Electron Energy Bands in Tellurium

The method of pseudopotentials was used to calculate the electron band structure of tellurium along the kZ axis. The calculation was performed in two stages. First, a model pseudopotential, based on the free-atom data of Herman and Skillman, was used to compute a preliminary band structure. Perturbation theory was then used to estimate the changes in the band structure caused by corrections to the model pseudopotential. The calculated band structure shows a direct energy gap at the top of the Brillouin zone (kZ=πc) and an indirect gap of about the same magnitude between the valence band edge at kZ=0 and the conduction band edge kZ=πc. It was found that s-p mixing is significant in the important valence and conduction bands. Because of this mixing, spin-orbit splitting, which was calculated in a second-order perturbation approximation, is much smaller than the corresponding splitting of the $5p$ free-atom level. The calculated band structure is consistent with the major features of the experimental infrared absorption spectrum including the 11-{μ} peak observed by Caldwell and Fan.