DIVALENT GOLD IN PEROVSKITE-TYPE CSAUI3

The distorted cesium gold iodide Cs2Au2I6 exhibits coexisting Au+ and Au3+ states at ambient conditions. The Mossbauer effect of Au-197 at 12.5 GPa (4.2 K) shows, however, that only one intrinsic Au2+ state is present at high pressures, indicating a crystal structure of the ideal perovskite type as found previously from high pressure X-ray diffraction studies at 300 K. The observed pressure dependences of the Au-197 hyperfine data may be correlated with Au electronic 6s and 5d populations, coordination polyhedral geometries, and interatomic distances.