Chemical thermodynamic representation of AmO2−x

The AmO2−x solid solution data set for the dependence of the oxygen potential on the composition, x, and temperature was retrieved from the literature and represented by a thermodynamic model. The data set was analysed by least-squares using equations derived from the classical thermodynamic theory for the solid solution of a solute in a solvent. Two representations of the AmO2−x data were used, namely the Am5/4O2–AmO2 and AmO3/2–AmO2 solid solution. No significant difference was found between the two, and the Am5/4O2–AmO2 solution was preferred on the basis of the phase diagram. From the results the Gibbs energy of formation of Am5/4O2 has been derived.