Mode coupling theory analysis of water dynamics detected by dielectric spectroscopy
Abstract
Mode-coupling theory (MCT), one of the most prominent models of the glass transition, also makes various specific predictions for the molecular dynamics in the liquid state of matter. They can be best experimentally tested by evaluating susceptibility spectra covering a broad frequency range. In the present work, we clarify whether the most recent broadband dielectric-spectroscopy results on water, whose glass transition is highly disputed, are compatible with MCT. The so-called fast beta process, expected within this theory, should be detectable at low temperatures only, inaccessible in water due to its inevitable crystallization upon cooling. Therefore, we also investigate data on aqueous LiCl solutions, which can be easily supercooled. We find that all the available broadband dielectric data on these solutions and pure water are well consistent with MCT. Notably, this includes the expected interrelation of the critical temperature dependence of the alpha relaxation to its often-neglected non-Debye spectral shape. Moreover, the available data on the fast beta process, detected in a 14.8 mol% LiCl solution, are also well consistent with the theory. We find a smooth development of the derived MCT parameters with salt concentration which supports the validity of the critical temperature Tc = 222 K and system parameter lambda = 0.55 deduced here for pure water. We also compare the current dielectric relaxation-time results to those determined by other experimental methods and address the question whether information on the controversial fragile-to-strong transition of water can be obtained from such data. Finally, we discuss the significance of the dominant dielectric relaxation process of water for the glass transition as described by MCT, especially considering scenarios questioning its association with the alpha relaxation.
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BibTeX
@misc{lunkenheimer2026mode,
title = {{Mode coupling theory analysis of water dynamics detected by dielectric spectroscopy}},
author = {Peter Lunkenheimer and Alois Loidl},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25328},
eprint = {2610.25328},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25328},
}
RIS
TY - UNPB
TI - Mode coupling theory analysis of water dynamics detected by dielectric spectroscopy
AU - Peter Lunkenheimer
AU - Alois Loidl
PY - 2026
DA - 2026/10/18
PB - arXiv
DO - 10.48550/arxiv.2610.25328
UR - https://arxiv.org/abs/2610.25328
AB - Mode-coupling theory (MCT), one of the most prominent models of the glass transition, also makes various specific predictions for the molecular dynamics in the liquid state of matter. They can be best experimentally tested by evaluating susceptibility spectra covering a broad frequency range. In the present work, we clarify whether the most recent broadband dielectric-spectroscopy results on water, whose glass transition is highly disputed, are compatible with MCT. The so-called fast beta process, expected within this theory, should be detectable at low temperatures only, inaccessible in water due to its inevitable crystallization upon cooling. Therefore, we also investigate data on aqueous LiCl solutions, which can be easily supercooled. We find that all the available broadband dielectric data on these solutions and pure water are well consistent with MCT. Notably, this includes the expected interrelation of the critical temperature dependence of the alpha relaxation to its often-neglected non-Debye spectral shape. Moreover, the available data on the fast beta process, detected in a 14.8 mol% LiCl solution, are also well consistent with the theory. We find a smooth development of the derived MCT parameters with salt concentration which supports the validity of the critical temperature Tc = 222 K and system parameter lambda = 0.55 deduced here for pure water. We also compare the current dielectric relaxation-time results to those determined by other experimental methods and address the question whether information on the controversial fragile-to-strong transition of water can be obtained from such data. Finally, we discuss the significance of the dominant dielectric relaxation process of water for the glass transition as described by MCT, especially considering scenarios questioning its association with the alpha relaxation.
ER -