Assessment of the temperature and pressure dependence of molar volume and phase diagrams of Cu and Zn

This study reports the thermodynamic assessment of the temperature and pressure dependence of molar volume of Cu and Zn, as well as their P-T phase diagrams based on the CALPHAD approach. The molar volume of fcc-Cu, hcp-Zn, and liquid phases as a function of both temperature and pressure was directly assessed from the data reported in the literature by implementing the CALPHAD-compatible equation of state (EOS). This EOS incorporates the quasi-harmonic model to eliminate the spurious predictions of negative heat capacity and thermal expansion at high pressure. Furthermore, the P-T phase diagram of each element was determined on the basis of the experimental results and calculated parameters. The experimentally estimated thermodynamic values are in good agreement with the calculated results.