ELECTRONIC AND OPTICAL-PROPERTIES OF HGI2

Empirical nonlocal pseudopotential calculations of the electronic band structure of undoped mercuric iodide in its red tetragonal form are presented. Values for the electron and hole effective masses, optical matrix elements for interband transitions, and complex dielectric function are reported. Excitonic effects on the absorption coefficient near the fundamental band gap are included within the effective-mass approximation. The resulting absorption spectra and the polarization dependence are in good agreement with experiment. The dielectric-function spectra for photon energies between 2 and 10 eV are also calculated and they are in fair agreement with available data.