Structure of polydisperse dipolar hard-sphere fluids

We report Monte Carlo simulations of dipolar hard-sphere fluids with a nonu niform distribution of the dipole strengths or different hard-sphere diamet ers. Dipolar polydispersity significantly reduces the spontaneous orientati onal order observed in the ferroelectric phase of monodisperse dipolar hard -sphere fluids at high densities and low temperatures. Equimolar binary mix tures of dipolar hard spheres of different diameters sigma(a) and sigma(b) also exhibit ferroelectric order. However, the order parameters are very de pendent on the ratio sigma(a)/sigma(b). Chains of dipolar hard spheres, typ ical of strongly interacting dipolar hard spheres at low densities and low temperatures, were observed in binary fluids of dipolar and neutral hard sp heres of different sizes. (C) 2000 American Institute of Physics. [S0021-96 06(00)50909-X].