Molecular secrets of deep eutectic solvents
Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
Final Report Abstract
Deep eutectic solvents are mixtures of two compounds possessing a eutectic melting point significantly below the melting point of the pure components. Most popular are mixtures of choline chloride, a pro-vitamin produced on a megaton scale. Our project focussed on two main tasks: Developing computational approaches for a reliable study of these liquids at the molecular scale and to apply these approaches to identify molecular features contributing to the unique behaviour of these liquids. During this project, a polarizable force field was developed for reline. Introducing an additional damping function was essential to screen the charge interactions between the chloride anion and the hydroxyl group of the cation. However, parameters of the non-bonded Thole screening function must be fitted against the first-principles molecular dynamics simulations. Therefore, we investigated the capabilities of invariant and equivariant machine learning interatomic potentials to study these liquids. The equivariant Allegro model in combination with an active learning scheme requests solely few thousand DFT calculations of a small system to simulate systems with several thousand atoms on the ns-time scale on a single GPU-node within one day. This facilitates reliable investigation of dynamical properties since at least five simulations are recommended to obtain a well converged average value. Thus, machine learning interatomic potentials provide highly accurate, and reliable structural and dynamical properties at a fraction of cost of first-principles molecular dynamics simulations. Our studies on the unique nature of deep eutectic solvents revealed that the incorporation of the chloride anion into the hydrogen bond network of the urea derivative is strongly correlated to the non-ideal mixing behaviour of choline chloride systems. Furthermore, we observe close contacts between two lithium atoms bridged by oxygen atoms of the organic compound in lithium bistriflimide systems. Please note, the close Li-Li-contacts play a negligible role in classical force field simulations, even with scaled charges. This highlights limitations of common classical force fields compared to approaches with forces on the accuracy of density functional theory calculations.
Publications
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Molecular Features of Reline and Homologous Deep Eutectic Solvents Contributing to Nonideal Mixing Behavior. The Journal of Physical Chemistry B, 124(35), 7586-7597.
Shayestehpour, Omid & Zahn, Stefan
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Molecular Features Contributing to the Non-ideal Mixing Behavior of Deep Eutectic Solvents Based on Urea Derivatives, IOM Biennial Report 2020/21, 38
Shayestehpour, Omid & Zahn, Stefan
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Data related to the publication "Ion Correlation in Choline Chloride-Urea Deep Eutectic Solvent (Reline) from Polarizable Molecular Dynamics Simulations", ZENODO, 2022
O. Shayestehpour & S. Zahn
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Ion Correlation in Choline Chloride–Urea Deep Eutectic Solvent (Reline) from Polarizable Molecular Dynamics Simulations. The Journal of Physical Chemistry B, 126(18), 3439-3449.
Shayestehpour, Omid & Zahn, Stefan
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Data related to the publication "Efficient molecular dynamics simulations of deep eutectic solvents with first-principles accuracy using machine learning interatomic potentials", ZENODO, 2023
O. Shayestehpour & S. Zahn
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Efficient molecular dynamics simulations of deep eutectic solvents with first principles accuracy using machine learning interatomic potentials, IOM Biennial Report 2022/23, 39
Shayestehpour, Omid & Zahn, Stefan
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Efficient Molecular Dynamics Simulations of Deep Eutectic Solvents with First-Principles Accuracy Using Machine Learning Interatomic Potentials. Journal of Chemical Theory and Computation, 19(23), 8732-8742.
Shayestehpour, Omid & Zahn, Stefan
