Enthalpy of formation and excess entropy for dilute copper-based alloys: Experimental and theoretical study

Abstract

Enthalpy of formation ΔH and excess free enthalpy G E of the binary dilute solutions Cu-M, where M goes from Ti to Ge in the periodic table, have been measured by liquid tin calorimetry ( ΔH) and solid galvanic cell experiments ( G E ). In the case of transition impurities in copper a simple one-electron theory provides the general features for the initial slope of the energy ΔE (or enthalpy ΔH) of formation. However for Fe, Mn, and Cr impurities experimental results confirm that it is necessary to take into account the magnetic decoupling of the impurity states. The double origin of the excess entropy ΔS E , i.e. vibrational and magnetic, is calculated. The comparison with the experimental results showed that for Ni, Fe and Co the spin fluctuations represent a very important part of ΔS E .