without OH Chemisorption During Reactions

2008 ◽  
Author(s):  
Mikhail Sekachev ◽  
Cheng-Xian Lin ◽  
Zhiyu Hu ◽  
Don Dareing
Keyword(s):  
Binding Energy ◽  
Total Energy ◽  
Platinum Nanoparticles ◽  
Cluster Size ◽  
Density Functional ◽  
Energy Gap ◽  
Computational Study ◽  
Basis Set ◽  
Functional Theory ◽  
The Stability

In this paper, various energies and geometries of pure platinum nanoparticles and those of platinum nanoparticles with adsorbed OH were investigated. Ten different platinum clusters of up to 28 atoms were studied using spin-unrestricted density functional theory (DFT) with a double numerical plus polarization basis set. Three different shapes were presented, and the effect of cluster size on binding energy, total energy, and HOMO-LUMO energy gap was investigated. The same set of calculations was performed for selected clusters with OH adsorbate on the Pt(111) surface. The results show that the stability of both the pure clusters and the clusters with adsorbed OH molecule increases with an increase of cluster size. This fact indicates that direct influence of the size of Pt cluster on the reaction rate is possible, and the understanding of how cluster size would affect binding energy is important. The effect of cluster size on total energy of molecule was shown to be a linear function independent of cluster type, as expected. We also found that optimized (stable) Pt clusters were bigger in size than that of the initial clusters, or clusters with bulk geometry.

scholarly journals Investigation of The Influence of Halogens, Cycloalkanes, Carbonyls and the Hydroxyl Groups on The Reactivity of 1, 3-Butadienes With Imine Dienophile: Insight From DFT, MEDT, and QTAIM

2021 ◽  
Author(s):  
Fredrick Asogwa ◽  
Hitler Louis ◽  
Dollars I. Kenthurky ◽  
Obieze C. Enudi
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Biological Activities ◽  
Diels Alder ◽  
Basis Set ◽  
Hydroxyl Groups ◽  
Oh Groups ◽  
Free Energy Of Activation ◽  
Homo And Lumo ◽  
Gibb’S Free Energy

Abstract The presence of nitrogen atom either on the diene or the dienophile structure gives rise to aza or imino-Diels-Alder reactions (DARs). Among hetero-DARs, imino-dienophiles yields numerous functionalized compounds with numerous biological activities including but not limited to antifungal, antibacterial and enzymatic properties. Density functional theory (DFT) using the B3LYP functional at the 6-31+G (d, p) basis set along with topological studies (QTAIM) were used for the investigation of 10 different (SD1-SD10) DARs which differ in the nature of substituents groups attached to the diene molecule. The study indicates higher electron density and stronger interaction for substituted dienes with the cycloalkanes, furan, carbonyl, and -OH groups. It was observed in the HOMO-LUMO energy differences that the bulky groups; SD3, SD4, and SD6 had destabilization energy of -7.86 and 0.09, -7.88 and 0.10 and -7.50 and -0.014 eV respectively in their HOMO and LUMO levels while the halogen substituted dienes SD1, SD2, and SD5 had -8.20 and -0.32, -8.31 and -0.34 and -8.19 and -0.20 eV respectively. The study showed that synthesis of hetero-nuclear aza-cyclohexene is achieved faster with furan substituent of energy gap 7.534 eV and molecular hardness of 3.677 compared to 7.799 (SD7) -8.100 eV (SD8) and 3.899 (SD7) - 4.050 (SD8) respectively scored by other substituents noting that smaller energy gap leads to higher reactivity. HCOCH3 (SD8) retarded the rate of the reaction by about 58% (unspontaneous) following the calculated Gibb’s free energy of activation while SD6 in the ELF analysis showed complete covalent character against other cycloalkanes that showed dual characteristics of a double and single bond between N-C at their transition states.

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.

CHLORINE GAS SENSING OF SnO2 NANOCLUSTERS AS A FUNCTION OF TEMPERATURE: A DFT STUDY

2019 ◽  
Vol 26 (04) ◽  
pp. 1850172
Author(s):  
MUDAR AHMED ABDULSATTAR ◽  
ADEEBH L. RESNE ◽  
SHROK ABDULLAH ◽  
RIYADH J. MOHAMMED ◽  
NOON KADHUM ALARED ◽  
...  
Keyword(s):  
Free Energy ◽  
Gibbs Free Energy ◽  
Density Functional ◽  
Tin Dioxide ◽  
Energy Gap ◽  
Gas Sensing ◽  
Free Energy Calculations ◽  
Measured Temperature ◽  
Chlorine Molecule ◽  
Chlorine Gas

Density functional theory combined with Gibbs free energy calculations is used to study the sensing behavior of tin dioxide (SnO[Formula: see text] clusters towards chlorine gas molecules. Studied SnO2 clusters’ results show the known property of tin dioxide being an oxygen-deficient semiconductor with the preferred stoichiometry SnO[Formula: see text]. The kind of reactions that result in sensing Cl2 molecules is investigated. These include oxygen replacement, chlorine molecule dissociation and van der Waals attachment. Oxygen replacement shows an increase in energy gap which is the case experimentally. Optimum sensing operating temperature towards Cl2 molecules that results from the intersection of the highest SnO2 adsorption and desorption Gibbs free energy lines is at 275∘C in agreement with the experimentally measured temperature of 260∘C.

SOLVENT EFFECTS ON THE ELECTRONIC STRUCTURE AND NON-LINEAR OPTICAL PROPERTIES OF PYRENE AND SOME OF ITS DERIVATIVES BASED ON DENSITY FUNCTIONAL THEORY

2021 ◽  
Vol 4 (4) ◽  
pp. 236-251
Author(s):  
A. S. Gidado ◽  
L. S. Taura ◽  
A. Musa
Keyword(s):  
Density Functional Theory ◽  
Gas Phase ◽  
Density Functional ◽  
Energy Gap ◽  
Chemical Reactivity ◽  
Basis Set ◽  
Lumo Energy ◽  
Functional Theory ◽  
Organic Optoelectronic ◽  
Homo Lumo

Pyrene (C16H10) is an organic semiconductor which has wide applications in the field of organic electronics suitable for the development of organic light emitting diodes (OLED) and organic photovoltaic cells (OPV). In this work, Density Functional Theory (DFT) using Becke’s three and Lee Yang Parr (B3LYP) functional with basis set 6-311++G(d, p) implemented in Gaussian 03 package was  used to compute total energy, bond parameters, HOMO-LUMO energy gap, electron affinity, ionization potential, chemical reactivity descriptors, dipole moment, isotropic polarizability (α), anisotropy of polarizability ( Δ∝) total first order hyper-polarizability () and second order hyperpolarizability (). The molecules used are pyrene, 1-chloropyrene and 4-chloropyrene  in gas phase and in five different solvents: benzene, chloroform, acetone, DMSO and water. The results obtained show that solvents and chlorination actually influenced the properties of the molecules. The isolated pyrene in acetone has the largest value of HOMO-LUMO energy gap of and is a bit closer to a previously reported experimental value of  and hence is the most stable. Thus, the pyrene molecule has more kinetic stability and can be described as low reactive molecule. The calculated dipole moments are in the order of 4-chloropyrene (1.7645 D) < 1-chloropyrene (1.9663 D) in gas phase. The anisotropy of polarizability ( for pyrene and its derivatives were found to increase with increasing polarity of the solvents.  In a nutshell, the molecules will be promising for organic optoelectronic devices based on their computed properties as reported by this work.

The Theory Investigation for the Antioxidant Activity of Phloretin: A Comparation with Naringenin

2014 ◽  
Vol 513-517 ◽  
pp. 359-362
Author(s):  
Ming Xun Yan ◽  
Jin Dong Gong ◽  
Ping Shen ◽  
Chang Ying Yang
Keyword(s):  
Density Functional Theory ◽  
Antioxidant Activity ◽  
Density Functional ◽  
Radical Scavenging ◽  
Basis Set ◽  
Hydroxyl Groups ◽  
Bond Dissociation Energies ◽  
Functional Theory ◽  
Dissociation Energies ◽  
Radical Scavenging Properties

Density functional theory (DFT) calculations, based on B3LYP/6-311G (d, p) basis set, were performed to evaluate the OH bond dissociation energies (BDEs) for phloretin, compared with naringenin, in order to assess the contribution of hydroxyl groups at different position to the radical-scavenging properties. It is indicated clearly that A6 OH is determined as the weakest O-H bond, give rise to the smallest BDE, 73.98 kcal/mol. BDE of B4 OH decreases 2.5 kcal/mol in benzene, very close to that of A6OH, indicated that B4 OH group is also mainly contributed to the reaction with free radicals, especially in non-polar environments.

scholarly journals Quantum Chemical Study on the Influence of Dodecyl Trimethyl Ammonium Bromide on the CH4 Adsorption of Coal

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 894
Author(s):  
Shuo Liu ◽  
Jiaxing Gao ◽  
Yibo Tang ◽  
Junfeng Wang ◽  
Shaocheng Ge
Keyword(s):  
Adsorption Capacity ◽  
Density Functional ◽  
Molecular Model ◽  
Quantum Chemical Study ◽  
Basis Set ◽  
Ammonium Bromide ◽  
Microscopic Mechanism ◽  
Ch4 Adsorption ◽  
Dodecyl Trimethyl Ammonium Bromide ◽  
Adsorption Energies

The adsorption of dodecyl trimethyl ammonium bromide (DTAB) on coal can affect the wettability of coal and change the water absorption of coal. After DTAB treatment, the change in the CH4 adsorption capacity of coal is worth further study. To reveal the microscopic mechanism of the influence of DTAB on the CH4 adsorption capacity of coal, we employed the density functional theory (DFT) with the 6-311 G (d, p) basis set. DFT-based computations interpreted the adsorption process of CH4 and DTAB on coal molecules and determined the stable structure, adsorption distance, Mulliken overlapping populations, and adsorption energies of the two adsorption configurations. The results showed that the adsorption energies of CH4 and DTAB on the molecular model of coal were 2.15 and 42.69 kJ/mol and the adsorption stability distances were 0.261 and 0.238 nm, respectively. The DTAB–coal configuration was more stable than the CH4–coal configuration. When there was competitive adsorption between DTAB and CH4 on coal, the coal molecules preferentially adsorb the DTAB. Infrared spectroscopy and adsorption experiments were also carried out, and the calculation results of quantum chemistry are consistent with the experimental results.

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