Orientational order in dipolar fluids consisting of nonspherical hard particles
نویسندگان
چکیده
We investigate fluids of dipolar hard particles by a certain variant of density-functional theory. The proper treatment of the long range of the dipo-lar interactions yields a contribution to the free energy which favors ferromag-netic order. This corrects previous theoretical analyses. We determine phase diagrams for dipolar ellipsoids and spherocylinders as a function of the aspect ratio of the particles and their dipole moment. In the nonpolar limit the results for the phase boundary between the isotropic and nematic phase agree well with simulation data. Adding a longitudinal dipole moment favors the nematic phase. For oblate or slightly elongated particles we find a ferromag-netic liquid phase, which has also been detected in computer simulations of fluids consisting of spherical dipolar particles. The detailed structure of the phase diagram and its evolution upon changing the aspect ratio are discussed in detail.
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