Isostructural solid-solid transition in crystalline systems with short-ranged interaction

Monte Carlo simulations show that dense systems of spherical particles with a short-ranged attractive interaction can undego a first-order transition from a dense to a more expanded solid phase with the same structure. This phase transition is analogous to the liquid-vapor transition in systems with longer-ranged attractive forces. In particular, the solid-solid transition terminates in a critical point. Numerical simulations on a square-well model indicate that a solid-solid transition will occur both in two and in three dimensions if the width of the attractive well is less than 7% of the hard-core diameter. For a hard-core Yukawa model, the transition occurs at a comparable value of the width of the attractive well. We argue that the solid-solid phase transition should be experimentally observable in mixtures of uncharged colloids and nonadsorbing polymers.