ROLE OF D-ELECTRONS IN THE ZINCBLENDE SEMICONDUCTORS ZNS, ZNSE, AND ZNTE

We perform ab initio pseudopotential total-energy calculations for ZnS , ZnSe, and ZnTe. Unlike in most previous calculations, we include Zn 3d orbitals (and, in case of ZnTe, Te 4d orbitals as well) as part of the valence states in order to study the behavior of the d electrons a nd their influence on energy levels. The results for the structural an d electronic properties are in better agreement with experimental data than in the case where d electrons are considered as part of the core states. The role of the d electrons in determining the bonding streng th of the material and the character of the states near the band gap i s analyzed and discussed.