The x-ray-photoelectron spectrum of the valence band of CuCl is compared with recent band-structure calculations to obtain information about the electronic structure and the energy gap. The gap at room temperature is found to be larger than 2 eV; too large to expect a decrease to zero at high pressures. A drastic change in the chemical structure of the material is therefore necessary to cause the recently reported high-temperature superconductivity at moderate pressures. In addition to the one-hole density of states possibly obtained from photoelectron spectroscopy, we also studied with Auger spectroscopy the two-hole density of states. From this we obtain the hole-hole Coulomb repulsion energies as well as some information about the hybridization.

• Received 9 March 1979

DOI:https://doi.org/10.1103/PhysRevB.20.4287