Search

TiO 2 (titania) is one of the promising materials for photocatalytic applications. In this paper we report on recently obtained theoretical results for N and S doped, as well as N+S co-doped 6-layer (101) anatase nanotube (NT). First principles calculations in our study have been performed using a modified B3LYP hybrid exchange-correlation functional within density functional theory (DFT). Here we discuss the energy of defect formation mechanism and electronic band structure for nanotubes under study. We also report on influence of dopant concentration on the NT's band structure and discuss the defect–defect interactions. [ABSTRACT FROM AUTHOR]

Nanocrystalline zinc peroxide (nano-ZnO 2) was synthesized through a hydrothermal process and comprehensively studied using several experimental techniques. Its crystal structure was characterized by X-ray diffraction, and the average crystallite size of 22 nm was estimated by Rietveld refinement. The temperature-dependent local environment around zinc atoms was reconstructed using reverse Monte Carlo (RMC) analysis from the Zn K-edge X-ray absorption spectra. The indirect band gap of about 4.6 eV was found using optical absorption spectroscopy. Lattice dynamics of nano-ZnO 2 was studied by infrared and Raman spectroscopy. In situ Raman measurements indicate the stability of nano-ZnO 2 up to 250 °C above which it decomposes into ZnO and O 2. The obtained experimental results were supported by first-principles density functional theory (DFT) calculations. • The ZnO 2 nanopowder sample was produced by a hydrothermal process. • The ZnO 2 nanopowder consists of hollow structures with a size of 200–500 nm. • The static disorder in nano-ZnO 2 dominates significantly the vibrational one. • DFT simulations reproduce well electronic and vibrational properties of ZnO 2. • Thermal decomposition of ZnO 2 to wurtzite ZnO around 250 °C was observed. [ABSTRACT FROM AUTHOR]

• Hybrid B1WC functional describes well the properties of and oxygen vacancy behavior in BaCoO 3. • Triclinic ideal BaCoO 3 is more stable than the cubic one. • Site symmetry approach within the supercell model allows one to obtain minimum energy states. We use the hybrid B1WC density functional calculations and the supercell model to analyze properties of BaCoO 3 (BCO) in the corner-sharing CoO 6 octahedra geometry. We compare the atomic and electronic structures for ideal and defective BCO containing a single oxygen vacancy (Vo). We find that the ideal BCO is better described by the triclinic space group (SG) P 1 supercell than the cubic SG Pm 3 ¯ m model. The site symmetry approach allows us to derive several Vo supercell models on the basis of SGs P 4 mm , Pmm 2 or Amm 2 from the aristotype cubic SG Pm 3 ¯ m. The low symmetry Pmm2 model suggests the 0.4 eV formation energy of Vo in BCO. Furthermore, stability of this result is confirmed by the calculation of Vo in the supercell without symmetry (SG P1). The ideal and defective BCO are characterized by the intermediate spin (IS) states of Co4+ and Co4+&Co3+ ions, respectively. Additional complexity is introduced by the smooth Co magnetic moment dependence on the Co–Vo distance. [ABSTRACT FROM AUTHOR]