Molecular dynamics simulations of choline chloride and phenyl propionic acid deep eutectic solvents: Investigation of structural and dynamics properties.

The prediction of deep eutectic composition is hard and so far, has been distinguished by trial and error. Therefore, in this work, molecular dynamics simulations were performed for specifying the composition of the eutectic point of phenyl propionic acid (Phpr) and choline chloride (ChCl) mixtures. The distinctive properties of the Phpr and ChCl eutectic mixture at the composition of the eutectic point were investigated and were compared to other eutectic mixtures with the different mole fractions of Phpr and ChCl. Structural properties such as radial distribution function (RDF), coordination number, hydrogen-bond number, interaction energies, and dipole moment of species, as well as dynamical properties such as mean square displacement (MSD), viscosity, and self-diffusion coefficient were analyzed. The obtained results of structural properties indicated that each chloride anion is surrounded by two Phpr molecules for deep eutectic point states that is in good agreement with available experimental reports. Moreover, the viscosity of studied mixtures evaluated by the Green-Kubo method was found to be consistent with the reported experimental data. Besides, the stress-autocorrelation function (SACF) and convergency of viscosity with time were calculated. Finally, the eutectic point could be detected by the changes in the trends of total van der Waals interaction energies and the viscosity.