Calculated optical spectra of IV-VI semiconductors PbS, PbSe and PbTe

A complete ab initio calculation of the optical properties of the semiconductor compounds PbS, PbSe and PbTe which crystallize in the rock-salt structure, is presented. The electronic structure has been obtained in two approximations for the exchange and correlation potential, the local density approximation and the generalized gradient approximation, comparing the relevant results. Our study includes the spin-orbit interaction. We have calculated the imaginary part of the dielectric function ε2(ω) and the real part ε1(ω) using the Kramers-Kronig relations. In addition, other optical parameters such as the absorption coefficient, the complex refraction index, and the reflectivity are presented. The main features showed by the optical function curves, can be understood on the bases of the band structure of these compounds, and our results can be satisfactory compared with experiments.