IONIC-DIFFUSION IN CU6PS5BR STUDIED BY CU-63 NMR

Applying Cu-63 NMR technique, we observed exchange between the nonequivalent copper sites in crystalline Cu6PS5Br, known as a member of the mineral ''argyrodite''. Below 200 K, where the motion of the copper(I) ion is slow, we could distinguish several nonequivalent copper sites. On increasing the temperature, the chemical exchange between the nonequivalent cation sites was seen oo the Cu-63 NMR spectra. We could determine the activation energy for this motion to be 35 kJ mol(-1), in good agreement with the published ionic conductivity.