High pressure phases of CuI

In addition to the 14-kbar transition in CuI reported by Bridgman, there have been reports of phase transitions at 4-kbar and 5-kbar on the basis of optical observations. X-ray diffraction results using a diamond anvil cell give no indication of any structural change up to 14-kbar. This transformation is very sluggish and is not completed until a pressure of about 30-kbar is attained. Furthermore, another phase transition, not previously reported occurs at approximately 53-kbar. These results have been verified by resistivity measurements in the belt apparatus. The structures of the two high-pressure phases have not yet been completely solved, but both of them appear to require unit cells that are supercells of the starting zincblende structure.