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We have estimated theoretically the photocatalytic suitability of thinnest single-wall fluorite-structured titania (4,4) nanotube (NT) possessing three layers each (O-Ti-O) and doped by Sc, V, Cr, Mn, Fe, Co, Ni, Cu and Zn atoms substituted for host Ti atoms. For this goal, we have performed large-scale ab initio calculations on TiO 2 NTs with three-layer morphology doped by 3 d transition metals, using ( i ) the method of linear combination of atom-centered Gaussian-type orbitals (LCAO) based on the hybrid density functional theory (DFT) incorporating the Hartree-Fock (HF) exchange contribution (DFT+HF) and ( ii ) the method of linearized augmented cylindrical waves (LACW) with the muffin-tin approximation based on the local density functional approach (LDA). We have compared the ground state electronic structure, particularly the one-electron densities of states (DOSs) from the LCAO and LACW calculations for periodic arrangements of the 3 d -metal dopant atoms. The results show clear evidence for a potential photocatalytic application for water splitting in the case of the Sc-doped titania nanotubes only. These NTs show both a reduced band gap of 2.0 eV relative to the pristine NT and an absence of defect-induced levels between the redox potentials of hydrogen and oxygen, so that electron-hole recombination becomes unlikely. Other 3 d dopants with higher atomic number, although their band gap also covers the favorable green to orange region of the solar spectrum, are unsuitable because their defect-induced levels are positioned between the redox potential of oxygen and hydrogen, which can be expected to lead to rapid electron-hole recombination. [ABSTRACT FROM AUTHOR]

Uranium L 3 -edge X-ray absorption spectroscopy was used to study the atomic structure of uranium dioxide (UO 2 ). The extended X-ray absorption fine structure (EXAFS) was interpreted within the ab initio multiple-scattering approach combined with classical molecular dynamics to account for thermal disorder effects. Nine force-field models were validated, and the role of multiple-scattering contributions was evaluated. [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]

Cubic copper nitride (Cu 3 N) has anti-perovskite structure, and its properties are strongly affected by anisotropic thermal vibrations of copper atoms. Ab initio molecular dynamics (AIMD) simulations were performed in the temperature range from 300 K to 700 K in order to probe the details of Cu 3 N lattice dynamics. The Cu K-edge extended X-ray absorption fine structure (EXAFS) spectrum of bulk Cu 3 N was used to validate AIMD simulations at 300 K. The AIMD results suggest strong anharmonicity of the Cu–N and Cu–Cu bonds, the rigidity of NCu 6 octahedra and strong correlation in atomic motion within –N–Cu–N– atom chains as well as support anisotropy of copper thermal vibrations. • Ab initio molecular dynamics simulations of Cu 3 N were performed at 300–700 K. • The Cu–N and Cu–Cu bonding is strongly anharmonic. • Thermal vibrations of Cu atoms are anisotropic, and NCu 6 octahedra are rigid. • Strong correlation in atomic motion is present within –N–Cu–N– atom chains. [ABSTRACT FROM AUTHOR]

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]

[Display omitted] • Pulsed laser deposition of few-layer MoS 2 or WS 2 shell on GaN nanowires. • Sulfurization of sputter-deposited MoO 3 or WO 3 sacrificial layers to produce core–shell GaN-WS 2 and GaN-MoS 2. • Ab initio DFT electronic structure calculations of GaN-MoS 2 and GaN-WS 2. One-dimensional (1D) nanostructures – nanowires (NWs) – exhibit attractive properties for integration in different types of functional devices. Their properties can be enhanced even further or tuned for a specific application by combining different promising materials, such as layered van der Waals materials and conventional semiconductors, into 1D-1D core–shell heterostructures. In this work, we demonstrated growth of GaN-MoS 2 and GaN-WS 2 core–shell NWs via two different methods: (1) two-step process of sputter-deposition of a sacrificial transition metal oxide coating on GaN NWs followed by sulfurization; (2) pulsed laser deposition of few-layer MoS 2 or WS 2 on GaN NWs from the respective material targets. As-prepared nanostructures were characterized via scanning and transmission electron microscopies, X-ray diffraction, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. High crystalline quality core–shell NW heterostructures with few-layer MoS 2 and WS 2 shells can be prepared via both routes. The experimental results were supported by theoretical electronic structure calculations, which demonstrated the potential of the synthesised core–shell NW heterostructures as photocatalysts for efficient hydrogen production from water. [ABSTRACT FROM AUTHOR]