Abstract
Thermochemical data on fullerenes are relatively scarce. However, some thermochemical information can be derived from gas-phase experiments using the Knudsen cell mass spectrometry method.
The third-law treatment can be carried out on the observed data, though one has to make the crucial presumption that the change in the thermodynamic potential DeltaPhi(T)(0) in the course of the reactions considered is negligible: DeltaPhi(T)(0) = 0. It would be difficult to check the presumption directly in the experiment, but it can be checked computationally.
Model reactions like C-60 + C-70(-) = C-60(-) + C-70 are selected. The change in the thermodynamic potential DeltaPhi(T)(0) and the change in the standard entropy DeltaS(T)(0) are computed.
For example, at a temperature of T = 1000 K, the standard changes for the reaction evaluated using the SAM1 method are DeltaPhi(T)(0) = 1.513 cal/(mol K) and DeltaS(T)(0) = -0.054 cal/(mol K). Overall, the computations support the critical thermodynamic presumption.