The thermodynamic properties of fullerene C60 dimer obtained by fullerite C60 compression in the temperature range from T → 0 to 340 K

The temperature dependence of the heat capacity of a sample obtained by compression of C-60 under a 8 GPa pressure at 290 K and identified as a predominantly crystalline fullerene C-60 dimer, (C-60)(2), was studied by precision adiabatic vacuum calorimetry at temperatures from T --> 0 to 340 K and standard pressure. The experimental results were used to calculate the C-p(o)(T), H-o(T)-H-o(0), S-o(T)-S-o(0), and G(o)(T)-H-o(0) thermodynamic functions of the dimer in the same temperature range. Fractal dimensions D of the heat capacity function in the multifractal variant of the Debye theory of the heat capacity of solids were determined. It was found that D equaled one at temperatures T > 20 K, which was evidence of a chain structure of the dimer. The standard entropy of formation of the (C-60)(2) dimeric phase from the corresponding simple substance (graphite) at 298.15 K and standard pressure and the entropy of transformation of initial fullerite C-60 into the (C-60)(2) dimeric phase under the same physical conditions were calculated.