  A simple Kronig-Penney model is used to study the effect of nonlinear
interactions on the electronic properties of ordered and disordered electrified
chains. In the case of ordered potentials, we found that the nonlinearity
suppresses the Wannier-Stark effect caused by the electric field. In the case
of disordered potentials, the nonlinearity gives rise to a transition from
superlocalized to weakly localized states.
