High-pressure phase of copper(I) iodide

The structural properties of copper(I) iodide have been investigated at pressures up to 40 GPa using the angle-dispersive x-ray diffraction technique with an image-plate area detector. A previously unreported structural phase transition is observed in the region of 17.3 to 18.2 GPa, from the antilitharge structured phase CuI-V (space group P4/nmm) to an orthorhombic structure (space group Cmcm). The latter has been labeled CuI-VIII and can be considered as a heavily distorted rocksalt arrangement, with the cation environment closer to fivefold coordination than regular octahedral. No evidence was found for the rocksalt structured phase observed at {~}12 GPa by previous workers.