The Effect of Electric Fields on the Structure of Water/Acetonitrile Mixtures

Abstract

We study the effect of external electric fields on the structure of water/acetonitrile mixtures at high acetonitrile content by molecular dynamics simulations. We find that the linear response regime extends up to roughly 0.03 V /nm in these mixtures, then nonlinear behavior sets in. The most pronounced nonlinear effect of electric field is a change of relative orientations of neighboring acetonitrile molecules, from predominantly antiparallel to predominantly parallel. Nevertheless, the hydrogen bond network topology remains remarkably stable and conserves its overall properties in the whole range of considered applied fields up to 0.5 V /nm, which is far beyond the dielectric breakdown limit of pure water.

Probing Isolated Water Molecules in Aqueous Acetonitrile Solutions Using Oxygen K-Edge X-ray Absorption Spectroscopy

“…36,37 The structures of liquid water and small water clusters confined by ACN were obtained via MD simulations using GROMACS 2022.4. 38 As discussed in Section S2 of the Supporting Information, the molecular potential of ACN was used with the six-site potential model described by Kowsari and Tohidifar, 39 based on the comparison of several molecular potentials by Sourpis et al 40 The molecular potential of water was used with TIP4P/2005. 41 The inner-shell spectrum of liquid water was obtained by summing 14,900 spectra of small water clusters over a simulation time of 100 ns.…”

“…To investigate the relationship between the sharp profiles of the main-edge peaks in the O K-edge XAS spectra of aqueous ACN solutions and the structures of the water clusters in aqueous ACN solutions, inner-shell calculations of small water clusters of different sizes were performed using the program package GSCF3. , The structures of liquid water and small water clusters confined by ACN were obtained via MD simulations using GROMACS 2022.4 . As discussed in Section S2 of the Supporting Information, the molecular potential of ACN was used with the six-site potential model described by Kowsari and Tohidifar, based on the comparison of several molecular potentials by Sourpis et al The molecular potential of water was used with TIP4P/2005 . The inner-shell spectrum of liquid water was obtained by summing 14,900 spectra of small water clusters over a simulation time of 100 ns.…”