“Structure Breaking” Effect of Hydrated Cs<sup>+</sup>

Schwenk, Christian F.; Hofer, Thomas S.; Rode, Bernd M.

doi:10.1021/jp037179v

Cited by 97 publications

(111 citation statements)

References 38 publications

(62 reference statements)

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“…Recently, both ab initio BornOppenheimer and Car-Parrinello MD method have been applied in simulations of hydrated monovalent cation systems. [10][11][12][13][14][15][16] Previous investigations of the Tl(III) ion in aqueous solution 17 have supplied structural details and a hydration energy coinciding with the experimental data. Ligand exchange processes between first and second shell were not observed, while the mean residence time of a ligand (MRT) in the second shell (12.8 ps) is 7.5 times higher than the MRT of pure water, thus classifying Tl(III) ion as a strongly structure-forming ion.…”

Section: Introductionmentioning

confidence: 60%

Tl(I)‐the strongest structure‐breaking metal ion in water? A quantum mechanical/molecular mechanical simulation study

et al. 2007

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Structural and dynamical properties of the Tl(I) ion in dilute aqueous solution have been investigated by ab initio quantum mechanics in combination with molecular mechanics. The first shell plus a part of the second shell were treated by quantum mechanics at Hartree-Fock level, the rest of the system was described by an ab initio constructed potential. The radial distribution functions indicate two different bond lengths (2.79 and 3.16 A) in the first hydration shell, in good agreement with large-angle X-ray scattering and extended X-ray absorption fine structure spectroscopy results. The average first shell coordination number was found as 5.9, and several other structural parameters such as coordination number distributions, angular distribution functions, and tilt- and theta-angle distributions were evaluated. The ion-ligand vibration spectrum and reorientational times were obtained via velocity auto correlation functions. The Tl-O stretching force constant is very weak with 5.0 N m(-1). During the simulation, numerous water exchange processes took place between first and second hydration shell and between second shell and bulk. The mean ligand residence times for the first and second shell were determined as 1.3 and 1.5 ps, respectively, indicating Tl(I) to be a typical "structure-breaker". The calculated hydration energy of -84 +/- 16 kcal mol(-1) agrees well with the experimental value of -81 kcal mol(-1). All data obtained for structure and dynamics of hydrated Tl(I) characterize this ion as a very special case among all monovalent metal ions, being the most potent "structure-breaker", but at the same time forming a distinct second hydration shell and thus having a far-reaching influence on the solvent structure.

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Section: Introductionmentioning

confidence: 60%

Tl(I)‐the strongest structure‐breaking metal ion in water? A quantum mechanical/molecular mechanical simulation study

et al. 2007

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“…The observed differences in waterexchange kinetics between the two ions have been related previously 171,[273][274][275] to the structure-forming nature of Na + and the structure-breaking nature of K + .…”

Section: B Hydration Structure and Dynamicsmentioning

confidence: 99%

“…The QM/MM MD simulations rely on the quantum-mechanical charge field (QMCF) approach, 158,159 which belongs to the family of adaptive QM/MM methods 148,149,160 and has been applied with success in the past to investigations of solvated ions, 153,154 molecules, 161,162 coordination complexes, 163,164 and biomolecular systems. 165,166 Single-determinantal approaches such as ab initio HartreeFock 167,168 (HF) or DFT 169,170 have a limited accuracy/reliability 120,[123][124][125][126][127]155,[171][172][173][174][175][176] in the description of hydration phenomena. Thus, a correlated ab initio method is employed here to describe the QM subsystem (ion and first hydration shell), namely, resolution-of-identity secondorder Møller-Plesset perturbation 177,178 (RIMP2).…”

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

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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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“…The solvation of ions and ion pairs influences the nature of reactions in solution media. [1][2][3][4][5] The concept of two ion pair states, namely, the contact ion pair (CIP) and the solvent separated ion pair (SSIP), was proposed independently by Winstein 6 and by Fuoss. 7 The general scheme for any solvolysis reaction or any reaction that involves participation of solvent can be represented by CA ↔ C + |A¯ ↔ C + || A¯ ↔ C + + A¯ (1) where the C + |A¯ represents the CIP and C + ||A¯ represents the SSIP.…”

Section: Introductionmentioning

confidence: 99%

Model Dependence of Solvent Separated Sodium Chloride Ion Pairs in Water-DMSO Mixtures

Asthana

Chowdhury

Das

et al. 2006

Computational Science – ICCS 2006

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Abstract. Constrained molecular dynamics simulations have been used to investigate ion pairing in water -DMSO mixtures. The potentials of mean force between the sodium -chloride ion pair are constructed by estimating the mean forces between the ion pair at various interionic separations and then integrating the mean forces. Two compositions of the solvent mixture with DMSO mole fractions of 0.21 and 0.35 are considered. Two model potentials for water and DMSO have been considered. One of the main observations is that the contact ion pair which is dominantly present in both the individual solvents is conspicuously absent in the mixture compositions studied. While solvent separated ion pairs dominate in all the mixture compositions, there is a presence of a second solvent separated ion pair in the water-DMSO mixture of composition with mole fraction of DMSO = 0.21. The potentials of mean force are verified by dynamical trajectories of the ion pair. The dynamics of the solvation shells has also been investigated in detail.

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“Structure Breaking” Effect of Hydrated Cs⁺

Cited by 97 publications

References 38 publications

Tl(I)‐the strongest structure‐breaking metal ion in water? A quantum mechanical/molecular mechanical simulation study

Tl(I)‐the strongest structure‐breaking metal ion in water? A quantum mechanical/molecular mechanical simulation study

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

Model Dependence of Solvent Separated Sodium Chloride Ion Pairs in Water-DMSO Mixtures

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“Structure Breaking” Effect of Hydrated Cs+

Cited by 97 publications

References 38 publications

Tl(I)‐the strongest structure‐breaking metal ion in water? A quantum mechanical/molecular mechanical simulation study

Tl(I)‐the strongest structure‐breaking metal ion in water? A quantum mechanical/molecular mechanical simulation study

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

Model Dependence of Solvent Separated Sodium Chloride Ion Pairs in Water-DMSO Mixtures

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“Structure Breaking” Effect of Hydrated Cs⁺