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Basic molecular mechanisms underlying complex permittivity of water and ice
Vladimir I Gaiduk1, Derrick S F Crothers
1Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, Vvedensky Sq. 1, Fryazino, 141190, Moscow Region, Russia.
The Journal of Physical Chemistry. A
|July 28, 2006
Summary
This study analyzes dielectric-loss spectra of water and ice using a semiphenomenological approach. The model accurately predicts experimental spectra by considering molecular mechanisms and shows an increasing association factor with lower temperatures.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Dielectric Properties of Matter
Background:
- Far-infrared (FIR) spectra of water and ice are complex and influenced by various molecular motions.
- Understanding these motions is crucial for accurately modeling the dielectric properties of water and ice across different phases and temperatures.
Purpose of the Study:
- To analyze four key dielectric-loss frequency dependences contributing to FIR spectra of water and ice.
- To develop and validate a semiphenomenological model for predicting these spectra.
- To investigate the temperature dependence of molecular interactions in water and ice.
Main Methods:
- Analysis of four dielectric-loss frequency dependences (epsilon''j(nu)).
- Application of a semiphenomenological (SP) approach utilizing autocorrelation function spectra.
- Modeling of molecular mechanisms including libration, H-bond vibrations, and reorientations.
Main Results:
- The developed SP model demonstrates excellent agreement with experimental FIR spectra for liquid water, supercooled water, and ice.
- A formula for an 'association factor' (zeta) was derived, relating dipole moments of vibrating water molecules.
- The association factor shows a sharp increase as temperature decreases below 300 K.
Conclusions:
- The semiphenomenological model effectively captures the dielectric-loss spectra of water and ice by incorporating fundamental molecular mechanisms.
- The proposed 'association factor' provides insights into the temperature-dependent molecular ordering and interactions in water.
- The findings contribute to a better understanding of the physical chemistry of water and ice.