The 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 calorimetry1 and the Gibbs energy of formation determined by high temperature emf cells2 seem to give results that are in unreasonably poor agreement. It was recently discovered3 that 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 gives very good correlation with the compounds formed between Pu and the Group Villa metals as shown in Fig. 1. Although these authors did not indicate that heats or entropies of formation could be calculated from their data, a third law calculation using Kopp’s law of the additivity of heat capacity4 shows that the entropy term derived from the observed Gibbs energy of formation