Thermodynamic properties of UFe2: agreement with the Campbell correlation of Laves phase compounds

The reported value of the heat of formation of UFe2 determined by acid solution calorimetry and the Gibbs energy of formation determined by high temperature emf cells give results that are in poor agreement. A well defined correlation exists between the heat of formation and the unalloyed radius ratio of AB2 type Laves compounds. When this test is applied it is found that the emf data of Yoshihara and Kauno for UFe2 give good correlation with the compounds formed between Pu and the Group VIIIa metals. These authors did not indicate that heats or entropies of formation could be calculated from their data, a third law calculation using Kopp's low of the additivity of heat capacity shows that the entropy term derived from the observed Gibbs energy of formation is reasonable. The thermal functions were calculated in this manner after making a small correction for the Curie point anomaly in Fe at 1033 K. The Curie point of UFe2 was estimated to be 193 K. The thermodynamic functions are given and were calculated from the Gibbs energies of formation at 1000 K