Theoretical Calculation of the Water Ion Product KW

Tawa, Gregory J.; Pratt, Lawrence R.

doi:10.1021/ja00110a019

Cited by 47 publications

(59 citation statements)

References 39 publications

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“…An important facet of this issue is that the radii parameters in the dielectric models, which are initially established fully empirically, depend on solution thermodynamic conditions such as temperature, pressure, and composition, and on solute conformation [69][70][71][72][73]. The Li + (aq) case gives direct example of this difficulty: the partial molar volume of the Li + (aq) is negative, -6.4 cm 3 /mol [66].…”

Section: Variations Of Hydration Free Energiesmentioning

confidence: 99%

“…Use of the Born model directly without an empirical attribution of pressure dependence to the Born radii but with the measured pressure dependence of the solvent dielectric constant [89] contributes -0.3 cm 3 /mol, a negligible magnitude here. The density dependences of hydration free energies for the auto-dissociation reaction 2H 2 O ⇀ ↽ H 3 O + + OH − in water were studied some time ago [71] from the point of view of a dielectric continuum model with the conclusion that a non-trivial density dependence was required of the dielectric model by the experimental data. In contrast, the formula Eq.…”

Section: Pressure Variation Of Hydration Free Energiesmentioning

confidence: 99%

“…In this way, quasi-chemical developments also address lingering foundational problems with dielectric models in applications to solution chemistry. Parameterization of dielectric models to describe variations of hydration free energies with temperature, pressure, composition, and solute conformation [69][70][71][72][73] are as relevant as the foundational issues. For the quasi-chemical models used here, some empirical parameterization is still required for the ligands that form the exterior of the complex.…”

Section: Dielectric Models and Electronic Structure Calculations For mentioning

confidence: 99%

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Quasi-chemical theory and implicit solvent models for simulations

Pratt

Rempe

1999

Simulation and Theory of Electrostatic Interactions in Solution

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100

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Abstract. A statistical thermodynamic development is given of a new implicit solvent model that avoids the traditional system size limitations of computer simulation of macromolecular solutions with periodic boundary conditions. This implicit solvent model is based upon the quasi-chemical approach, distinct from the common integral equation trunk of the theory of liquid solutions. The idea is geometrically to define molecular-scale regions attached to the solute macromolecule of interest. It is then shown that the quasi-chemical approach corresponds to calculation of a partition function for an ensemble analogous to, but not the same as, the grand canonical ensemble for the solvent in that proximal volume. The distinctions include: (a) the defined proximal volume -the volume of the system that is treated explicitly -resides on the solute; (b) the solute conformational fluctuations are prescribed by statistical thermodynamics and the proximal volume can fluctuate if the solute conformation fluctuates; and (c) the interactions of the system with more distant, extra-system solution species are treated by approximate physical theories such as dielectric continuum theories. The theory makes a definite connection to statistical thermodynamic properties of the solution and fully dictates volume fluctuations, which can be awkward in more ambitious approaches. It is argued that with the close solvent neighbors treated explicitly the thermodynamic results become less sensitive to the inevitable approximations in the implicit solvent theories of the more distant interactions. The physical content of this theory is the hypothesis that a small set of solvent molecules are decisive for these solvation problems. A detailed derivation of the quasi-chemical theory escorts the development of this proposal. The numerical application of the quasi-chemical treatment to Li + ion hydration in liquid water is used to motivate and exemplify the quasi-chemical theory. Those results underscore the fact that the quasi-chemical approach refines the path for utilization of ion-water cluster results for the statistical thermodynamics of solutions.

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Section: Variations Of Hydration Free Energiesmentioning

confidence: 99%

Section: Pressure Variation Of Hydration Free Energiesmentioning

confidence: 99%

Section: Dielectric Models and Electronic Structure Calculations For mentioning

confidence: 99%

See 1 more Smart Citation

Quasi-chemical theory and implicit solvent models for simulations

Pratt

Rempe

1999

Simulation and Theory of Electrostatic Interactions in Solution

Self Cite

100

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“…Continuum dielectric solvation modeling is an appropriate approach to studying these solution processes; it is physical, computationally feasible, and can provide a basis for more molecular theory [9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Molecular modeling of trifluoromethanesulfonic acid for solvation theory

Paddison

Pratt

Zawodzinski

et al. 1998

Fluid Phase Equilibria

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Reported here are theoretical calculations on the trifluoromethanesulfonic (triflic) acid and water molecules, establishing molecular scale information necessary to molecular modeling of the structure, thermodynamics, and ionic transport of Nafion R membranes. The optimized geometry determined for the isolated triflic acid molecule, obtained from ab initio molecular orbital calculations, agrees with previous studies. In order to characterize side chain flexibility and accessibility of the acid proton, potential energy and free energy surfaces for rotation of both carbon-sulfur and sulfuroxygen(hydroxyl) bonds are presented. A continuum dielectric solvation model is used to obtain free energies of electrostatic interaction with the solvent. Electrostatic solvation is predicted to reduce the free energy barrier to rotation of the F3C-SO3 bond to about 2.7 kcal/mol. This electrostatic effect is associated with slight additional polarization of the CF bond in the eclipsed conformation. The energetic barrier to rotation of the acid hydroxyl group away from the sulfonic acid oxygen plane, out into the solvent is substantially flattened by electrostatic solvation effects. The maximum free energy change for those solvent accessible proton conformations is less than one kcal/mol. We carried out additional ab initio electronic structure calculations with a probe water molecule interacting with the triflic acid. The minimum energy structures found here for the triflic acid molecule with the probe water revise results reported previously. To investigate the reaction path for abstraction of a proton from triflic acid, we found minimum energy structures, energies, and free energies for: (a) a docked configuration of triflate anion and hydronium cation and (b) a transition state for proton interchange between triflic acid and a water molecule. Those configurations are structurally similar but energetically substantially different. The activation free energy for that proton interchange is predicted to be 4.7 kcal/mol above the reaction end-points.

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“…This correlation length is strongly influenced by temperature-dependent fluctuations of the density and orientation of the solvent molecules. See also the work on aqueous acid reported in [53], which implied a small increase of effective solute radius with temperature. For related discussion of cavity fluctuations see [44].…”

Section: %=(2) +(3$mentioning

confidence: 95%

Advanced dielectric continuum models of solvation, their connection to microscopic solvent models, and application to electron transfer reactions

Rostov

Basilevsky

Newton

1999

Simulation and Theory of Electrostatic Interactions in Solution

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Abstract. Some recent advances in dielectric continuum models for static and dynamic aspects of molecular solvation are discussed, and connections with molecular-level solvent models are noted. The traditional Bom-Onsager-Kkkwood (BKO) model is compared to a more flexible model (the so-called frequency-resolved cavity model (FRCM)) which assigns distinct inner and outer solute cavities in accommodating, respective] y, the inertialess (optical) and inertial solvent response. Sample calculations of solvent reorganization energy (,&) are presented for various thermal and optical electron transfer (ET) processes, based on self-consistent reaction field models using molecular orbital (MO) or configuration interaction (CI) solvent wave fimctions.

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Theoretical Calculation of the Water Ion Product KW

Cited by 47 publications

References 39 publications

Quasi-chemical theory and implicit solvent models for simulations

Quasi-chemical theory and implicit solvent models for simulations

Molecular modeling of trifluoromethanesulfonic acid for solvation theory

Advanced dielectric continuum models of solvation, their connection to microscopic solvent models, and application to electron transfer reactions

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