Demixing phase transition in a mixture of hard-sphere dipoles and neutral hard spheres

For a mixture of hard-sphere dipoles and neutral hard spheres we calculate the correlation functions from integral equations and evaluate the concentration structure factor Scc(k). For large enough dipolar interaction, this structure factor becomes infinite, indicating a demixing phase transition. This instability is also found for charged hard spheres in a dipolar solvent and is the reason for the problems faced previously in investigations of hard-sphere model electrolytes.