Giant dynamic isotope effect in supercooled water
| Autor: | Caupin, Fr��d��ric, Ragueneau, Pierre, Issenmann, Bruno |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: | |
| Popis: | Light and heavy water show similar anomalies in thermodynamic and dynamic properties. While a simple temperature shift apparently helps in collapsing data for both isotopes, it lacks a clear justification and requires additional ad hoc scaling factors. Here we report shear viscosity data $\eta$ for heavy water supercooled down to $244\,\mathrm{K}$, together with data for light water with improved accuracy. The isotopic effect on viscosity is extreme for water, with a viscosity ratio exceeding 2.2 at $244\,\mathrm{K}$. As temperature $T$ decreases, $\eta$ and self-diffusion $D_\mathrm{s}$ decouple, as manifested by an increasing Stokes-Einstein ratio $D_\mathrm{s} \eta/T$. The Stokes-Einstein ratios for the two isotopes are reconciled by a $+7\,\mathrm{K}$ shift of the light water data, without the need for a scaling factor. Our results are consistent with simulations and suggest that this isotopic temperature shift mirrors that of water's thermodynamic and structural anomalies in the supercooled region, possibly related to the existence of a liquid-liquid transition. Comment: 5 pages, 3 figures. Introduced the Stokes-Einstein ratio $D_\mathrm{s} \eta /T$ and modified Fig. 3. Improved the discussion |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|