A crystalline cluster model of the electronic structure of copper chloride

A crystalline cluster calculation has been performed to obtain the electronic structure of copper chloride. Several clusters have been used and it has been shown that the energy spectra so obtained do not differ significantly and that they reproduce the experimental data as well as the best of the existing band-structure calculations. The main sources of errors in the crystalline cluster model have also been investigated. The muffin-tin approximation introduces effects on the cluster bands smaller than those resulting from the Xalpha approximation or changes in the cluster size. However, for highly ionic crystals such as CuCl, the convergence of the bands as the cluster size increases is very fast and it has been observed that for these highly ionic crystals the cluster-size effects are not large enough to modify the qualitative behaviour of the cluster energy spectrum.