Neutron powder diffraction studies were carried out at pressures of up to 7.3kbar, and temperatures of up to 740K. The existence of a solid phase at pressures above about 2kbar and temperatures greater than about 700K was confirmed. This phase was labelled CuCl-III and had a cubic structure (Im¯3m). The Cl anions formed a body-centered cubic sub-lattice in which the Cu cations were randomly distributed over the 12(d) tetrahedral sites at (¼,0,½)  et cetera. The basic structure and nature of the thermally induced disorder appeared to be similar to those which were exhibited by the ambient-pressure super-ionic phases, -AgI and -CuBr. It was concluded that CuCl could no longer be considered to be a non-superionic, and therefore anomalous, member of the family of binary tetrahedrally coordinated halides.

S.Hull, D.A.Keen: Journal of Physics - Condensed Matter, 1996, 8[34], 6191-8