P. Schmidbeurmann et W. Lottermoser, FE-57-MOSSBAUER SPECTRA, ELECTRONIC AND CRYSTAL-STRUCTURE OF MEMBERS OF THE CUS2-FES2 SOLID-SOLUTION SERIES, Physics and chemistry of minerals, 19(8), 1993, pp. 571-577
Members of the (Cu, Fe)S2 solid solution crystallize in the pyrite str
ucture type, space group Pa 3, Cu and Fe being statistically distribut
ed on the metal sites. Within this series, a semiconductor to metal tr
ansition can be detected between 25 and 38 mole% CuS2 . Compositional
dependent Fe-57-Moessbauer spectra reveal Fe2+ in low-spin configurati
on. A minimum of the quadrupole splitting and the slope in the Fe-57-i
somer shift in the intermediate part of the system, near 30 mole% CUS2
, can be correlated with the onset of metallic conductivity, whereas t
he structural parameters are not influenced by this transition. The an
alysis of the compositional dependency of the quadrupole splitting, in
comparison to the isotypic system (Co, Fe) S2, leads to the conclusio
n that Cu in solid (Cu, Fe)S2 compounds is Cu+ with an Ar-3 d10 electr
onic configuration.