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Christopher W. Outhwaite - One of the best experts on this subject based on the ideXlab platform.
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The point ion modified Poisson–Boltzmann Theory for a planar electric double layer with different permittivities for the electrode, inner layer and diffuse layer
Molecular Physics, 2014Co-Authors: Christopher W. Outhwaite, Lutful Bari BhuiyanAbstract:The planar electric double layer is modelled by an electrode, inner layer and diffuse layer whose constant permittivities differ. A point ion modified Poisson–Boltzmann analysis is made of the model with the ions in the diffuse layer having a distance of closest approach to the electrode, which is greater than the inner layer thickness and mimics the ion radius of a primitive model electrolyte. Comparisons are made with existing Monte Carlo simulations for uncharged and charged electrodes. For 1:1 and 2:1 electrolytes with a charged electrode, the modified Poisson–Boltzmann Theory successfully predicts the singlet ion normalised density functions and the mean electrostatic potential. With the uncharged electrode, the neglect of ion size is more critical and the theoretical predictions are now poor at the higher concentrations.
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A MODIFIED POISSON-Boltzmann STUDY OF THE SINGLET ION DISTRIBUTION AT CONTACT WITH THE ELECTRODE FOR A PLANAR ELECTRIC DOUBLE LAYER.
Collection of Czechoslovak Chemical Communications, 2010Co-Authors: Whasington Silvestre-alcantara, Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:The properties of the singlet ion distributions at and around contact in a restricted primitive model double layer are characterized in the modified Poisson-Boltzmann Theory. Comparisons are made with the corresponding exact Monte Carlo simulation data, the results from the Gouy-Chapman-Stern Theory coupled to an exclusion volume term, and the mean spherical approximation. Particular emphasis is given to the behaviour of the theoretical predictions in relation to the contact value theorem involving the charge profile. The simultaneous behaviour of the coion and counterion contact values is also examined. The performance of the modified Poisson-Boltzmann Theory in regard to the contact value theorems is very reasonable with the contact characteristics showing semi-quantitative or better agreement overall with the simulation results. The exclusion-volume-treated Gouy-Chapman-Stern Theory reveals a fortuitous cancellation of errors, while the mean spherical approximation is poor.
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Monte-Carlo simulation of mixed electrolytes next to a plane charged surface
Journal of Colloid and Interface Science, 2008Co-Authors: Stanisław Lamperski, Christopher W. OuthwaiteAbstract:Monte-Carlo simulations of the electric double layer are performed for two electrolyte mixtures next to a plane, uniformly charged, surface. Simulations are made at parameters corresponding to a Poisson-Boltzmann Theory which is corrected to include the excluded volume effects of the ions. The corrected Poisson-Boltzmann Theory is found to have some deficiencies. The structural properties disagree with simulation results while the Theory can be adjusted to give agreement with experiment for the relative concentration excesses of small univalent counterions.
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Some simulation and modified Poisson–Boltzmann Theory results for the contact values of an electrolyte near a charged electrode
Journal of Electroanalytical Chemistry, 2006Co-Authors: Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:Abstract Since the development of a contact value theorem by Henderson et al. it has been known that the prediction of the venerable Gouy–Chapman (GC) Theory for the contact value of the density profile of an electrolyte near an electrode is incorrect. The more recent semi-empirical work of Fawcett and Henderson and the simulations of Boda and Henderson have shown that the contact value of the charge profile at low electrode charge is also given incorrectly by the GC Theory, at least for a binary symmetric restricted primitive model electrolyte. In the present study we examine the contact values of the profiles of the double layer formed by the electrolyte species in a binary symmetric restricted primitive model electrolyte as a function of the electrode charge by means of simulation. It is difficult to extract detailed information from simulation values of the density and charge profiles at large electrode charge because the contact values of these profiles are dominated by the large quadratic term in the electrode charge. However, we find from our simulations for a fairly wide range of concentrations and electrode charges, that the product of the counterion and coion profiles is a sensitive probe with which to study the double layer because it is a direct test of the basis of the GC approximation that the counterion and coion profiles are exponentials of ± zeψ ( x )/ kT and so have a product that is identically one. We find that this product is not one or even a constant as the electrode charge is varied and, thus, the GC contact values do not agree even qualitatively with the simulation results. In contrast, the modified Poisson–Boltzmann Theory is quite successful in accounting for the behavior of this product.
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Planar electric double layer for a restricted primitive model electrolyte at low temperatures.
Langmuir, 2006Co-Authors: Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:Monte Carlo simulation and the modified Poisson-Boltzmann Theory are used to investigate the planar electric double layer for a restricted primitive model electrolyte at low temperatures. Capacitance as a function of temperature at low surface charge is determined for 1:1, 2:2, 2:1, and 3:1 electrolytes. Negative adsorption can occur for 1:1 electrolytes at low surface charge with low electrolyte concentration. The 1:1 electrolyte diffuse layer potential as a function of surface charge displays a maximum at low densities. At high densities, the diffuse layer potential is negative with a negative slope. The Gouy-Chapman-Stern Theory fails in this low-temperature regime, whereas the modified Poisson-Boltzmann Theory is fairly successful in this regard.
Douglas Henderson - One of the best experts on this subject based on the ideXlab platform.
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A MODIFIED POISSON-Boltzmann STUDY OF THE SINGLET ION DISTRIBUTION AT CONTACT WITH THE ELECTRODE FOR A PLANAR ELECTRIC DOUBLE LAYER.
Collection of Czechoslovak Chemical Communications, 2010Co-Authors: Whasington Silvestre-alcantara, Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:The properties of the singlet ion distributions at and around contact in a restricted primitive model double layer are characterized in the modified Poisson-Boltzmann Theory. Comparisons are made with the corresponding exact Monte Carlo simulation data, the results from the Gouy-Chapman-Stern Theory coupled to an exclusion volume term, and the mean spherical approximation. Particular emphasis is given to the behaviour of the theoretical predictions in relation to the contact value theorem involving the charge profile. The simultaneous behaviour of the coion and counterion contact values is also examined. The performance of the modified Poisson-Boltzmann Theory in regard to the contact value theorems is very reasonable with the contact characteristics showing semi-quantitative or better agreement overall with the simulation results. The exclusion-volume-treated Gouy-Chapman-Stern Theory reveals a fortuitous cancellation of errors, while the mean spherical approximation is poor.
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some simulation and modified poisson Boltzmann Theory results for the contact values of an electrolyte near a charged electrode
Journal of Electroanalytical Chemistry, 2007Co-Authors: L B Bhuiyan, C. W. Outhwaite, Douglas HendersonAbstract:Abstract Since the development of a contact value theorem by Henderson et al. it has been known that the prediction of the venerable Gouy–Chapman (GC) Theory for the contact value of the density profile of an electrolyte near an electrode is incorrect. The more recent semi-empirical work of Fawcett and Henderson and the simulations of Boda and Henderson have shown that the contact value of the charge profile at low electrode charge is also given incorrectly by the GC Theory, at least for a binary symmetric restricted primitive model electrolyte. In the present study we examine the contact values of the profiles of the double layer formed by the electrolyte species in a binary symmetric restricted primitive model electrolyte as a function of the electrode charge by means of simulation. It is difficult to extract detailed information from simulation values of the density and charge profiles at large electrode charge because the contact values of these profiles are dominated by the large quadratic term in the electrode charge. However, we find from our simulations for a fairly wide range of concentrations and electrode charges, that the product of the counterion and coion profiles is a sensitive probe with which to study the double layer because it is a direct test of the basis of the GC approximation that the counterion and coion profiles are exponentials of ± zeψ ( x )/ kT and so have a product that is identically one. We find that this product is not one or even a constant as the electrode charge is varied and, thus, the GC contact values do not agree even qualitatively with the simulation results. In contrast, the modified Poisson–Boltzmann Theory is quite successful in accounting for the behavior of this product.
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Some simulation and modified Poisson–Boltzmann Theory results for the contact values of an electrolyte near a charged electrode
Journal of Electroanalytical Chemistry, 2006Co-Authors: Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:Abstract Since the development of a contact value theorem by Henderson et al. it has been known that the prediction of the venerable Gouy–Chapman (GC) Theory for the contact value of the density profile of an electrolyte near an electrode is incorrect. The more recent semi-empirical work of Fawcett and Henderson and the simulations of Boda and Henderson have shown that the contact value of the charge profile at low electrode charge is also given incorrectly by the GC Theory, at least for a binary symmetric restricted primitive model electrolyte. In the present study we examine the contact values of the profiles of the double layer formed by the electrolyte species in a binary symmetric restricted primitive model electrolyte as a function of the electrode charge by means of simulation. It is difficult to extract detailed information from simulation values of the density and charge profiles at large electrode charge because the contact values of these profiles are dominated by the large quadratic term in the electrode charge. However, we find from our simulations for a fairly wide range of concentrations and electrode charges, that the product of the counterion and coion profiles is a sensitive probe with which to study the double layer because it is a direct test of the basis of the GC approximation that the counterion and coion profiles are exponentials of ± zeψ ( x )/ kT and so have a product that is identically one. We find that this product is not one or even a constant as the electrode charge is varied and, thus, the GC contact values do not agree even qualitatively with the simulation results. In contrast, the modified Poisson–Boltzmann Theory is quite successful in accounting for the behavior of this product.
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Planar electric double layer for a restricted primitive model electrolyte at low temperatures.
Langmuir, 2006Co-Authors: Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:Monte Carlo simulation and the modified Poisson-Boltzmann Theory are used to investigate the planar electric double layer for a restricted primitive model electrolyte at low temperatures. Capacitance as a function of temperature at low surface charge is determined for 1:1, 2:2, 2:1, and 3:1 electrolytes. Negative adsorption can occur for 1:1 electrolytes at low surface charge with low electrolyte concentration. The 1:1 electrolyte diffuse layer potential as a function of surface charge displays a maximum at low densities. At high densities, the diffuse layer potential is negative with a negative slope. The Gouy-Chapman-Stern Theory fails in this low-temperature regime, whereas the modified Poisson-Boltzmann Theory is fairly successful in this regard.
Lutful Bari Bhuiyan - One of the best experts on this subject based on the ideXlab platform.
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The point ion modified Poisson–Boltzmann Theory for a planar electric double layer with different permittivities for the electrode, inner layer and diffuse layer
Molecular Physics, 2014Co-Authors: Christopher W. Outhwaite, Lutful Bari BhuiyanAbstract:The planar electric double layer is modelled by an electrode, inner layer and diffuse layer whose constant permittivities differ. A point ion modified Poisson–Boltzmann analysis is made of the model with the ions in the diffuse layer having a distance of closest approach to the electrode, which is greater than the inner layer thickness and mimics the ion radius of a primitive model electrolyte. Comparisons are made with existing Monte Carlo simulations for uncharged and charged electrodes. For 1:1 and 2:1 electrolytes with a charged electrode, the modified Poisson–Boltzmann Theory successfully predicts the singlet ion normalised density functions and the mean electrostatic potential. With the uncharged electrode, the neglect of ion size is more critical and the theoretical predictions are now poor at the higher concentrations.
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A MODIFIED POISSON-Boltzmann STUDY OF THE SINGLET ION DISTRIBUTION AT CONTACT WITH THE ELECTRODE FOR A PLANAR ELECTRIC DOUBLE LAYER.
Collection of Czechoslovak Chemical Communications, 2010Co-Authors: Whasington Silvestre-alcantara, Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:The properties of the singlet ion distributions at and around contact in a restricted primitive model double layer are characterized in the modified Poisson-Boltzmann Theory. Comparisons are made with the corresponding exact Monte Carlo simulation data, the results from the Gouy-Chapman-Stern Theory coupled to an exclusion volume term, and the mean spherical approximation. Particular emphasis is given to the behaviour of the theoretical predictions in relation to the contact value theorem involving the charge profile. The simultaneous behaviour of the coion and counterion contact values is also examined. The performance of the modified Poisson-Boltzmann Theory in regard to the contact value theorems is very reasonable with the contact characteristics showing semi-quantitative or better agreement overall with the simulation results. The exclusion-volume-treated Gouy-Chapman-Stern Theory reveals a fortuitous cancellation of errors, while the mean spherical approximation is poor.
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Some simulation and modified Poisson–Boltzmann Theory results for the contact values of an electrolyte near a charged electrode
Journal of Electroanalytical Chemistry, 2006Co-Authors: Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:Abstract Since the development of a contact value theorem by Henderson et al. it has been known that the prediction of the venerable Gouy–Chapman (GC) Theory for the contact value of the density profile of an electrolyte near an electrode is incorrect. The more recent semi-empirical work of Fawcett and Henderson and the simulations of Boda and Henderson have shown that the contact value of the charge profile at low electrode charge is also given incorrectly by the GC Theory, at least for a binary symmetric restricted primitive model electrolyte. In the present study we examine the contact values of the profiles of the double layer formed by the electrolyte species in a binary symmetric restricted primitive model electrolyte as a function of the electrode charge by means of simulation. It is difficult to extract detailed information from simulation values of the density and charge profiles at large electrode charge because the contact values of these profiles are dominated by the large quadratic term in the electrode charge. However, we find from our simulations for a fairly wide range of concentrations and electrode charges, that the product of the counterion and coion profiles is a sensitive probe with which to study the double layer because it is a direct test of the basis of the GC approximation that the counterion and coion profiles are exponentials of ± zeψ ( x )/ kT and so have a product that is identically one. We find that this product is not one or even a constant as the electrode charge is varied and, thus, the GC contact values do not agree even qualitatively with the simulation results. In contrast, the modified Poisson–Boltzmann Theory is quite successful in accounting for the behavior of this product.
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Planar electric double layer for a restricted primitive model electrolyte at low temperatures.
Langmuir, 2006Co-Authors: Lutful Bari Bhuiyan, Christopher W. Outhwaite, Douglas HendersonAbstract:Monte Carlo simulation and the modified Poisson-Boltzmann Theory are used to investigate the planar electric double layer for a restricted primitive model electrolyte at low temperatures. Capacitance as a function of temperature at low surface charge is determined for 1:1, 2:2, 2:1, and 3:1 electrolytes. Negative adsorption can occur for 1:1 electrolytes at low surface charge with low electrolyte concentration. The 1:1 electrolyte diffuse layer potential as a function of surface charge displays a maximum at low densities. At high densities, the diffuse layer potential is negative with a negative slope. The Gouy-Chapman-Stern Theory fails in this low-temperature regime, whereas the modified Poisson-Boltzmann Theory is fairly successful in this regard.
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Structure functions of rod-like DNA fragment and polystyrenesulfonate solutions in the modified Poisson-Boltzmann Theory
Physica A-statistical Mechanics and Its Applications, 1996Co-Authors: Lutful Bari Bhuiyan, Christopher W. Outhwaite, J. Van Der MaarelAbstract:The partial structure functions of aqueous solutions of rod-like DNA fragments and polystyrenesulfonic acid are calculated in the modified Poisson-Boltzmann Theory. The cylindrical cell model appropriate for linear polyelectrolyte solutions with monovalent counterions and without any added salt is utilized. The predicted results are compared with the corresponding results from the classical Poisson-Boltzmann Theory, and experimental small angle neutron scattering data obtained in the monomer concentration range 0.05-0.2 mol/dm3. It is seen that both the modified Poisson-Boltzmann and the Poisson-Boltzmann results lead to a very good fit to the experimental structure functions.
Derek Y. C. Chan - One of the best experts on this subject based on the ideXlab platform.
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a simple algorithm for calculating electrical double layer interactions in asymmetric electrolytes poisson Boltzmann Theory
Joint International Conference on Information Sciences, 2002Co-Authors: Derek Y. C. ChanAbstract:Abstract A simple, general, and numerically robust algorithm is presented for calculating the disjoining pressure and interaction free energy per unit area between two identically charged flat plates due to electrical double layer interactions according to the nonlinear Poisson–Boltzmann Theory. The result is applicable to electrolytes with any number of ionic species having any combination of valencies as well as to constant potential, constant charge, or charge regulation boundary conditions on the plates. The algorithm is very simple to implement on commonly available numerical software environments and is therefore particularly suitable for use in data analysis.
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Long-range electrostatic attractions between identically charged particles in confined geometries and the Poisson-Boltzmann Theory
Langmuir, 2000Co-Authors: John E. Sader, Derek Y. C. ChanAbstract:There has been much speculation about the origin of long-range electrostatic attractions between identical colloidal particles in confined geometries. Recently, we proved that such attractive interactions are not to be found in the well-established Poisson−Boltzmann Theory, when the particles are immersed in a 1:1 electrolyte whose average ion concentrations are equal. A subsequent approximate analytical investigation (Europhys. Lett. 1999, 46, 407−413) has suggested that such attractive interactions result from a combination of the effects of confinement, imbalance of the average ionic concentrations, and polarization effects in the confining surface. Consequently, we extend our previous proof to encompass the general case of an electrolyte possessing any number of ionic species, where there is no restriction on their average concentrations. In so doing, we rigorously prove that within the framework of the Poisson−Boltzmann Theory the interaction between identical colloidal particles is never attractive,...
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Computation of forces between spherical colloidal particles : nonlinear Poisson-Boltzmann Theory
Journal of Colloid and Interface Science, 1994Co-Authors: Steven L Carnie, Derek Y. C. Chan, Jim StankovichAbstract:Abstract A numerical scheme has been developed to calculate the electrical double-layer force between two spherical colloidal particles based on the nonlinear Poisson-Boltzmann Theory. Results for identical spheres interacting under constant surface potential, constant surface charge, or equilibrium dissociation of ionizable surface groups are given. The method can be readily applied to the case of nonidentical spheres. These results serve as benchmarks for delineating the accuracy of approximate methods for the calculation of the interaction between particles based on the Deryaguin approximation, the superposition approximation, and the Hogg-Healy-Fuerstenau approximation, as well as numerical solutions of the problem based on the linearized Poisson-Boltzmann (Debye-Huckel) Theory.
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interaction free energy between identical spherical colloidal particles the linearized poisson Boltzmann Theory
Journal of Colloid and Interface Science, 1993Co-Authors: Steven L Carnie, Derek Y. C. ChanAbstract:Abstract The linearized Poisson-Boltzmann Theory is used to calculate the electrical double-layer interaction free energy between identical spherical colloidal particles. Results are given for interaction under conditions of constant surface potential, constant surface charge, and for the case in which charge regulation due to the dissociation of surface groups may be modeled by a linear relationship between the surface charge and the surface potential. Accurate results are obtained using a two-center expansion for the solution of the linearized Poisson-Boltzmann equation and numerical implementations of the algorithm are given for a full range of particles sizes, κa, and particle separations, κh.
Steven L Carnie - One of the best experts on this subject based on the ideXlab platform.
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Interactions between Two Spherical Particles with Nonuniform Surface Potentials: The Linearized Poisson-Boltzmann Theory.
Journal of Colloid and Interface Science, 1999Co-Authors: Jim Stankovich, Steven L CarnieAbstract:Abstract Using the linearized Poisson–Boltzmann Theory, electrical double layer interactions are calculated between two nonuniform spherical colloidal particles with mean potential zero. Most results are for the case of surface potentials modeled by a single spherical harmonic and aligned relative to each other. As previously observed for flat surfaces, interactions decay more rapidly as a function of separation between spheres with such periodic, “single-mode” potentials than between spheres with uniform potentials. The Deryaguin approximation for single-mode spheres is tested and calculations are made of the force and torque that particles in a doublet exert on one another. Many of the concepts developed from models of flat plates with periodic aligned surface potentials are shown to be useful in this more general case. Attempts to explain recent differential electrophoresis experiments on the basis of nonuniform double layers fail in that the maximum restraining torques produced under plausible assumptions about the amplitude of nonuniformity are an order of magnitude smaller than those implied by the measurements. The main reason for this is that the torques are too small at the separations characteristic of a secondary minimum. The effect of misalignment of single-mode spheres is assessed by calculating the distribution of interaction energies over a set of relative orientations generated by quasi-random sampling. Finally, a method for generating spheres with “random” surface potentials is devised and potentials of mean force are calculated for pairs of spheres with such surface potentials. Comparison with the single-mode case is kept at a qualitative level, in the absence of detailed knowledge of how realistic such “random” surfaces are.
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Computation of forces between spherical colloidal particles : nonlinear Poisson-Boltzmann Theory
Journal of Colloid and Interface Science, 1994Co-Authors: Steven L Carnie, Derek Y. C. Chan, Jim StankovichAbstract:Abstract A numerical scheme has been developed to calculate the electrical double-layer force between two spherical colloidal particles based on the nonlinear Poisson-Boltzmann Theory. Results for identical spheres interacting under constant surface potential, constant surface charge, or equilibrium dissociation of ionizable surface groups are given. The method can be readily applied to the case of nonidentical spheres. These results serve as benchmarks for delineating the accuracy of approximate methods for the calculation of the interaction between particles based on the Deryaguin approximation, the superposition approximation, and the Hogg-Healy-Fuerstenau approximation, as well as numerical solutions of the problem based on the linearized Poisson-Boltzmann (Debye-Huckel) Theory.
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interaction free energy between identical spherical colloidal particles the linearized poisson Boltzmann Theory
Journal of Colloid and Interface Science, 1993Co-Authors: Steven L Carnie, Derek Y. C. ChanAbstract:Abstract The linearized Poisson-Boltzmann Theory is used to calculate the electrical double-layer interaction free energy between identical spherical colloidal particles. Results are given for interaction under conditions of constant surface potential, constant surface charge, and for the case in which charge regulation due to the dissociation of surface groups may be modeled by a linear relationship between the surface charge and the surface potential. Accurate results are obtained using a two-center expansion for the solution of the linearized Poisson-Boltzmann equation and numerical implementations of the algorithm are given for a full range of particles sizes, κa, and particle separations, κh.