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Hydration of alkali ions from first principles molecular dynamics revisited
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10.1063/1.2424710
/content/aip/journal/jcp/126/3/10.1063/1.2424710
http://aip.metastore.ingenta.com/content/aip/journal/jcp/126/3/10.1063/1.2424710

Figures

Image of FIG. 1.
FIG. 1.

Radial distribution functions (a) , (b) , (c) , and (d) for in liquid water. The dashed line in each panel represents the corresponding running coordination number .

Image of FIG. 2.
FIG. 2.

Radial distribution functions (a) , (b) , (c) , and (d) for in liquid water. The dashed line in each panel represents the corresponding running coordination number .

Image of FIG. 3.
FIG. 3.

Radial distribution functions (a) , (b) , (c) , and (d) for in liquid water. The dashed line in each panel represents the corresponding running coordination number .

Image of FIG. 4.
FIG. 4.

Dependence of the instantaneous coordination number for (left) and (right) on the geometrical cutoff distance.

Image of FIG. 5.
FIG. 5.

Typical hydration structure for (a) , (b) , and (c) . The hydration structure of and shown in (a) and (b) can be assigned as tetrahedral and distorted trigonal bipyramid (or square pyramidal) structure, respectively. The hydration structure of cannot be characterized by a definite geometry.

Image of FIG. 6.
FIG. 6.

Distribution of the OH bond length (left) and the HOH bond angle (right) of hydration water molecules. For comparison, the corresponding distributions for the bulk are shown as dashed lines.

Image of FIG. 7.
FIG. 7.

Distribution of the cosine of the tilt angle between the dipole vector of hydration water molecule and the vector pointing from water oxygen to the metal ion. Open circles, squares, and triangles refer to the cases of , , and aqueous system, respectively.

Image of FIG. 8.
FIG. 8.

Mean square displacement (MSD) for water molecules in our two systems composed of (, Na, and K) and , . Open circles, squares, and triangles indicate the displacement of water molecules in the system including one , one , and one ion, respectively. Filled circles, squares, and triangles represent the MSD of water molecule for the systems with two , two , and two , respectively. The reference data for bulk water, estimated from a 64 molecules system in the same cubic cell, are shown as dashed line.

Image of FIG. 9.
FIG. 9.

Orientational autocorrelation function of water molecules in the two simulated systems composed of (, Na, and K) and , . Open circles, squares, and triangles indicate the autocorrelation function for the system including one , one , and one ion, respectively. Filled circles, squares, and triangles are for the systems with two , two , and two , respectively. The reference data for bulk water composed of 64 molecules are shown as dashed line.

Image of FIG. 10.
FIG. 10.

Distribution of molecular dipole moments of waters calculated from maximally localized Wannier function centers for (a) , (b) , and (c) aqueous solutions. The water molecules contained in our systems are classified into the hydration water molecules in the first shell, in the second shell, and the others intended as the rest of the solvent.

Image of FIG. 11.
FIG. 11.

(Left) Distribution of the O-WFC distance for water molecules in the first solvation shell of the alkali ion (solid line) and in the bulk (dashed line). The corresponding scatter graphs in the plane of (, ) are shown in right panel, where , Na, and K. A data accumulation leading to a high density in the distribution is seen in the regions marked with arrows.

Image of FIG. 12.
FIG. 12.

Schematic structure of hydrogen bond network formed around a hydration water molecule of the alkali ion. Hydrogen bonds are indicated by dashed lines.

Tables

Generic image for table
Table I.

Validation of pseudopotential-based PW-DFT approach for the aqueous alkali ion complexes (, Na, and K). Cation-oxygen distances are given in Å and hydration energies in kcal/mol. PW-DFT results agree excellently with quantum chemistry quantities computed at the MP2/6–311++ level of theory (Ref. 32).

Generic image for table
Table II.

Self-diffusion coefficients of water and metal ions for our aqueous systems with one alkali ion and two alkali ions compared. The experimental values were taken for aqueous solutions of alkali chlorides at the concentration in unit of M shown in parenthesis. (One alkali ion and two alkali ions in the present simulation correspond to about 0.9 and 1.8 M, respectively.) The theoretical value for bulk water was estimated as from the slope of the mean-square displacement given in Fig. 8.

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/content/aip/journal/jcp/126/3/10.1063/1.2424710
2007-01-16
2014-04-16
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Hydration of alkali ions from first principles molecular dynamics revisited
http://aip.metastore.ingenta.com/content/aip/journal/jcp/126/3/10.1063/1.2424710
10.1063/1.2424710
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