Spectral statistics of the quenched normal modes of a network-forming molecular liquid

TL;DR

This study analyzes the spectral properties of quenched normal modes in ST2 water across different densities, revealing that their fluctuations follow random matrix theory predictions and most modes are extended rather than localized.

Contribution

It provides a comprehensive spectral analysis of normal modes in a network-forming liquid, connecting spectral fluctuations to random matrix theory and mode localization.

Findings

Fluctuations follow Gaussian orthogonal ensemble predictions.

Most normal modes are extended, not localized.

Spectral properties vary across different density regimes.

Abstract

We evaluate the density of states of the quenched normal modes of ST2 water, and their statistical fluctuations, for a range of densities spanning three regimes of behavior of a hydrogen bonded liquid: a lower-density regime of random tetrahedral network formation; in the vicinity of a liquid-liquid critical point; and in a higher-density regime of fragile glass-forming behavior. For all cases we find that the fluctuations around the mean spectral densities obey the predictions of the Gaussian orthogonal ensemble of random matrix theory. We also measure the participation ratio of the normal modes across the entire frequency range, and find behavior consistent with the majority of modes being of an extended nature, rather than localized.