Self-consistent electronic spectrum of trigonal Te. Pressure dependence of energy spectrum

The behavior of the energy bands and core levels of trigonal Te under hydrostatic pressure up to 38 kbar is calculated within the $X_{\alpha }$ scheme for $\alpha =\frac{2}{3} \mathrm{and} 1$ using the fully self-consistent symmetrized orthogonalized-plane-wave method. The results are compared with those of the self-consistent pseudopotential method and experiments. The optical gap is direct and remains at $H$ at all pressures. The margins to the next valence-band maximum and conduction-band minimum increase with increasing pressure. At room temperature the optical gap is estimated to be less than $\mathrm{kT}$ at ≈ 40 kbar. The valence density of states shows a close resemblance to the x-ray-photoemission spectra. The core levels are found to be insensitive to pressure. The relativistically corrected $\alpha =1\mathrm{}$ core levels are more negative than the experimental ones (except $3s$). This allows positive relaxation corrections.