  We study the behavior of ambient temperature water under the combined effects
of nanoscale confinement and applied electric field. Using molecular
simulations we analyze the thermodynamic causes of field-induced expansion at
some, and contraction at other conditions. Repulsion among parallel water
dipoles and mild weakening of interactions between partially aligned water
molecules prove sufficient to destabilize the aqueous liquid phase in isobaric
systems in which all water molecules are permanently exposed to a uniform
electric field. At the same time, simulations reveal comparatively weak
field-induced perturbations of water structure upheld by flexible hydrogen
bonding. In open systems with fixed chemical potential, these perturbations do
not suffice to offset attraction of water into the field; additional water is
typically driven from unperturbed bulk phase to the field-exposed region. In
contrast to recent theoretical predictions in the literature, our analysis and
simulations confirm that classical electrostriction characterizes usual
electrowetting behavior in nanoscale channels and nanoporous materials.
