A layer model for the band structure of SnI2

Abstract

The electronic band structure of tin iodide has been computed within the overlap reduced semiempirical tight-binding method. It is shown that the monoclinic lattice of SnI2 can be well approximated by a layered hexagonal lattice of the PbI2-type. The band structure obtained with this simpler model indicates, in accordance with the experimental absorption spectrum, that SnI2 has an indirect fundamental gap of about 2.1 eV, followed by a region of direct weak transitions and then by a strong excitonic series. The analogy with the excitonic series at the absorption edge in PbI2 gives information on the nature of these excitons in both compounds. The bands of SnI2 in the monoclinic lattice are also given for comparison.