Fluid of hard spheres with dipolar-like patch interaction and effect of adding an isotropic adhesion

Abstract

We compare two fluid models of spherical molecules with anisotropic, purely surface interactions. Both models admit an analytical solution of the molecular Ornstein–Zernike integral equation, within the Percus–Yevick approximation plus orientational linearization. In the first model, the molecular surface corresponds to a unique non-uniform patch, with a potential obtained by truncating a long-ranged dipolar interaction exactly at the contact distance between two hard sphere particles. In the second model, a further isotropic adhesion is added to the intermolecular potential. The study is focused on the local orientational ordering. Differences and similarities with respect to hard spheres with full long-ranged dipolar forces are analysed in detail. The effect of the competition between anisotropic patch interaction and isotropic adhesion is investigated through the pair correlation function as well as via two novel anisotropic order parameters.

Keywords:

• anisotropic surface interactions
• hard spheres with dipolar-like patch
• molecular Ornstein–Zernike integral equation
• pair correlation function
• local orientational order

Acknowledgements

The support of the PRIN-COFIN under Grant No. 2007B58EAB is gratefully aknowledged.