The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Andrei Sanov - One of the best experts on this subject based on the ideXlab platform.
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Photoelectron Angular Distributions of Pyridinide: A Benchmark Application of the Mixed s–p Model to a Truly Polyatomic Anion
The journal of physical chemistry. A, 2013Co-Authors: Lori M. Culberson, Christopher C. Blackstone, Andrei SanovAbstract:We report a photoelectron imaging study of the pyridinide Anion, C5H4N–, obtained by deprotonation of pyridine at the C4 position. The photoelectron angular distributions are used to test the theoretical formalism for photodetachment from mixed-character s–p states, demonstrating its first application to a truly Polyatomic system. The mixed s–p model describes the initial state of the Anion in terms of a superposition of one s orbital and one p orbital centered on the deprotonated carbon. Using the model parameter values determined from ab initio calculations, without any fits to the experimental data, the theory yields good quantitative agreement to the experiment. The agreement is demonstrated using either the canonical Hartree–Fock highest-occupied molecular orbital of the Anion or the corresponding Dyson orbital. The results confirm the predictive power of the mixed s–p model and suggest that despite its approximate nature it captures the essential physics of the photoemission process.
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photoelectron angular distributions of pyridinide a benchmark application of the mixed s p model to a truly Polyatomic Anion
Journal of Physical Chemistry A, 2013Co-Authors: Lori M. Culberson, Christopher C. Blackstone, Andrei SanovAbstract:We report a photoelectron imaging study of the pyridinide Anion, C5H4N–, obtained by deprotonation of pyridine at the C4 position. The photoelectron angular distributions are used to test the theoretical formalism for photodetachment from mixed-character s–p states, demonstrating its first application to a truly Polyatomic system. The mixed s–p model describes the initial state of the Anion in terms of a superposition of one s orbital and one p orbital centered on the deprotonated carbon. Using the model parameter values determined from ab initio calculations, without any fits to the experimental data, the theory yields good quantitative agreement to the experiment. The agreement is demonstrated using either the canonical Hartree–Fock highest-occupied molecular orbital of the Anion or the corresponding Dyson orbital. The results confirm the predictive power of the mixed s–p model and suggest that despite its approximate nature it captures the essential physics of the photoemission process.
N. N. Pestereva - One of the best experts on this subject based on the ideXlab platform.
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Charge Transport by Polyatomic Anion Diffusion in Sc2(WO4)3
Chemistry of Materials, 2008Co-Authors: Yongkai Zhou, Stefan Adams, R. Prasada Rao, Doreen D. Edwards, Arkady Neiman, N. N. PesterevaAbstract:Discussions about the nature of the charge carriers in the scandium tungstate and other isostructural tungstates and molybdates have persisted in the literature since a variety of experimental indications pointed toward trivalent cations as the mobile species. Here variations of the structure over a wide temperature range are analyzed by XRD and computational methods, demonstrating that the negative thermal expansion persists throughout the range of 11 ¯ 1300 K. Over a limited temperature range (
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charge transport by Polyatomic Anion diffusion in sc2 wo4 3
Chemistry of Materials, 2008Co-Authors: Yongkai Zhou, Stefan Adams, Doreen D. Edwards, Arkady Neiman, Prasada R Rao, N. N. PesterevaAbstract:Discussions about the nature of the charge carriers in the scandium tungstate and other isostructural tungstates and molybdates have persisted in the literature since a variety of experimental indications pointed toward trivalent cations as the mobile species. Here variations of the structure over a wide temperature range are analyzed by XRD and computational methods, demonstrating that the negative thermal expansion persists throughout the range of 11 ¯ 1300 K. Over a limited temperature range ( <500 K) molecular dynamics simulations with an optimized forcefield reproduce this negative thermal expansion. Likewise, charge transport is monitored both experimentally by impedance spectroscopy and Tubandt experiments and computationally based on the molecular dynamics simulation trajectories. Extended isothermal-isobaric simulations suggest a complex migration of Polyatomic tungstate Anions as the energetically most favorable transport mechanism in Sc 2 (WO 4 ) 3 . A bond valence analysis depicts possible diffusion pathways for WO 4 2- , although there is no indication of a pathway for Sc 3+ . The hopping mechanism of tungstate ions from one equilibrium site to another one follows the instantaneous diffusion pathways. A long-range transport still requires the rare formation of WO 4 2- Frenkel defects limiting the accuracy of the simulated absolute conductivity. Both MD simulations and bond valence analysis suggest WO 4 2- be the mobile species, which follow the interstitialcy diffusion mechanism. Our 3-section Tubandt-type experiments qualitatively show that the transfer of W occurs in the form of a negatively charged complex. This should be the first example of Polyatomic diffusion species and opens a new field in the search for new ionic conductors.
Lori M. Culberson - One of the best experts on this subject based on the ideXlab platform.
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Photoelectron Angular Distributions of Pyridinide: A Benchmark Application of the Mixed s–p Model to a Truly Polyatomic Anion
The journal of physical chemistry. A, 2013Co-Authors: Lori M. Culberson, Christopher C. Blackstone, Andrei SanovAbstract:We report a photoelectron imaging study of the pyridinide Anion, C5H4N–, obtained by deprotonation of pyridine at the C4 position. The photoelectron angular distributions are used to test the theoretical formalism for photodetachment from mixed-character s–p states, demonstrating its first application to a truly Polyatomic system. The mixed s–p model describes the initial state of the Anion in terms of a superposition of one s orbital and one p orbital centered on the deprotonated carbon. Using the model parameter values determined from ab initio calculations, without any fits to the experimental data, the theory yields good quantitative agreement to the experiment. The agreement is demonstrated using either the canonical Hartree–Fock highest-occupied molecular orbital of the Anion or the corresponding Dyson orbital. The results confirm the predictive power of the mixed s–p model and suggest that despite its approximate nature it captures the essential physics of the photoemission process.
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photoelectron angular distributions of pyridinide a benchmark application of the mixed s p model to a truly Polyatomic Anion
Journal of Physical Chemistry A, 2013Co-Authors: Lori M. Culberson, Christopher C. Blackstone, Andrei SanovAbstract:We report a photoelectron imaging study of the pyridinide Anion, C5H4N–, obtained by deprotonation of pyridine at the C4 position. The photoelectron angular distributions are used to test the theoretical formalism for photodetachment from mixed-character s–p states, demonstrating its first application to a truly Polyatomic system. The mixed s–p model describes the initial state of the Anion in terms of a superposition of one s orbital and one p orbital centered on the deprotonated carbon. Using the model parameter values determined from ab initio calculations, without any fits to the experimental data, the theory yields good quantitative agreement to the experiment. The agreement is demonstrated using either the canonical Hartree–Fock highest-occupied molecular orbital of the Anion or the corresponding Dyson orbital. The results confirm the predictive power of the mixed s–p model and suggest that despite its approximate nature it captures the essential physics of the photoemission process.
Antonio Franconetti - One of the best experts on this subject based on the ideXlab platform.
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electronically tunable Anion π interactions in pyrylium complexes experimental and theoretical studies
Physical Chemistry Chemical Physics, 2014Co-Authors: Antonio Franconetti, Sorel Jatunov, Manuel Angulo, Lidia Contrerasbernal, Manuel Gomezguillen, R Pradogotor, Francisca CabreraescribanoAbstract:Noncovalent interactions of Anions with electron-deficient aromatic rings that have been studied so far involve non-heteroaromatic or nitrogen-based heteroaromatic systems. Here we report the first case of an organic oxygenated aromatic system, in particular the tri-aryl-pyrylium tetrafluoroborate system, for which noncovalent Anion–π interactions of the pyrylium cation with the tetrafluoroborate Anion have been experimentally detected and demonstrated by means of 19F NMR spectroscopy in solution. A series of pyrylium tetrafluoroborate salts were synthesized in the presence of BF3·Et2O, by direct reaction of 4-substituted benzaldehydes with 4-substituted acetophenones or via the previously obtained chalcone of the less reactive ketone. Correlations of 19F NMR chemical shifts of tetrafluoroborate Anion for most of the synthesized tri-arylpyrylium tetrafluoroborate complexes with both the pyrylium cation molecular weight and the standard substituent Hammett constants, demonstrate Anion–π+ interaction to act between the Polyatomic Anion BF4− and the pyrylium aromatic system. DFT calculations reveal that an additional (C–H)+–Anion hydrogen bond involving the H(5) of pyrylium ring exists for these fluorescent dyes that show a tunable cup-to-cap shape cavity. The strong fluorescence emission observed for some representative pyrylium tetrafluoroborates described herein, makes them a promising class of tunable emission wavelength dyes for laser technology applications.
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Electronically tunable Anion−π interactions in pyrylium complexes: experimental and theoretical studies
Physical chemistry chemical physics : PCCP, 2014Co-Authors: Antonio Franconetti, Lidia Contreras-bernal, Sorel Jatunov, Manuel Gómez-guillén, Manuel Angulo, Rafael Prado-gotor, Francisca Cabrera-escribanoAbstract:Noncovalent interactions of Anions with electron-deficient aromatic rings that have been studied so far involve non-heteroaromatic or nitrogen-based heteroaromatic systems. Here we report the first case of an organic oxygenated aromatic system, in particular the tri-aryl-pyrylium tetrafluoroborate system, for which noncovalent Anion–π interactions of the pyrylium cation with the tetrafluoroborate Anion have been experimentally detected and demonstrated by means of 19F NMR spectroscopy in solution. A series of pyrylium tetrafluoroborate salts were synthesized in the presence of BF3·Et2O, by direct reaction of 4-substituted benzaldehydes with 4-substituted acetophenones or via the previously obtained chalcone of the less reactive ketone. Correlations of 19F NMR chemical shifts of tetrafluoroborate Anion for most of the synthesized tri-arylpyrylium tetrafluoroborate complexes with both the pyrylium cation molecular weight and the standard substituent Hammett constants, demonstrate Anion–π+ interaction to act between the Polyatomic Anion BF4− and the pyrylium aromatic system. DFT calculations reveal that an additional (C–H)+–Anion hydrogen bond involving the H(5) of pyrylium ring exists for these fluorescent dyes that show a tunable cup-to-cap shape cavity. The strong fluorescence emission observed for some representative pyrylium tetrafluoroborates described herein, makes them a promising class of tunable emission wavelength dyes for laser technology applications.
Yongkai Zhou - One of the best experts on this subject based on the ideXlab platform.
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Novel polyAnion conduction in Sc2(WO4)3 type negative thermal expansion oxides
physica status solidi (b), 2010Co-Authors: Yongkai Zhou, Arkady Neiman, Stefan AdamsAbstract:The relationship between the Polyatomic Anion conduction and negative thermal expansion (NTE) in Sc 2 -(WO 4 ) 3 type structure has been investigated by a combination of computational, electrochemical and X-ray diffraction approaches. The motion of the effective charge carriers in solid-state ionics can be visualised by molecular dynamics (MD) simulations if proper initial structure and force-field are known. By successfully reproducing the NTE for a large temperature range, we have designed and verified a valid force-field to predict the mobile species in Sc 2 (WO 4 ) 3 . Using the same force-field a series of correlated WO 2- 4 migrations are observed in extended isothermal-isobaric MD simulations. Tubandt-type electrolysis experiments confirmed that the mobile species in Sc 2 (WO 4 ) 3 is Anionic. Scandium tungstate is thus the prototype of novel class of ionic conductors, a WO 2- 4 Anion conductors. The relationship of the ion transport in this unique ion conductors with Polyatomic mobile charge carriers to the NTE is discussed.
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Mechanism of defect formation and polyAnion transport in solid scandium tungstate type oxides
Monatshefte für Chemie - Chemical Monthly, 2009Co-Authors: Yongkai Zhou, R. Prasada Rao, Stefan AdamsAbstract:The unique diffusion mechanism in the novel Polyatomic Anion conductor scandium tungstate is studied by molecular dynamics simulations of systems with artificially induced WO_4 ^2− defects and compared to our previous simulations of defect-free structure models. The diffusion activation energy obtained from structures with built-in defects is smaller than for the defect-free models and in the case of tungstate vacancies close to the experimental value, suggesting that extrinsic tungstate vacancies due to the volatility of WO_3 are important for the experimental conductivity. The validity of the force field used for the molecular dynamics simulations is further verified by investigating the orthorhombic to monoclinic phase transition of Sc_2(WO_4)_3 under compression. The lattice compressibility in both phases and the phase transition is qualitatively reproduced, though the simulated phase transition pressure occurred is about 0.55 GPa higher than the experimental one. Graphical abstract
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Charge Transport by Polyatomic Anion Diffusion in Sc2(WO4)3
Chemistry of Materials, 2008Co-Authors: Yongkai Zhou, Stefan Adams, R. Prasada Rao, Doreen D. Edwards, Arkady Neiman, N. N. PesterevaAbstract:Discussions about the nature of the charge carriers in the scandium tungstate and other isostructural tungstates and molybdates have persisted in the literature since a variety of experimental indications pointed toward trivalent cations as the mobile species. Here variations of the structure over a wide temperature range are analyzed by XRD and computational methods, demonstrating that the negative thermal expansion persists throughout the range of 11 ¯ 1300 K. Over a limited temperature range (
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charge transport by Polyatomic Anion diffusion in sc2 wo4 3
Chemistry of Materials, 2008Co-Authors: Yongkai Zhou, Stefan Adams, Doreen D. Edwards, Arkady Neiman, Prasada R Rao, N. N. PesterevaAbstract:Discussions about the nature of the charge carriers in the scandium tungstate and other isostructural tungstates and molybdates have persisted in the literature since a variety of experimental indications pointed toward trivalent cations as the mobile species. Here variations of the structure over a wide temperature range are analyzed by XRD and computational methods, demonstrating that the negative thermal expansion persists throughout the range of 11 ¯ 1300 K. Over a limited temperature range ( <500 K) molecular dynamics simulations with an optimized forcefield reproduce this negative thermal expansion. Likewise, charge transport is monitored both experimentally by impedance spectroscopy and Tubandt experiments and computationally based on the molecular dynamics simulation trajectories. Extended isothermal-isobaric simulations suggest a complex migration of Polyatomic tungstate Anions as the energetically most favorable transport mechanism in Sc 2 (WO 4 ) 3 . A bond valence analysis depicts possible diffusion pathways for WO 4 2- , although there is no indication of a pathway for Sc 3+ . The hopping mechanism of tungstate ions from one equilibrium site to another one follows the instantaneous diffusion pathways. A long-range transport still requires the rare formation of WO 4 2- Frenkel defects limiting the accuracy of the simulated absolute conductivity. Both MD simulations and bond valence analysis suggest WO 4 2- be the mobile species, which follow the interstitialcy diffusion mechanism. Our 3-section Tubandt-type experiments qualitatively show that the transfer of W occurs in the form of a negatively charged complex. This should be the first example of Polyatomic diffusion species and opens a new field in the search for new ionic conductors.