Memory and Multipolar Effects on Dielectric Relaxation
H. Híjar , I. Santamaría-Holek

Facultad de Ciencias, Universidad Nacional Autonoma de Mexico, Circuito Exterior de Ciudad Universitaria, 04510, D.F. Mexico

Abstract: A mesoscopic entropy production approach is used in order to obtain the Fokker-Planck equation governing the evolution of the probability distribution function of a system of polar molecules in an external time-dependent electric field and in contact with a heat reservoir. A non-Markovian description is considered through the presence of memory functions entering into the linear relations coupling generalized fluxes and forces. This Fokker-Planck equation allows us to construct a coupled hierarchy of macroscopic evolution equations for the polarization vector, the quadrupolar moment tensor, i.e. the order parameter tensor, etc. This hierarchy is approximated up to the octupolar moment and the coupling between the quadrupolar and dipole moments is considered explicitly. Under this approximation the effects of order parameter relaxation on the complex susceptibility of the system are derived. Non-Markovian effects are taken into account by introducing different memory functions and the way in which they affect both the real and imaginary part of the complex susceptibility is studied in detail.