We calculated the electronic structure, magnetism and optical properties of the Sc-doped, Y-doped, and (Sc, Y)-codoped anatase TiO2 (101) surface using a projector augmented wave (PAW) method with GGA + U approximation. Sixteen doping systems were considered in the present work. The lattice distortion results in the generation of an internal local electric field. In addition, the difference between positive and negative spin charge densities leads to the generation of magnetism. With the exception of the [email protected] system, the width of band gap of the other doping systems increases to varying degrees, leading to a blueshift of the absorption edge. The photocatalytic activity of all the doping systems was improved to different degrees. The absorption intensity and absorption range of the [email protected]&[email protected] system in the visible-light region is the highest amongst all doping systems. This mainly attributed to the formation of hole states and the presence of impurity bands. 相似文献
Recent experiments reported fascinating phenomenon of photoluminescence (PL) blueshift in Ge-doped ZnO. To understand it, we examined the structural, electronic and optical properties of Ge-doped ZnO (ZnO:Ge) systematically by means of density functional theory calculations. Our results show that Ge atoms tend to cluster in heavily doped ZnO. Ge clusters can limit the conductivity of doped ZnO but reinforce the near-band-edge emission. The substitutional Ge for Zn leads to Fermi level pinning in the conduction band, which indicates Ge-doped ZnO is of n-type conductivity character. It is found that the delocalized Ge 4s states hybridize with conduction band bottom, and is dominant in the region near the Fermi level, suggesting that Ge-4s states provides major free carriers in ZnO:Ge crystal. The observed blueshift of PL in Ge-doped ZnO originates from the electron transition energy from the valence band to the empty levels above Fermi level larger than the gap of undoped ZnO. The electron transition between the gap states induced by oxygen vacancy and conduction band minimum may be the origin of the new PL peak at 590 nm. 相似文献
The structural, electronic and optical properties of tungsten-doped TiO2 have been investigated using density functional theory with plane wave basis sets and ultrasoft pseuodopotential. Substitutional W doping at Ti sites create W 5d states just below the conduction band minimum while interstitial W doping gives isolated W 5d states in the middle of forbidden region. Averaged bond lengths show that W doping at Ti sites produce minimum structural distortion as compared to the interstitial W-doped TiO2. Substitutional W-doped TiO2 has better visible light absorption compared to interstitial W-doped TiO2 and has stable configuration which provide reasonable explanation for the experimental findings. Tungsten doping in TiO2 with different doping concentrations is investigated as an enabling concept for enhancing the visible light absorption. Optical properties show that optimal W doping concentration would improve the visible light absorption. 2.08% W doping concentration gives strong visible and ultraviolet light absorption among all doped models found consistent with experiments. 相似文献
Six surface models for the Fe3O4(1 1 0) surface were studied using the density functional theory (DFT), namely the AB-terminated surface (AB model), the AB-terminated with FeA vacancy (AB-FeA vac model), the AB-terminated with FeB vacancy (AB-FeB vac model), the B-terminated surface (B model), the B-terminated surface with FeB vacancy (B-FeB vac model), and the B-terminated surface with O vacancy (B-O vac model). Here, A and B denoted the Fe cations in tetrahedrally (FeA) and octahedrally (FeB) coordinated interstices. The stability, the electronic structure and the magnetic properties of the six surface models were also calculated. The results predict that the B-O vac model is more stable than other surface models. The half-metallic property remains in the AB and B models, while the other four surface models exhibit metallic properties. At the same time, the AB, AB-FeA vac, AB-FeB vac, B and the B-FeB vac models have ferrimagnetic properties, while the B-O vac model has antiferromagnetic property. 相似文献
Potential energy curves, equilibrium interatomic distances, term energies and harmonic vibration frequencies for the 16 lowest states of neutral carbon monoxide and the six lowest states of singly ionized carbon monoxide are calculated by density functional theory (DFT) and linear-response time-dependent density functional (LR-TDDFT) theory. The results are compared with experimental data. The two theories, DFT and LR-TDDFT, are described briefly. 相似文献
The main objective of this study is to understand the sensing origin of anatase TiO2 and provide an insight into why gas sensitivity of anatase TiO2 is not so excellent.
Magnesium based spinel chalcogenides MgY2Z4 (Z = S and Se) have recently become a focus of renewed research interest owing to their high magnesium mobility; making them potential candidates for Mg batteries. In addition, the existence of a >1 eV band gaps in MgY2Z4 compounds also make them interesting for opto-electronic device operating in the visible to UV range of electromagnetic spectrum. Our calculations indicate that the electronic properties computed using the mBJ-LDA + SOC are in good agreement with earlier DFT calculations. The optical properties of the two compounds are examined as a function of incident photon energy, which indicate that these materials can be utilized in optical devices operating in visible and UV region of electromagnetic spectrum. The transport properties are also computed using BoltzTrap code where the variation of electrical conductivity, thermal conductivity and Seebeck coefficient with chemical potential and temperature is examined. 相似文献
Density functional theory slab calculations have been used to investigate the structure of the Ni(1 1 0)c(2 × 2)-CN adsorption phase. The results show excellent agreement with experimental quantitative determinations of this structure by photoelectron diffraction and low energy electron diffraction. In particular, they show that a lying-down orientation with the C–N axis along [0 0 1] perpendicular to the close-packed Ni rows on the surface is strongly favoured over end-on adsorption (with the C–N axis perpendicular to the surface). This geometry is also favoured over a lying-down geometry with the C–N axis aligned along the azimuth, as originally proposed for this system and supported by cluster calculations. 相似文献
