Dynamics of polarization relaxation in a dipolar mixture at a solid--liquid interface

Dynamics of polarization relaxation in a dipolar mixture at solid–liquid interface is investigated theoretically by using time dependent density functional theory. The time dependence of the building up of polarization of different dipolar species next to a newly charged solid surface is calculated by solving both Markovian and non-Markovian equations of motion for density and momentum variables. The inhomogeneity of the interface is taken into account in the dynamical theory. The theory also includes the various intra- and interspecies molecular correlations and the surface–molecule interactions. Both the molecular size and the dipole moment of various species in the dipolar mixture can be unequal. The initial inhomogeneity of the interface is calculated by using a weighted density functional theory. Explicit numerical results are obtained for the polarization relaxation in a binary dipolar liquid at varying distances from the solid surface and the dynamics of interfacial relaxation of the two species are compared with that in the bulk phase. A slowing down of the rate of relaxation is found for interfacial molecules of both the species. However, the extent of slowing down is found to be different for different species. Also, the rate of relaxation is found to change nonmonotonically with distance from the surface due to the layering of solvent molecules at the interface. © 2000 American Institute of Physics.