Shear viscosity and Stokes-Einstein violation in supercooled light and heavy water

TL;DR

This study measures shear viscosity of supercooled heavy and light water, revealing a significant isotope effect and discrepancies with previous data, contributing to understanding water's anomalous dynamics.

Contribution

The paper provides new, more accurate viscosity measurements of supercooled heavy water and compares isotope effects, challenging previous findings and enhancing knowledge of water's dynamic properties.

Findings

Viscosity of heavy water increases 15-fold below melting point.

Viscosity ratio between isotopes reaches 2.2 at low temperature.

Discrepancies with previous capillary flow data suggest possible electro-osmotic bias.

Abstract

We report shear viscosity of heavy water supercooled $33\,\mathrm{K}$ below its melting point, revealing a 15-fold increase compared to room temperature. We also confirm our previous data for the viscosity of supercooled light water, and reach a better accuracy. Our measurements, based on the spontaneous Brownian motion of $350\,\mathrm{nm}$ spheres, disagree at the lowest temperature with the only other available data, based on Poiseuille flow in a narrow capillary, which may have been biased by electro-osmotic effects. The viscosity ratio between the two isotopes reaches 2.2 at the lowest temperature. A companion Letter [F. Caupin, P. Ragueneau, and B. Issenmann, arXiv:2112.09010] discusses this giant dynamic isotopic effect. Here we provide a detailed description of the experiment and its analysis. We review the literature data about dynamic properties of water (viscosity, self-diffusion coefficient, and rotational correlation time), discuss their temperature dependence and compare their decoupling in the two isotopes.