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Hydration free energies of monovalent ions in transferable intermolecular potential four point fluctuating charge water: An assessment of simulation methodology and force field performance and transferability
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10.1063/1.2771550
/content/aip/journal/jcp/127/6/10.1063/1.2771550
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/6/10.1063/1.2771550

Figures

Image of FIG. 1.
FIG. 1.

The dependence of the LJ-decoupling free energy path on the separation-shifted scaling parameter for the ion of set A in TIP4P-FQ water. The bottom curve corresponds to (unmodified interaction). The remaining curves from bottom to top correspond to values ranging from in unit increments. The darker curve with solid points represents the free energy path for a nearly optimal value of .

Image of FIG. 2.
FIG. 2.

Finite-size corrections to the free energy relative to for the ion of set A as a function of system size, plotted in terms of . The solid horizontal line represents an extrapolated free energy of determined from a best fit to the finite-size corrected values of (solid points and error bars) obtained for various system sizes. The dashed curve, dashed line, and dotted curve represent , , and , respectively, for this ion.

Image of FIG. 3.
FIG. 3.

Computed values of for the ion of set A as a function of system size, plotted in terms of . The solid horizontal line represents an extrapolated free energy of determined from a best fit to the finite-size corrected values of (squares) obtained for various system sizes. The upper solid curve is derived from the extrapolated free energy by removing the , , and corrections and is compared with values of obtained by removing the ion self-energy in situ. The lower dashed curve is derived from the extrapolated free energy by removing the and corrections and is compared with values of obtained by decoupling the ionic lattice and manually removing the vacuum self-energy via Eq. (7).

Image of FIG. 4.
FIG. 4.

Dipole and quadrupole moment contributions to the vacuum-liquid interfacial potential for a thick slab of TIP4P-FQ water. The upper dotted curve represents , the potential due to dipole orientational polarization along the direction of the surface normal. The lower dashed curve is the potential due to the molecular quadrupole moment density. The solid curve is the sum of the dipole and quadrupole contributions which is compared to a value of (dotted horizontal line) obtained by direct integration of the charge density .

Image of FIG. 5.
FIG. 5.

Neutral salt energies of the polarizable ion set A in TIP4P-FQ water less than the salt energies of Lamoureux and Roux (Ref. 39) computed in polarizable SWM4-DP water. For each cation, the bars represent each of the four anions , , , and , in order.

Image of FIG. 6.
FIG. 6.

Neutral salt energies of the nonpolarizable ion set E in TIP4P-FQ water less than the salt energies of Jensen and Jorgensen computed in nonpolarizable TIP4P water. For each cation, the bars represent each of the four anions , , , and , in order.

Image of FIG. 7.
FIG. 7.

Neutral salt hydration energies computed using the polarizable ion set A in TIP4P-FQ less than the salt energies derived from the absolute free energies of Kelly et al. For each cation, the bars represent each of the four anions , , , and , in order.

Image of FIG. 8.
FIG. 8.

Salt hydration energies computed using the nonpolarizable ion set E less than the salt energies computed from the absolute free energies of Kelly et al. For each cation, the bars represent each of the four anions , , , and , in order.

Image of FIG. 9.
FIG. 9.

Radial distributions functions for the set A cations computed in TIP4P-FQ water. The corresponding peak positions reported for SWM4-DP water (Table III) are marked for comparison.

Image of FIG. 10.
FIG. 10.

Radial distributions functions for the set A anions computed in TIP4P-FQ water. The corresponding peak positions reported for SWM4-DP water (Table III) are marked for comparison.

Tables

Generic image for table
Table I.

Ion LJ parameters and computed absolute free energies of hydration for monovalent ions in TIP4P-FQ water including various correction terms as described in Sec. II E. As a consequence of our decoupling method, the vacuum self-energy contribution of is already included in . All energies are in units of . Parentheses indicate the standard error of and do not reflect any uncertainties in the applied corrections.

Generic image for table
Table II.

Experimentally derived absolute hydration energies for monovalent ions corresponding to idealized standard states of in the liquid and gas phases. The values are offset so that the absolute hydration free energy for is the same for each set and is equal to . Values for Tissandier et al. containing typographical errors for , , and are substituted with the corrected values as described by Kelly et al. The standard state correction applied by Marcus appears to be inconsistent with that employed in more recent studies; the values listed above have been corrected.

Generic image for table
Table III.

Coordination numbers and positions for the first minimum and maximum of the ion-oxygen radial distribution function of the set A ions in TIP4P-FQ water and in SWM4-DP water. Coordination numbers in the present study are determined by the integration of the RDF to the first minimum.

Generic image for table
Table IV.

Coordination numbers and positions for the first minimum and maximum of the ion-oxygen radial distribution functions of the set E ions in TIP4P-FQ water and in TIP4P water. Coordination numbers in the present study are determined by the integration of the RDF to the first minimum.

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/content/aip/journal/jcp/127/6/10.1063/1.2771550
2007-08-14
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Hydration free energies of monovalent ions in transferable intermolecular potential four point fluctuating charge water: An assessment of simulation methodology and force field performance and transferability
http://aip.metastore.ingenta.com/content/aip/journal/jcp/127/6/10.1063/1.2771550
10.1063/1.2771550
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