Electronic and optical properties of copper halides mixed crystal CuCl1-xIx

The effects of chemical disorder on the electronic and optical properties of mixed CuCl1-xIx crystals are studied on the basis of a modified virtual crystal approximation, which incorporates compositional disorder as an effective potential. We use a simple tight-binding (TB) theory including d electron orbitals on the cation site. We show that such an approach provides analytical results for calculating energy gaps and bowing parameters. The band structures of CuCl and CuI are discussed. The variation of the energy with alloy concentration in the pseudo-binary system formed with these compounds is reported and interpreted. The essential features of disorder-induced changes in electronic and optical structure are exhibited from the TB results by two characterization parameters: the subband energy spacings, and the density of states. (C) 1998 Published by Elsevier Science B.V.