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arXiv · 2105.00640

Effects of hydrophobic solute on water normal modes

Kambham Devendra Reddy·Albin Joy·Rajib Biswas
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Abstract

The vibrational modes of water get significantly modified by external solutes; this becomes particularly important when the solute is hydrophobic. In this work, we examine the effects of a tiny hydrophobe, methane, on the normal modes of water, using small cluster-based harmonic normal mode analysis of aqueous methane system. We estimate the vibrational density of states and also the infrared spectral density. We compare the methane-water data with the bulk water response. We decompose these modes based on different vibrational characters. The stretch-bend decomposition reflects a pronounced coupling between the methane asymmetric stretch mode and the water symmetric stretch mode. We examine the methane-water data in terms of the symmetry of the central water molecule's vibrations and find that asymmetric modes do not contribute. We also find that the vibrational modes having non-zero contributions from methane molecule are extremely localized in nature.

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Kambham Devendra Reddy, Albin Joy, Rajib Biswas. 2021-05-03. Effects of hydrophobic solute on water normal modes. https://arxiv.org/abs/2105.00640

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