Quantum Mechanical Approaches for Piezoelectricity Study in Perovskites

In this chapter, we show the procedures we have been used to theoretically investigate the piezoelectric effects in perovskites. The construction of extended basis sets using the generator coordinate Hartree-Fock (GCHF) method is shown, as well as the strategies used to contract extended basis sets and to evaluate their quality in molecular calculations. Besides, we show adequate procedures to choice polarization and diffuse functions to best represent the studied crystal. In addition, we also discuss conditions under which GCHF basis sets and standard basis sets from literature can be used to theoretical investigation of piezoelectricity in perovskites. We finalize the chapter presenting and discussing the results for investigations of piezoelectricity with standard basis sets for barium and lanthanum titanates. To conclude, we present evidences that BaTiO3 and LaTiO3 may have piezoelectric properties caused by electrostatic interactions

Contracted GTF basis sets applied to the theoretical interpretation of the Raman spectrum of hexaaquachromium(III) ion

Contracted GTF basis sets designed with aid of the Generator Coordinate Hartree-Fock (GCHF) method for H(2S), O2-(1S), and Cr3+(4F) atomic species are applied to perform theoretical interpretation of the Raman spectrum of hexaaquachromium(III) ion. The 16s, 16s 10p, and 24s17p13d GTF basis sets were contracted to [4s] for H atom, [6s4p], and [9s6p3d] for O2- and Cr3+, respectively, by Dunning's scheme. For Cr3+, the [9s6p3d] basis set was enriched with f polarization function and used in combination com [4s] and [6s4p] in the study of our interest. The results obtained in this report show that the contracted GTF basis sets used are a useful alternative for the theoretical interpretation of Raman spectrum of hexaaquachromium(III) ion and that GCHF method is an effective alternative to selection of GTF basis sets for theoretical study of vibrational properties of poliatomic species. © 2003 Elsevier Science B.V. All rights reserved

Synthesis, characterization, thermal behavior, and DFT calculation of solid 1,4-bis(3-carboxy-3-oxo-prop-1-enyl) benzene of some trivalent lanthanides

Solid-state Ln(2)L(3)center dot nH(2)O compounds, where Ln represents trivalent lanthanides (from Eu to Lu and Y, except Dy) and L is 1,4-bis(3-carboxy-3-oxo-prop-1-enyl) benzene, have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry, X-ray powder diffractometry, infrared spectroscopy, and complexometry were used to characterize and to study the thermal behavior of these compounds. The dehydration of the compounds occurred until at 445 K (Y), at 440 K (Tb), and at 489 K (Eu, Gd, Ho, Er, Tm, Yb, and Lu). After dehydration, the DTA curves showed two other thermal events that are associated with the thermal decomposition of the compounds with formation of the respective oxides. The results also provided information about the composition, dehydration, crystallinity, and thermal decomposition of these compounds. Furthermore, the theoretical and experimental spectroscopic data suggest the possible modes of coordination of the ligand with the metals.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Thermal and spectroscopic study of the 3,4-(methylenedioxy) cinnamate compounds of transition metals in the solid state

In this study, the trans-3,4-(methylenedioxy)cinnamic acid was used as precursor for the synthesis of transition metal compounds, which were characterized by coupled TG-DTA/FT-IR system, elemental analysis, FT-IR spectroscopic study and titrimetric analysis with EDTA. The characterization by these techniques allowed to determine the hydration water content, number of ligand coordinated to the metal, thermal behavior and thermal stability, as well as monitor the main gaseous products released in each decomposition step. The elemental and titrimetric analyses were performed in order to support TG-DTA data. A theoretical FT-IR calculation was made using the Gauss View 5.0.2 W program and the vibration frequencies obtained were compared with the experimental ones showing as a result a difference of around 30 cm(-1) between them. In these spectra were analyzed the main vibration modes as COO- (carboxylate group), -C=C- (aromatic ring, alkene), -C-O- and -CH2 (methylenedioxy group) and -C-H (alkenes, aromatic). (C) 2014 Elsevier B.V. All rights reserved.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Preparation, thermal characterization, and DFT study of the bacterial cellulose

Bacterial cellulose (BC)-triethanolamine (TEA) membranes have been prepared by the immersion of never dried BC membranes in BC-TEA aqueous solutions. Scanning electron microscopy showed that TEA covers BC nanofibrils, causing the aggregation of them. The thermal analysis differential scanning calorimetry (DSC) and thermogravimetric analysis (TG), together with the DTG curves, showed that moisture retention is improved with TEA addition, through the formation of hydrogen bonds between water molecules and hydroxyl groups of TEA and BC. Peaks related to water retention in DSC curves of BC-TEA samples were shifted to higher temperatures, around 120 A degrees C, in comparison with that observed for the same BC peak, about 52 A degrees C. TG curves of BC-TEA samples provided information regarded to mass losses in this range (from ambient up to 150 A degrees C, the mass losses are 72, 52, and 10 %, respectively, for BC-TEA 1 M, BC-TEA 0.1 M, and BC-TEA 0.01 M samples), which are gradually higher than mass loss of 5 % in this range, shown in BC curve. Through spectroscopic techniques (FT-IR spectroscopy and Raman scattering), vibration groups of BC and TEA were identified. Density functional theory studies strongly suggest BC-TEA interactions through hydrogen bonds formation.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Molecular structures and vibrational frequencies for [PdX2(tdmPz)] (X = Cl-, SCN-): A DFT study

Theoretical molecular structures of the complexes [PdCl2(tdmPz)] (1) and [Pd(SCN)(2)(tdmPz)] (2) (tdmPz = 1-thiocarbamoyl-3,5-dimethylpyrazole) were investigated using B3LYP/DFT method. The new complexes were prepared and characterized by elemental analysis and IR spectroscopy. The calculated bond distances and angles indicated a square planar coordination polyhedron around the palladium center for (1) whereas complex (2) exhibited a slightly distortion in its square planar coordination environment. The theoretical infrared spectra of C, symmetry (electronic state (1)A) of the compounds are in agreement with the experimental data. The molecular orbital description HOMO and LUMO for compounds (1) and (2) were also described in this work. (C) 2009 Elsevier B.V. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Synthesis, characterization and thermal behavior of solid state of some mefenamate of trivalent lanthanides (La, Ce, Pr and Nd)

Solid-state Ln(Mef)(3) compounds, where Ln stands for some trivalent lanthanides (La, Ce, Pr and Nd) and Mef is the mefenamate (C15H14NO (2) (-) ) ligand, were synthesized. The characterization and thermal and spectroscopic study of the compounds were performed using elemental analysis, complexometry, image analysis by field emission gun, simultaneous thermogravimetry and differential scanning calorimetry coupled to Fourier transform infrared spectroscopy, X-ray diffractometry, near-infrared and mid-infrared spectroscopy. All the analyses showed that the compounds were obtained in the anhydrous state. The thermoanalytical results showed that the stability and thermal behavior were markedly influenced by the atmosphere used. Moreover, the curves show that the thermal decomposition takes place in two or three steps, with the formation of lanthanide oxide (La2O3, CeO2, Pr6O11 and Nd2O3), as the final residue. Furthermore, the theoretical and experimental spectroscopic data suggested the possible modes of coordination of the ligand with the metals. The DR spectra provided information about the ligand absorption bands and the f-f transitions of Nd3+ and Pr3+ ions123191103CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESPsem informaçã

Molecular structures and vibrational frequencies for cis-[PdCl2(tmen)] and cis-[Pd(N-3)(2)(tmen)]: A DFT study

Theoretical molecular structures of the complexes cis-[PdCl2(tmen)] and cis-[Pd(N-3)(2)(tmen)] (tmen = N,N,N',N'-tetramethylethylenediamine) were investigated using B3LYP/DFT method. The calculated molecular parameters, bond distances and angles, revealed a square-planar geometry around the metallic center for both compounds with the azide being linear. The theoretical infrared spectra of C, symmetry (electronic state (1)A) of the compounds are in agreement with the experimental data. (C) 2007 Elsevier B.V. All rights reserved

Synthesis, cytotoxic activity and DNA interaction of Pd(II) complexes bearing N'-methyl-3,5-dimethyl-1-thiocarbamoylpyrazole.

International audienceA new series of complexes of general formulae [PdX2(tmdmPz)] {X = Cl (1), Br (2), I (3), SCN (4); tmdmPz = N′-methyl-3,5-dimethyl-1-thiocarbamoylpyrazole} have been synthesized and characterized by elemental analysis, molar conductivities, IR, 1H and 13C{1H} NMR spectroscopy. In these complexes, the tmdmPz coordinates to Pd(II) center as a neutral N,S-chelating ligand. The geometries of the complexes have been optimized with the DFT method. Cytotoxicity evaluation against LM3 (mammary adenocarcinoma) and LP07 (lung adenocarcinoma) cell lines indicated that complexes 1-4 were more active than cisplatin. The binding of the complexes with a purine base (guanosine) was investigated by 1H NMR and mass spectrometry, showing that the coordination of guanosine occurs through N7. Electrophoretic DNA migration studies showed that all of them modify the DNA tertiary structure

Synthesis, characterization, thermal studies, and DFT calculations on Pd(II) complexes containing N-methylbenzylamine

This work describes the synthesis, characterization, and the thermal behavior investigation of four palladium(II) complexes with general formulae [PdX(2)(mba)(2)], in which mba = N-methylbenzylamine and X = OAc(-) (1), Cl(-) (2), Br(-) (3) or I(-) (4). The complexes were characterized by elemental analysis, infrared vibrational spectroscopy, and (1)H nuclear magnetic resonance. The stoichiometry of the complexes was established by means of elemental analysis and thermogravimetry (TG). TG/DTA curves showed that the thermodecomposition of the four complexes occurred in 3-4 steps, leading to metallic palladium as final residue. The palladium content found in all curves was in agreement with the mass percentages calculated for the complexes. The following thermal stability sequence was found: 3 > 2 > 4 > 1. The geometry optimization of 1, 2, 3, and 4, calculated using the DFT/B3LYP method, yielded a slightly distorted square planar environment around the Pd(II) ion made by two anionic groups and two nitrogen atoms from the mba ligand (N1 and N2), in a trans-relationship