RDFs and integrated values from the AMOEBA simulations: (a) chloride/(water oxygen) and (b) chloride/(water hydrogen). The black curves are for the default chloride ion polarizability simulation while the blue curves are for the reduced ion polarizability simulation.
The log of the distribution of the coordination number of (aq) from the AMOEBA simulation. The curve shown in black is for the default ion polarizability simulation while the blue curve is for the reduced ion polarizability simulation.
(a) The distributions of , the distance between the center of mass of the first solvation shell water O atoms and the and ions, from the AMOEBA simulations. (b) The distributions divided by .
Three snapshots of typical configurations of the first hydration shell from a simulation with the AMOEBA force field (default ion polarizability).
The distribution of the magnitude of (a) the anion and (b) first-shell water molecule dipole moments . In (a) the solid and filled circles represent the distribution of for the ion calculated at the MP2-ChelpG level and the classical AMOEBA model level, respectively (default chloride ion polarizability case). The curves without symbols are for the reduced chloride ion polarizability simulations. In (b) the solid and filled circles represent the distribution of for water molecules in the first solvation shell of the anion at the MP2-ChelpG level and at the classical AMOEBA model level, respectively (default chloride ion polarizability case). The curves without symbols are for the reduced chloride ion polarizability simulations.
Shown are the distributions of charges on the ion calculated using the ChelpG scheme and the QTAIM analysis. The curves with filled circles are from the ChelpG analysis; the black curve is for the default chloride ion polarizability simulation while the blue curve is for the reduced polarizability case. The curves labeled with open circles are from the QTAIM analysis; the black curve is for the default chloride ion polarizability simulation while the red curve is for the reduced polarizability case. The ion/(first-shell water) cluster QM/MM calculations included electrostatic interactions with more distant waters via the charge model described in Sec. II.
(a) Contour plot of the total electron density for the dimer. The chosen plane contains the hydrogen bond between the ion and the water hydrogens. (b) Contour plot of the electron density difference between the complex and the separated ion and water molecule. The configuration and plane are the same as in (a). Red indicates reduced electron density and shades of blue imply increased electron density.
The magnitude of the average dipole moment of water molecules neighboring a ion as a function of increasing cluster size . On the left, the system modeled included the ion and the given number of water molecules. On the right, six waters were treated quantum mechanically in the first shell and the rest of the waters in the QM/MM cluster were represented with AMOEBA charges distributed as described in Sec. II. On the right, average dipoles over the nearest six waters are presented, but those waters interact with increasing numbers of surrounding AMOEBA waters.
The effect of basis set on the dipole moment of an isolated water molecule calculated at the MP2-level.
The effect of the charge model on the calculated dipole moment of a water molecule in a water dimer by the ChelpG charges, in which one water molecule is treated at the MP2-level and the other one is represented by a charge model. The final entry is the result when both water molecules are treated at the MP2-level followed by ChelpG determination of the dipole of one of the waters.
Charges on the chloride ion estimated by the ChelpG and QTAIM methods. Columns 2–4 display the results for the ChelpG method with a single charge on the chloride ion, the ChelpG method with an added dipole on the chloride ion, and the QTAIM method, respectively. The final column is the estimated dipole moment on the chloride ion obtained from the calculations in column 3.
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