scholarly journals The Born model can accurately describe electrostatic ion solvation

2020 ◽  
Vol 22 (43) ◽  
pp. 25126-25135
Author(s):  
Timothy T. Duignan ◽  
X. S. Zhao
Keyword(s):  
Oxygen Atom ◽  
Linear Response ◽  
Ion Solvation ◽  
Response Model ◽  
Free Energies ◽  
Born Model ◽  
Repulsion Force ◽  
Solvation Free Energies

The solvation free energies of ions in water are consistent with the Born linear response model if the centre on which the ion–water repulsion force acts is moved from the oxygen atom towards the hydrogens.

scholarly journals The Born Model Can Accurately Describe Electrostatic Ion Solvation.

2020 ◽  
Author(s):  
Timothy Duignan ◽  
Xiu Song Zhao
Keyword(s):  
Electrolyte Solutions ◽  
Ion Solvation ◽  
Water Model ◽  
Repulsive Interaction ◽  
Free Energies ◽  
Hydrogen Atoms ◽  
Ionic Charge ◽  
Born Model ◽  
Reasonable Choice ◽  
Solvation Free Energies

<p>Accurate models of the free energies of ions in solution are crucial for understanding and modelling the huge number of important applications where electrolyte solutions play a crucial role such as electrochemical energy storage. The Born model, developed to describe ion solvation free energies, is widely considered to be critically flawed as it predicts a linear response of water to ionic charge, which fails to match water's supposed intrinsic preference to solvate anions over cations. Here, we demonstrate that this asymmetric response observed in simulation is the result of an arbitrary choice that the oxygen atom should be the centre of a water molecule. We show that an alternative and reasonable choice, which places the centre 0.5 Å towards the hydrogen atoms, results in a linear and charge symmetric response of water to ionic charge for a classical water model consistent with the Born model. This asymmetry should therefore be regarded as a property of the short range repulsive interaction not an intrinsic electrostatic property of water. We also show that this new water centre results in a more reasonable neutral cavity potential. </p><p></p>

scholarly journals The Born Model Can Accurately Describe Electrostatic Ion Solvation.

2020 ◽  
Author(s):  
Timothy Duignan ◽  
Xiu Song Zhao
Keyword(s):  
Electrolyte Solutions ◽  
Ion Solvation ◽  
Water Model ◽  
Repulsive Interaction ◽  
Free Energies ◽  
Hydrogen Atoms ◽  
Ionic Charge ◽  
Born Model ◽  
Reasonable Choice ◽  
Solvation Free Energies

<p>Accurate models of the free energies of ions in solution are crucial for understanding and modelling the huge number of important applications where electrolyte solutions play a crucial role such as electrochemical energy storage. The Born model, developed to describe ion solvation free energies, is widely considered to be critically flawed as it predicts a linear response of water to ionic charge, which fails to match water's supposed intrinsic preference to solvate anions over cations. Here, we demonstrate that this asymmetric response observed in simulation is the result of an arbitrary choice that the oxygen atom should be the centre of a water molecule. We show that an alternative and reasonable choice, which places the centre 0.5 Å towards the hydrogen atoms, results in a linear and charge symmetric response of water to ionic charge for a classical water model consistent with the Born model. This asymmetry should therefore be regarded as a property of the short range repulsive interaction not an intrinsic electrostatic property of water. We also show that this new water centre results in a more reasonable neutral cavity potential. </p><p></p>

scholarly journals Real single ion solvation free energies with quantum mechanical simulation

2017 ◽  
Vol 8 (9) ◽  
pp. 6131-6140 ◽  
Author(s):  
Timothy T. Duignan ◽  
Marcel D. Baer ◽  
Gregory K. Schenter ◽  
Christopher J. Mundy
Keyword(s):  
Ion Pairs ◽  
Electrolyte Solutions ◽  
Ion Solvation ◽  
Quantum Mechanical ◽  
Free Energies ◽  
Ongoing Debate ◽  
Mechanical Simulation ◽  
Solvation Free Energies

Single ion solvation free energies are one of the most important properties of electrolyte solutions and yet there is ongoing debate about what these values are. Only the values for neutral ion pairs are known.

scholarly journals Computing Ion Solvation Free Energies Using the Dipolar Poisson Model

2009 ◽  
Vol 113 (17) ◽  
pp. 5694-5697 ◽  
Author(s):  
Patrice Koehl ◽  
Henri Orland ◽  
Marc Delarue
Keyword(s):  
Poisson Model ◽  
Ion Solvation ◽  
Free Energies ◽  
Solvation Free Energies

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

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