Density functional theory (DFT) computations of the electronic structures of undoped, B- and N-doped CNT(3,3), CNT(5,5) carbon nanotubes, and graphene with adsorbed chromate anions CrO4 2− were performed within molecular cluster approach. Relaxed geometries, binding energies, charge differences of the adsorbed CrO4 2− anions, and electronic wave function contour plots were calculated using B3LYP hybrid exchange-correlation functional. Oscillator strengths of electronic transitions of CrO4 2− anions adsorbed on the surfaces of studied carbon nanostructures were calculated by the TD-DFT method. Calculations reveal covalent bonding between the anion and the adsorbents in all studied adsorption configurations. For all studied types of adsorbent structures, doping with N strengthens chemical bonding with CrO4 2− anions, providing a ~2-eV increase in binding energies comparatively to adsorption of the anion on undoped adsorbents. Additional electronic transitions of CrO4 2− anions appear in the orange-green spectral region when the anions are adsorbed on the N-doped low-diameter carbon nanotubes CNT(3,3) and CNT(5,5).

Potential applicability of undoped, B-, and N-doped carbon nanotubes (CNTs) for elaboration of the working materials of gas sensors of hydrogen halide molecules HX (X 5 F, Cl, Br) is analyzed in computational studies of molecular adsorption on the CNTs surfaces. Density Functional Theory (DFT)-based geometryoptimized calculations of the electronic structure of undoped, B-, and N-doped CNTs of (3,3) and (5,5) chiralities with adsorbed HX (X 5 F, Cl, Br) molecules are performed within molecular cluster approach. Relaxed geometries, binding energies between the adsorbates and the nanotubes, charge states of the adsorbates and the electronic wave function contours are calculated and analyzed in the context of gas sensing applications. Obtained results are supplemented by calculations of adsorption of hydrogen halides on B(N)-doped graphene sheets which are considered as model approximation for large-diameter CNTs. It is found that the B-doped CNTs are perspective for elaboration of sensing materials for detection of HCl and HBr molecules. The undoped and the N-doped CNTs are predicted to be less suitable materials for detection of hydrogen halide gases HX (X 5 F, Cl, Br).

The possibility of band gap engineering (BGE) in RAlO 3 (R = Y, La, Gd, Yb, Lu) perovskites in the context of trap depths of intrinsic point defects was investigated comprehensively using experimental and theoretical approaches. The optical band gap of the materials, E g , was determined via both the absorption measurements in the VUV spectral range and the spectra of recombination luminescence excitation by synchrotron radiation. The experimentally observed effect of E g reduction from ∼8.5 to ∼5.5 eV in RAlO 3 perovskites with increasing R 3+ ionic radius was confirmed by the DFT electronic structure calculations performed for RM III O 3 crystals (R = Lu, Y, La; M III = Al, Ga, In). The possibility of BGE was also proved by the analysis of thermally stimulated luminescence (TSL) measured above room temperature for the far-red emitting (Y/Gd/La)AlO 3 :Mn 4+ phosphors, which confirmed decreasing of the trap depths in the cation sequence Y → Gd → La. Calculations of the trap depths performed within the super cell approach for a number of intrinsic point defects and their complexes allowed recognizing specific trapping centers that can be responsible for the observed TSL. In particular, the electron traps of 1.33 and 1.43 eV (in YAlO 3 ) were considered to be formed by the energy level of oxygen vacancy (V O ) with different arrangement of neighboring Y Al and V Y , while shallower electron traps of 0.9–1.0 eV were related to the energy level of Y Al antisite complexes with neighboring V O or (V O + V Y ). The effect of the lowering of electron trap depths in RAlO 3 was demonstrated for the V O -related level of the (Y Al + V O + V Y ) complex defect for the particular case of La substituting Y.

Results of X-ray diffraction studies of Gd(Mg0.95 x,ZnxMn 0.05)B5O10 down-converting phosphor as a function of Mg-Zn composition are presented. Lattice parameters and unit cell volumes of GdMg0.95-xZnxMn0.05B5O10 pentaborates are examined....

Herein, the peculiarities of complex phosphate formation in self-fluxes of Cs-M-Bi-P-O (M = Ca, Sr, Ba and Pb) systems with Cs/P = 0.7-1.3 at fixed ratios of Bi/P = 0.2 and Bi/M = 1.0 were studied and discussed. Three novel isostructural diphosphates with the general composition CsMBi(PO) (M = Ca, Sr and Pb) and the original framework topology were synthesized and characterized via single-crystal and powder X-ray diffraction, SEM, DTA, and FTIR- and UV-VIS-spectroscopy. In addition, electronic structure (DFT) and Voronoi-Dirichlet polyhedra (VDP) characteristics calculations and crystallochemical analysis were performed. In the structure of the new compounds, the MO and BiO polyhedra are connected via common oxygen vertices forming infinite helical-like chains, which are linked by PO groups into a 3D-framework with pentagonal tunnels, where the Cs cations are located. The structural peculiarities are discussed considering perspectives for the creation of new luminescent materials. The dielectric bandgaps, E, of the CsMBi(PO) crystals reveal an ∼0.2 eV low-energy shift in the Ca-Sr-Pb sequence of M cations, which reveals the possibility to tune the optical absorbance spectra of the crystals via the synthesis of solid solutions with various contents of M cations. The glass-ceramic synthetic approach is also proposed as a convenient method for the creation of new diphosphates, and the applicability of this method is verified for CsCaBi(PO).