Transferable orthogonal tight-binding parameters for ZnS and CdS

Abstract

Calculations of Slater–Koster (SK) parameters appearing in the tight-binding method usingsp3d5 basis sets for both the cationic and anionic species are presented for ZnS and CdS. We haveadjusted these parameters to match the band structures obtained from the full potentiallinear augmented plane wave method. This operation has been carried out for a variety ofstructures namely zinc blende, wurtzite, rocksalt, CsCl and for a wide range ofnear-neighbor distances. The SK parameters have slightly different values for the samenear-neighbor distance in different structures. Therefore, a least-squares fitting has beenperformed separately for each parameter as a function of only the near-neighbor distance toguarantee the transferability of these parameters to different structural environments. Thefitted parameters are then used to calculate the electronic structure of small-sizedclusters of ZnS and CdS in given geometries and the results are compared with ab initio results. A fairly good agreement found in the one-electron energy spectrumand total energy confirms transferability of the parameters to different lengthscales. A detailed account of the calculation procedure and calibration results isgiven in the present paper. These parameters can be used to study the electronicstructure of large-sized clusters where first-principles methods are computationallydemanding. It may be mentioned that the SK parameters do not satisfy theR − (l + l′ + 1) Harrison scaling law for larger values of the near-neighbor distanceR.