LIQUID-LIKE BEHAVIOR LN SOLIDS

The van der Waals approach to predict liquid-vapor coexistence, become s exact in the limit of weak, long-ranged attractive forces. However, for shorter ranged attractions, the liquid range shrinks and eventuall y disappears altogether. When the width of the attractive well becomes very small (less than 7% of the diameter of particles), an iso-struct ural solid-solid transition, reminiscent of the liquid-vapor transitio n, appears in the crystalline phase. This transition, that should be e xperimentally observable in certain colloidal suspensions, ends in a c ritical point. In quasi-two dimensional systems (e.g. confined colloid s), this critical point induces the formation of a stable hexatic phas e.