Molecular orbital calculations employing the SCF-Xα scattered-wave cluster method have been used to model the electronic structures of the thiospinel minerals linnaeite (Co3S4), carrollite (CuCo2S4) and greigite (Fe3S4). The results, which are in agreement with previously postulated qualitative models, support mixing of highest energy occupied orbitals (octahedral site eg and tetrahedral site e orbitals) in Co3S4 and CuCo2S4 with consequent metallic conductivity and temperature independent (Pauli) paramagnetism. This contrasts with Fe3S4 in which spin-splitting of the orbitals in the valence region results in localized outermost electrons and ordered magnetism. The physical properties of thiospinels can be understood in terms of these molecular orbital models.

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