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Wayde N. Martens - One of the best experts on this subject based on the ideXlab platform.
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Thermal decomposition of Hydronium jarosite (H3O)Fe 3(SO4)2(OH)6
Journal of Thermal Analysis and Calorimetry, 2020Co-Authors: Ray L. Frost, J Kloprogge, Rachael-anne Wills, Wayde N. MartensAbstract:Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic Hydronium jarosite. Five mass loss steps are observed at 262, 294, 385, 557 and 619°C. The mass loss step at 557°C is sharp and marks a sharp loss of sulphate as SO from the Hydronium jarosite. Mass spectrometry through evolved gases confirms the first three mass loss steps to dehydroxylation, the fourth to a mass loss of the hydrated proton and a sulphate and the final step to the loss of the remaining sulphate. Changes in the molecular structure of the Hydronium jarosite were followed by infrared emission spectroscopy. This technique allows the infrared spectrum at the elevated temperatures to be obtained. Infrared emission spectroscopy confirms the dehydroxylation has taken place by 400 and the sulphate loss by 650°C. Jarosites are a group of minerals formed in evaporite deposits and form a component of the efflorescence. The minerals can function as cation and heavy metal collectors. Hydronium jarosite has the potential to act as a cation collector by the replacement of the proton with a heavy metal cation.
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location of hydrogen atoms in Hydronium jarosite
Pacific Rim Conference on Multimedia, 2014Co-Authors: Henry J. Spratt, Llew Rintoul, Maxim Avdeev, Michael C Pfrunder, John C Mcmurtrie, Wayde N. MartensAbstract:Various models for the crystal structure of Hydronium jarosite were determined from Rietveld refinements against neutron powder diffraction patterns collected at ambient temperature and also single-crystal X-ray diffraction data. The possibility of a lower symmetry space group for Hydronium jarosite that has been suggested by the literature was investigated. It was found the space group is best described as \(R\bar{3}m\), the same for other jarosite minerals. The Hydronium oxygen atom was found to occupy the \(\overline{3} m\) site (3a Wyckoff site). Inadequately refined Hydronium bond angles and bond distances without the use of restraints are due to thermal motion and disorder of the Hydronium hydrogen atoms across numerous orientations. However, the acquired data do not permit a precise determination of these orientations; the main feature up/down disorder of Hydronium is clear. Thus, the highest symmetry model with the least disorder necessary to explain all data was chosen: The Hydronium hydrogen atoms were modeled to occupy an m (18 h Wyckoff site) with 50 % fractional occupancy, leading to disorder across two orientations. A rigid body description of the Hydronium ion rotated by 60° with H–O–H bond angles of 112° and O–H distances of 0.96 A was optimal. This rigid body refinement suggests that hydrogen bonds between Hydronium hydrogen atoms and basal sulfate oxygen atoms are not predominant. Instead, hydrogen bonds are formed between Hydronium hydrogen atoms and hydroxyl oxygen atoms. The structure of Hydronium alunite is expected to be similar given that alunite supergroup minerals are isostructural.
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location of hydrogen atoms in Hydronium jarosite
Science & Engineering Faculty, 2014Co-Authors: Henry J. Spratt, Llew Rintoul, Maxim Avdeev, Michael C Pfrunder, John C Mcmurtrie, Wayde N. MartensAbstract:Various models for the crystal structure of Hydronium jarosite were determined from Rietveld refinements against neutron powder diffraction patterns collected at ambient temperature and also single-crystal X-ray diffraction data. The possibility of a lower symmetry space group for Hydronium jarosite that has been suggested by the literature was investigated. It was found the space group is best described as R3¯m, the same for other jarosite minerals. The Hydronium oxygen atom was found to occupy the 3¯m site (3a Wyckoff site). Inadequately refined Hydronium bond angles and bond distances without the use of restraints are due to thermal motion and disorder of the Hydronium hydrogen atoms across numerous orientations. However, the acquired data do not permit a precise determination of these orientations; the main feature up/down disorder of Hydronium is clear. Thus, the highest symmetry model with the least disorder necessary to explain all data was chosen: The Hydronium hydrogen atoms were modeled to occupy an m (18 h Wyckoff site) with 50 % fractional occupancy, leading to disorder across two orientations. A rigid body description of the Hydronium ion rotated by 60° with H–O–H bond angles of 112° and O–H distances of 0.96 A was optimal. This rigid body refinement suggests that hydrogen bonds between Hydronium hydrogen atoms and basal sulfate oxygen atoms are not predominant. Instead, hydrogen bonds are formed between Hydronium hydrogen atoms and hydroxyl oxygen atoms. The structure of Hydronium alunite is expected to be similar given that alunite supergroup minerals are isostructural.
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The thermal decomposition of Hydronium jarosite and ammoniojarosite
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Henry J. Spratt, Llew Rintoul, Maxim Avdeev, Wayde N. MartensAbstract:The thermal decomposition of Hydronium jarosite and ammoniojarosite was studied using thermogravimetric analysis and mass spectrometry, in situ synchrotron X-ray diffraction and infrared emission spectroscopy. There was no evidence for the simultaneous loss of water and sulfur dioxide during the desulfonation stage as has previously been reported for Hydronium jarosite. Conversely, all hydrogen atoms are lost during the dehydration and dehydroxylation stage from 270 to 400 °C and no water, hydroxyl groups or Hydronium ions persist after 400 °C. The same can be said for ammoniojarosite. The first mass loss step during the decomposition of Hydronium jarosite has been assigned to the loss of the Hydronium ion via protonation of the surrounding hydroxyl groups to evolve two water molecules. For ammoniojarosite, this step corresponds to the protonation of a hydroxyl group by ammonium, so that ammonia and water are liberated simultaneously. Iron(II) sulfate was identified as a possible intermediate during the decomposition of ammoniojarosite (421-521 °C) due to a redox reaction between iron(III) and the liberated ammonia during decomposition. Iron(II) ions were also confirmed with the 1,10-phenanthroline test. Iron(III) sulfate and other commonly suggested intermediates for Hydronium and ammoniojarosite decomposition are not major crystalline phases; if they are formed, then they most likely exist as an amorphous phase or a different low temperature phases than usual. [ABSTRACT FROM AUTHOR]
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Thermal decomposition of Hydronium jarosite (H3O)Fe3(SO4)2(OH)6
Journal of thermal analysis and calorimetry, 2006Co-Authors: Russ Frost, J Kloprogge, Ronnie WILLS, Wayde N. MartensAbstract:Thermogravimetry combined with mass spectrometry has been used to study the thermal decomposition of a synthetic Hydronium jarosite. Five mass loss steps are observed at 262, 294, 385, 557 and 619C. The mass loss step at 557C is sharp and marks a sharp loss of sulphate as SO 3 from the Hydronium jarosite. Mass spectrometry through evolved gases confirms the first three mass loss steps to dehydroxylation, the fourth to a mass loss of the hydrated proton and a sulphate and the final step to the loss of the remaining sulphate. Changes in the molecular structure of the Hydronium jarosite were followed by infrared emission spectroscopy. This technique allows the infrared spectrum at the elevated temperatures to be obtained. Infrared emission spectroscopy confirms the dehydroxylation has taken place by 400 and the sulphate loss by 650C. Jarosites are a group of minerals formed in evaporite deposits and form a component of the efflorescence. The minerals can function as cation and heavy metal collectors. Hydronium jarosite has the potential to act as a cation collector by the replacement of the proton with a heavy metal cation.
Collin D Wick - One of the best experts on this subject based on the ideXlab platform.
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Hydronium behavior at the air water interface with a polarizable multistate empirical valence bond model
Journal of Physical Chemistry C, 2012Co-Authors: Collin D WickAbstract:Molecular dynamics simulations were carried out to understand the propensity of the Hydronium ion for the air–water interface with a polarizable multistate empirical valence bond (MS-EVB) model. Reasonable agreement with experiment for radial distribution functions and very good agreement for Hydronium diffusion were found for the model. The polarizable MS-EVB model had no free energy minimum at the air–water interface. However, when polarizability on the Hydronium ion alone was removed, a free energy of around −1.5 kcal/mol was calculated at the air–water interface. This discrepancy was found to be due to the behavior of water molecules in the first solvation shell of a Hydronium ion. These water molecules contained a moderate amount of Hydronium character, resulting in the delocalization of the Hydronium ion. For the system with polarizable Hydronium ions, this delocalization was the same at the interface as in the bulk, but for the system without polarizable Hydronium ions, the delocalization increased...
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Hydronium Behavior at the Air–Water Interface with a Polarizable Multistate Empirical Valence Bond Model
Journal of Physical Chemistry C, 2012Co-Authors: Collin D WickAbstract:Molecular dynamics simulations were carried out to understand the propensity of the Hydronium ion for the air–water interface with a polarizable multistate empirical valence bond (MS-EVB) model. Reasonable agreement with experiment for radial distribution functions and very good agreement for Hydronium diffusion were found for the model. The polarizable MS-EVB model had no free energy minimum at the air–water interface. However, when polarizability on the Hydronium ion alone was removed, a free energy of around −1.5 kcal/mol was calculated at the air–water interface. This discrepancy was found to be due to the behavior of water molecules in the first solvation shell of a Hydronium ion. These water molecules contained a moderate amount of Hydronium character, resulting in the delocalization of the Hydronium ion. For the system with polarizable Hydronium ions, this delocalization was the same at the interface as in the bulk, but for the system without polarizable Hydronium ions, the delocalization increased...
Liem X Dang - One of the best experts on this subject based on the ideXlab platform.
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Solvation of the Hydronium ion at the water liquid/vapor interface
Journal of Chemical Physics, 2003Co-Authors: Liem X DangAbstract:In this study, we used constrained molecular dynamics techniques to investigate the transport of a Hydronium ion across the water liquid/vapor interface. The computed transfer free energy was nearly unchanged as the Hydronium ion approached the Gibbs dividing surface. The ion crossed the interface with no substantial minimum free energy, and transport of the Hydronium ion involved a change in the solvent composition of the solvation shells around the ion.
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solvation of the Hydronium ion at the water liquid vapor interface
Journal of Chemical Physics, 2003Co-Authors: Liem X DangAbstract:In this study, we used constrained molecular dynamics techniques to investigate the transport of a Hydronium ion across the water liquid/vapor interface. The computed transfer free energy was nearly unchanged as the Hydronium ion approached the Gibbs dividing surface. The ion crossed the interface with no substantial minimum free energy, and transport of the Hydronium ion involved a change in the solvent composition of the solvation shells around the ion.
Wolfgang Domcke - One of the best experts on this subject based on the ideXlab platform.
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ab initio investigation of the structure and spectroscopy of Hydronium water clusters
Journal of Physical Chemistry A, 2002Co-Authors: And Andrzej L Sobolewski, Wolfgang DomckeAbstract:Ab initio (MP2, CASSCF, CASPT2) and DFT/B3LYP calculations have been performed to explore the structures and the electronic and vibrational spectra of Hydronium−water clusters as well as the corresponding cluster cations. Minimum-energy and transition-state structures have been optimized at the MP2 and DFT/B3LYP levels. Whereas protonated water clusters can exist both in Eigen-type structures, H3O+(H2O)n, as well as in Zundel-type structures, H5O2+(H2O)n, the neutral radical clusters are found to prefer Eigen-type structures, H3O(H2O)n. While H3O(H2O)3, like the Hydronium radical, is a metastable species, it exhibits a significantly higher barrier for hydrogen detachment (7 kcal/mol), indicating the possibility of kinetic stability of larger H3O(H2O)n clusters at low temperatures. Remarkably, Hydronium−water clusters are charge-separated species, consisting of a Hydronium cation and a localized electron cloud, which are connected by a water network. The vertical electronic excitation energies of the vario...
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Ab Initio Investigation of the Structure and Spectroscopy of Hydronium−Water Clusters
Journal of Physical Chemistry A, 2002Co-Authors: And Andrzej L Sobolewski, Wolfgang DomckeAbstract:Ab initio (MP2, CASSCF, CASPT2) and DFT/B3LYP calculations have been performed to explore the structures and the electronic and vibrational spectra of Hydronium−water clusters as well as the corresponding cluster cations. Minimum-energy and transition-state structures have been optimized at the MP2 and DFT/B3LYP levels. Whereas protonated water clusters can exist both in Eigen-type structures, H3O+(H2O)n, as well as in Zundel-type structures, H5O2+(H2O)n, the neutral radical clusters are found to prefer Eigen-type structures, H3O(H2O)n. While H3O(H2O)3, like the Hydronium radical, is a metastable species, it exhibits a significantly higher barrier for hydrogen detachment (7 kcal/mol), indicating the possibility of kinetic stability of larger H3O(H2O)n clusters at low temperatures. Remarkably, Hydronium−water clusters are charge-separated species, consisting of a Hydronium cation and a localized electron cloud, which are connected by a water network. The vertical electronic excitation energies of the vario...
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hydrated Hydronium a cluster model of the solvated electron
Physical Chemistry Chemical Physics, 2002Co-Authors: And Andrzej L Sobolewski, Wolfgang DomckeAbstract:Ab initio (ROHF, CASSCF, CASPT2) and DFT/B3LYP calculations have been performed for the electronic ground state and the lowest excited singlet states of the water dimer and Hydronium–water clusters. It has been found that a barrierless hydrogen-transfer reaction path exists in the first excited singlet state of the water dimer, leading to OH and H3O radicals. The microsolvation of the Hydronium radical has been investigated, considering up to two solvation shells of water molecules. Solvated H3O is found to be a charge-separated complex, consisting of the Hydronium cation and a localized electron cloud, which are connected by a water network. Results are reported on the stability of these clusters and their electronic and vibrational spectroscopic properties. The calculated electronic and vibrational spectra of the clusters exhibit striking similarities with the spectral signatures of the hydrated electron. It is argued that H3O(H2O)n clusters could be the carriers of the characteristic spectroscopic properties of the hydrated electron.
W V Steele - One of the best experts on this subject based on the ideXlab platform.
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molecular dynamics study of structure and transport of water and Hydronium ions at the membrane vapor interface of nafion
Journal of Physical Chemistry C, 2008Co-Authors: Myvizhi Esai Selvan, David J Keffer, Brian J Edwards, W V SteeleAbstract:Through the use of molecular dynamics simulation, we examine the structural and transport properties of water and Hydronium ions at the interface of a Nafion polymer electrolyte membrane and a vapor phase. The effect of humidity was studied by examining water contents of 5%, 10%, 15%, and 20% by weight. We observe a region of water depletion in the membrane near the vapor interface. We report the vehicular diffusion of Hydronium ions and water as components parallel and perpendicular to the interface. In the interfacial region, for Hydronium ions, we find that the component of the vehicular diffusivity parallel to the interface is largely unchanged from that in the bulk hydrated membrane, but the component perpendicular to the interface has increased, due to local decrease in density. We find similar behavior with water in the interfacial region. On the basis of these diffusivities, we conclude that there is no observable additional resistance to mass transport of the vehicular component of water and Hydronium ions due to the interface. In terms of structure at the interface, we find that there is a decrease in the fraction of fully hydrated Hydronium ions. This translates into a lower probability of forming Eigen ions, which are necessary for structural diffusion. Finally, we observe that the Hydronium ions display a preferential orientation at the interface with their oxygen atoms exposed to the vapor phase.
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Molecular Dynamics Study of Structure and Transport of Water and Hydronium Ions at the Membrane/Vapor Interface of Nafion
Journal of Physical Chemistry C, 2008Co-Authors: Myvizhi Esai Selvan, David J Keffer, Brian J Edwards, W V SteeleAbstract:Through the use of molecular dynamics simulation, we examine the structural and transport properties of water and Hydronium ions at the interface of a Nafion polymer electrolyte membrane and a vapor phase. The effect of humidity was studied by examining water contents of 5%, 10%, 15%, and 20% by weight. We observe a region of water depletion in the membrane near the vapor interface. We report the vehicular diffusion of Hydronium ions and water as components parallel and perpendicular to the interface. In the interfacial region, for Hydronium ions, we find that the component of the vehicular diffusivity parallel to the interface is largely unchanged from that in the bulk hydrated membrane, but the component perpendicular to the interface has increased, due to local decrease in density. We find similar behavior with water in the interfacial region. On the basis of these diffusivities, we conclude that there is no observable additional resistance to mass transport of the vehicular component of water and Hydronium ions due to the interface. In terms of structure at the interface, we find that there is a decrease in the fraction of fully hydrated Hydronium ions. This translates into a lower probability of forming Eigen ions, which are necessary for structural diffusion. Finally, we observe that the Hydronium ions display a preferential orientation at the interface with their oxygen atoms exposed to the vapor phase.
