ELECTRIC-FIELD-INDUCED PHASE-TRANSITION IN ELECTRORHEOLOGICAL FLUIDS

We study an electrorheological fluid consisting of spherical dielectric particles in a liquid of low dielectric constant. At a fixed temperature, there are two critical electric fields E(c2) < E(c1). When the applied field E < E(c2), the system is a fluid with no long-range order. When E(c2) < E < E(c1), the particles form chains between two electrodes, but the distribution of these chains is random. This state is similar to an induced nematic liquid crystal. As E exceeds E(c1), the system is a solid whose ideal structure is a body-centered tetragonal lattice with a1 = square-root 6ax, a2 = square-root 6ay, and a3 = 2az, where a is the radius of dielectric spheres and z is the field direction.