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Ab initio molecular dynamics calculations of ion hydration free energies
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10.1063/1.3137054
/content/aip/journal/jcp/130/20/10.1063/1.3137054
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/20/10.1063/1.3137054

Figures

Image of FIG. 1.
FIG. 1.

The binding energies and optimized distances between a molecule and VASP PBE PPs globally scaled by a factor of . [(a) and (c)] ; [(b) and (d)] . The PPs have no core electrons. Dashed lines are cubic spline fits. is meant as a counter example to for gas phase behavior; its behavior in water will not be the focus of this work.

Image of FIG. 2.
FIG. 2.

for as varies. The bare ion contributions, Ewald corrections, and electrostatic potential shift due to the quadrupole moment have been subtracted. Crosses: , ; circles: , ; triangles, same as crosses but are for SPC/E water. The dashed lines are cubic least-squared fits to the crosses and triangles.

Image of FIG. 3.
FIG. 3.

(a) Integrated changes in electron density, , as a function of spatial coordinate for the various values of . and are the densities for the neutral and the charged systems, respectively. All charged species, have been shifted to . Symbols correspond to actual grid points, the continuous lines are cubic interpolations. [(b)–(d)] Isosurface plots of the electron density difference, (, white , blue ), for , 0.6, and 1.0. Periodic boundary conditions apply; the prominent, eight blue spheres represent the (periodically replicated) changes in densities, and some changes in water dipole moments are apparent too. See Sec. II B for technical details.

Image of FIG. 4.
FIG. 4.

Pair correlation functions between and the O (solid line) and H (dashed line) sites of molecules. (a) ; (b) . The instantaneous hydration numbers are depicted in the insets.

Image of FIG. 5.
FIG. 5.

Logarithm of the probability of instantaneous hydration numbers multiplied by thermal energy, in units of kcal/mol. (a) ; (b) . Squares and dashed lines: ; circles and solid lines: . is determined by counting all water oxygen atoms within 2.08, 2.75, 2.90, and 2.92 Å of the four ions, respectively. These distances are determined by locating the first minimum in the ion-water .

Image of FIG. 6.
FIG. 6.

[(a) and (b)] Pair correlation functions between classical force field and the O (solid line) and H (dashed line) sites of PBE molecules. (a) ; (b) . (c) for classical force field as varies. Crosses and triangles are for AIMD and classical force field treatments of water in simulation cells. The bare ion contributions, Ewald corrections, and electrostatic potential shift due to the quadrupole moment have been subtracted. The dashed lines are cubic least-squared fits.

Image of FIG. 7.
FIG. 7.

Pair correlation functions between and the O (solid line) and H (dashed line) sites of molecules. (a) ; (b) . The instantaneous hydration numbers are depicted in the insets.

Image of FIG. 8.
FIG. 8.

for and as varies. The bare ion contributions, Ewald corrections, and global shift in the electrostatic potential due to the quadrupole moment have been accounted for. The dashed lines are cubic least-squared fits.

Tables

Generic image for table
Table I.

hydration free energies using different computational protocols. densities and are in units of and kcal/mol, respectively. Experimental values adjusted for surface potentials and standard state contributions are marked with a dagger (see text).

Generic image for table
Table II.

hydration free energies. The asterisk denotes AIMD adjusted for finite simulation cell size and packing effects (see text). Also listed are for plus . The SPC/E results for and contain the packing correction. densities and are in units of and kcal/mol, respectively. Experimental values adjusted for surface potentials are depicted with a dagger; see text for details.

Generic image for table
Table III.

hydration free energies, and hydration free energy changes. densities and are in units of and kcal/mol, respectively. All simulations are based on the PBE functional, except that the formalism with is applied for Ni predictions marked with an . The asterisk denotes adjusted for packing effects. Experimental values adjusted for surface potentials are depicted with a dagger; see text for details.

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/content/aip/journal/jcp/130/20/10.1063/1.3137054
2009-05-27
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Ab initio molecular dynamics calculations of ion hydration free energies
http://aip.metastore.ingenta.com/content/aip/journal/jcp/130/20/10.1063/1.3137054
10.1063/1.3137054
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