# Size dependence of dynamic fluctuations in liquid and supercooled water

## TL;DR

This study investigates how dynamic fluctuations in liquid and supercooled water depend on size and temperature, revealing a significant increase in correlated mobile regions upon supercooling, with the influence length scale growing substantially.

## Contribution

It provides the first detailed analysis of size-dependent dynamic fluctuations in supercooled water, quantifying the growth of correlated regions with cooling.

## Key findings

- Supercooling enhances spatially localized dynamic fluctuations.
- The maximum size of correlated mobile regions increases by two orders of magnitude upon cooling.
- The upper limit of influence reaches a few thousand molecules at the lowest temperature.

## Abstract

We study the evolution of dynamic fluctuations averaged over different space lengths and time scales to characterize spatially and temporally heterogeneous behavior of TIP4P/2005 water in liquid and supercooled states. Analysing a million particle simulated system we provide evidence of the existence, upon supercooling, of a significant enhancement of spatially localized dynamic fluctuations stemming from regions of correlated mobile molecules. We show that both the magnitude of the departure from the value expected for the system-size dependence of an uncorrelated system and the molecular size at which such trivial regime is finally recovered clearly increase upon supercooling. This provides a means to estimate an upper limit to the maximum length scale of influence of the regions of correlated mobile molecules. Notably, such upper limit grows two orders of magnitude on cooling, reaching a value corresponding to a few thousand molecules at the lowest investigated temperature.