Investigation into the nature of copper and silver sites in argentian tetrahedrites using EXAFS spectroscopy

Synchrotron radiation has been used to collect Cu K-edge and Ag K-edge EXAFS from several tetrahedrite, (Cu,Ag)₁₀(Zn,Fe,Cu)₂Sb₄S₁₃, minerals. The results have been used to investigate the coordination environment of the Ag and Cu, and to determine which sites in the structure are occupied by silver atoms when they replace copper. The Ag EXAFS spectrum of a sample with high silver content reveals an interaction between silver and antimony which may explain the anomalous decrease in unit cell size found in natural tetrahedrites when the silver content increases beyond four atoms per unit formula.