THE TEMPERATURE-SIZE PHASE-DIAGRAM OF LARGE SF6 CLUSTERS BY COMPUTER-SIMULATION

We report the full temperature-size phase diagram for closed-shell sulfur hexafluoride (SF6) clusters by molecular dynamics simulation. A bulk-like phase behaviour is observed in the size range N=19 to the thermodynamic limit. The solid-solid transition temperature is roughly unchanged from the thermodynamic limit to a size of approximate to 1000 molecules and decreases as clusters get smaller. A triple point is observed at T approximate to 60 K for N approximate to 30. The main features of the diagram can be explained in terms of the simple thermodynamic model of transition temperature depression based on surface tension difference between the phases.