Density Functional Theory
Mostrando 25-36 de 269 artigos, teses e dissertações.
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25. TD-DFT Analysis of the Dissymmetry Factor in Camphor
The fact that the dissymmetry lgeb (g-factor) of camphor is large has been known for decades, and the interpretation of the observed data has also been known for a long time. However, due to the ability of quantum chemical methods to describe chiroptical phenomena more appropriately, additional approaches based on these methods have been successful employed.
J. Braz. Chem. Soc.. Publicado em: 2020-03
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26. Screening of the Au:Pt Atomic Ratio Supported in SrCO3: Effects on the Performance of the Solvent-Free Oxidation of Benzyl Alcohol
We have prepared, by a sol-immobilization method, bimetallic catalysts with different Au:Pt atomic ratios supported on commercial SrCO3. The catalytic performance for the oxidation reaction of benzyl alcohol of such materials was compared to the monometallic counterparts, aiming at the obtaining of the best composition of the material. It was found that the
J. Braz. Chem. Soc.. Publicado em: 2020-03
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27. Experimental and Theoretical Study of LiMn2O4 Synthesized by the Solution Combustion Method Using Corn Starch as Fuel
Lithium manganese oxide, LiMn2O4, was synthesized in two temperature stages, where the first consisted by an ecofriendly solution combustion method at 300 °C. Finally, the as-burned powders were thermal treated at 500 and 700 °C. The structural and morphological changes were evaluated by the Rietveld method and density functional theory (DFT) calculations.
J. Braz. Chem. Soc.. Publicado em: 2020-02
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28. Acid-Catalyzed Z-E Isomerization of γ-Alkylidenebutenolides: An Experimental and DFT Study
The Z-E isomerization of γ-alkylidenebutenolide analogues to natural nostoclides and other natural butenolides was investigated using 1H nuclear magnetic resonance (NMR) and high performance liquid chromatography (HPLC) data as well as density functional theory (DFT) calculations at the wB97x-D/6-31G(d,p) level, including solvent effects with the polarizabl
J. Braz. Chem. Soc.. Publicado em: 2020-01
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29. USO DA TEORIA DO FUNCIONAL DE DENSIDADE NA ANÁLISE DE SPIN CROSSOVER EM AULAS DE QUÍMICA INORGÂNICA
Spin crossover is a property found in some coordination compounds formed by the first series of transition metals with d4-d7 configuration. These complexes, when stimulated by an external factor (temperature, light, etc.), can be converted from their low spin states to high spin states, or vice versa. However, this issue is not addressed in the Inorganic Che
Quím. Nova. Publicado em: 2020-01
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30. Investigating Surface Properties and Lithium Diffusion in Brookite-TiO2
Surfaces properties of TiO2 in the brookite phase and the lithium diffusion are studied using density functional theory (DFT) and interatomic potential simulations. Simulations predict that the brookite surfaces have a higher intrinsic Lewis acidity compared to the other polymorphs due to the presence of four coordinated Ti atoms on the surface in contrast t
J. Braz. Chem. Soc.. Publicado em: 2020-01
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31. Microstructural Evolution and Phase Transformation of a Ti-5Nb-5Al Alloy During Annealing Treatment
The microstructural evolution and phase transformation of a Ti-5Nb-5Al alloy during isothermal annealing treatment were studied in this paper. The microstructural evolution was analyzed by X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with X-ray energy dispersive spectroscopy (EDS) and electron backscattering diffraction (EBSD). The fi
Mat. Res.. Publicado em: 05/12/2019
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32. SPECTROSCOPIC CHARACTERIZATION OF PEDOT:PSS CONDUCTING POLYMER BY RESONANCE RAMAN AND SERRS SPECTROSCOPIES
Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) synthesis was monitored by resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) spectroscopies and both the oxidation of the polymer and the effects of chain length were assessed by vibrational analysis. It was supported by theoretical models of oligomers, with charge
Quím. Nova. Publicado em: 05/12/2019
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33. Structure and Absolute Configuration of Secondary Metabolites from Two Strains of Streptomyces chartreusis Associated with Attine Ants
The antibiotic streptazolin (1), its E-isomer (2), along with the stereoisomers strepchazolin A (3) and strepchazolin B (4) and the inorganic compound cyclooctasulfur (5) were produced in solid culture by Streptomyces chartreusis ICBG377, which was isolated from the fungal garden of the leaf-cutter ant Acromyrmex subterraneus brunneus. This is the first time
J. Braz. Chem. Soc.. Publicado em: 24/10/2019
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34. THEORETICAL STUDIES ON THE NEW HIGH-NITROGEN EXPLOSIVES N14 AND N18
The power of a compound is enhanced by the direct connection of nitrogen atoms, and its stability can be improved through conjugated structure. So novel high energy density materials N14 (1,6-dihydro-1,2,3,3a,4,5,5a,6,7,8,8a,9,10,10a-tetradecazapyrene) and N18 (1,2,2a,3,4,4a,5,6,6a,7,8,8a,9,10,10a,11,12a-octadecazacoronene) were designed, and their structure
Quím. Nova. Publicado em: 21/10/2019
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35. ESTUDO ELETRÔNICO DA REATIVIDADE DA 8-HIDROXIQUINOLINA SUBSTITUÍDA FRENTE AO SÍTIO DE LIGAÇÃO DO PEPTÍDEO β-AMILOIDE AO ÍON ZINCO
In this work, density functional theory (DFT) was used to study the caused effect on reactivity of 8-hydroxyquinoline (8-HQ) by substituent groups (-H, -CH3, -OCH3, -Cl and -NO2) on different positions of the 8-HQ structure. DFT was also used to obtain the electronic profile of β-amyloid peptide (Aβ) bind site to Zinc. The energies and absolute hardness (�
Quím. Nova. Publicado em: 21/10/2019
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36. A New Cytotoxic Naphthoquinone and Other Chemical Constituents of Sinningia reitzii
Phytochemical study of Sinningia reitzii (Gesneriaceae) led to the isolation of three new naphtoquinones, 6,7-dimethoxydunnione, 7-hydroxy-6-methoxydunnione, and 5-hydroxy-6,7-dimethoxydunnione from the tubers, together with four known compounds, 7-hydroxydunnione, 8-hydroxydunnione, 5-hydroxy-6,7-dimethoxy-α-dunnione, and 8-hydroxydeydrodunnione. Aerial pa
J. Braz. Chem. Soc.. Publicado em: 21/10/2019