Accurately calculating vibrational spectroscopies through atomistic simulations holds the promise of simultaneously validating the underlying molecular model and providing molecular level insights into the experimental spectra. However, obtaining quantitative agreement with the variety of vibrational spectroscopies (e.g., infrared and Raman spectroscopy) through a single model has proven difficult due to a number of factors, including the accuracy of the model, sampling limitations, and treatment of nuclear quantum effects. In this contribution, we address one of these aspects, the accuracy of the model, in a systematic and parameter-free approach by mapping the polarizability of water clusters obtained from high-level electronic structure into a computationally tractable functional form through a many-body expansion. We build a many-body polarizability model upon a Thole-type polarizable dipole model, which provides an effective N-body polarizability, and refine this N-body polarizability with explicit one-body, monomer polarizabilities and two-body, interaction induced polarizabilities terms. When applied to water, our approach results in a full-dimensional many-body model for the polarizability that accurately reproduces the polarizability of water systems from small clusters to bulk. Importantly, when used in combination with our previously reported many-body potential (MB-pol), our approach allows us to rigorously model Raman spectra from first principles.

Many-body expansions of the polarizability of water: Toward first principles modeling of vibrational spectroscopies

248th National Meeting (2014)

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