The intermediate solid solution (ISS) of the Cu-Fe-S system: Phase equilibria calculation at elevated temperatures based on Gibbs energy modeling
Year: 2026
Type: article
Abstract: The phase equilibria of the Cu-Fe-S system are calculated from liquidus to medium temperatures based on Gibbs energy modeling of the intermediate solid solution (ISS). The compound energy formalism is used for a suitable thermodynamic model to account for the pronounced solid solution character of ISS. The obtained Gibbs energy as a function of composition and temperature allows the computation of complex phase relations with high-temperature modifications of bornite and pyrrhotite, pyrite and chalcopyrite, of which a Gibbs energy expression as a function of temperature is also provided. For the first time, a direct comparison is made public between the well-known experimental isoplethal phase diagram along the CuFe–S join, which was provided more than fifty years ago by Barton (1973) , and a thermodynamically computed phase diagram section. A detailed comparison with experimental phase equilibria data on the homogeneity range of ISS at 800 °C, 760 °C, 700 °C and 600 °C with calculated results is carried out. In total three isoplethal and four isothermal sections of the Cu-Fe-S phase diagram are computed, and the agreement with experimental data available in the literature ranges from fair to very satisfactory.
Source: Chemical Geology
Author: Peter Waldner
Institution: Montanuniversität Leoben
Language: English
Subfield: Mechanical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,550
OpenAlex ID: W7118488656