Computation of methodology-independent single-ion solvation properties from molecular simulations. IV. Optimized Lennard-Jones interaction parameter sets for the alkali and halide ions in water
- Laboratory of Physical Chemistry, ETH Zuerich, CH-8093 Zuerich (Switzerland)
The raw single-ion solvation free energies computed from atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions and treatment of electrostatic interactions used during these simulations. However, as shown recently [M. A. Kastenholz and P. H. Huenenberger, J. Chem. Phys. 124, 224501 (2006); M. M. Reif and P. H. Huenenberger, J. Chem. Phys. 134, 144103 (2010)], the application of appropriate correction terms permits to obtain methodology-independent results. The corrected values are then exclusively characteristic of the underlying molecular model including in particular the ion-solvent van der Waals interaction parameters, determining the effective ion size and the magnitude of its dispersion interactions. In the present study, the comparison of calculated (corrected) hydration free energies with experimental data (along with the consideration of ionic polarizabilities) is used to calibrate new sets of ion-solvent van der Waals (Lennard-Jones) interaction parameters for the alkali (Li{sup +}, Na{sup +}, K{sup +}, Rb{sup +}, Cs{sup +}) and halide (F{sup -}, Cl{sup -}, Br{sup -}, I{sup -}) ions along with either the SPC or the SPC/E water models. The experimental dataset is defined by conventional single-ion hydration free energies [Tissandier et al., J. Phys. Chem. A 102, 7787 (1998); Fawcett, J. Phys. Chem. B 103, 11181] along with three plausible choices for the (experimentally elusive) value of the absolute (intrinsic) hydration free energy of the proton, namely, {Delta}G{sub hyd} {sup O-minus} [H{sup +}]=-1100, -1075 or -1050 kJ mol{sup -1}, resulting in three sets L, M, and H for the SPC water model and three sets L{sub E}, M{sub E}, and H{sub E} for the SPC/E water model (alternative sets can easily be interpolated to intermediate {Delta}G{sub hyd} {sup O-minus} [H{sup +}] values). The residual sensitivity of the calculated (corrected) hydration free energies on the volume-pressure boundary conditions and on the effective ionic radius entering into the calculation of the correction terms is also evaluated and found to be very limited. Ultimately, it is expected that comparison with other experimental ionic properties (e.g., derivative single-ion solvation properties, as well as data concerning ionic crystals, melts, solutions at finite concentrations, or nonaqueous solutions) will permit to validate one specific set and thus, the associated {Delta}G{sub hyd} {sup O-minus} [H{sup +}] value (atomistic consistency assumption). Preliminary results (first-peak positions in the ion-water radial distribution functions, partial molar volumes of ionic salts in water, and structural properties of ionic crystals) support a value of {Delta}G{sub hyd} {sup O-minus} [H{sup +}] close to -1100 kJ{center_dot}mol{sup -1}.
- OSTI ID:
- 21560153
- Journal Information:
- Journal of Chemical Physics, Vol. 134, Issue 14; Other Information: DOI: 10.1063/1.3567022; (c) 2011 American Institute of Physics; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
74 ATOMIC AND MOLECULAR PHYSICS
BOUNDARY-VALUE PROBLEMS
BROMINE IONS
CESIUM IONS
CHLORINE IONS
FLUORINE IONS
FREE ENERGY
HALIDES
HYDRATION
HYDROGEN IONS 1 PLUS
INTERACTIONS
IODINE IONS
LENNARD-JONES POTENTIAL
LITHIUM IONS
POTASSIUM IONS
RUBIDIUM IONS
SIMULATION
SODIUM IONS
SOLUTIONS
VAN DER WAALS FORCES
WATER
CATIONS
CHARGED PARTICLES
DISPERSIONS
ENERGY
HALOGEN COMPOUNDS
HOMOGENEOUS MIXTURES
HYDROGEN COMPOUNDS
HYDROGEN IONS
IONS
MIXTURES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
POTENTIALS
SOLVATION
THERMODYNAMIC PROPERTIES