Dielectric response of nanoscopic spherical colloids in alternating electric fields: a dissipative particle dynamics simulation.

We study the response of single nanosized spherical colloids in electrolyte solution to an alternating electric field (AC field) by computer simulations. We use a coarse-grained mesoscopic simulation approach that accounts in full for hydrodynamic and electrostatic interactions as well as for thermal fluctuations. The solvent is modeled as a fluid of single dissipative particle dynamics (DPD) beads, and the colloidal particle is modeled as a rigid body made of DPD beads. We compute the mobility and the polarizability of a single colloid and investigate systematically the effect of amplitude and frequency of the AC fields. Even though the thickness of the Debye layer is not 'thin' compared to the radius of the colloid, and the thermal fluctuations are significant, the results are in good agreement with the theoretical prediction of the Maxwell-Wagner-O'Konski theory, especially for uncharged colloids.