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Preparation and reactions

Cu2S can be prepared by treating copper with sulfur or H2S.² The rate depends on the particle size and temperature.³ Cu2S reacts with oxygen to form SO2:⁴

The production of copper from chalcocite is a typical process in extracting the metal from ores. Usually, the conversion involves roasting, to give Cu2O and sulfur dioxide:⁵

Cuprous oxide readily converts to copper metal upon heating.

Structure

Stoichiometric

Two forms (a dimorphism) of Cu2S are known. The so-called low temperature monoclinic form ("low-chalcocite") has a complex structure with 96 copper atoms in the unit cell.⁶ The hexagonal form, stable above 104 °C,⁷ has 24 crystallographically distinct Cu atoms. Its structure has been described as approximating to a hexagonal close packed array of sulfur atoms with Cu atoms in planar 3 coordination. This structure was initially assigned an orthorhombic cell due to the twinning of the sample crystal.

Non-stoichiometric

As illustrated by the mineral djurleite, a cuprous sulfide is also known. With the approximate formula Cu1.96S, this material is non-stoichiometric (range Cu1.934S-Cu1.965S) and has a monoclinic structure with 248 copper and 128 sulfur atoms in the unit cell.⁸ Cu2S and Cu1.96S are similar in appearance and hard to distinguish one from another.⁹

Phase transition

The electrical resistivity increases abruptly at the phase transition point around 104 °C, with the precise temperature depending on the stoichiometry.¹⁰¹¹

See also

• Copper sulfide for an overview of all copper sulfide phases
• Copper monosulfide, CuS
• Chalcocite
• Djurleite
• LK-99 - compound evaluated in 2023 for possible superconductivity

References

1. Potter, R. W. (1977). "An electrochemical investigation of the system copper-sulfur". Economic Geology. 72 (8): 1524–1542. Bibcode:1977EcGeo..72.1524P. doi:10.2113/gsecongeo.72.8.1524. /wiki/Bibcode_(identifier) ↩

2. Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. p. 1373. ISBN 978-0-08-022057-4. 978-0-08-022057-4 ↩

3. Blachnik R., Müller A. (2000). "The formation of Cu2S from the elements I. Copper used in form of powders". Thermochimica Acta. 361: 31. doi:10.1016/S0040-6031(00)00545-1. /wiki/Doi_(identifier) ↩

4. Wiberg, Egon and Holleman, Arnold Frederick (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5 /wiki/ISBN_(identifier) ↩

5. Wiberg, Egon and Holleman, Arnold Frederick (2001) Inorganic Chemistry, Elsevier ISBN 0-12-352651-5 /wiki/ISBN_(identifier) ↩

6. Evans, H. T. (1979). "Djurleite (Cu1.94S) and Low Chalcocite (Cu2S): New Crystal Structure Studies". Science. 203 (4378): 356–8. Bibcode:1979Sci...203..356E. doi:10.1126/science.203.4378.356. PMID 17772445. S2CID 6132717. /wiki/Bibcode_(identifier) ↩

7. Wells A.F. (1984) Structural Inorganic Chemistry, 5th ed., Oxford Science Publications, ISBN 0-19-855370-6 /wiki/ISBN_(identifier) ↩

8. Evans, H. T. (1979). "Djurleite (Cu1.94S) and Low Chalcocite (Cu2S): New Crystal Structure Studies". Science. 203 (4378): 356–8. Bibcode:1979Sci...203..356E. doi:10.1126/science.203.4378.356. PMID 17772445. S2CID 6132717. /wiki/Bibcode_(identifier) ↩

9. Evans H.T. (1981). "Copper coordination in low chalcocite and djurleite and other copper-rich sulfides" (PDF). American Mineralogist. 66 (7–8): 807–818. http://www.minsocam.org/ammin/AM66/AM66_807.pdf ↩

10. Garisto, Dan (2023-08-16). "LK-99 isn't a superconductor — how science sleuths solved the mystery". Nature. 620 (7975): 705–706. Bibcode:2023Natur.620..705G. doi:10.1038/d41586-023-02585-7. PMID 37587284. S2CID 260955242. https://www.nature.com/articles/d41586-023-02585-7 ↩

11. Jain, Prashant K. "Phase transition of copper (I) sulfide and its implication for purported superconductivity of LK-99." arXiv preprint arXiv:2308.05222 (2023). https://arxiv.org/abs/2308.05222 ↩