Mondal, S and Bagchi, B (2021) Anomalous dielectric response of nanoconfined water. In: Journal of Chemical Physics, 154 (4).
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Abstract
In order to develop a microscopic level understanding of the anomalous dielectric properties of nanoconfined water (NCW), we study and compare three different systems, namely, (i) NCW between parallel graphene sheets (NCW-GSs), (ii) NCW inside graphene covered nanosphere (NCW-Sph), and (iii) a collection of one- and two-dimensional constrained Ising spins with fixed orientations at the termini. We evaluate the dielectric constant and study the scaling of ϵ with size by using linear response theory and computer simulations. We find that the perpendicular component remains anomalously low at smaller inter-plate separations (d) over a relatively wide range of d. For NCW-Sph, we could evaluate the dielectric constant exactly and again find a low value and a slow convergence to the bulk. To obtain a measure of surface influence into the bulk, we introduce and calculate correlation lengths to find values of �9 nm for NCW-GS and �5 nm for NCW-Sph, which are surprisingly large, especially for water. We discover that the dipole moment autocorrelations exhibit an unexpected ultrafast decay. We observe the presence of a ubiquitous frequency of �1000 cm-1, associated only with the perpendicular component for NCW-GS. This (caging) frequency seems to play a pivotal role in controlling both static and dynamic dielectric responses in the perpendicular direction. It disappears with an increase in d in a manner that corroborates with the estimated correlation length. A similar observation is obtained for NCW-Sph. Interestingly, one- and two-dimensional Ising model systems that follow Glauber spin-flip dynamics reproduce the general characteristics. © 2021 Author(s).
| Item Type: | Journal Article |
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| Publication: | Journal of Chemical Physics |
| Publisher: | American Institute of Physics Inc. |
| Additional Information: | The copyright of this article belongs to American Institute of Physics Inc. |
| Keywords: | Dielectric properties; Graphene; Ising model, Correlation lengths; Dielectric response; Linear-response theory; Microscopic levels; Plate separation; Slow convergences; Surface influences; Two-dimensional ising model, Spin fluctuations |
| Department/Centre: | Division of Chemical Sciences > Solid State & Structural Chemistry Unit |
| Date Deposited: | 23 Feb 2021 07:41 |
| Last Modified: | 23 Feb 2021 07:41 |
| URI: | http://eprints.iisc.ac.in/id/eprint/67932 |
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