Contribution of electronic entropy to the order-disorder transition of Cu3Au

Cu₃Au experiences a phase transition at 662 K from an ordered low-temperature phase to a disordered solid solution. While significant work has been devoted to characterizing the enthalpy of this transition, the apportionment of the entropy has remained out of reach. Current estimates of the vibrational and configurational entropy for the transition are larger than the total entropy of the transition experimentally measured by calorimetry, while calculations of the electronic entropy via ab initio methods have remained difficult. This work calculates an electronic entropy difference of −6.29 J/mol K based on a recent formalism that links experimentally measured electronic transport data and equilibrium thermodynamic properties. The application of this formalism brings some estimates of the vibrational and configurational entropy in line with the calorimetrically measured total entropy