ELECTRONIC AND OPTICAL-PROPERTIES OF COPPER HALIDES MIXED-CRYSTAL CUCL1-XBRX

The effects of chemical disorder on electronic and optical properties of mixed CuCl1-xBrx crystals are studied on the basis of a modified vi rtual 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 CuBr are discussed. The variation of the energy with alloy concentration in the pseudobin ary system formed with these compounds is reported and interpreted. Th e essential features of disorder-induced changes in electronic and opt ical structure are exhibited from the TB results by two characterizati on parameters: the subband energy spacings, and the density of states. (C) 1998 Elsevier Science Ltd.