Field stimulated diffusion in dielectric liquids

A liquid dielectric partly inserted into a homogeneous electric field is considered. Equations were derived for the determination of the relative change ΔN E-2N-1 in the number of liquid molecules following the application of the field E stimulating the diffusion. Then ΔN was related with the change in permittivity ε by calculating the contribution ΔεN to the nonlinear dielectric effect (NDE) and due to the electric field stimulated diffusion. The values of ΔεNE-2 were calculated numerically for halogen derivatives of benzene and for nitrobenzene. We obtained positive values of the same order of magnitude as the experimentally measured [1] data of ΔεexpE-2 as well as negative contributions due to reorientation of dipolar molecules ΔεorE-2 calculated from the Onsager model. Moreover, we have shown correlation between the experimental data on (∂ε/∂T)p, viscosity and NDE and suggest that it originates in the electric field stimulated diffusion.The equation for ΔεNE-2 was derived from the principle of equality of the liquid's chemical potentials within the field E and outside it. Thus, the only asumptions made were the axioms of thermodynamics.In conclusion we can say that in the interpretation of NDE the value of ΔεN should be taken into account in no lesser degree than Δεor

Electric-field-induced structural changes in water confined between two graphene layers

An external electric field changes the physical properties of polar-liquids due to the reorientation of their permanent dipoles. For example it should affect significantly the physical properties of water confined in a nanochannel. The latter effect is profoundly enhanced, if the field is applied along the nanochannel. Using molecular dynamics simulations, we predict that an in-plane electric field applied parallel to the channel polarizes water molecules which are confined between two graphene layers, resulting in distinct-ferroelectricity and electrical hysteresis. We found that electric fields alter the in-plane order of the hydrogen bonds: reversing the electric field does not restore the system to the non-polar initial state, instead a residual dipole moment remains in the system. Our study provides insights into the ferroelectric state of water when confined in nanochannels and shows how this can be tuned by an electric field