Water in Hydration Shell of an Iodide Ion: Structure and Dynamics of Solute-Water Hydrogen Bonds and Vibrational Spectral Diffusion from First-Principles Simulations

Abstract

The dynamics of hydrogen bonds and vibrational spectral diffusion of water in the hydration shell of an iodide ion and in bulk have been investigated for aqueous iodide solutions of two different concentrations by using ab initio molecular dynamics simulations. The effects of dispersion interactions on the dynamics have also been investigated by using a dispersion corrected density functional. For the dilute solution containing a single iodide ion, three time scales are found for the spectral diffusion of solvation shell water: A short time scale of ∼150 fs, a slower time scale of ∼2-3 ps and a yet longer time scale of ∼14-16 ps. The long time scale of ∼14-16 ps is not noticed when calculations are done for all OD modes for both the dilute and concentrated solutions. It is found that a clear separation between the solvation shell and bulk water does not exist in terms of OD stretching frequencies for the concentrated solution. The dynamics of vibrational spectral diffusion is explained in terms of hydrogen bond dynamics, other dynamical modes such as orientational relaxation and molecular diffusion, and also structural aspects of water molecules in the solvation shells. The current results are compared with those of available experimental and other theoretical studies.

Origin of the blueshift of water molecules at interfaces of hydrophilic cyclic compounds

“…The wavelet function provides a frequency at time t = b . In previous studies, the wavelet analysis was successfully applied for spectral dynamics of water molecules in ion solutions ( 42 – 44 ). Here, the Morlet-Grossmann function ( 45 ) was chosen as the mother wavelet ψ( t ) where λ and σ are the parameters.…”

Isotope effects in aqueous solvation of simple halides

“…All profiles present reasonable agreement with previous classical simulations. [23][24][25][26][27][28] Hydrogen bonding was defined in terms of a geometrical criterion. 13,29,30 In particular, a water molecule was considered H-bonded to a given X solute, provided the oxygenhalide distance falls within the first ionic solvation shell (i.e., r OX − ≤ r min ) and the H-O-X angle was θ HOX − ≤ 30 • .…”

Ion effect on the dynamics of water hydrogen bonding network: A theoretical and computational spectroscopy point of view

“…In order to describe the profound influences of the hydrated ions on the surrounding water molecules, the concept of a hydration shell is commonly adapted (Boisson et al, ; Bylaska, Valiev, Rustad, & Weare, ; Dang & Chang, ; Eiberweiser, Nazet, Hefter, & Buchner, ; Fournier, Carpenter, De Marco, & Tokmakoff, ; Karmakar & Chandra, ; Mancinelli, Botti, Bruni, Ricci, & Soper, ; Marcus, ; Masia & Rey, ; Mason, Ansell, Neilson, & Rempe, ; Morita, Westh, Nishikawa, & Koga, ; Nigro, Re, Laage, Rey, & Hynes, ; Park, Odelius, & Gaffney, ; Pluharova, Laage, & Jungwirth, ; Rinne, Gekle, & Netz, ; Schienbein, Schwaab, Forbert, Havenith, & Marx, ; Stirnemann, Wernersson, Jungwirth, & Laage, ; Tielrooij et al, ; Turton, Hunger, Hefter, Buchner, & Wynne, ; Vila Verde & Lipowsky, ; Xie, Yang, & Gao, ; Yadav, Choudhary, & Chandra, ; Q. Zhang, Chen, et al, ; Q. Zhang, Wu, et al, ; R. Zhang & Zhuang, ). In principle, the hydration shell should include the first few layers of water next to the solute.…”