Electronic Energy Bands in ZnS: Potential in Zincblende and Wurtzite

This paper reports on the calculation of the crystal potential in ZnS. Experimental evidence relating to the nature of the chemical bond is reviewed, and it is concluded that the bonding is a mixture of covalent and ionic with effective charges of +{} for Zn, -{} for S. Radially symmetric sp³ valence electron densities are constructed for each ion and normalized within each equivalent volume sphere to the appropriate net ion charge. It is concluded that the same charge densities are appropriate for zincblende and wurtzite. Calculation using these charge densities then shows the crystal potential to be the same for both modifications in two corresponding prominent crystallographic directions. Hence, there is justification for using the same spherical potential for the cellular calculation of electronic energy bands in both structures. Finally, the close geometrical relationship of the two structures implies that many of the LCAO integrals which will arise in interpolating the band structures are identical.