Intermediate-Range Order in Water Ices

TL;DR

This study uses NRIXS measurements and ab initio calculations to analyze intermediate-range order in various water ice phases, revealing that spectral fine structures serve as fingerprints of this order and challenging localization assumptions.

Contribution

It demonstrates that ab initio real-space multiple scattering calculations accurately reproduce NRIXS spectra, linking spectral features to intermediate-range order in ice phases.

Findings

Spectra can be well modeled by ab initio calculations.

Spectral features serve as fingerprints of intermediate-range order.

Results impact understanding of wavefunction localization in ice.

Abstract

We report measurements of the non-resonant inelastic x-ray scattering (NRIXS) from the O 1s orbitals in ice Ih, and also report calculations of the corresponding spectra for ice Ih and several other phases of water ice. We find that the intermediate-energy fine structure may be calculated well using an ab initio real-space full multiple scattering approach, and that it provides a strong fingerprint of the intermediate-range order for some ice phases. These results have important consequences for future NRIXS measurements of high-pressure phases of ice and also may call into question the assumption that the wavefunctions for final states within a few eV of the absorption edge are strongly localized.