First-principles molecular dynamics simulations in the canonical ensemble at temperatures of 333 and 363 K and at the corresponding experimental densities are carried out to investigate the behavior of the 1:2 choline chloride/urea (reline) deep eutectic solvent and its equimolar mixture with water. Analysis of atom-atom radial and spatial distribution functions and of the H-bond network reveals the microheterogeneous structure of these complex liquid mixtures. In neat reline, the structure is governed by strong H-bonds of the trans- and cis-H atoms of urea to the chloride ion. In hydrous reline, water competes for the anions, and the H atoms of urea have similar propensities to bond to the chloride ions and the O atoms of urea and water. The vibrational spectra exhibit relatively broad peaks reflecting the heterogeneity of the environment. Although the 100 ps trajectories allow only for a qualitative assessment of transport properties, the simulations indicate that water is more mobile than the other species and its addition also fosters faster motion of urea.
Bibliographical noteFunding Information:
Financial support for this collaborative project from the Abu Dhabi Petroleum Institute Research Center (Project Code LTR14009) and through a grant from the National Science Foundation (CHE-1265849) is gratefully acknowledged. E.O.F. also acknowledges support from the University of Minnesota through a Graduate School Doctoral Dissertation Fellowship. Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory (LLNL) under Contract DE-AC52-07NA27344 with computing support from the Institutional Computing Grand Challenge program. Additional computer resources were provided by the Minnesota Supercomputing Institute at the University of Minnesota.