The low temperature heat capacities and thermodynamic functions of fluorofullerenes C_(60)F_(48) and C_(60)F_(46)

摘要

The heat capacities of fluorinated fullerenes C_(60)F_(48) and C_(60)F_(46) have been measured in an adiabatic automatic calorimeter over the temperature range from 5 to 356 K. The heat capacity curve of C_(60)F_(48) reveals gradual lambda transition between temperatures 315 K and 345 K. Thermodynamic properties of C_(60)F_(48) in the transition range are as follows: T_(trs) = 329.6+-0.4 K, triangle open_(trs)H = 7.0+-0.7 kJ*mol~(-1) and triangle open_(trs)S = 21+-2 J*K~(-1)*mol~(-1). The c_p curve of C_(60)F_(46) exhibits glassy crystal-to-crystal transition in the temperature interval from 210 K to 245 K. The thermodynamic functions H_T~0 - H_0~0, S_T~0 - S_0~0 and G_T~0 - H_0~0 of C_(60)F_(48) and C_(60)F_(46) have been calculated on the basis of the heat capacity data.