Is zinc HCP_ZN or HCP_A3?

Abstract The thermodynamic description of (Zn) solid solutions in current thermodynamic databases and publications is based on a phase HCP_ZN which is treated as separate from the hexagonal close-packed prototype phase HCP_A3. It is shown that this approach not only produces artifacts in the Mg–Zn system, but that it entirely fails when considering alloys based on Cd. Zn-rich, Cd-rich and Mg-rich solid solutions must all be modeled based on HCP_A3. The necessity to model pertinent Zn-rich or Cd-rich hcp e -phases separately from HCP_A3 is also emphasized. The elimination of the HCP_ZN phase description demands revision of current thermodynamic databases.