Polyamorphism of ice at low temperatures from constant-pressure simulations

TL;DR

This study uses molecular dynamics simulations to explore the complex polyamorphic behavior of amorphous ice at low temperatures and pressures, revealing multiple high-density forms and their network topology evolution.

Contribution

It provides new insights into the existence of various amorphous ice forms and their metastability, expanding understanding of ice's polyamorphic nature at low temperatures.

Findings

Confirmed existence of very high-density amorphous ice

Identified a continuum of HDA forms

Linked network topology evolution to metastability

Abstract

We report results of MD simulations of amorphous ice in the pressure range 0 - 22.5 kbar. The high-density amorphous ice (HDA) prepared by compression of Ih ice at T = 80 K is annealed to T = 170 K at intermediate pressures in order to generate relaxed states. We confirm the existence of recently observed phenomena, the very high-density amorphous ice and a continuum of HDA forms. We suggest that both phenomena have their origin in the evolution of the network topology of the annealed HDA phase with decreasing volume, resulting at low temperatures in the metastability of a range of densities.