The Experts below are selected from a list of 210 Experts worldwide ranked by ideXlab platform
Benedito J. Costa Cabral - One of the best experts on this subject based on the ideXlab platform.
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Magnetic properties and core Electron Binding energies of liquid water
The Journal of chemical physics, 2018Co-Authors: N. Galamba, Benedito J. Costa CabralAbstract:The magnetic properties and the core and inner valence Electron Binding energies of liquid water are investigated. The adopted methodology relies on the combination of molecular dynamics and Electronic structure calculations. Born-Oppenheimer molecular dynamics with the Becke and Lee-Yang-Parr functionals for exchange and correlation, respectively, and includes an empirical correction (BLYP-D3) functional and classical molecular dynamics with the TIP4P/2005-F model were carried out. The Keal-Tozer functional was applied for predicting magnetic shielding and spin-spin coupling constants. Core and inner valence Electron Binding energies in liquid water were calculated with symmetry adapted cluster-configuration interaction. The relationship between the magnetic shielding constant σ(17O), the role played by the oxygen atom as a proton acceptor and donor, and the tetrahedral organisation of liquid water are investigated. The results indicate that the deshielding of the oxygen atom in water is very dependent on the order parameter (q) describing the tetrahedral organisation of the hydrogen bond network. The strong sensitivity of magnetic properties on changes of the Electronic density in the nuclei environment is illustrated by a correlation between σ(17O) and the energy gap between the 1a1[O1s] (core) and the 2a1 (inner valence) orbitals of water. Although several studies discussed the eventual connection between magnetic properties and core Electron Binding energies, such a correlation could not be clearly established. Here, we demonstrate that for liquid water this correlation exists although involving the gap between Electron Binding energies of core and inner valence orbitals.
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Dynamics, magnetic properties, and Electron Binding energies of H2O2 in water.
The Journal of chemical physics, 2017Co-Authors: Benedito J. Costa CabralAbstract:Results for the magnetic properties and Electron Binding energies of H2O2 in liquid water are presented. The adopted methodology relies on the combination of Born-Oppenheimer molecular dynamics and Electronic structure calculations. The Keal-Tozer functional was applied for predicting magnetic shieldings and H2O2 intramolecular spin-spin coupling constants. Electron Binding energies were calculated with Electron propagator theory. In water, H2O2 is a better proton donor than proton acceptor, and the present results indicate that this feature is important for understanding magnetic properties in solution. In comparison with the gas-phase, H2O2 atoms are deshielded in water. For oxygen atoms, the deshielding is mainly determined by structural/conformational changes. Hydrogen-bond interactions explain the deshielding of protons in water. The predicted chemical shift for the H2O2 protons in water (δ∼11.8 ppm) is in good agreement with experimental information (δ=11.2 ppm). The two lowest Electron Binding ener...
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Dynamics, magnetic properties, and Electron Binding energies of H2O2 in water.
The Journal of chemical physics, 2017Co-Authors: Benedito J. Costa CabralAbstract:Results for the magnetic properties and Electron Binding energies of H2O2 in liquid water are presented. The adopted methodology relies on the combination of Born-Oppenheimer molecular dynamics and Electronic structure calculations. The Keal-Tozer functional was applied for predicting magnetic shieldings and H2O2 intramolecular spin-spin coupling constants. Electron Binding energies were calculated with Electron propagator theory. In water, H2O2 is a better proton donor than proton acceptor, and the present results indicate that this feature is important for understanding magnetic properties in solution. In comparison with the gas-phase, H2O2 atoms are deshielded in water. For oxygen atoms, the deshielding is mainly determined by structural/conformational changes. Hydrogen-bond interactions explain the deshielding of protons in water. The predicted chemical shift for the H2O2 protons in water (δ∼11.8 ppm) is in good agreement with experimental information (δ=11.2 ppm). The two lowest Electron Binding energies of H2O2 in water (10.7±0.5 and 11.2±0.5 eV) are in reasonable agreement with experiment. In keeping with data from photoElectron spectroscopy, an ∼1.6 eV red-shift of the two first ionisation energies relative to the gas-phase is observed in water. The strong dependence of magnetic properties on changes of the Electronic density in the nuclei environment is illustrated by a correlation between the σ(17O) magnetic shielding constant and the energy gap between the [2a] lowest valence and [1a] core orbitals of H2O2.
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Electron Binding energies and the fundamental gap of a push-pull dye in a polar environment: p-nitroaniline in liquid water
Chemical Physics Letters, 2017Co-Authors: Benedito J. Costa CabralAbstract:The outer valence Electron Binding energies and the fundamental gap of p-nitroaniline (PNA) in water were determined by Electron propagator theory. The adopted methodology relies on the calculation of Electron Binding energies by using configurations generated by Born-Oppenheimer molecular dynamics of PNA in water. The fundamental gap (Eg) of PNA in water was estimated from the first ionisation energy (IE) and the first vertical Electron affinity VEA (Eg = IE-VEA). In liquid water Eg is predicted to be 6.5±0.56.5±0.5 eV (OVGF), which is ∼3.3 eV greater than the experimental optical gap (3.25 eV).
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Electron Binding energies of free base porphyrin and magnesium-porphyrin: A sequential Born–Oppenheimer molecular dynamics/quantum mechanics approach
Journal of Molecular Structure-theochem, 2009Co-Authors: Hugo F. M. C. Martiniano, Benedito J. Costa CabralAbstract:Abstract The Electronic properties of free base porphyrin (H2P) and magnesium-porphyrin (MgP) were investigated through a sequential Born–Oppenheimer molecular dynamics/quantum mechanics approach. The quantum mechanics calculations for the Electronic density of states were performed with Green’s function or Electron propagator theory and also with a recent series of approximations for the exchange-correlation functional proposed by Truhlar and collaborators. The distortions of the porphyrin structures were analysed through normal-coordinate structural decomposition. The role played by thermal effects on structural distortions of H2P and MgP and their relationship with Electron Binding energies are discussed. Our results indicate that distortions of the porphyrin macrocycle induced by thermal effects do not influence in a significant way Electron Binding energies for the valence states of H2P and MgP. However, some correlation has been observed between nonplanar breathing distortions and Electron Binding energies of Mg(1s), Mg(2s), and Mg(2p) states, which can be blue-shifted by ∼0.8 eV.
Delano P Chong - One of the best experts on this subject based on the ideXlab platform.
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DFT calculation of core-Electron Binding energies
Journal of Electron Spectroscopy and Related Phenomena, 2003Co-Authors: Yuji Takahata, Delano P ChongAbstract:Abstract A total of 59 core-Electron Binding energies (CEBEs) were studied with the Amsterdam Density Functional Program (ADF) program and compared with the observed values. The results indicate that a polarized triple-zeta basis set of Slater-type orbitals is adequate for routine assessment of the performance of each method of computation. With such a basis set, seven density functionals were tested. In addition, the performance of 21 energy density functionals were computed from the density calculated with the statistical average of orbital potentials (SAOP). Among all the choices tested, the best density functional for core-Electron Binding energies of C to F turns out to be the combination of Perdew-Wang (1986) functional for exchange and the Perdew-Wang (1991) functional for correlation, confirming earlier studies based on contracted Gaussian-type orbitals. For this best functional, five Slater-type orbital basis sets were examined, ranging from polarized double-zeta quality to the largest set available in the ADF package. For the best functional with the best basis set, the average absolute deviation (AAD) of the calculated value from experiment is only 0.16 eV.
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DFT Calculations of Core-Electron Binding Energies of the Peptide Bond
The Journal of Physical Chemistry A, 2002Co-Authors: Delano P Chong, Philippe Aplincourt, Christophe BureauAbstract:Although an efficient DFT method using the generalized transition-state model to calculate core−Electron Binding energies had been successfully applied to over 200 cases, with an average absolute d...
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Density functional calculation of core‐Electron Binding energies of isomers of C3H6O2 and C3H5NO
International Journal of Quantum Chemistry, 2000Co-Authors: Delano P Chong, Germán CavigliassoAbstract:The core-Electron Binding energies of six isomers of C3H6O2 and four isomers of C3H5NO were calculated by a DFT/uGTS/scaled-pVTZ approach. An average absolute deviation from experiment of 0.15 eV was found for 14 C, N, and O 1s energies. The results confirm the distinctive nature of the X-ray photoElectron spectra (XPS) of isomers and support the use of Electron spectroscopy complemented by accurate theoretical predictions as a tool for chemical analysis. © 1999 John Wiley & Sons, Inc. Int J Quant Chem 76: 44–50, 2000
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Accurate density-functional calculation of core-Electron Binding energies with a scaled polarized triple-zeta basis set. VI: Extension to boron-containing molecules.
Canadian Journal of Chemistry, 1999Co-Authors: Germán Cavigliasso, Delano P ChongAbstract:Our procedure for calculating core-Electron Binding energies (CEBEs), based on the unrestricted generalized transition state model using B88/P86 functional, was extended to boron-containing molecules. Both unscaled (cc-pVTZ, cc-pVQZ, cc-pV5Z) and scaled (scaled-pVTZ and scaled-pVQZ) basis sets were used. The average absolute deviation from experiment for boron CEBEs with the scaled-pVTZ basis set was found to be 0.24 eV, compared to 0.23 eV for the much larger cc-pV5Z basis set.Keywords: DFT, boron, core-Electron Binding energies.
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Accurate density functional calculation of core Electron Binding energies
Journal of Electron Spectroscopy and Related Phenomena, 1997Co-Authors: Christophe Bureau, Delano P Chong, Gérard Lécayon, Joseph DelhalleAbstract:Abstract A recent procedure for computing accurate core Electron Binding energies (CEBEs) via density functional theory (DFT) is applied to acetonitrile, propionitrile, 2-cyanopropane, acrylonitrile, methacrylonitrile and the 2-methylglutaronitrile conformer of lowest energy. The first three systems have been studied in the past as model compounds to interpret the XPS spectrum of polyacrylonitrile (PAN) using post-Hartree–Fock finite-difference calculations, in order to solve a controversy in the assignment of chemically shifted atoms in the C 1s region. This assignment is revisited with the unrestricted generalized transition-state model and a combined functional of Becke's 1988 exchange with Perdew's 1986 correlation. Using Dunning's correlation-consistent polarized valence triple zeta basis sets with scaling improvements, we obtain predicted CEBEs for gas-phase acetonitrile, propionitrile and acrylonitrile in remarkable agreement with experiment (average absolute deviation 0.09 eV). The CEBEs of these systems confirm the overall trends of the previous attributions of their respective gas-phase XPS spectrum, except in the case of propionitrile. These results, as well as those on 2-cyanopropane, methacrylonitrile and 2-methylglutaronitrile, bring some additional information on the extrapolation of the results to the assignment of the C 1s contributions of polyacrylonitrile. © 1997 Elsevier Science B.V.
Cao Chen - One of the best experts on this subject based on the ideXlab platform.
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quantifying the substituent effect with penetrating shielding constant iv the relation of Electron Binding energy and group Electronegativity
Journal of Xiangtan Normal University, 1994Co-Authors: Cao ChenAbstract:In polyatomic molecule ABi, the Electron Binding energy of A atom which bonded with i Batoms can be expressed as where n,Z, S were the Principal quantum number, nuclear charge and eigen penetrating-shielding contrstant for A atom respectively; XB and XA were the Electronegativities of atoms B and A(Pauling scale); and b was empirical parameter.
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QUANTIFYING THE SUBSTITUENT EFFECT WITH PENETRATING-SHIELDING CONSTANT(IV)──the relation of Electron Binding energy and group Electronegativity
Journal of Xiangtan Normal University, 1994Co-Authors: Cao ChenAbstract:In polyatomic molecule ABi, the Electron Binding energy of A atom which bonded with i Batoms can be expressed as where n,Z, S were the Principal quantum number, nuclear charge and eigen penetrating-shielding contrstant for A atom respectively; XB and XA were the Electronegativities of atoms B and A(Pauling scale); and b was empirical parameter.
Julius Jellinek - One of the best experts on this subject based on the ideXlab platform.
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Electron Binding Energy Spectra of AlnMo- Clusters: Measurements, Calculations and Theoretical Analysis
The Journal of Physical Chemistry C, 2018Co-Authors: Paulo H. Acioli, Xinxing Zhang, Kit H. Bowen, Julius JellinekAbstract:Results of photoElectron spectroscopy measurements and density functional theory complemented with correction scheme calculations on Electron Binding energy (EBE) spectra of anionic AlnMo, n = 3–5 and 7, clusters are presented and analyzed. The analysis points to the important role of dynamical fluxionality and multiplicity of structural forms as contributing factors in the measured spectra. Using the example of Al4Mo– as a paradigmatic case, the separate roles of size, structure/symmetry, and composition in evolving the EBE spectra of precursor pure clusters (in this case, Al4– and Al5–) into those of bimetallic clusters are demonstrated utilizing a new methodology we developed recently (J. Phys. Chem. C 2017, 121, 16665).
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Theoretical determination of Electron Binding energy spectra of anionic magnesium clusters
European Physical Journal D, 2003Co-Authors: Paulo H. Acioli, Julius JellinekAbstract:A recently developed accurate scheme for converting the single-particle eigenenergies of the density functional theory into Electron Binding energies is used to compute the spectra of Electron Binding energies in \( {\rm{Mg}}_4^ - ,\;{\rm{Mg}}_{11}^ - ,\;{\rm{Mg}}_{16}^ - , \) and \( {\rm{Mg}}_{18}^ - \). The computations are performed for different isomeric forms of the clusters using both pseudopotential and all-Electron treatments. The results are compared with the data derived from Electron photodetachment experiments, and the role of the different isomers in the interpretation of these data is examined.
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Converting Kohn-Sham eigenenergies into Electron Binding energies.
The Journal of Chemical Physics, 2003Co-Authors: Julius Jellinek, Paulo H. AcioliAbstract:A new accurate scheme for converting the Kohn–Sham eigenenergies into Electron Binding energies is formulated. The accuracy of the scheme is illustrated in applications to ten atoms and three molecules.
Paulo H. Acioli - One of the best experts on this subject based on the ideXlab platform.
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Electron Binding Energy Spectra of AlnMo- Clusters: Measurements, Calculations and Theoretical Analysis
The Journal of Physical Chemistry C, 2018Co-Authors: Paulo H. Acioli, Xinxing Zhang, Kit H. Bowen, Julius JellinekAbstract:Results of photoElectron spectroscopy measurements and density functional theory complemented with correction scheme calculations on Electron Binding energy (EBE) spectra of anionic AlnMo, n = 3–5 and 7, clusters are presented and analyzed. The analysis points to the important role of dynamical fluxionality and multiplicity of structural forms as contributing factors in the measured spectra. Using the example of Al4Mo– as a paradigmatic case, the separate roles of size, structure/symmetry, and composition in evolving the EBE spectra of precursor pure clusters (in this case, Al4– and Al5–) into those of bimetallic clusters are demonstrated utilizing a new methodology we developed recently (J. Phys. Chem. C 2017, 121, 16665).
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Theoretical determination of Electron Binding energy spectra of anionic magnesium clusters
European Physical Journal D, 2003Co-Authors: Paulo H. Acioli, Julius JellinekAbstract:A recently developed accurate scheme for converting the single-particle eigenenergies of the density functional theory into Electron Binding energies is used to compute the spectra of Electron Binding energies in \( {\rm{Mg}}_4^ - ,\;{\rm{Mg}}_{11}^ - ,\;{\rm{Mg}}_{16}^ - , \) and \( {\rm{Mg}}_{18}^ - \). The computations are performed for different isomeric forms of the clusters using both pseudopotential and all-Electron treatments. The results are compared with the data derived from Electron photodetachment experiments, and the role of the different isomers in the interpretation of these data is examined.
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Converting Kohn-Sham eigenenergies into Electron Binding energies.
The Journal of Chemical Physics, 2003Co-Authors: Julius Jellinek, Paulo H. AcioliAbstract:A new accurate scheme for converting the Kohn–Sham eigenenergies into Electron Binding energies is formulated. The accuracy of the scheme is illustrated in applications to ten atoms and three molecules.