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arXiv · 2408.07638

Force Fields for Deep Eutectic Mixtures: Application to Structure and 2D-Infrared Spectroscopy

Kai Töpfer·Eric Boittier·Michael Devereux·Andrea Pasti·Peter Hamm·Markus Meuwly
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Abstract

Parametrizing energy functions for ionic systems can be challenging. Here, the total energy function for an eutectic system consisting of water, SCN$^-$, K$^+$ and acetamide is improved vis-a-vis experimentally measured properties. Given the importance of electrostatic interactions, two different types of models are considered: the first (model M0) uses atom-centered multipole whereas the other two (models M1 and M2) are based on fluctuating minimal distributed charges (fMDCM) that respond to geometrical changes of SCN$^-$. The Lennard-Jones parameters of the anion are adjusted to best reproduce experimentally known hydration free energies and densities which are matched to within a few percent for the final models irrespective of the electrostatic model. Molecular dynamics simulations of the eutectic mixtures with varying water content (between 0% and 100%) yield radial distribution functions and frequency correlation functions for the CN-stretch vibration. Comparison with experiments indicate that models based on fMDCM are considerably more consistent that those using multipoles. Computed viscosities from models M1 and M2 are within 30% of measured values and their change with increasing water content is consistent with experiments. This is not the case for model M0.

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Kai Töpfer, Eric Boittier, Michael Devereux, Andrea Pasti, Peter Hamm, Markus Meuwly. 2024-08-14. Force Fields for Deep Eutectic Mixtures: Application to Structure and 2D-Infrared Spectroscopy. https://doi.org/10.1021/acs.jpcb.4c05480

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