Anisotropic structure and dynamics of water under static electric fields.

Abstract

We study the structure and dynamics of water subject to a range of static external electric fields, using molecular dynamics simulations. In particular, we monitor the changes in hydrogen bond kinetics, reorientation dynamics, and translational motions of water molecules. We find that water molecules translate and rotate slower in electric fields because the tendency to reinstate the aligned orientation reduces the probability of finding a new hydrogen bond partner and hence increases the probability of reforming already ruptured bonds. Furthermore, dipolar alignment of water molecules with the field results in structural and dynamic anisotropies even though the angularly averaged metrics indicate only minor structural changes. Through comparison of selected nonpolarizable and polarizable water models, we find that the electric field effects are stronger in polarizable water models, where field-enhanced dipole moments and thus more stable hydrogen bonds lead to slower switching of hydrogen bond partners and reduced translational mobility, compared to a nonpolarizable water model.