Fe掺杂SnO_2稀磁半导体超精细场的第一性原理计算

采用基于密度泛函理论线性缀加平面波方法的WIEN2k程序,计算Fe掺杂SnO2稀磁半导体的电子结构和磁性,计算中性电荷态Fe0和电荷受主态Fe1-或Fe2-。结果表明,Fe掺杂SnO2的基态都是铁磁态,O空位更容易出现在Fe原子周围。中性电荷态Fe0磁矩较小,Fe1-或Fe2-态磁矩变大,并且计算的磁超精细场和磁矩与穆斯堡尔谱测量结果相符合。电子结构分析表明,掺杂Fe-3d轨道与氧八面体O-2p轨道相互作用,造成3d轨道能级分裂。不同电荷态下,能级分裂的程度不同,从而影响电子填充3d轨道的模式。3d轨道中未成对电子数增加,处于高自旋态的Fe原子是产生巨磁矩的原因。

Photocatalytic and Photoelectronic Properties of Anatase TiO_2 Modified by Cu Ions Plasma and Its Theoretic Study by the First Principle Study

Highly oxidation. SEM analysis ordered anatase titania nanotube method was used to characterize arrays （TINT） were fabricated by anodic the morphology of the prepared samples. TiNT samples doped with Cu ions were prepared by home-made Metal Vapor Vacuum Arc ions sources （MEVVA, BNU, China） implanter. Photo-electric response and methyl orange decomposition ability of implanted samples under UV and visible light were tested, and the results indicated that the performance of Cu/TiNT enhanced significantly under visible light; it was noteworthy that the photocurrent density of A-Cu/TiNT was 0.102 mA/cm^2, which was 115 times that of pure TINT, and degradation ability of TiNT also strongly enhanced under visible light. In a word, the absorption spectrum of implanted anatase titania shifted to a longer wavelength region. Theoretic study on Cu-doped anatase based on density functional theory was carried out in this paper to validate the experiment results. The calculation results are depicted as follows： Intermittent energy band appeared around the Fermi energy after doping with Cu metal, the width of which was 0.35 eV and the location of valence and conduction bands shifted to the lower energy level by 0.22 eV; more excitation and jump routes were opened for the electrons. The narrowed band gaps allowed the photons with lower energy （at longer wavelength, such as visible light） to be absorbed, which accorded well with the experimental results.

Theoretic and Experimental Studies on Titania Nanotube Doped with Ag Metal Ions

The electronic state density and energy bands of Ag-doped anatase TiO2 are studied by WIEN2k software package based on DFT. The calculation results show that the band-gap of anatase titania became bigger after doping with Ag metal ions. The band-gap transfers from 2.04 to 2.5 eV, but a new energy band appears among the forbidden band after the Ag atom substitution. The interband width of Ag-TiO2 is 0.17 eV, which is located at –0.07 eV; more excitation and jump routes are opened for the electrons. The lowest excitation energy can achieve 1.2 eV, which may allow the photons with lower energy （at longer wavelength, such as visible light） to be absorbed. Ag ions are implanted into the titania nanotube sample by MEVVA （Metal Vapor Vacuum Arc） implanter. The photo-electrochemical response and photo-degradation experiment of titania nanotube samples implanted with Ag ions are tested under UV and visible light; the results indicated that the performance of implanted titania naotubes is enhanced both under UV and visible light; it is worth mentioning that the photocurrent density can reach 0.145 mA/cm2 under visible light, which is 181 times higher than those of pure TiNT, and the k value of degradation methyl orange can obtain 0.30 h-1, which is 71 times higher than that of pure TiNT. All the experimental results are consistent well with the theoretic ones.

First-Principles Study of the Optical Properties of SrHfO₃

The optical properties of SrHfO3,were studied by first principle using the density functional theory.The dielectric functions and optical constants are calculated using the full potential–linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation(GGA)by Wien2k package. The theoretical calculated optical properties and energy loss(EEL)spectrum yield a static refractive index of1. 924and a Plasmon energy of 27eVfor cubic phase. The complex dielectric functions are calculated which are in good agreement with the available experimental results.

First Principles Studies on the Electronic Structure and Band Structure of Paraelectric SrTiO₃by Different Approximations

The electronic structure, energy band structure, total density of states (DOS) and electronic density of perovskite SrTiO3 in the cubic phase are calculated by the using full potential-linearized augmented plane wave (FP-LAPW) method in the framework density functional theory (DFT) with the generalized gradient approximation (GGA) by WIEN2k package. The calculated band structure shows a direct band gap of 2.5 eV at the Γ point in the Brillouin zone.The total DOS is compared with experimental x-ray photoemission spectra. From the DOS analysis, as well as charge-density studies, I have conclude that the bonding between Sr and TiO2 is mainly ionic and that the TiO2 entities bond covalently.The calculated band structure and density of state of SrTiO3 are in good agreement with theoretical and experimental results.

Silica Nano-Networks as Stretches on Segmented SU8 Rods for Sub-Wavelength Photonics

The optical properties of CdBr2 were studied by first principle using the density functional theory. The dielectric functions and optical constants are calculated using the full potential-linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA). The theoretical calculated optical properties and energy Loss (EEL) spectrum yield a static refractive index of 2.1 and a plasmon energy of 13eV for hexagonal phase. The results, in comparison with the published data, are in good agreement with the experimental and previous theoretical results.

Investigation of the Optical Properties of CdBr₂

The optical properties of CdBr2 were studied by first principle using the density functional theory. The dielectric functions and optical constants are calculated using the full potential-linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA). The theoretical calculated optical properties and energy Loss (EEL) spectrum yield a static refractive index of 2.1 and a plasmon energy of 13eV for hexagonal phase. The results, in comparison with the published data, are in good agreement with the experimental and previous theoretical results.

Ab Initio Study of Electronic Properties of a Armchair (7,7) Carbon Nanotube

The electronic structure, band gap and density of states of (7,7) Armchair carbon nanotube by the full potentiallin- earized augmented plane wave (FP-LAPW)method in the framework density functional theory (DFT) with the generalized gradient approximation (GGA) were studied. The calculated band structure and density of state of Armchair (7,7) carbon nanotube were in good agreement with theoretical and experimental results.

Electronic structure of the rare-earth superstoichiometric dihydride GdH_(2.25)

With the WIEN2 k simulation code,ab initio calculations of electronic structure and of equilibrium properties for the superstoichiometric rare-earth dihydride GdH_(2.25)using the full-potential linearized augmented plane-wave(FP-LAPW)method within density functional theory(DFT)in generalized gradient approximation(GGA)were performed.The lattice parameter,bulk modulus,pressure derivative,density of states(DOS)and energy band structures were determined.The GGA-optimized lattice parameter agrees much better with the experimental findings than the local density approximation(LDA)one.The non-negligible electronic DOS at Fermi level confirms that GdH_(2.25)has a metallic character.The Fermi energy(E_(F))falls at a level where most of the states are rare-earth 5 d conduction states while negligible contributions of both interstitial(tetrahedral and octahedral)H s states are observed near EF.It is found that hybridization exists between s electronic orbital of both interstitial H atoms and d electronic orbitals of Gd.

First-principles study of the electronic structure of a superstoichiometric rare earth dihydride GdH2.25

We performed ab initio calculations of electronic structure and equilibrium properties for the rare earth superstoichiometric dihydride GdH2.25 （with the space group Pm-3m （No. 221）） using the full-potential linearized augmented plane wave method （FP-LAPW） approach within the density functional theory （DFT） in the generalized gradient approximation （GGA） and local density approximation （LDA） as implemented in the WIEN2k simulation code at 0 K. The equilibrium properties were determined, the density of states, electronic density and the energy band structures were studied in details. It was concluded that the GGA optimized lattice parameter agreed much better with the experimental findings than the LDA one, The non negligible electronic density of states at the Fermi level confirmed that the GdH2.25 had a metallic character. The Fermi energy EF fell at a level where most of the states were rare-earth 5d-eg conduction states while negligible contributions of both interstitial （tetrahedral and octahedral） H s-states were observed near EF, From electronic density, the bonding between Gd and tetrahedral H atoms was of prominent covalency, while was ionic between Gd and octahedral H atoms.