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Disentangling Coupling Effects in the Infrared Spectra of Liquid Water

submitted on 10.10.2018 and posted on 12.10.2018 by Kelly M. Hunter, Farnaz A. Shakib, Francesco Paesani

A quantitative characterization of intermolecular and intramolecular couplings that modulate the OH-stretch vibrational band in liquid water has so far remained elusive. Here, we take up this challenge by combining the centroid molecular dynamics (CMD) formalism, which accounts for nuclear quantum effects, with the MB-pol potential energy function, which accurately reproduces the properties of water across all phases, to model the infrared (IR) spectra of various isotopic water solutions with different levels of vibrational couplings, including those that cannot be probed experimentally. Analysis of the different IR OH-stretch lineshapes provides direct evidence for the partially quantum-mechanical nature of hydrogen bonds in liquid water, which is emphasized by synergistic effects associated with intermolecular coupling and many-body electrostatic interactions. Furthermore, we quantitatively demonstrate that intramolecular coupling, which results in Fermi resonances due to the mixing between HOH-bend overtones and OH-stretch fundamentals, are responsible for the shoulder located at ∼3250 cm-1 of the IR OH-stretch band of liquid water.


National Science Foundation, Air Force Office of Scientific Research


Email Address of Submitting Author


University of California, San Diego


United States

ORCID For Submitting Author


Declaration of Conflict of Interest

No conflict of interest