scholarly journals A quantum chemical study on the effect of titanium dioxide modification with non-metals on its spectral characteristics

2020 ◽  
Vol 11 (4) ◽  
pp. 539-546
Author(s):  
O. V. Smirnova ◽  
◽  
A. G. Grebenyuk ◽  
V. V. Lobanov ◽  
◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Quantum Chemical ◽  
Density Functional ◽  
Spectral Characteristics ◽  
Quantum Chemical Study ◽  
Visible Region ◽  
Wavelength Region ◽  
Basis Set ◽  
Oxidation States ◽  
Impurity Atoms

The experimental results obtained in the study on the possibility of sensitizing titanium dioxide (polymorphic anatase phase) to the visible region of the spectrum by doping and co-doping with impurities of non-metals in order to create effective photocatalysts for the decomposition of organic compounds have been analyzed. The presence of impurity atoms appears to result in a change in the electronic structure of the titanium dioxide matrix, in the appearance of “impurity bands” and in the narrowing of the energy gap of titanium dioxide. Such a modification is accompanied by an extension of the spectral range of sensitivity of photoactive solids to the long-wavelength region of the spectrum and, therefore, can be used to improve the catalytic properties of these materials. Spectral manifestations of carbon impurities in titanium dioxide in the form of carbide and carbonate, as well as sulfur in the forms of sulfite, sulfide, and sulfate, have been studied by the density functional theory method. A Ti14H22O39 cluster model was chosen for the titanium dioxide matrix. The calculations were carried out in the framework of the cluster approximation, using functional B3LYP and basis set 6-31G (d, p). Comparison of the results of quantum chemical calculations with the available experimental data shows that the impurity sulfur and carbon atoms in titanium dioxide, which are in different coordination states and different oxidation states, appear in different spectral ranges. This circumstance makes it possible to elucidate the structure of the samples based on the experimental spectra. A change in the coordination and oxidation states of impurity atoms leads to spectral shifts and splitting of peaks, which can reach 1.5 eV (XPS). The presence of admixtures of non-metals leads to a change in color (deepening in the case of sulfide or carbide) of the samples, appearing in the corresponding UV spectra.

Study on Pyrrole 4-Pyrazoline Derivatives: Experimental and Quantum Chemical Approaches

2016 ◽  
Vol 69 (6) ◽  
pp. 672 ◽  
Author(s):  
R. N. Singh ◽  
Poonam Rawat ◽  
Vikas Baboo
Keyword(s):  
Dft Calculations ◽  
13C Nmr ◽  
Quantum Chemical ◽  
Density Functional ◽  
Electronic Absorption Spectra ◽  
Quantum Chemical Study ◽  
Basis Set ◽  
Dft Methods ◽  
Pyrrole Derivatives ◽  
1H And 13C Nmr

As part of a study on pyrrole derivatives we report here a combined experimental and quantum chemical study of pyrrole 4-pyrazoline biheterocyclic derivatives. The structure of the synthesised compounds have been studied using experimental IR, UV, 1H and 13C NMR spectroscopic analyses along with density functional theory (DFT) calculations using the B3LYP functional with 6–311+G (d,p) basis set. The global, local reactivity, and thermodynamic parameters support the analysis. All the experimental vibrational bands have been discussed and assigned to normal modes on the basis of our calculations. In addition, the computed 1H and 13C NMR data, obtained by DFT calculations, are found to be in good agreement with the experimental data and serve as valuable tools in identifying the products. The vibrational analysis shows red shifts in vN–H and vC=O stretching vibrations as a result of dimer formation. The theoretical electronic absorption spectra have been calculated by using time dependent-DFT methods. The static first hyperpolarizability (β0) values for the synthesized pyrrole–pyrazoline derivatives 4A–D are calculated as 16.97 × 10–30, 47.64 × 10–30, 65.40 × 10–30, 65.39 × 10–30 esu, respectively, and increase from 4A to 4C as a result of the addition of an –NO2 acceptor in 4B and two –NO2 group acceptors in 4C. However, an additional –Cl group in 4D on the phenyl ring attached to the pyrazoline moiety does not result in a clear change from 4C. The calculated static and dynamic hyperpolarizability results show that the investigated molecules might be used as non-linear optical materials.

scholarly journals SPECTRAL CHARACTERISTICS OF CONFORMATION ISOMERS OF MESO-OCTAMETHYL-CALIX(4)PYRROLE BASED ON QUANTUM-CHEMICAL CALCULATIONS

2018 ◽  
Vol 59 (5) ◽  
pp. 30
Author(s):  
Oleg V. Surov ◽  
Mikhail A. Krestianinov ◽  
Nugzar Zh. Mamardashvili
Keyword(s):  
Density Functional Theory ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Density Functional ◽  
Dynamic Equilibrium ◽  
Electronic Absorption Spectra ◽  
Spectral Characteristics ◽  
Structure Optimization ◽  
Basis Set ◽  
Functional Theory

The structure optimization and calculation of electronic absorption spectra of meso-octa-methylcalix(4)pyrrole conformers was performed  by density- functional theory using hybrid B3LYP functional in cc-pVTZ basis set of Gaussian 09 package. Analysis of experimental UV-Vis spectra of solutions of calix(4)pyrrole was carried out in various solvents. The conclusion on the existence of a dynamic equilibrium between conformers in solutions of meso-octamethylcalix(4)pyrrole was made.

scholarly journals QUANTUM-CHEMICAL STUDY OF THE MECHANISM OF REACTION OF BENZOELACETHYLENE WITH DITIO- AND DISELENOMALONAMIDES

2020 ◽  
Vol 2020 (1) ◽  
pp. 127-135
Author(s):  
Elena Chirkina
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Polarizable Continuum Model ◽  
Basis Set ◽  
Mechanism Of Reaction ◽  
The Density Functional Theory ◽  
Two Stages ◽  
Polarizable Continuum

A mechanism of the interaction of benzoylacetylene with dithio- and diselenomalonamides has been proposed on the basis of quantum-chemical calculations in the framework of the density functional theory using the B3LYP/6-311++G(d,p) basis set taking into account solvent effects (AcOH) within the polarizable continuum model, PCM, with inclusion of the HCl molecule in the calculated space. It is shown that the reaction involves two stages to afford heterocyclic compounds of the dithiine and diselenine type

scholarly journals IR spectral manifestation of tin impurity sites in titanium dioxide

2021 ◽  
Vol 12 (3) ◽  
pp. 184-189
Author(s):  
O. V. Smirnova ◽  
◽  
A. G. Grebenyuk ◽  
V. V. Lobanov ◽  
T. A. Khalyavka ◽  
...  
Keyword(s):  
Titanium Dioxide ◽  
Absorption Spectrum ◽  
Ir Spectra ◽  
Band Gap ◽  
Density Functional ◽  
Spectral Characteristics ◽  
Basis Set ◽  
Ultraviolet Region ◽  
Vis Spectroscopy ◽  
Ft Ir

It is known that titanium dioxide as photocatalyst has significant drawback - limited absorption spectrum in the ultraviolet region makes it impossible to use solar energy. To expands the absorption spectrum of TiO2, the doping of impurities (metal, non-metal, etc.) were used. They affected the electronic structure and spectral characteristics of TiO2. The aim of our work was to investigate the influence of tin impurities on spectral characteristics of titanium dioxide using experimental and theoretical methods. The TiO2 powders modified by different amount of tin (Sn/TiO2) were synthesized by sol-gel method. The samples were characterized by SEM, EDX, FT-IR and UV-VIS spectroscopy. It has been found that Sn/TiO2 consists of fragmented agglomerates in the range of 5–10 mm. EDX spectroscopy prove that powders include Ti, O and Sn elements. Modification of titanium dioxide with tin leads to band gap narrowing of samples, which explains by insertion of Sn atoms into crystal lattice of titanium dioxide, because Ti4+ and Sn4+ ions radii are close. The band gap values increased with increasing of tin content. The work also analyzes the vibrational spectra of Sn/TiO2 both experimentally and theoretically. In order to interpret the results obtained, quantum chemical calculations on the spatial and electronic structures of cluster models of titanium dioxide (anatase) with inserted tin atoms using the density functional theory B3LYP method and the basis set 6-31G (d, p) were carried out and the corresponding FT-IR spectra have been simulated. By comparing the experimental and theoretical results, the influence has been analyzed of the number and arrangement of impurity tin atoms in clusters on the observed IR spectra of the samples. This makes it possible to forgive the most probable structural motives of titanium dioxide particles doped with tin atoms, as well as to establish the fact of the presence of tin atoms in the samples. Based on the comparison of the IR spectra of samples with different numbers of tin atoms, it is possible to quantify their composition.

scholarly journals Molecular Structure, Homo-Lumo and Vibrational Analysis Of Ergoline By Density Functional Theory

2021 ◽  
Vol 14 (14) ◽  
pp. 21-30
Author(s):  
Bhawani Datt Joshi ◽  
Ghanshyam Thakur ◽  
Manoj Kumar Chaudhary
Keyword(s):  
Density Functional Theory ◽  
Quantum Chemical ◽  
Density Functional ◽  
Graphical Representation ◽  
Energy Gap ◽  
Quantum Chemical Study ◽  
Vibrational Analysis ◽  
Basis Set ◽  
Potential Energy Distribution ◽  
Functional Theory

In this work, quantum chemical study on a natural product ergoline has been presented using density functional theory (DFT) employing 6-311++G(d,p) basis set. A complete vibrational assignment has been performed for the theoretical FT-IR and Raman wavenumbers along with the potential energy distribution (PED) with the result of quantum chemical calculations. The structure–activity relationship has been interpreted by mapping electrostatic potential surface (MEP). Graphical representation of frontier molecular orbitals with their energy gap have been analyzed theoretically for both the gaseous and solvent environment employing time dependent density functional theory (TDDFT) employing 6-31G basis set.

Quantum chemical study of the spectral characteristics of fluorescein dyes bound to chitosan

2021 ◽  
Author(s):  
Anastasia Rogova ◽  
Marina Gerasimova ◽  
Felix Tomilin ◽  
Evgenia Slyusareva
Keyword(s):  
Quantum Chemical ◽  
Spectral Characteristics ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Fluorescein Dyes

Structural, electronic, and mechanical properties of anatase titanium dioxide

2019 ◽  
Vol 15 (2) ◽  
pp. 306-316 ◽  
Author(s):  
Debashish Dash ◽  
Chandan Kumar Pandey ◽  
Saurabh Chaudhary ◽  
Susanta Kumar Tripathy
Keyword(s):  
Mechanical Properties ◽  
Titanium Dioxide ◽  
Electronic Properties ◽  
Density Functional ◽  
Paper Industry ◽  
Ground Level ◽  
Basis Set ◽  
Indirect Transition ◽  
Content Type ◽  
Valence Region

PurposeThe purpose of this paper is to analyze various properties of anatase titanium dioxide (TiO2) nanoparticles. Further, it proposes to implement Linear Combinations of Atomic Orbitals (LCAO) basis set under the framework of density functional theory and outline how LCAO is able to provide improved results in terms of various mechanical properties rather than plane wave and other theoretical results.Design/methodology/approachThis paper provides an exploratory study on anatase TiO2by implementing OLCAO–DFT–LDA–LBFGS–EOS–PZ algorithms to find out various ground-level properties. The data so obtained are complemented by various analysis using mathematical expressions, description of internal processes occurred and comparison to others’ analytical results.FindingsThe paper provides some empirical insights on how mechanical properties of anatase TiO2improved by implementing LCAO methodology. From the analysis of electronic properties, it is seen that the anatase TiO2supports the inter band indirect transition from O-2p in valence region to Ti-3d in the conduction region.Research limitations/implicationsMost of the electronic properties are underestimated because a single exchange-correlation potential is not continuous across the gap. This gap can be enhanced by implementing Green’s function in place of DFT and the other way is to implement self-interaction correction.Practical implicationsThe use of anatase TiO2is primarily used for catalytic applications. This is also used to enhance the quality of paper in the paper industry. Additionally, this is used as a prime ingredient in cosmetic industry.Originality/valueThis paper fulfills an identified need to study how LCAO, another basis set, plays an important role in improving material properties.

Quantum chemical study on the formation of isopropyl cyanide and its linear isomer in the interstellar medium

2020 ◽  
pp. 1-11
Author(s):  
Keshav Kumar Singh ◽  
Poonam Tandon ◽  
Alka Misra ◽  
Shivani ◽  
Manisha Yadav ◽  
...  
Keyword(s):  
Amino Acids ◽  
Interstellar Medium ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Dark Cloud ◽  
Water Ice ◽  
Hydrocarbon Radicals

Abstract The formation mechanism of linear and isopropyl cyanide (hereafter n-PrCN and i-PrCN, respectively) in the interstellar medium (ISM) has been proposed from the reaction between some previously detected small cyanides/cyanide radicals and hydrocarbons/hydrocarbon radicals. n-PrCN and i-PrCN are nitriles therefore, they can be precursors of amino acids via Strecker synthesis. The chemistry of i-PrCN is especially important since it is the first and only branched molecule in ISM, hence, it could be a precursor of branched amino acids such as leucine, isoleucine, etc. Therefore, both n-PrCN and i-PrCN have significant astrobiological importance. To study the formation of n-PrCN and i-PrCN in ISM, quantum chemical calculations have been performed using density functional theory at the MP2/6-311++G(2d,p)//M062X/6-311+G(2d,p) level. All the proposed reactions have been studied in the gas phase and the interstellar water ice. It is found that reactions of small cyanide with hydrocarbon radicals result in the formation of either large cyanide radicals or ethyl and vinyl cyanide, both of which are very important prebiotic interstellar species. They subsequently react with the radicals CH2 and CH3 to yield n-PrCN and i-PrCN. The proposed reactions are efficient in the hot cores of SgrB2 (N) (where both n-PrCN and i-PrCN were detected) due to either being barrierless or due to the presence of a permeable entrance barrier. However, the formation of n-PrCN and i-PrCN from the ethyl and vinyl cyanide always has an entrance barrier impermeable in the dark cloud; therefore, our proposed pathways are inefficient in the deep regions of molecular clouds. It is also observed that ethyl and vinyl cyanide serve as direct precursors to n-PrCN and i-PrCN and their abundance in ISM is directly related to the abundance of both isomers of propyl cyanide in ISM. In all the cases, reactions in the ice have smaller barriers compared to their gas-phase counterparts.

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.

scholarly journals M(VI) Oxidation State Stabilization in Iron, Cobalt and Nickel Heteroligand Metal Chelates Containing 3,7,11,15-Tetraazaporphine and Two Axial Oxo Ligands: Quantum-Chemical Simulation

2020 ◽  
Vol 21 (4) ◽  
pp. 1494 ◽  
Author(s):  
Oleg V. Mikhailov ◽  
Denis V. Chachkov
Keyword(s):  
Oxidation State ◽  
Quantum Chemical ◽  
Density Functional ◽  
Chemical Elements ◽  
Basis Set ◽  
Chemical Calculation ◽  
Deprotonated Form ◽  
Iron Cobalt ◽  
Cobalt And Nickel ◽  
Oxo Ligands

The quantum-chemical calculation of iron, cobalt and nickel heteroligand complexes with the double deprotonated form of (NNNN)-donor atomic ligand—3,7,11,15-tetraazaporphine—and two oxo ligands has been carried out. Data on the structural and standard thermodynamic parameters, NBO analysis and multiplicity of the ground states of these complexes have been presented. The given calculation has been made by using the density functional theory (DFT) method with the OPBE/TZVP basis set. Based on the results of this calculation, the possibility of the existence of oxidation state VI for the chemical elements indicated above—unusual for iron and cobalt, and for nickel, unknown at all—has been shown.

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