Abstract
A thorough review and critical evaluation of all experimental sulfur potential and phase diagram data available from the literature has been made for optimizing the Gibbs energy of the copper-sulfur liquid phase at 1 bar total pressure. The extended modified quasichemical model serves as a basis for the mathematical expression of the Gibbs energy of binary Cu-S solutions over the complete composition range. A structurally versatile molten phase ranging from highly metallic via sulfur-rich to pure sulfuric is described simultaneously by a single Gibbs energy function. In combination with the recently published Gibbs energies of all Cu-S solid phases, the complete T–x phase diagram as well as for the first time the {text{log(}}p_{{{text{S}}2}} /{text{bar)}} - 1 /T diagram is calculated. A limited set of obtained model parameters reproduces a large body of data within experimental uncertainties.
Highlights
THE liquid phase of the copper-sulfur system is characterized by the existence of two extended regions of miscibility gaps between them the solid solution digenite melts congruently at a stoichiometry around Cu2S
According to the review of Chakrabarti and Laughlin[1] the liquidus maximizes at 1403 ± 2 K (1130 ± 2 °C) in relation with the congruent melting point of digenite while the liquid solution demixes within two miscibility gaps above 1378 K (1105 °C) at copper-rich compositions on one side of digenite and above 1086 K (813 °C) at higher sulfur compositions on the other side
Nine condensed Cu-S phases are reported for 1 bar total pressure, which are the solids anilite Cu1.75S, covellite CuS, high- and low-temperature chalcocite, djurleite, digenite and the terminal phases based on Cu and S
Summary
THE liquid phase of the copper-sulfur system is characterized by the existence of two extended regions of miscibility gaps between them the solid solution digenite melts congruently at a stoichiometry around Cu2S. Nine condensed Cu-S phases are reported for 1 bar total pressure, which are the solids anilite Cu1.75S, covellite CuS, high- and low-temperature chalcocite, djurleite, digenite and the terminal phases based on Cu and S. Sharma and Chang[5] took into account the same approach for the liquid solution and considered covellite, high-temperature chalcocite and digenite for a thermodynamic analysis of the Manuscript submitted November 6, 2019.
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