Role of dipolar correlations in the IR spectra of water and ice

TL;DR

This study uses advanced simulations to analyze the IR spectra of water and ice, revealing the significant role of dipolar correlations and hydrogen bonds in shaping spectral features.

Contribution

It introduces a detailed decomposition of IR spectral lineshapes based on dipole correlation functions, highlighting the importance of intermolecular charge fluctuations.

Findings

Intermolecular charge fluctuations dominate IR spectra.

Network bending modes are identified in far IR.

Simulations accurately reproduce experimental spectra.

Abstract

We report simulated infrared spectra of deuterated water and ice using Car-Parrinello molecular dynamics with maximally localized Wannier functions. Experimental features are accurately reproduced within the harmonic approximation. By decomposing the lineshapes in terms of intra and intermolecular dipole correlation functions we find that short-range intermolecular dynamic charge fluctuations associated to hydrogen bonds are prominent over the entire spectral range. Our analysis reveals the origin of several spectral features and identifies network bending modes in the far IR range.