High-density amorphous ice: A path-integral simulation

TL;DR

This study uses path-integral molecular dynamics to explore how quantum nuclear motion influences the structural and thermodynamic properties of high-density amorphous ice, revealing notable volume and bond length changes at low temperatures.

Contribution

It provides the first detailed quantum simulation analysis of HDA ice, highlighting quantum effects on its properties and comparing results with classical models.

Findings

Quantum motion increases molar volume by 6% at 50 K.

Intramolecular O--H distance increases by 1.4% due to quantum effects.

Bulk modulus increases linearly with pressure, slope 7.1.

Abstract

Structural and thermodynamic properties of high-density amorphous (HDA) ice have been studied by path-integral molecular dynamics simulations in the isothermal-isobaric ensemble. Interatomic interactions were modeled by using the effective q-TIP4P/F potential for flexible water. Quantum nuclear motion is found to affect several observable properties of the amorphous solid. At low temperature (T = 50 K) the molar volume of HDA ice is found to increase by 6%, and the intramolecular O--H distance rises by 1.4% due to quantum motion. Peaks in the radial distribution function of HDA ice are broadened respect to their classical expectancy. The bulk modulus, B, is found to rise linearly with the pressure, with a slope dB/dP = 7.1. Our results are compared with those derived earlier from classical and path-integral simulations of HDA ice. We discuss similarities and discrepancies with those earlier simulations.