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The electronic structure and frequency dependent dielectric function () of rocksalt semiconductors PbSe and PbTe are investigated using the local density approximation ͑LDA͒ and the generalized gradient approximation as two different exchange and correlation approximations, within the full-potential linearized augmented plane-wave approach. Spin-orbit coupling has been incorporated in the study. The results are presented and compared with other recent calculations and experimental data. Structural properties are also obtained by means of calculations of total energy as a function of lattice parameters. The bulk structural parameters are sensitive to the choice of exchange and correlation approximation. The essential features of the band structure and density of states of PbSe and PbTe are reproduced by our calculations and agree quite well with available experimental results. The position of the minimum energy gap is correctly predicted, although the value of the gap is as usual, underestimated by the local density approximation with respect to the experimental data. This gap value is improved by the inclusion of the generalized gradient approximation. Also, we have calculated the real ͓ 1 ()͔ and imaginary ͓ 2 ()͔ parts of () for both compounds, in the framework of the LDA scheme for exchange and correlation. The inclusion of spin-orbit coupling leads to a richer structure in both 1 () and 2 (). The agreement with experimental results is satisfactory.

We have performed an ab initio calculation of the germanium selenide electronic structure, adopting the LDA and GGA approximations for the exchange-correlation potential within the DFT. These calculations have been carried out with and without the inclusion of the spin-orbit interaction. The subtle changes it produces in the band structure, the density of states and the optical properties have been discussed. Also, we propose the s-Ge state contribution at the edge of the valence band as having an important role. Based on our electronic structure, we discuss germanium selenide experimental core spectra and optical properties. We found excellent agreement between our results and available experimental core spectra data, and our calculated optical functions of GeSe explain the origin of the optical transitions, comparing them satisfactorily against existing experimental data.

While the orthorhombic IV–VI compounds show the typical layered behavior of that crystallography, we show that the presence of sulphur induces important changes to the band gap behaviour: both in its location, and in its character as well. Our modelling of tin sulfide (SnS) and tin selenide (SnSe), performed within an ab initio density‐functional theory (DFT) with a FP‐LAPW method, shows that the spin–orbit interaction produces slight splittings of bands in both compounds, especially in the conduction band, which are in very good agreement with measured values of the core spectra. In addition to these splittings, for SnS we found the novel feature that the spin–orbit relocates the band gap in the BZ, while it does not affect that of SnSe. Furthermore, several aspects of the crystals anisotropy may be explained upon our results on the hybridized band structure, the density of states (DOS) and the optical spectra (complex dielectric function and absorption coefficient). We satisfactorily compare our results with those available in the literature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The ordered (100) surface of layered In4Se3 single crystals is characterized by semiconducting quasi-one-dimensional indium (In) chains. A band with significant dispersion in the plane of the surface is observed near the valence band maximum. The band exhibits an anisotropic dispersion with ∼1eV band width along the In chain direction. The dispersion of this band is largely due to the hybridization of In-s and Se-p orbitals, but the hybridization between In-s and Se-p and In-p and Se-p orbitals is also critical in establishing the band gap.

Losovyj, Yaroslav B.; Makinistian, L.; Albanesi, E. A.; Pethukov, A. G.; Liu, Jing; Galiy, P.; Dveriy, O. R.; and Dowben, Peter A., "The anisotropic band structure of layered In 4 Se 3 (001)" (2008 There is discernable and significant band dispersion along both high symmetry directions for cleaved ordered surfaces of the layered In 4 Se 3 ͑001͒. The extent of dispersion of approximately 1 eV is observed along the surface chain rows, and about 0.5 eV perpendicular to the surface "furrows," consistent with theoretical expectations. A possible surface state exists at the surface Brillouin zone edge, in the direction perpendicular to the chains, in a gap of the projected bulk band structure. Excluding the possible surface state, the experimental hole mass is 5.5 times greater along the chains than perpendicular to the chains, but the dispersion is easier to discern.

The valence-band offset at the zincblende AlN/GaN (110) interface is calculated self-consistently by means of the linear muffin-tin orbital method using up to 5+5 layer supercells. The value obtained is Ev(GaN)−Ev(AlN)=0.85 eV corresponding to a type I offset. Assuming interface orientation and polytype effects on the valence-band maximum to be reasonably small, a type I offset can also be expected for wurtzite interfaces. By means of separate calculations, we also test the validity of two simplified approaches, the self-consistent dipole approximation (SCD) of Lambrecht, Segall and Andersen and the dielectric midgap energy (DME) model of Cardona and Christensen. We find that the SCD results are in very good agreement and the DME results, in fairly good agreement with the fully self-consistent results. The interface local densities of states show no indication of interface states in the main gap.