Towards the Role of the Range of Intermolecular Interactions

It has been traditionally believed that, unlike simple fluids whose properties are determined primarily by the short-range repulsions, the properties of complex fluids are strongly affected by the long-range electrostatic interactions. In the course of investigations, extensive and systematic computer simulations have been performed on typical quadrupolar, dipolar and associating fluids using available realistic potential models. The structural characteristics as well as dielectric constant and the thermodynamic properties of both the homogeneous liquid and supercritical fluid phases, and vapor-liquid equilibria have also been considered. The obtained results lead to the conclusion that the structure of pure fluids, both polar and associating, is governed by the same molecular mechanism as for simple fluids, i.e. by the short-range interactions, whereas the long-range part of the electrostatic forces, regardless of their strength, plays only a marginal role and may be treated as a perturbation only. However, it turns out that for mixtures of charged particles the situation is much more complex and that the observed behavior is very sensitive to the details of intermolecular interactions.