Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions

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Title
Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions
Author(s)
Jun-Ho Choi; Heejae Kim; Seongheun Kim; Sohee Lim; Bonghwan Chon; Minhaeng Cho
Publication Date
2015-05
Journal
JOURNAL OF CHEMICAL PHYSICS, v.142, no.20, pp.204102 -
Publisher
AMER INST PHYSICS
Abstract
The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O - D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O - D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O - D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O - D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O - D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O - D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O - D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O - D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O - D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O - D stretch mode is shown to be important and the asymmetric line shapes of the O - D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We anticipate that this computational approach will be of critical use in interpreting linear and nonlinear vibrational spectroscopies of HDO molecule that is considered as an excellent local probe for monitoring local electrostatic and hydrogen-bonding environment in not just salt but also other confined and crowded solutions. © 2015 AIP Publishing LLC
URI
https://pr.ibs.re.kr/handle/8788114/2031
ISSN
0021-9606
Appears in Collections:
Center for Molecular Spectroscopy and Dynamics(분자 분광학 및 동력학 연구단) > Journal Papers (저널논문)
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