The Clausius–Mossotti Factor

Scientific papers dealing with the dielectric or dielectrophoretic properties of bioparticles often refer to the Clausius‐Mossotti (CM) factor to describe their polarizabilities. This factor arises when dealing with the polarization of a particle embedded in a medium whose dielectric properties differ from that of the particle. Evaluation of the local field intensity acting on a molecule within a dielectric medium is central to the formulation of the CM factor. The complex form of the CM factor is required when time dependent electric fields are used. The chapter introduces the concepts of complex permittivity (ϵ * ) and complex conductivity (σ * ). The complex permittivity description of a dielectric material is employed to take into account the fact that it is not a perfect insulator, but exhibits energy losses associated with an electric field‐induced movement of free charges (e.g., a leakage current) or the relaxation of permanent dipoles.