ions. Depending on their composition, these copper sulfides are either semiconductors or metallic conductors.

At very high pressures, a copper disulfide, CuS₂, can be synthesized. Its crystal structure is analogous to that of pyrite, with all sulfur atoms occurring as S-S units. Copper disulfide is a metallic conductor due to the incomplete occupancy of the sulfur p band. Different stoichiometric compositions can be obtained by changing the redox