Density functional theory for the phase diagram of rigid C-60 molecules

A density functional theory of freezing combined with a thermodynamically consistent integral equation method is used to predict the phase diagram of rigid C-60 molecules interacting via the Girifalco potential. It is found that the freezing line crosses the Liquid-vapor binodal lines near the critical point and the liquid phase exists in a very narrow range of temperatures (<20 K), in qualitative agreement with the molecular dynamics (MD) simulations of Cheng et al. But, quantitatively, the present result falls between the MD simulations and the Monte Carlo simulations of Hagen et al., the latter of which have predicted nonexistence of a liquid phase.