Meaning and Measurability of Single‐Ion Activities, the Thermodynamic Foundations of pH, and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials

Rockwood, Alan L.

doi:10.1002/cphc.201500044

Cited by 31 publications

(28 citation statements)

References 32 publications

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“…The calculation of neutral-set or real solvation free energies by simulation offers two main advantages: 22 (i) they can be directly compared to experimental data; (ii) they alleviate methodological difficulties related to the calculation of the potential from the sampled configurations (M-vs. P-conventions). However, real solvation free energies intermingle two distinct physical effects, [23][24][25] namely, the chemical solvation of the ion by the surrounding solvent molecules and the work required for the ion to penetrate the solvent surface. The former effect is local, predominantly quadratic in the ion charge (besides the linear component related to the potential at the uncharged cavity 17 ) and relevant in terms of microscopic properties (e.g., solvation strength and its influence on the spectroscopic or reactivity properties of the ion).…”

Section: Discussionmentioning

confidence: 99%

“…As a result, it delivers bulk-liquid potentials and single-ion solvation free energies that are intrinsic, 1,2,15-17 i.e., potentials measured outside the solvent molecules and free energies excluding the contribution from crossing the polarized solvent surface. In particular, comparison of the latter free energies with measurable real 1,2,15-22 quantities (including the effect of the surface potential 17,[22][23][24][25][26] gives in principle access to C • wat . However, the Born model has two major shortcomings: (i) it is inaccurate in terms of short-range ion-solvent interactions (omission of electrostriction, dielectric saturation, solvation structure, chargeasymmetry effects, and specific ion-solvent interactions such as many-body effects, electronic polarization, charge transfer, and hydrogen-bonding; see Sec.…”

Section: Introductionmentioning

confidence: 99%

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Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Hofer

Hünenberger

2018

The Journal of Chemical Physics

104

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The absolute intrinsic hydration free energy G • H + ,wat of the proton, the surface electric potential jump χ • wat upon entering bulk water, and the absolute redox potential V • H + ,wat of the reference hydrogen electrode are cornerstone quantities for formulating single-ion thermodynamics on absolute scales. They can be easily calculated from each other but remain fundamentally elusive, i.e., they cannot be determined experimentally without invoking some extra-thermodynamic assumption (ETA). The Born model provides a natural framework to formulate such an assumption (Born ETA), as it automatically factors out the contribution of crossing the water surface from the hydration free energy. However, this model describes the short-range solvation inaccurately and relies on the choice of arbitrary ion-size parameters. In the present study, both shortcomings are alleviated by performing first-principle calculations of the hydration free energies of the sodium (Na + ) and potassium (K + ) ions. The calculations rely on thermodynamic integration based on quantum-mechanical molecular-mechanical (QM/MM) molecular dynamics (MD) simulations involving the ion and 2000 water molecules. The ion and its first hydration shell are described using a correlated ab initio method, namely resolution-of-identity second-order Møller-Plesset perturbation (RIMP2). The next hydration shells are described using the extended simple point charge water model (SPC/E). The hydration free energy is first calculated at the MM level and subsequently increased by a quantization term accounting for the transformation to a QM/MM description. It is also corrected for finite-size, approximate-electrostatics, and potentialsummation errors, as well as standard-state definition. These computationally intensive simulations provide accurate first-principle estimates for G • H + ,wat , χ • wat , and V • H + ,wat , reported with statistical errors based on a confidence interval of 99%. The values obtained from the independent Na + and K + simulations are in excellent agreement. In particular, the difference between the two hydration free energies, which is not an elusive quantity, is 73.9 ± 5.4 kJ mol 1 (K + minus Na + ), to be compared with the experimental value of 71.7 ± 2.8 kJ mol 1 . The calculated values of G • H + ,wat , χ • wat , and V • H + ,wat ( 1096.7 ± 6.1 kJ mol 1 , 0.10 ± 0.10 V, and 4.32 ± 0.06 V, respectively, averaging over the two ions) are also in remarkable agreement with the values recommended by Reif and Hünenberger based on a thorough analysis of the experimental literature ( 1100 ± 5 kJ mol 1 , 0.13 ± 0.10 V, and 4.28 ± 0.13 V, respectively). The QM/MM MD simulations are also shown to provide an accurate description of the hydration structure, dynamics, and energetics. Published by AIP Publishing.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Hofer

Hünenberger

2018

The Journal of Chemical Physics

104

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“…These processes are understood in qualitative, or even semi-quantitative terms, but to give a fully complete and accurate energy accounting one would need to know quantities such as partial molar entropies of ions, and these are only accessible via reactions analogous to Equation (64) in combination with knowledge of partial molar electronic entropies of metals. Similarly, the evaluation of the Gibbs free energy of the process must include single ion activities or equivalent information [18].…”

Section: Applications and Discussionmentioning

confidence: 99%

Partial Molar Entropy and Partial Molar Heat Capacity of Electrons in Metals and Superconductors

Rockwood¹

2016

JMP

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There are at least two valid approaches to the thermodynamics of electrons in metals. One takes a microscopic view, based on models of electrons in metals and superconductor and uses statistical mechanics to calculate the total thermodynamic functions for the model-based system. Another uses partial molar quantities, which is a rigorous thermodynamic method to analyze systems with components that can cross phase boundaries and is particularly useful when applied to a system composed of interacting components. Partial molar quantities have not been widely used in the field of solid state physics. The present paper will explore the application of partial molar electronic entropy and partial molar electronic heat capacity to electrons in metals and superconductors. This provides information that is complementary information from other approaches to the thermodynamics of electrons in metals and superconductors and can provide additional insight into the properties of those materials. Furthermore, the application of partial molar quantities to electrons in metals and superconductors has direct relevance to long-standing problems in other fields, such as the thermodynamics of ions in solution and the thermodynamics of biological energy transformations. A unifying principle between reversible and irreversible thermodynamics is also discussed, including how this relates to the completeness of thermodynamic theory.

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“…Considering the dilute solutions, such that activity coefficients approach unity, [24][25][26] Eqs. (1)-(3) can be transformed to the corresponding Eqs.…”

Section: Theoretical Approachmentioning

confidence: 99%

Quantification of the binding preference of selected dyes at a solid-liquid interface in organized media

Shah

Ali

Bibi

2020

JSCS

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The binding behavior of anionic dyes, acid yellow 17 and acid blue 25, at an activated carbon-liquid interface has been investigated in organized media based on aqueous sodium dodecyl sulfate using differential electronic spectroscopy. The quantification of interactions occurring in the system was realized using a simple physical model, emphasizing the displacement of bound dyes from the carbon surface. The quantities of displaced dyes were comparable; however, acid blue 25 was relatively easily desorbed compared to acid yellow 17. These differences can be attributed to differences in the dye size and hydrophobicity. The model is valid for the premicellar region of the surfactant. The results throw light on some characteristics of solid-liquid interfaces.

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Meaning and Measurability of Single‐Ion Activities, the Thermodynamic Foundations of pH, and the Gibbs Free Energy for the Transfer of Ions between Dissimilar Materials

Cited by 31 publications

References 32 publications

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Absolute proton hydration free energy, surface potential of water, and redox potential of the hydrogen electrode from first principles: QM/MM MD free-energy simulations of sodium and potassium hydration

Partial Molar Entropy and Partial Molar Heat Capacity of Electrons in Metals and Superconductors

Quantification of the binding preference of selected dyes at a solid-liquid interface in organized media

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