Electronic and optical properties of red HgI2

Within the local-density approximation we have used the linear muffin-tin orbital method, without geometrical approximations, to calculate the electronic structure of red HgI2. Using the self-consistent potential we have calculated the energy bands and from these derived the anisotropic frequency-dependent dielectric function and the reflectivity spectrum. The calculated dielectric function is in good agreement with the experimental data in contrast to previous theoretical work. The effect bf the spin-orbit coupling on the optical properties has also been studied and found to be significant. In this work we predict a rather large anisotropy in the dielectric function resulting from the low-symmetry crystal structure.