Computer simulation of polarization of mobile charges on the surface of a dielectric sphere in transient electric fields

The polarization of mobile charges on the surface of a dielectric sphere subjected to electric fields is simulated using a random walk method. The effects of field strength and charge density on the polarization time constant and the polarization strength are investigated in the limit where the characteristic electric energy is much larger than the thermal energy. A linear region and a nonlinear region are seen, with the transition between these regions determined by the ratio of the strength of the Coulomb interactions between the charges to the driving force from the applied electric field. The steady-state polarizability agrees well with the modified Maxwell-Wagner model, while the polarization time constant can differ by a factor of about 2, depending on the dielectric mismatch. The simulated effects are in qualitative agreement with experimental observations. (C) 1998 Elsevier Science B.V. All rights reserved.