Spectral Signatures of the Diffusional Anomaly in Water

TL;DR

This paper demonstrates that the diffusional anomaly in water can be characterized by analyzing the power spectrum's  region, linking molecular environment, hydrogen bond dynamics, and diffusivity.

Contribution

It introduces a spectral analysis method to connect molecular-scale phenomena with macroscopic diffusional anomalies in water.

Findings

Spectral  behavior correlates with water's diffusional anomaly.

Monitoring  exponents provides insights into hydrogen bond network reorganizations.

Experimental spectral analysis can probe supercooled water's density-dependent dynamics.

Abstract

Analysis of power spectrum profiles for various tagged particle quantities in bulk SPC/E water is used to demonstrate that variations in mobility associated with the diffusional anomaly are mirrored in the exponent of the \onebyf\ region. Monitoring of \onebyf behaviour is shown to be a simple and direct method for linking phenomena on three distinctive length and time scales: the local molecular environment, hydrogen bond network reorganisations and the diffusivity. The results indicate that experimental studies of supercooled water to probe the density dependence of $1/f^\alpha$ spectral features, or equivalent stretched exponential behaviour in time-correlation functions, will be of interest.