Theoretical study of the saturated vapor pressure and enthalpy of sublimation of C-60 and C-70 fullerites

Using the correlative method of the unsymmetrized self-consistent field for strongly anharmonic crystals and the virial expansion for a gas we undertook a theoretical study of the thermodynamic equilibrium between fullerites and their vapors. Results are presented here for the saturated vapor pressure and the enthalpy of sublimation for two, more widespread fullerites, C-60 and C-70 The calculations have been made over the whole interval from the equilibrium point with orientationally ordered modifications up to the spinodal temperature of the two-phase systems crystal-vapor T-S. For C-60 it has been estimated as T-S approximate to 1917 K. We estimate the triple point parameters for C-60: T-tr approximate to 1460 K, P-tr approximate to 740 Torr, and for C-70: T-tr approximate to 1500 K, P-tr approximate to 655 Torr.