APPLICATION OF A SPHERICALLY AVERAGED POTENTIAL TO SOLID C-70 IN THE DISORDERED PHASE

A spherically averaged potential was used to calculate solid state pro perties for C-70 in the disordered fee phase. Each molecule was treate d as a spherical shell of 70 carbons with radius of 3.8 Angstrom deter mined by fitting the equation of state to the experimental X-ray powde r diffraction data, The anharmonic properties were treated by using th e extended Mie-Gruneisen theory, This approach enabled us to compute c ompressibility and thermal expansion as well as the phase transition p oint between the solid and the vapor phases of C-70 The calculated ent halpy of sublimation, 193 kJ/mol, lies within the range of measured he ats, while the predicted sublimation point of 1023 K is higher than th e experimentally determined one.