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The electronic structure of MgB₂ with different lattice parameters, which represents the influence of pressure, has been studied from HF calculation. It has been found that the density of states at the Fermi level decreases with the decrease in lattice constant, which implies that the pressure can reduce the superconductivity of MgB₂. It was also found that more electrons are introduced from the Mg layer to the B layer with increasing pressure, resulting in the number of holes on the B layer being reduced, thus reducing superconductivity. The electron density population at different pressures clearly shows that the triangle-shaped electron distribution in the B plane, extended along the B–B bonds, indicates the typical sp² orbitals. On the other hand, there is no covalency feature between Mg and B atoms, indicating the ionic bonding property between Mg and B layers.

The semiconductor ZnO of large gap of 3,4 eV is of great interest for the technological applications as chemical sensors, UV light emission, optical memories, laser emission, solar cells, etc. These applications depend on the electron structure of material. We adopt the density functional theory (DFT) calculation by using the program Wien2K, within the Generalized Gradient Approximation (GGA) and modified Becke–Johnson (mBJ) for studying the electron behavior of ZnO. The features of the valence band derived from the hybridization of Zn-3d and O-2p states. The electron charge density calculated by these simulation methods indicates a charge transfer between zinc and oxygen inducing a difference in electronegativity between both species (Zn and O), responsible to ionic character of bonding in ZnO. The predictions based on the GGA and mBJ calculations are confirmed by the results of the experimental spectroscopic analysis Auger Electron Spectroscopy (AES) and Electron Energy Loss Spectroscopy (EELS).

In this paper, the results of the first principles calculations within the framework of the density functional theory of the electronic spectrum of a GeS crystal are presented. The density of states and interband optical transitions are investigated. It was found that GeS compounds have semiconducting properties with a bandgap of 1.52 eV. The main contribution of the bands in the vicinity of the Fermi level is from the 3$p$ and 3$s$ states of the S and Ge atoms, respectively. The highest amplitude, about 2.3 eV ($𝜀\perp )$, is mainly associated with the interband optical transitions between the states $\mathrm{\text{S}}(p)+\mathrm{\text{Ge}}(s)\to \mathrm{\text{Ge}}(p)+\mathrm{\text{S}}(s)$. The results of the luminescence studies of GeS and GeS:Gd layered crystals at room-temperature are presented. A noticeable increase in the intensity of the luminescence radiation in GeS:Gd has been established. The reason for the increase in the effectiveness of photoluminescence is due to the overlapping of optical transitions of GeS at 695 nm wavelength with the radiation lines of Gd${}^{3+}$ion at that same energy.

The results of calculations of the electron structure for Ag₂S and Ag₂Se crystals from first-principle in the framework of density functional theory (DFT) are presented in this work. The origin of the bands from $s,p$ and $d$ electron states of Ag, S and Se atoms are investigated. It was established that the orthorhombic Ag₂Se crystal shows semiconductor properties in P222₁ and P2₁2₁2₁ space groups and semimetallic properties in Im-3m space groups with cubic crystal system. Monoclinic crystal type of Ag₂S shows semiconductor properties in P2₁/c space group. However, semimetallic properties manifested itself in monoclinic Ag₂S in P2₁ and cubic Ag₂S structure in Im-3m phases.

Ultrasoft X-ray emission spectra (USXES) and X-ray absorption near-edge structure (XANES) spectra with the use of synchrotron radiation in the range of P L_2,3-edges were obtained for the first time for nanostructures with InP quantum dots grown on GaAs 〈100〉 substrates by vapor-phase epitaxy from metal–organic compounds. These spectra represent local partial density of states in the valence and conduction bands. The additional XANES peak is detected; its intensity depends on the number of monolayers forming quantum dots. Assumptions are made on the band-to-band origin of luminescence spectra in the studied nanostructures.

Nitrogen-doped diamond-like carbon (N-DLC) films were synthesized by plasma immersion ion implantation and deposition (PIII-D) at room temperature (RT). During the process of deposition, N₂ flow was changed from 0 to 10 sccm. Lifshitz–van der Waals/acid–base (LW-AB) approach was employed to study the surface electronic state of the films, X-ray photoelectron spectroscopic (XPS) and valence band spectra (VBS) were used to study chemical bonds and electron structure information inside the films. Bandgap of the films were calculated by the data from ultraviolet spectrophotometer. The results showed that synthesized films were n-type semiconductors and doping of nitrogen element will affect the accepted–electron capability of the film. The change tendency of the bandgap coincides with that of the ratio of acidic to alkaline component of the polar acid-alkali surface energy. There was much sp hybrid electronic state existed in the films, which mainly sp²C=C/C=N and sp³C–C/C–N bonds.