Thermal transport anomalies of electrolyte solutions in the water supercooled regime: signatures of the liquid-liquid water phase transition
File(s)
Published version
Author(s)
Zhao, Guansen
Bresme, Fernando
Type
Journal Article
Abstract
Water exhibits remarkable anomalies when supercooled, attributed to a hypothesized liquid–liquid phase transition (LLPT) between low-density and high-density liquid (HDL) phases. Using non-equilibrium molecular dynamics simulations, we explore thermal transport and coupled effects in supercooled NaCl and LiCl solutions (1–4 m, 200–300 K). At 1 m, thermal conductivity exhibits a pronounced minimum near 220 K, coinciding with maxima in isothermal compressibility and minima in the speed of sound, both of which are signatures of critical fluctuations. The anomalies progressively diminish with increasing salt concentration and vanish at 4 m, suggesting suppression of the LLPT. The Soret coefficient exhibits striking behavior, which is initially thermophobic at high temperatures (>280 K, solute migrates toward the cold side), becomes thermophilic upon cooling (solute migrates toward the hot side), and then reverts to thermophobic below 220 K. This behavior correlates with structural changes in the hydrogen-bond network of water. In particular, we find that the deep minima in the Soret coefficient, corresponding to the strongest thermophilic response in NaCl and LiCl, occur in thermodynamic states characterized by a low fraction of HDL-like structures, indicating a predominance of highly tetrahedrally ordered water environments. Furthermore, Seebeck coefficients exhibit sign reversals near 220–230 K, highlighting the thermoelectric sensitivity to structural transformations and temperature. These findings establish thermal transport as a sensitive probe of supercooled water, revealing that electrolyte solutions preserve the water’s anomalies deep into the supercooled regime.
Date Issued
2025-12-14
Date Acceptance
2025-11-06
Citation
Journal of Chemical Physics, 2025, 163 (22)
ISSN
0021-9606
Publisher
American Institute of Physics
Journal / Book Title
Journal of Chemical Physics
Volume
163
Issue
22
Copyright Statement
© 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/41363752
PII: 3374445
Subjects
Chemistry
Chemistry, Physical
CONDUCTIVITY
DIFFUSION
HALIDE AQUEOUS-SOLUTIONS
HEAT
HYDRATION
MODEL
MOLECULAR-DYNAMICS
Physical Sciences
Physics
Physics, Atomic, Molecular & Chemical
Science & Technology
SIMULATIONS
SODIUM-CHLORIDE
SORET COEFFICIENTS
Publication Status
Published
Coverage Spatial
United States
Article Number
224505
Date Publish Online
2025-12-09