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Rafael R. Pappalardo - One of the best experts on this subject based on the ideXlab platform.
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a general study of actinyl hydratIon by molecular dynamics simulatIons using ab initio force fields
Journal of Chemical Physics, 2019Co-Authors: Sergio Perezconesa, Rafael R. Pappalardo, José M. Martínez, Francisco Torrico, Enrique Sánchez MarcosAbstract:A set of new ab initio force fields for aqueous [AnO2]2+/+ (An = Np(vi,v), Pu(vi), Am(vi)) has been developed using the Hydrated Ion (HI) model methodology previously used for [UO2]2+. Except for the non-electrostatic contributIon of the HI-bulk water interactIon, the interactIon potentials are individually parameterized. TranslatIonal diffusIon coefficients, hydratIon enthalpies, and vibratIonal normal mode frequencies were calculated from the MD simulatIons. Physico-chemical properties satisfactorily agree with experiments validating the robustness of the force field strategy. The solvatIon dynamics and structure for all hexavalent actinoids are extremely similar and resemble our previous analysis of the uranyl catIon. This supports the idea of using the uranyl catIon as a reference for the study of other minor actinyls. The comparison between the NpO22+ and NpO2+ hydratIon only provides significant differences in first and second shell distances and second-shell mean residence times. We propose a single general view of the [AnO2]2+/+ hydratIon structure: aqueous actinyls are amphiphilic anisotropic solutes which are equatorially conventIonal spherically symmetric catIons capped at the poles by clathrate-like water structures.
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Development of a polarizable and flexible model of the Hydrated Ion potential to study the intriguing case of Sc(III) hydratIon
Theoretical Chemistry Accounts, 2017Co-Authors: Daniel Z. Caralampio, Rafael R. Pappalardo, José M. Martínez, E. Sánchez MarcosAbstract:The hydratIon number of $$\hbox {Sc}^{3+}$$ Sc 3 + aquaIon is still an ongoing debate from both experimental and theoretical perspectives, in fact values between 6 and 9 have been proposed. This theoretical study presents the development of $$\hbox {Sc}^{3+}$$ Sc 3 + – $$\hbox {H}_{2}\hbox {O}$$ H 2 O intermolecular potentials based on ab initio potential energy surfaces of two scandium hydrates: $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_6]^{3+}$$ [ Sc ( H 2 O ) 6 ] 3 + and $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_7]^{3+}$$ [ Sc ( H 2 O ) 7 ] 3 + . A flexible and polarizable catIon and water model has been employed based on the mobile charge density harmonic oscillator (MCDHO) potential. Two classical molecular dynamics simulatIons of $$\hbox {Sc}^{3+}$$ Sc 3 + in water were carried out with these two new potentials. Data analysis shows very similar results from both simulatIons: The hydratIon number obtained is 6 and the average Sc–O distance for the first hydratIon shell is $$2.15\pm 0.01$$ 2.15 ± 0.01 Å. Estimated hydratIon enthalpy is very close to the experimental one. The simulated Sc K -edge EXAFS spectrum obtained from the structural informatIon provided by the MD simulatIon agrees fairly well with the experimental spectrum, as well as the main bands of the vibratIonal power spectra with the IR and Raman spectra.
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Development of a polarizable and flexible model of the Hydrated Ion potential to study the intriguing case of Sc(III) hydratIon
Theoretical Chemistry Accounts, 2017Co-Authors: Daniel Z. Caralampio, Rafael R. Pappalardo, José M. Martínez, E. Sánchez MarcosAbstract:The hydratIon number of $$\hbox {Sc}^{3+}$$ Sc 3 + aquaIon is still an ongoing debate from both experimental and theoretical perspectives, in fact values between 6 and 9 have been proposed. This theoretical study presents the development of $$\hbox {Sc}^{3+}$$ Sc 3 + – $$\hbox {H}_{2}\hbox {O}$$ H 2 O intermolecular potentials based on ab initio potential energy surfaces of two scandium hydrates: $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_6]^{3+}$$ [ Sc ( H 2 O ) 6 ] 3 + and $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_7]^{3+}$$ [ Sc ( H 2 O ) 7 ] 3 + . A flexible and polarizable catIon and water model has been employed based on the mobile charge density harmonic oscillator (MCDHO) potential. Two classical molecular dynamics simulatIons of $$\hbox {Sc}^{3+}$$ Sc 3 + in water were carried out with these two new potentials. Data analysis shows very similar results from both simulatIons: The hydratIon number obtained is 6 and the average Sc–O distance for the first hydratIon shell is $$2.15\pm 0.01$$ 2.15 ± 0.01 Å. Estimated hydratIon enthalpy is very close to the experimental one. The simulated Sc K -edge EXAFS spectrum obtained from the structural informatIon provided by the MD simulatIon agrees fairly well with the experimental spectrum, as well as the main bands of the vibratIonal power spectra with the IR and Raman spectra.
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A Hydrated Ion model of [UO2]2+ in water: Structure, dynamics, and spectroscopy from classical molecular dynamics.
The Journal of chemical physics, 2016Co-Authors: Sergio Pérez-conesa, Rafael R. Pappalardo, José M. Martínez, Francisco Torrico, Enrique Sánchez MarcosAbstract:A new ab initio interactIon potential based on the Hydrated Ion concept has been developed to obtain the structure, energetics, and dynamics of the hydratIon of uranyl in aqueous solutIon. It is the first force field that explicitly parameterizes the interactIon of the uranyl hydrate with bulk water molecules to accurately define the second-shell behavior. The [UO2(H2O)5]2+ presents a first hydratIon shell U–O average distance of 2.46 A and a second hydratIon shell peak at 4.61 A corresponding to 22 molecules using a coordinatIon number definitIon based on a multisite solute cavity. The second shell solvent molecules have longer mean residence times than those corresponding to the divalent monatomic catIons. The axial regIons are relatively de-populated, lacking direct hydrogen bonding to apical oxygens. Angle-solved radial distributIon functIons as well as the spatial distributIon functIons show a strong anisotropy in the Ion hydratIon. The [UO2(H2O)5]2+ solvent structure may be regarded as a combinatIon...
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collecting high order interactIons in an effective pairwise intermolecular potential using the Hydrated Ion concept the hydratIon of cf3
Journal of Chemical Physics, 2014Co-Authors: Elsa Galbis, Rafael R. Pappalardo, Jorge Hernandezcobos, Enrique Sánchez MarcosAbstract:This work proposes a new methodology to build interactIon potentials between a highly charged metal catIon and water molecules. These potentials, which can be used in classical computer simulatIons, have been fitted to reproduce quantum mechanical interactIon energies (MP2 and BP86) for a wide range of [M(H2O)n](m+)(H2O)l clusters (n going from 6 to 10 and l from 0 to 18). A flexible and polarizable water shell model (Mobile Charge Density of Harmonic Oscillator) has been coupled to the catIon-water potential. The simultaneous consideratIon of poly-Hydrated clusters and the polarizability of the interacting particles allows the inclusIon of the most important many-body effects in the new polarizable potential. ApplicatIons have been centered on the californium, Cf(III) the heaviest actinoid experimentally studied in solutIon. Two different strategies to select a set of about 2000 structures which are used for the potential building were checked. Monte Carlo simulatIons of Cf(III)+500 H2O for three of the intermolecular potentials predict an aquaIon structure with coordinatIon number close to 8 and average R(Cf-O) in the range 2.43-2.48 A, whereas the fourth one is closer to 9 with R(Cf-O) = 2.54 A. Simulated EXAFS spectra derived from the structural Monte Carlo distributIon compares fairly well with the available experimental spectrum for the simulatIons bearing 8 water molecules. An angular distributIon similar to that of a square antiprism is found for the octa-coordinatIon.
Enrique Sánchez Marcos - One of the best experts on this subject based on the ideXlab platform.
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a general study of actinyl hydratIon by molecular dynamics simulatIons using ab initio force fields
Journal of Chemical Physics, 2019Co-Authors: Sergio Perezconesa, Rafael R. Pappalardo, José M. Martínez, Francisco Torrico, Enrique Sánchez MarcosAbstract:A set of new ab initio force fields for aqueous [AnO2]2+/+ (An = Np(vi,v), Pu(vi), Am(vi)) has been developed using the Hydrated Ion (HI) model methodology previously used for [UO2]2+. Except for the non-electrostatic contributIon of the HI-bulk water interactIon, the interactIon potentials are individually parameterized. TranslatIonal diffusIon coefficients, hydratIon enthalpies, and vibratIonal normal mode frequencies were calculated from the MD simulatIons. Physico-chemical properties satisfactorily agree with experiments validating the robustness of the force field strategy. The solvatIon dynamics and structure for all hexavalent actinoids are extremely similar and resemble our previous analysis of the uranyl catIon. This supports the idea of using the uranyl catIon as a reference for the study of other minor actinyls. The comparison between the NpO22+ and NpO2+ hydratIon only provides significant differences in first and second shell distances and second-shell mean residence times. We propose a single general view of the [AnO2]2+/+ hydratIon structure: aqueous actinyls are amphiphilic anisotropic solutes which are equatorially conventIonal spherically symmetric catIons capped at the poles by clathrate-like water structures.
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A Hydrated Ion model of [UO2]2+ in water: Structure, dynamics, and spectroscopy from classical molecular dynamics.
The Journal of chemical physics, 2016Co-Authors: Sergio Pérez-conesa, Rafael R. Pappalardo, José M. Martínez, Francisco Torrico, Enrique Sánchez MarcosAbstract:A new ab initio interactIon potential based on the Hydrated Ion concept has been developed to obtain the structure, energetics, and dynamics of the hydratIon of uranyl in aqueous solutIon. It is the first force field that explicitly parameterizes the interactIon of the uranyl hydrate with bulk water molecules to accurately define the second-shell behavior. The [UO2(H2O)5]2+ presents a first hydratIon shell U–O average distance of 2.46 A and a second hydratIon shell peak at 4.61 A corresponding to 22 molecules using a coordinatIon number definitIon based on a multisite solute cavity. The second shell solvent molecules have longer mean residence times than those corresponding to the divalent monatomic catIons. The axial regIons are relatively de-populated, lacking direct hydrogen bonding to apical oxygens. Angle-solved radial distributIon functIons as well as the spatial distributIon functIons show a strong anisotropy in the Ion hydratIon. The [UO2(H2O)5]2+ solvent structure may be regarded as a combinatIon...
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collecting high order interactIons in an effective pairwise intermolecular potential using the Hydrated Ion concept the hydratIon of cf3
Journal of Chemical Physics, 2014Co-Authors: Elsa Galbis, Rafael R. Pappalardo, Jorge Hernandezcobos, Enrique Sánchez MarcosAbstract:This work proposes a new methodology to build interactIon potentials between a highly charged metal catIon and water molecules. These potentials, which can be used in classical computer simulatIons, have been fitted to reproduce quantum mechanical interactIon energies (MP2 and BP86) for a wide range of [M(H2O)n](m+)(H2O)l clusters (n going from 6 to 10 and l from 0 to 18). A flexible and polarizable water shell model (Mobile Charge Density of Harmonic Oscillator) has been coupled to the catIon-water potential. The simultaneous consideratIon of poly-Hydrated clusters and the polarizability of the interacting particles allows the inclusIon of the most important many-body effects in the new polarizable potential. ApplicatIons have been centered on the californium, Cf(III) the heaviest actinoid experimentally studied in solutIon. Two different strategies to select a set of about 2000 structures which are used for the potential building were checked. Monte Carlo simulatIons of Cf(III)+500 H2O for three of the intermolecular potentials predict an aquaIon structure with coordinatIon number close to 8 and average R(Cf-O) in the range 2.43-2.48 A, whereas the fourth one is closer to 9 with R(Cf-O) = 2.54 A. Simulated EXAFS spectra derived from the structural Monte Carlo distributIon compares fairly well with the available experimental spectrum for the simulatIons bearing 8 water molecules. An angular distributIon similar to that of a square antiprism is found for the octa-coordinatIon.
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A molecular dynamics study on Rh3+ hydratIon: development and applicatIon of a first principles Hydrated Ion–water interactIon potential
Theoretical Chemistry Accounts, 2003Co-Authors: José M. Martínez, Rafael R. Pappalardo, Patrick J. Merkling, Keith Refson, Enrique Sánchez MarcosAbstract:The Rh3+ aquaIon exhibits one of the largest residence times of water molecules in the first hydratIon shell. The extreme stability of this hexaHydrated Ion in water solutIons makes Rh3+ an extremely suitable candidate to be studied using the Hydrated Ion model. According to this approach, the representative catIonic entity in aqueous solutIon is the Ion plus its first hydratIon shell (i.e. the Hydrated Ion) and not the bare Ion. Our group has successfully applied that concept in the framework of classical statistical simulatIons based on first principles Ion–water interactIon potentials. The methodology is now applied to the [Rh(H2O)6]3+ case based on a previous generalizatIon in which some of the contributIons were found to be transferable among the cases already studied (Cr3+, Al3+, Mg2+, Be2+). In this contributIon a flexible hydrate model is presented, in which rigid first-shell water molecules have rotatIonal and translatIonal degrees of freedom, allowing for internal dynamics of the Hydrated Ion entity. The potential presented is thoroughly tested by means of a set of molecular dynamics simulatIons. Structural, dynamical, energetic and spectroscopic informatIon is retrieved from the simulatIons, allowing the estimatIon of properties such as Ion hydratIon energy, vibratIonal spectra of the intermolecular modes, catIon mobility, rotatIonal dynamics of the Hydrated Ion and first-shell water molecules and residence times of the second-shell water molecules. ExtensIon of the Ewald sum to terms r−4, r−6 and r−7 is presented and applied to systems of different size ([Rh(H2O)6]3++(n−6)H2O, n=50, 100, 200, 500, 1000 and 2500) and cutoff radii.
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Coupling a polarizable water model to the Hydrated Ion–water interactIon potential: A test on the Cr3+ hydratIon
The Journal of Chemical Physics, 2000Co-Authors: José M. Martínez, Rafael R. Pappalardo, Jorge Hernández-cobos, Humberto Saint-martin, Iván Ortega-blake, Enrique Sánchez MarcosAbstract:A strategy to build interactIon potentials for describing Ionic hydratIon of highly charged monoatomic catIons by computer simulatIons, including the polarizable character of the solvent, is proposed. The method is based on the Hydrated Ion concept that has been previously tested for the case of Cr3+ aqueous solutIons [J. Phys. Chem. 100, 11748 (1996)]. In the present work, the interactIon potential of [Cr(H2O6)]3+ with water has been adapted to a water model that accounts for the polarizable character of the solvent by means of a mobile charge harmonic oscillator representatIon (MCHO model) [J. Chem. Phys. 93, 6448 (1990)]. Monte Carlo simulatIons of the Cr3+ hexahydrate plus 512 water molecules have been performed to study the energetics and structure of the Ionic solutIon. The results show a significant improvement in the estimate of the hydratIon enthalpy [ΔHhydr(Cr3+)=−1109.6±70 kcal/mol] that now matches the experimental value within the uncertainty of this magnitude. The use of the polarizable wate...
José M. Martínez - One of the best experts on this subject based on the ideXlab platform.
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a general study of actinyl hydratIon by molecular dynamics simulatIons using ab initio force fields
Journal of Chemical Physics, 2019Co-Authors: Sergio Perezconesa, Rafael R. Pappalardo, José M. Martínez, Francisco Torrico, Enrique Sánchez MarcosAbstract:A set of new ab initio force fields for aqueous [AnO2]2+/+ (An = Np(vi,v), Pu(vi), Am(vi)) has been developed using the Hydrated Ion (HI) model methodology previously used for [UO2]2+. Except for the non-electrostatic contributIon of the HI-bulk water interactIon, the interactIon potentials are individually parameterized. TranslatIonal diffusIon coefficients, hydratIon enthalpies, and vibratIonal normal mode frequencies were calculated from the MD simulatIons. Physico-chemical properties satisfactorily agree with experiments validating the robustness of the force field strategy. The solvatIon dynamics and structure for all hexavalent actinoids are extremely similar and resemble our previous analysis of the uranyl catIon. This supports the idea of using the uranyl catIon as a reference for the study of other minor actinyls. The comparison between the NpO22+ and NpO2+ hydratIon only provides significant differences in first and second shell distances and second-shell mean residence times. We propose a single general view of the [AnO2]2+/+ hydratIon structure: aqueous actinyls are amphiphilic anisotropic solutes which are equatorially conventIonal spherically symmetric catIons capped at the poles by clathrate-like water structures.
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Development of a polarizable and flexible model of the Hydrated Ion potential to study the intriguing case of Sc(III) hydratIon
Theoretical Chemistry Accounts, 2017Co-Authors: Daniel Z. Caralampio, Rafael R. Pappalardo, José M. Martínez, E. Sánchez MarcosAbstract:The hydratIon number of $$\hbox {Sc}^{3+}$$ Sc 3 + aquaIon is still an ongoing debate from both experimental and theoretical perspectives, in fact values between 6 and 9 have been proposed. This theoretical study presents the development of $$\hbox {Sc}^{3+}$$ Sc 3 + – $$\hbox {H}_{2}\hbox {O}$$ H 2 O intermolecular potentials based on ab initio potential energy surfaces of two scandium hydrates: $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_6]^{3+}$$ [ Sc ( H 2 O ) 6 ] 3 + and $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_7]^{3+}$$ [ Sc ( H 2 O ) 7 ] 3 + . A flexible and polarizable catIon and water model has been employed based on the mobile charge density harmonic oscillator (MCDHO) potential. Two classical molecular dynamics simulatIons of $$\hbox {Sc}^{3+}$$ Sc 3 + in water were carried out with these two new potentials. Data analysis shows very similar results from both simulatIons: The hydratIon number obtained is 6 and the average Sc–O distance for the first hydratIon shell is $$2.15\pm 0.01$$ 2.15 ± 0.01 Å. Estimated hydratIon enthalpy is very close to the experimental one. The simulated Sc K -edge EXAFS spectrum obtained from the structural informatIon provided by the MD simulatIon agrees fairly well with the experimental spectrum, as well as the main bands of the vibratIonal power spectra with the IR and Raman spectra.
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Development of a polarizable and flexible model of the Hydrated Ion potential to study the intriguing case of Sc(III) hydratIon
Theoretical Chemistry Accounts, 2017Co-Authors: Daniel Z. Caralampio, Rafael R. Pappalardo, José M. Martínez, E. Sánchez MarcosAbstract:The hydratIon number of $$\hbox {Sc}^{3+}$$ Sc 3 + aquaIon is still an ongoing debate from both experimental and theoretical perspectives, in fact values between 6 and 9 have been proposed. This theoretical study presents the development of $$\hbox {Sc}^{3+}$$ Sc 3 + – $$\hbox {H}_{2}\hbox {O}$$ H 2 O intermolecular potentials based on ab initio potential energy surfaces of two scandium hydrates: $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_6]^{3+}$$ [ Sc ( H 2 O ) 6 ] 3 + and $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_7]^{3+}$$ [ Sc ( H 2 O ) 7 ] 3 + . A flexible and polarizable catIon and water model has been employed based on the mobile charge density harmonic oscillator (MCDHO) potential. Two classical molecular dynamics simulatIons of $$\hbox {Sc}^{3+}$$ Sc 3 + in water were carried out with these two new potentials. Data analysis shows very similar results from both simulatIons: The hydratIon number obtained is 6 and the average Sc–O distance for the first hydratIon shell is $$2.15\pm 0.01$$ 2.15 ± 0.01 Å. Estimated hydratIon enthalpy is very close to the experimental one. The simulated Sc K -edge EXAFS spectrum obtained from the structural informatIon provided by the MD simulatIon agrees fairly well with the experimental spectrum, as well as the main bands of the vibratIonal power spectra with the IR and Raman spectra.
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A Hydrated Ion model of [UO2]2+ in water: Structure, dynamics, and spectroscopy from classical molecular dynamics.
The Journal of chemical physics, 2016Co-Authors: Sergio Pérez-conesa, Rafael R. Pappalardo, José M. Martínez, Francisco Torrico, Enrique Sánchez MarcosAbstract:A new ab initio interactIon potential based on the Hydrated Ion concept has been developed to obtain the structure, energetics, and dynamics of the hydratIon of uranyl in aqueous solutIon. It is the first force field that explicitly parameterizes the interactIon of the uranyl hydrate with bulk water molecules to accurately define the second-shell behavior. The [UO2(H2O)5]2+ presents a first hydratIon shell U–O average distance of 2.46 A and a second hydratIon shell peak at 4.61 A corresponding to 22 molecules using a coordinatIon number definitIon based on a multisite solute cavity. The second shell solvent molecules have longer mean residence times than those corresponding to the divalent monatomic catIons. The axial regIons are relatively de-populated, lacking direct hydrogen bonding to apical oxygens. Angle-solved radial distributIon functIons as well as the spatial distributIon functIons show a strong anisotropy in the Ion hydratIon. The [UO2(H2O)5]2+ solvent structure may be regarded as a combinatIon...
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A molecular dynamics study on Rh3+ hydratIon: development and applicatIon of a first principles Hydrated Ion–water interactIon potential
Theoretical Chemistry Accounts, 2003Co-Authors: José M. Martínez, Rafael R. Pappalardo, Patrick J. Merkling, Keith Refson, Enrique Sánchez MarcosAbstract:The Rh3+ aquaIon exhibits one of the largest residence times of water molecules in the first hydratIon shell. The extreme stability of this hexaHydrated Ion in water solutIons makes Rh3+ an extremely suitable candidate to be studied using the Hydrated Ion model. According to this approach, the representative catIonic entity in aqueous solutIon is the Ion plus its first hydratIon shell (i.e. the Hydrated Ion) and not the bare Ion. Our group has successfully applied that concept in the framework of classical statistical simulatIons based on first principles Ion–water interactIon potentials. The methodology is now applied to the [Rh(H2O)6]3+ case based on a previous generalizatIon in which some of the contributIons were found to be transferable among the cases already studied (Cr3+, Al3+, Mg2+, Be2+). In this contributIon a flexible hydrate model is presented, in which rigid first-shell water molecules have rotatIonal and translatIonal degrees of freedom, allowing for internal dynamics of the Hydrated Ion entity. The potential presented is thoroughly tested by means of a set of molecular dynamics simulatIons. Structural, dynamical, energetic and spectroscopic informatIon is retrieved from the simulatIons, allowing the estimatIon of properties such as Ion hydratIon energy, vibratIonal spectra of the intermolecular modes, catIon mobility, rotatIonal dynamics of the Hydrated Ion and first-shell water molecules and residence times of the second-shell water molecules. ExtensIon of the Ewald sum to terms r−4, r−6 and r−7 is presented and applied to systems of different size ([Rh(H2O)6]3++(n−6)H2O, n=50, 100, 200, 500, 1000 and 2500) and cutoff radii.
Guido Grundmeier - One of the best experts on this subject based on the ideXlab platform.
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transport processes of Hydrated Ions at polymer oxide metal interfaces part 2 transport on oxide covered iron and zinc surfaces
Electrochimica Acta, 2009Co-Authors: R Posner, T Titz, K Wapner, M Stratmann, Guido GrundmeierAbstract:Abstract The study of Ion transport processes on non-polymer coated bare oxide covered iron and zinc surfaces showed that the presence of adsorbed Ions determines the Ion distributIon on oxide/metal surfaces in humid atmosphere. For fundamental studies of Ion ingress at polymer/oxide/metal interfaces, already the transport analysis in the absence of the polymer reveals important mechanistic aspects. Sophisticated spectroscopic techniques were applied for the correlatIon of electrochemical data with local surface chemistry. In-situ Scanning Kelvin Probe (SKP) measurements of the local interfacial potentials of oxide covered iron and zinc substrates and ex situ time-of-flight secondary Ion mass spectroscopy (ToF-SIMS) analysis showed that the surface layer charge influences the Ion transport processes. A model is proposed to explain the basic mechanism of Hydrated Ion transport on oxide covered zinc and iron.
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transport processes of Hydrated Ions at polymer oxide metal interfaces part 1 transport at interfaces of polymer coated oxide covered iron and zinc substrates
Electrochimica Acta, 2009Co-Authors: R Posner, K Wapner, M Stratmann, Guido GrundmeierAbstract:Abstract Localised electrochemical and spectroscopic techniques were jointly applied for the evaluatIon of Hydrated Ion transport processes along polymer/oxide/metal interfaces. In situ Scanning Kelvin Probe (SKP) studies of the local interfacial potentials of organically coated oxide covered zinc and iron substrates were performed in humid nitrogen atmospheres. They were supported by ex situ small spot X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary Ion mass spectroscopy (ToF-SIMS) analysis of the interfacial Ion distributIon. Based on the experimental results it is concluded that also in atmospheres of strongly reduced oxygen partial pressure at which no corrosive delaminatIon takes place, a negatively charged layer of adsorbed hydroxide Ions determines Ion transport processes along interfaces between polymer films and oxide covered metals. No Ion transport was observed for zinc substrates while Hydrated catIons were selectively transported along the polymer/iron interface. The reductIon of oxygen molecules on the highly reactive iron oxide surface is assumed to be responsible for the generatIon of adsorbed interfacial hydroxide Ions. On the other hand such oxygen reductIon induced hydroxide formatIon in humid nitrogen atmospheres with strongly reduced oxygen partial pressure does not seem to take place on oxide covered zinc. The variatIon of free volumes at the polymer/substrate interface did not lead to a principal change of this phenomenon.
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Transport processes of Hydrated Ions on oxide covered iron and zinc surfaces and interfaces. Part 1: Transport at polymer/oxide/metal interfaces
Electrochimica Acta, 2009Co-Authors: R Posner, K Wapner, M Stratmann, Guido GrundmeierAbstract:Abstract Localised electrochemical and spectroscopic techniques were jointly applied for the evaluatIon of Hydrated Ion transport processes along polymer/oxide/metal interfaces. In situ Scanning Kelvin Probe (SKP) studies of the local interfacial potentials of organically coated oxide covered zinc and iron substrates were performed in humid nitrogen atmospheres. They were supported by ex situ small spot X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary Ion mass spectroscopy (ToF-SIMS) analysis of the interfacial Ion distributIon. Based on the experimental results it is concluded that also in atmospheres of strongly reduced oxygen partial pressure at which no corrosive delaminatIon takes place, a negatively charged layer of adsorbed hydroxide Ions determines Ion transport processes along interfaces between polymer films and oxide covered metals. No Ion transport was observed for zinc substrates while Hydrated catIons were selectively transported along the polymer/iron interface. The reductIon of oxygen molecules on the highly reactive iron oxide surface is assumed to be responsible for the generatIon of adsorbed interfacial hydroxide Ions. On the other hand such oxygen reductIon induced hydroxide formatIon in humid nitrogen atmospheres with strongly reduced oxygen partial pressure does not seem to take place on oxide covered zinc. The variatIon of free volumes at the polymer/substrate interface did not lead to a principal change of this phenomenon.
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Transport processes of Hydrated Ions at polymer/oxide/metal interfaces: Part 2. Transport on oxide covered iron and zinc surfaces
Electrochimica Acta, 2008Co-Authors: R Posner, T Titz, K Wapner, M Stratmann, Guido GrundmeierAbstract:Abstract The study of Ion transport processes on non-polymer coated bare oxide covered iron and zinc surfaces showed that the presence of adsorbed Ions determines the Ion distributIon on oxide/metal surfaces in humid atmosphere. For fundamental studies of Ion ingress at polymer/oxide/metal interfaces, already the transport analysis in the absence of the polymer reveals important mechanistic aspects. Sophisticated spectroscopic techniques were applied for the correlatIon of electrochemical data with local surface chemistry. In-situ Scanning Kelvin Probe (SKP) measurements of the local interfacial potentials of oxide covered iron and zinc substrates and ex situ time-of-flight secondary Ion mass spectroscopy (ToF-SIMS) analysis showed that the surface layer charge influences the Ion transport processes. A model is proposed to explain the basic mechanism of Hydrated Ion transport on oxide covered zinc and iron.
E. Sánchez Marcos - One of the best experts on this subject based on the ideXlab platform.
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Development of a polarizable and flexible model of the Hydrated Ion potential to study the intriguing case of Sc(III) hydratIon
Theoretical Chemistry Accounts, 2017Co-Authors: Daniel Z. Caralampio, Rafael R. Pappalardo, José M. Martínez, E. Sánchez MarcosAbstract:The hydratIon number of $$\hbox {Sc}^{3+}$$ Sc 3 + aquaIon is still an ongoing debate from both experimental and theoretical perspectives, in fact values between 6 and 9 have been proposed. This theoretical study presents the development of $$\hbox {Sc}^{3+}$$ Sc 3 + – $$\hbox {H}_{2}\hbox {O}$$ H 2 O intermolecular potentials based on ab initio potential energy surfaces of two scandium hydrates: $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_6]^{3+}$$ [ Sc ( H 2 O ) 6 ] 3 + and $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_7]^{3+}$$ [ Sc ( H 2 O ) 7 ] 3 + . A flexible and polarizable catIon and water model has been employed based on the mobile charge density harmonic oscillator (MCDHO) potential. Two classical molecular dynamics simulatIons of $$\hbox {Sc}^{3+}$$ Sc 3 + in water were carried out with these two new potentials. Data analysis shows very similar results from both simulatIons: The hydratIon number obtained is 6 and the average Sc–O distance for the first hydratIon shell is $$2.15\pm 0.01$$ 2.15 ± 0.01 Å. Estimated hydratIon enthalpy is very close to the experimental one. The simulated Sc K -edge EXAFS spectrum obtained from the structural informatIon provided by the MD simulatIon agrees fairly well with the experimental spectrum, as well as the main bands of the vibratIonal power spectra with the IR and Raman spectra.
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Development of a polarizable and flexible model of the Hydrated Ion potential to study the intriguing case of Sc(III) hydratIon
Theoretical Chemistry Accounts, 2017Co-Authors: Daniel Z. Caralampio, Rafael R. Pappalardo, José M. Martínez, E. Sánchez MarcosAbstract:The hydratIon number of $$\hbox {Sc}^{3+}$$ Sc 3 + aquaIon is still an ongoing debate from both experimental and theoretical perspectives, in fact values between 6 and 9 have been proposed. This theoretical study presents the development of $$\hbox {Sc}^{3+}$$ Sc 3 + – $$\hbox {H}_{2}\hbox {O}$$ H 2 O intermolecular potentials based on ab initio potential energy surfaces of two scandium hydrates: $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_6]^{3+}$$ [ Sc ( H 2 O ) 6 ] 3 + and $$[\hbox {Sc}(\hbox {H}_{2}\hbox {O})_7]^{3+}$$ [ Sc ( H 2 O ) 7 ] 3 + . A flexible and polarizable catIon and water model has been employed based on the mobile charge density harmonic oscillator (MCDHO) potential. Two classical molecular dynamics simulatIons of $$\hbox {Sc}^{3+}$$ Sc 3 + in water were carried out with these two new potentials. Data analysis shows very similar results from both simulatIons: The hydratIon number obtained is 6 and the average Sc–O distance for the first hydratIon shell is $$2.15\pm 0.01$$ 2.15 ± 0.01 Å. Estimated hydratIon enthalpy is very close to the experimental one. The simulated Sc K -edge EXAFS spectrum obtained from the structural informatIon provided by the MD simulatIon agrees fairly well with the experimental spectrum, as well as the main bands of the vibratIonal power spectra with the IR and Raman spectra.
