Ground state of an electrorheological fluid

The ground state of an electrorheological fluid is examined for high dielectric contrast (${\mathrm{\epsilon }}_{\mathit{p}}$/${\mathrm{\epsilon }}_{\mathit{f}}$→∞). In contrast to the result of Tao and Sun [Phys. Rev. Lett. 67, 398 (1991)] for the dipole limit, three structures are found to be degenerate: face-centered cubic, hexagonal close packed, and body-centered tetragonal. However, particle column surface energy favors the body-centered tetragonal structure, which has a lower surface energy per particle at the critical volume fraction of particles.