Digenite Cu2-x S: thermodynamic analysis of sulfur activities

Gibbs energy modeling of the intermediate copper-sulfur phase digenite is performed at a total pressure of 1 bar using experimental sulfur activity data from the literature. A two-sublattice approach used in the framework of the compound energy formalism takes into account structural considerations. A limited set of optimized model quantities is obtained, which allows reproduction of all sulfur activity data available in the literature over a wide homogeneity and temperature range of the phase. Phase equilibria calculations applying the modeled Gibbs energy for digenite give very satisfactory phase relations in accordance with experimental data. A partial phase diagram within the composition range 0.0 a parts per thousand currency sign x (S) a parts per thousand currency sign 0.7 up to elevated temperatures is calculated.