Transferable Orthogonal Tight Binding Parameters for CdS, CdSe and CdTe

Tight Binding (TB) method was first developed by Slater and Koster[1] for band structure calculations. With the advent of nanostructures, the method is experiencing revival due to its computational speed and capability of retaining the quantum mechanical description essential for electronic structure calculations. Despite being a parametric technique, TB method has added advantage of transferability of the parameters with adequate accuracy. Calculations of Slater Koster (SK) parameters appearing in the tight binding method using spd basis sets for both the cationic and anionic species are presented in the present work for CdS, CdSe and CdTe. The importance of inclusion of d orbitals and the next neighbor interaction has been proved to be essential by Sarma et. al. [2]. We have employed similar method with significant modifications. We have adjusted the SK parameters to match the band structures obtained from the full potential linear augmented plane wave method as implemented in the Wien2k package [4]. The calculations have been carried out for a variety of structures viz. zinc blend, wurtzite, rock salt, CsCl which are the high pressure phases of the II-VI semiconductors [3]. Along with the structures a wide range of lattice parameter values are used to get possible variations in the near neighbor distances. These modifications are necessary since the fitted SK parameters are to be used for nanostructures which need not have the same geometry as the parent bulk material. A least square fitting has been performed separately for each parameter as a function of near neighbor distance to guarantee the transferability of these parameters to different structural environments. The parameters are fitted in a polynomial form to be used to calculate the electronic structure of small sized clusters. Such type of polynomial fitting of SK parameters has been reported for metals and elemental semiconductors [5]. We are reporting these for the