DIFFERENTIAL-THEORY OF FLUIDS BELOW THE CRITICAL-TEMPERATURE - STUDY OF THE LENNARD-JONES FLUID AND OF A MODEL OF C-60

The hierarchical reference theory (HRT) is applied to the Lennard-Jone s fluid below the critical temperature T-c. This study completes a pre vious one performed above T-c using the same kind of approximate closu re for the direct correlation function. Results for several thermodyna mic quantities and for the two-particle correlations are reported and compared both with other theories and with simulation data. In the two -phase region the theory correctly yields rigorously hat isotherms; th is feature allows a straightforward and accurate determination of the coexistence curve without resorting to the Maxwell construction. In th e critical region our analysis is consistent with the previously devel oped one for T > T-c and displays nontrivial critical exponents. We al so study a fluid with the Girifalco model potential for C-60 The criti cal point of the liquid-vapor transition is found at T-c = 2138 K and rho(c) = 0.50 nm(-3). When the HRT result is supplemented with Verlet' s freezing criterion a triple point is found at T-t = 1979 K and rho(t ) = 0.848 nm(-3).