Hydration of Sodium(I) and Potassium(I) Revisited: A Comparative QM/MM and QMCF MD Simulation Study of Weakly Hydrated Ions

Azam, Syed Sikander; Hofer, Thomas S.; Randolf, Bernhard R.; Rode, Bernd M.

doi:10.1021/jp8093462

Cited by 78 publications

(54 citation statements)

References 52 publications

(69 reference statements)

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“…The corresponding data of a single sodium ion in water were reported as 2.34 Å for the first and 5.0 Å for the second hydration layer. 39 As expected, the orientation of water molecules around the chloride ion is highly determined by hydrogen bonding, forming a rather weak hydration shell (Fig. 4b).…”

Section: View Article Onlinesupporting

confidence: 72%

Ab initio quantum mechanical simulations confirm the formation of all postulated species in ionic dissociation

Wiedemair

Weiss²,

Rode

2014

Phys. Chem. Chem. Phys.

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A single sodium chloride molecule in aqueous solution was simulated by the ab initio quantum mechanical charge field-molecular dynamics (QMCF-MD) approach. During a series of simulations the solvated molecule (CIP), dissociated solvated ions and -most noticeably -a solvent separated ion pair (SSIP) were observed and the structural and dynamical characteristics of these systems were investigated. In addition to a detailed structural analysis of the observed species, vibrational spectra and charge distributions were calculated to elucidate the mechanism of the NaCl dissociation.

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Section: View Article Onlinesupporting

confidence: 72%

Ab initio quantum mechanical simulations confirm the formation of all postulated species in ionic dissociation

Wiedemair

Weiss²,

Rode

2014

Phys. Chem. Chem. Phys.

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“…Similar to our previous QM/MM MD studies on the Na + and K + ions, 219 the simulated systems consisted of cubic boxes (average edge-length of about L = 3.9 nm) subject to periodic boundary conditions in the isothermal-isobaric (NPT) ensemble at 298.15 K and 1 bar, and encompassing one solute particle along with N S = 2000 water molecules. The consideration of relatively large systems permitted to use a long cutoff distance R C = 1.8 nm, applied here on the basis of interatomic distances.…”

Section: B Thermodynamic Cyclementioning

confidence: 99%

“…In our previous QM/MM MD studies on the Na + and K + ions, 219 basis sets of the LANL2DZ ECP family 254,255 were used for the ions. These basis sets rely on an effective core potential (ECP) accounting for the electrons of the helium shell by means of pre-optimized effective potentials.…”

Section: S(x)mentioning

confidence: 99%

“…The corresponding RDFs g(r) are also shown explicitly (red and blue curves, respectively), both at the MM (solid) and the QM/MM (dashed, curves from Ref. 219) levels. The associated values ofr andg are reported numerically in Table I.…”

Section: J Optimization Of the Lennard-jones Interaction Parametersmentioning

confidence: 99%

“…For these parameter values, the comparison between the MM and QM/MM RDFs (the latter from Ref. 219) is also presented in Fig. 3(b).…”

Section: J Optimization Of the Lennard-jones Interaction Parametersmentioning

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

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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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Hydrated germanium (II): Irregular structural and dynamical properties revealed by a quantum mechanical charge field molecular dynamics study

et al. 2009

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Structural and dynamical properties of Ge (II) in aqueous solution have been investigated using the novel ab initio quantum mechanical charge field (QMCF) molecular dynamics (MD) formalism. The first and second hydration shells were treated by ab initio quantum mechanics at restricted Hartree-Fock (RHF) level using the cc-pVDZ-PP basis set for Ge (II) and Dunning double-zeta plus polarization basis sets for O and H. Besides ligand exchange processes and mean ligand residence times to observe dynamics, tilt- and theta-angle distributions along with an advanced structural parameter, namely radial and angular distribution functions (RAD) for different regions were also evaluated. The combined radial and angular distribution depicted through surface plot and contour map is presented to provide a detailed insight into the density distribution of water molecules around the Ge(2+) ion. A strongly distorted hydration structure with two trigonal pyramidal substructures within the first hydration shell is observed, which demonstrates the lone-pair influence and provides a new basis for the interpretation of the catalytic and pharmacological properties of germanium coordination compounds.

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Hydration of Sodium(I) and Potassium(I) Revisited: A Comparative QM/MM and QMCF MD Simulation Study of Weakly Hydrated Ions

Cited by 78 publications

References 52 publications

Ab initio quantum mechanical simulations confirm the formation of all postulated species in ionic dissociation

Ab initio quantum mechanical simulations confirm the formation of all postulated species in ionic dissociation

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

Hydrated germanium (II): Irregular structural and dynamical properties revealed by a quantum mechanical charge field molecular dynamics study

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