Empty liquid phase of colloidal ellipsoids: The role of shape and interaction anisotropy

We study the effect of anisotropic excluded volume and attractive interactions on the vapor-liquid phase transition of colloidal ellipsoids. In our model, the hard ellipsoid is embedded into an ellipsoidal well, where both the shape of the hard ellipsoid and that of the added enclosing ellipsoidal well can be varied independently. The bulk properties of these particles are examined by means of a van der Waals type perturbation theory and validated with replica exchange Monte Carlo simulations. It is shown that both the critical volume fraction (eta(c)) and the critical temperature (T-c) of the vapor-liquid phase transition vanish with increasing shape anisotropy for oblate shapes, while eta(c) -> 0 and T-c not equal 0 are obtained for very elongated prolate shapes. These results suggest that the chance to stabilize empty liquids (a liquid phase with vanishing density) is higher in suspensions of rod-like colloidal ellipsoids than in those of plate-like ones. (C) 2014 AIP Publishing LLC.