ELECTRONIC-ENERGY LEVELS OF CINNABAR (ALPHA-HGS)

We have calculated the electronic energy levels of trigonal mercury sulfide in the semiempirical tight-binding scheme. The atomic levels 3s, 3p of sulfur and 6s, 6p of mercury constitute the starting basis set. The computed two-center overlap integrals are subsequently scaled by a common multiplicative factor to reproduce the experimental optical gap. The effect of the atomic virtual level 4s of sulfur on the conduction bands is also taken into account. The calculated valence-band structure agrees well with the ultraviolet-photoelectron- spectroscopy (UPS) data. The complete band structure is consistent with the absorption measurements which indicate an indirect absorption edge immediately followed by the direct one (at the zone center). This picture can also explain the dependence of the absorption coefficient on the polarization of the exciting light in terms of the symmetry of the levels and the selection rules. © 1979 The American Physical Society.