Thermodynamic properties of 1D and 2D polymerized fullerite C60 between 0 and 340 K at standard pressure

The temperature dependence of heat capacity of one-dimensionally (1D) and two-dimensionally (2D) polymerized C60 produced by heating monomeric C60 up to 550 K at a pressure of 5 GPa and to 960 K at a pressure of 3.5 GPa, respectively, with the subsequent quenching of the samples to normal conditions has been studied in the 5–340 K range using the adiabatic vacuum calorimeter. The experimental objects were structurally identified as orthorhombic (1D) and tetragonal (2D, with some amount of 2D rhombohedral phase) crystalline modifications of polymerized C60. We extrapolated the experimental temperature dependence of heat capacity Cp0 down to 0 K and from this dependence we have calculated the following thermodynamic functions over the 0–340 K interval, enthalpy H0(T)−H0(0), entropy S0(T)−S0(0) and Gibbs function G0(T)−H0(0). Assuming that S0(0)=0, we have estimated the standard entropies of formation ΔfS0 for studied 1D and 2D polymers and entropies of hypothetical transitions, occurring at T=298.15 K and standard pressure, from monomeric C60 to 1D and 2D polymers, as well as of the mutual transition between 1D and 2D phases under the same physical conditions.