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Abstract: The band structure, total and projected densities of states, and distributions of the valence and difference electron densities for copper and silver oxides are calculated in the framework of the density functional theory in the local approximation with ab initio norm-conserving pseudopotentials in the basis set of pseudoatomic orbitals. The results obtained are compared with the experimental data and calculations performed by other authors. The energy spectrum and spatial distribution of electrons in crystals are similar to each other. Metal ions are bonded to each other through charge density channels with a weakly pronounced maximum at the center of the empty tetrahedron.

Abstract: This paper reports on the results of investigations into the phase composition of HgI2 microcrystals formed in the bulk and on the surface of different nanocrystalline matrices: pressed, finely dispersed (with a specific surface of more than 210 m2/g) aluminum oxide powders; porous borosilicate glasses with pore radii ranging from 2 to 20 nm; and Al2O3-HgI2 and SiO2-HgI2 nanocrystalline composites. The results of spectroscopic analysis (diffuse reflection, absorption, and luminescence spectroscopy) are complemented by the data of atomic-force microscopy (AFM) and x-ray diffraction. The experimental results indicate that nonequilibrium modifications, namely, the high-temperature yellow phase and the orange phase metastable in bulk crystals at all temperatures, can be stabilized in HgI2 nanoparticles at room temperature.

Abstract: Differential (wavelength-modulated) absorption of sulfoselenide solid-solution nanocrystals has been studied in a glassy fluorophosphate matrix near the fundamental absorption edge at 360–620 nm. The observed oscillations in the absorption are attributed to size quantization of electrons and holes under strong quantum-confinement conditions. The sulfur content in the mixed semiconductor has been refined from Raman scattering spectra in CdSxSe1−x samples with x=0.30, and the nanocrystal size (R≅30 ) has been derived from low-frequency Raman scattering spectra. These data were used to calculate the energies of electron-hole transitions in nanocrystals of mixed composition, and their subsequent comparison with experiment. The calculations were found to be in a good agreement with the observed experimental absorption spectrum for nanocrystals about 45 in size. The applicability of band-structure simulation for a nonspherical nanocrystal grown in a fluorophosphate glass matrix is discussed.