ISOSTRUCTURAL SOLID-SOLID TRANSITION

  Monte Carlo simulations show that dense systems of spherical particles with a short-ranged attractive interaction, can undergo 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. Introduction of size-polydispersity tends to suppress the solid-solid transition. We argue that the solid-solid phase transition should be experimentally observable in mixtures of uncharged colloids and non-adsorbing polymers.

• Introduction
• Square well systems in two and three dimensions
  • Solid-solid coexistence
  • Fluid-solid coexistence
  • Results
  • High density limit
• Cell model calculations
• Yukawa potential
• Square shoulder potential
• Polydispersity
• Conclusion