# Large-scale structure and hyperuniformity of amorphous ices

## TL;DR

This study reveals that amorphous ices exhibit hyperuniformity, with structural heterogeneities during phase transitions suppressing this property, challenging traditional views of glasses as frozen liquids and enhancing understanding of glass transformations.

## Contribution

It demonstrates the hyperuniformity of amorphous ices and how phase transitions affect their large-scale density fluctuations, providing new insights into glass structure and transformations.

## Key findings

- HDA and LDA are nearly hyperuniform.
- Structural heterogeneities suppress hyperuniformity during phase transitions.
- The results challenge the 'frozen-liquid' model of glasses.

## Abstract

We investigate the large-scale structure of amorphous ices and transitions between their different forms by quantifying their large-scale density fluctuations. Specifically, we simulate the isothermal compression of low-density amorphous ice (LDA) and hexagonal ice (Ih) to produce high-density amorphous ice (HDA). Remarkably, both HDA and LDA are nearly hyperuniform, meaning that they are characterized by an anomalous suppression of large-scale density fluctuations. By contrast, in correspondence with both non-equilibrium phase transitions to HDA, the presence of structural heterogeneities strongly suppresses the hyperuniformity and, remarkably, the system becomes hyposurficial (devoid of "surface-area" fluctuations). Our investigation challenges the largely accepted "frozen-liquid" picture, which views glasses as structurally arrested liquids. Beyond implications for water, our findings enrich our understanding of the structural transformations that occur in glasses with varying pressures.