  Electrical charging of parallel plates confining a model ionic liquid down to
nanoscale distances yields a variety of charge-induced changes in the
structural features of the confined film. That includes even-odd switching of
the structural layering and charging-induced solidification and melting, with
important changes of local ordering between and within layers, and of squeezout
behavior. By means of molecular dynamics simulations, we explore this variety
of phenomena in the simplest charged Lennard-Jones coarse-grained model
including or excluding the effect a neutral tail giving an anisotropic shape to
one of the model ions. Using these models and open conditions permitting the
flow of ions in and out of the interplate gap, we simulate the liquid squeezout
to obtain the distance dependent structure and forces between the plates during
their adiabatic appraoch under load. Simulations at fixed applied force
illustrate an effective electrical pumping of the ionic liquid, from a thick
nearly solid film that withstands the interplate pressure for high plate charge
to complete squeezout following melting near zero charge. Effective enthalpy
curves obtained by integration of interplate forces versus distance show the
local minima that correspond to layering, and predict the switching between one
minimum and another under squeezing and charging.
