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Dielectric Properties of Water in Charged Nanopores

Author(s): Underwood, Thomas R; Bourg, Ian C

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Abstract: In this study, we examine the spectral dielectric properties of liquid water in charged nanopores over a wide range of frequencies (0.3 GHz to 30 THz) and pore widths (0.3 to 5 nm). This has been achieved using classical molecular dynamics simulations of hydrated Na-smectite, the prototypical swelling clay mineral. We observe a drastic (20-fold) and anisotropic decrease in the static relative permittivity of the system as the pore width decreases. This large decrement in static permittivity reflects a strong attenuation of the main Debye relaxation mode of liquid water. Remarkably, this strong attenuation entails very little change in the time scale of the collective relaxation. Our results indicate that water confined in charged nanopores is a distinct solvent with a much weaker collective nature than bulk liquid water, in agreement with recent observations of water in uncharged nanopores. Finally, we observe remarkable agreement between the dielectric properties of the simulated clay system against a compiled set of soil samples at various volumetric water contents. This implies that saturation may not be the sole property dictating the dielectric properties of soil samples, rather that the pore-size distribution of fully saturated nanopores may also play a critically important role.
Publication Date: 1-Apr-2022
Citation: Underwood, Thomas R, Bourg, Ian C. (2022). Dielectric Properties of Water in Charged Nanopores. The Journal of Physical Chemistry B, 126 (14), 2688 - 2698. doi:10.1021/acs.jpcb.1c09688
DOI: doi:10.1021/acs.jpcb.1c09688
ISSN: 1520-6106
EISSN: 1520-5207
Pages: 2688 - 2698
Language: en
Type of Material: Journal Article
Journal/Proceeding Title: The Journal of Physical Chemistry B
Version: Final published version. This is an open access article.

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