Fractional Stokes-Einstein and Debye-Stokes-Einstein relations in a network forming liquid

TL;DR

This paper investigates how classical transport relations break down in a network-forming liquid, revealing the emergence of fractional relations at low temperatures and their consistency across different dynamical heterogeneities.

Contribution

It demonstrates the universal emergence of fractional SE and DSE relations in a water model and shows they apply to both mobile and immobile heterogeneities.

Findings

Fractional SE and DSE relations appear at low temperatures.

Exponents of fractional relations are consistent across regimes.

Both mobile and immobile heterogeneities follow the same fractional relations.

Abstract

We study the breakdown of the Stokes-Einstein (SE) and Debye-Stokes-Einstein (DSE) relations for translational and rotational motion in a prototypical model of a network-forming liquid, the ST2 model of water. We find that the emergence of ``fractional'' SE and DSE relations at low temperature is ubiquitous in this system, with exponents that vary little over a range of distinct physical regimes. We also show that the same fractional SE relation is obeyed by both mobile and immobile dynamical heterogeneities of the liquid.