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A first principles theoretical study of vibrational spectral diffusion and hydrogen bond dynamics in aqueous ionic solutions: in hydration shells of ions
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10.1063/1.3006032
/content/aip/journal/jcp/129/19/10.1063/1.3006032
http://aip.metastore.ingenta.com/content/aip/journal/jcp/129/19/10.1063/1.3006032

Figures

Image of FIG. 1.
FIG. 1.

The time dependence of the fluctuating frequency of an OD bond of a water as it escapes from the solvation shell of to which it was hydrogen bonded initially. The time when the escape occurs, i.e., when distance exceeds , is taken to be and the frequency and distance fluctuations are shown for 5 ps before and after the escape event. (a) The time dependence of the frequency of the OD bond and (b) the corresponding distance. The results of this figure and also of Figs. 2–8 are for the relatively dilute solution (system 1).

Image of FIG. 2.
FIG. 2.

(a) The distribution of OD stretch frequencies averaged over all OD modes (dashed), those in the bulk (dashed-dotted) and those in the hydration shell (solid). The dotted curve shows the corresponding distribution for pure water (Ref. 28). The inset shows the frequency distributions of bulk and hydration shell OD bonds each normalized to the maximum value of 1. (b) The frequency distributions for different values of the hydrogen bond angle . The solid, dashed, dotted, and dashed-dotted curves are for OD groups with hydrogen bond angles of , , , and , respectively. The top dashed curve represents averages over all OD groups.

Image of FIG. 3.
FIG. 3.

(a) The distribution of the distance for fixed values of the OD frequency. The black solid, red dashed-dotted, and blue dashed curves are for OD frequency , , and , respectively, where represents the deviation from the average frequency. (b) Joint probability distribution of OD frequency and distance. The contour levels of different fractions of the maximum value are shown in different color codes. The results are for water molecules in the hydration shell.

Image of FIG. 4.
FIG. 4.

The power spectra of the velocity time correlation of deuterium atoms of heavy water in the hydration shell (dashed) and in the bulk region (solid) of system 1.

Image of FIG. 5.
FIG. 5.

(a) The time dependence of the continuous (solid) and intermittent (dashed) correlation functions of -water hydrogen bonds. (b) The escape dynamics of water molecules from the hydration shell of . The solid and dashed curves are for the continuous (with an allowance time of 2 ps) and intermittent residence time correlation functions of water molecules in the solvation shell.

Image of FIG. 6.
FIG. 6.

The time variation in the (a) average frequency shifts of the hole modes after excitations in blue (solid curve) and in red (dashed curve) of the hydration shell OD modes. The corresponding results for the blue excitation after normalization by the initial frequency shift are shown in (b). The smooth gray solid curve in (b) represents the fit by a function of Eq. (13). See the text in Sec. V for definitions of the blue and red excitations that are used in the current work.

Image of FIG. 7.
FIG. 7.

The time variation in the (a) average frequency shifts of the remaining modes after excitations in blue (solid curve) and in red (dashed curve) of the hydration shell OD modes. The corresponding results for the red excitation after normalization by the initial frequency shift are shown in (b). As in the previous figure, the smooth gray solid curve in (b) represents the fit by a function of Eq. (13). The definitions of the blue and red excitations used in the current work are described in Sec. V.

Image of FIG. 8.
FIG. 8.

The time variation in the (a) average frequency shifts of the hole modes when all OD modes are considered in the calculations. The corresponding results after normalization by the initial frequency shifts are shown in (b). As before, the solid and dashed curves correspond to excitations in blue and red, respectively. The smooth gray solid curves in (b) represent the fits by a function of Eq. (13). The results of this figure and also of all the previous figures are for system 1 and the definitions of the blue and red excitations in the context of the present work are described in Sec. V.

Image of FIG. 9.
FIG. 9.

The time correlation functions of OD fluctuating frequencies averaged over all the water molecules of the relatively dilute (system 1) and concentrated (system 2) solutions. The lower and upper dashed curves correspond to the simulation results for systems 1 and 2, respectively. The gray solid curves represent the fits by a function as given by Eq. (13).

Image of FIG. 10.
FIG. 10.

The time dependence of the continuous and intermittent hydrogen bond correlation functions for systems 1 (solid) and 2 (dashed). The results of (a) are for only -water hydrogen bonds and those of (b) are for all the hydrogen bonds present in systems 1 and 2.

Image of FIG. 11.
FIG. 11.

The time dependence of the fluctuating frequency of an OD bond of a water as it escapes from the solvation shell of a ion of the concentrated solution (system 2). The time when the escape occurs, i.e., when distance exceeds , is taken to be and the frequency and distance fluctuations are shown for 8 ps before and after the escape event. (a) The time dependence of the frequency of the OD bond and (b) the corresponding distance.

Tables

Generic image for table
Table I.

The average lifetimes of chloride ion-water and all hydrogen bonds (HBs) of the relatively dilute (system 1) and concentrated (system 2) solutions. Results are also included for the residence times of water in the ion hydration shell. All time constants are expressed in picoseconds.

Generic image for table
Table II.

Spectral diffusion data for the hydration shell OD modes of the dilute solution (system 1). The time constants (ps), frequency , and weights of time dependent frequency shifts of hole and remaining modes for blue and red excitations of OD bonds in the hydration shell.

Generic image for table
Table III.

Spectral diffusion data for all OD modes of the relatively dilute (system 1) and concentrated (system 2) solutions. The units of different quantities are as in Table II.

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/content/aip/journal/jcp/129/19/10.1063/1.3006032
2008-11-20
2014-04-17
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: A first principles theoretical study of vibrational spectral diffusion and hydrogen bond dynamics in aqueous ionic solutions: D2O in hydration shells of Cl− ions
http://aip.metastore.ingenta.com/content/aip/journal/jcp/129/19/10.1063/1.3006032
10.1063/1.3006032
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