| Abstract: | Utilizing the results of published simulations for the liquid C 60 phase using a model of rigid C 60 molecules, it is pointed out that the liquid phase has a critical compressibility ratio Z c = p c /( c k B T c ) in terms of the usual critical thermodynamic variables (critical pressure p c , critical density c and critical temperature T c ), of 0.32. This is to be compared with the value 0.29 for the heavy condensed rare gases Ar, Kr and Xe, in spite of their much lower T c , and with the prediction of 0.27 from Dieterici's phenomenological equation of state. The global shape of the coexistence curve, as embodied in the behaviour of the normalized difference density ( l m g )/ c versus the average density ( l + g )/2 c , where l and g are the liquid and the gas densities, respectively, is also consistent with the shape of the coexistence curve of insulating fluids. Going beyond the assumption of rigid C 60 molecules has interesting consequences on the stability and observability of the liquid phase, and those effects are discussed. |
