A first principles simulation study of vibrational spectral diffusion in aqueous NaBr solutions: Dynamics of water in ion hydration shells

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

“…28,30 For the bromide ion, however, other dynamical modes were also found to contribute to the spectral diffusion of hydration shell water. 29 In the current study also it is found that a significant fraction of water molecules remain non-hydrogen-bonded inside the solvation shell, hence the dynamics of spectral diffusion of the hydration shell water involves not only hydrogen bond breaking but also other nonhydrogen-bonded dynamical modes such as diffusion and orientational relaxation. Also it is found that dispersion interactions do not alter the dynamics of vibrational spectral diffusion of water molecules inside the solvation shells of iodide ions in any qualitative manner.…”

“…We note that similar relations were also found for the spectral diffusion of water in the solvation shell of a Br − ion in earlier studies. 29 In particular, we note that for Br − ion also, a significant fraction of water molecules in its solvation shell was found to remain without being hydrogen bonded, hence non-hydrogen-bonded modes were also found to influence the slow second relaxation time of solvation shell water in addition to the breaking dynamics of ion−water hydrogen bonds. For the fluoride and chloride ions, 28,30 however, majority of water molecules in their solvation shells were found to be hydrogen bonded with the solute ion; hence, the second relaxation time was found to be very close to that of the corresponding halide ion−water hydrogen bond lifetime, i.e., the second relaxation time was found to be primarily determined by the breaking dynamics of the halide ion−water hydrogen bonds for these ions.…”

An ab initio molecular dynamics study of the hydrogen bonded structure, dynamics and vibrational spectral diffusion of water in the ion hydration shell of a superoxide ion

“…The fluctuating frequency is then calculated for all the OD bonds and over the entire trajectory. Further details of this method for OD stretch frequency calculations have been provided in previous work [25][26][27].…”

“…Ultrafast time-resolved infrared spectroscopy has provided new insights into the dynamics of vibrational spectral diffusion of aqueous ionic solutions [17][18][19][20][21][22][23]. On the theoretical side, the vibrational spectral diffusion of hydration shell water molecules has been studied in aqueous ionic solutions using a combination of classical molecular dynamics and perturbative methods [24] and also by ab initio molecular dynamics [25][26][27] simulations. These studies reveal a slow escape dynamics of water molecules from ion hydration shells and relates it to the long time component of the spectral dynamics of hydration shell water.…”

Ab initio molecular dynamics studies of hydrogen bonded structure, molecular motion, and frequency fluctuations of water in the vicinity of azide ions

“…For example, recent time dependent infrared spectroscopic studies of water [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] and aqueous solutions [16][17][18][19][20][21][22] have provided a wealth of information regarding how the fluctuation dynamics of vibrational frequencies of a solution can be different from those of pure water due to ion-solvent interactions. Recent theoretical studies of aqueous ionic solutions on vibrational spectral diffusion and related dynamical properties [23][24][25][26][27][28][29][30][31][32][33][34][35][36] have also provided important information on perturbation of molecular dynamics of an aqueous medium due to solute-solvent interactions.…”