CuCl: Electrical and optical properties at high pressure at temperatures from 400 °C to liquid-nitrogen conditions

Isobaric experiments using the Bridgman anvil technique have been conducted on CuCl to identify the electrical characteristics of the II-1{→}I, and the I{→}liquid and I{→}III phase transformations. Turning points in the resistance-versus-temperature curve identify known transition boundaries. Quenching temperature from phase III (5 kbar) to liquid-nitrogen conditions at approximately constant pressure and rapidly rewarming revealed ac electrical anomalies in the form of a first-order decrease in electrical resistance and a change in phase angle from -30^∘{} capacitive to -90^∘{} capacitive over the temperature range of 100-125 K. Examination of the recovered product showed evidence of disproportionation of copper chloride to free copper. Optical transmission studies in the diamond cell at about 50 kbar at room temperature show that the opaque disproportionated phase begins to develop a few minutes after the initiation of the zinc-blende to tetragonal phase transformation, and develops rapidly within 10-20 min, thereafter growing slowly.