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71.
H. Mehnane B. Bekkouche S. Kacimi A. Hallouche M. Djermouni A. Zaoui 《Superlattices and Microstructures》2012
We report investigations of the structural, electronic and optical properties of 36 half-Heusler compounds in comparison with II–VI semiconductors using the first-principles calculations based on the density functional theory. In this work, we demonstrate the similarity in the electronic structure of these materials with that of II–VI semiconductors through the analysis of lattice parameters, band gaps and static dielectric constants at ambient pressure. The evolution of these properties under pressure is also necessary to predict new candidates for the optoelectronic devices. 相似文献
72.
《Current Applied Physics》2018,18(2):226-230
This work presents a study of the electronic transport properties of PbSe pellets fabricated starting of PbSe nanostructures that exhibited a flake-like 2D morphology, which were synthesized by the co-precipitation method. Seebeck coefficient measurements revealed that the PbSe sample displays n-type conductivity, a maximum Seebeck coefficient of −512.6 μV/K around 380 K, and that the carriers scattering is dominated by acoustic and optical phonons. The Fermi level dependence on the temperature and the band gap energy are also reported. Interestingly, size-dependent confinement effects due probably to the reminiscent PbSe 2D character could be evidenced. 相似文献
73.
《Current Applied Physics》2018,18(2):200-208
The electronic structure and optical properties of La0.75Sr0.25MnO3-σ (LSMO3-σ) materials with 1 × 1 × 4 orthorhombic perovskite structure were performed by first-principles calculation. The structural changing of LSMO3 (ideal structure, σ = 0) was not obvious under generalized gradient approximation (GGA) and GGA + U arithmetic. On the contrary, the structural changing of LSMO3-σ (σ = 0.25, with oxygen vacancies defects in the z = 0, c/8, c/6, c/4, and c/2) with GGA + U were more obvious than the result of ideal. This structural distortion induced distinct changing in density of states (DOS) for LSMO3-σ materials. Oxygen vacancy defects caused a shift of the total density of states (TDOS) features toward low binding energies and LSMO3-σ keep half-metal properties as well as LSMO3 ideal structure. In addition, the hybridization between the Mn-eg and O-2p orbital was weakened and the partial density of states (PDOS) of Mn indicated a strong d-d orbital interaction. By the result of oxygen vacancy formation energy, oxygen vacancy defects can be more easily formed in La-O layers (z = 0 and c/6) to compare with other layers (z = c/8, c/4 and c/2). The calculation result of optical properties suggested that the ideal LSMO could be produced strong absorption in the range of ultraviolet and visible light, while the LSMO3-σ with oxygen vacancies defects were presented weak absorption in the range of visible light. 相似文献
74.
《Journal of Coordination Chemistry》2012,65(10):1812-1820
A Fe(III) complex with Cl counter ion based on a branched Schiff base has been synthesized and studied. The compound was produced by the reaction of the Schiff base with FeCl3 at room temperature in benzene–ethanol. The complex is symmetric, i.e., bis-chelate, with an octahedral coordination of Fe. The compound revealed phase transitions of the “solid–solid” type. The complex displayed a temperature-induced spin transition (S?=?1/2???5/2) which was detected by EPR. 相似文献
75.
The new adduct W4Br10 · 2SbBr3 and the new binary compound W4Br10 were obtained as products in a reaction cascade in which WBr6 was reacted with elemental antimony at successively increased temperatures. The crystal structures of both compounds were refined from X‐ray powder diffraction data and their electronic structures were analyzed by MO calculations. The cluster compounds W4Br10 · 2SbBr3 and W4Br10 appear as intermediates in the solid state nucleation of W6Br12. The overall reaction cascade involves tungsten clusters having tetrahedral (W4), square pyramidal (W5) and finally octahedral (W6) cluster cores. 相似文献
76.
Tatsuya Kikuchi Masumi Yoshida Shiki Matsuura Shungo Natsui Etsuji Tsuji Hiroki Habazaki Ryosuke O. Suzuki 《Journal of Physics and Chemistry of Solids》2014
Micro-, submicron-, and nano-scale titanium dioxide particles were reduced by reduction with a metallic calcium reductant in calcium chloride molten salt at 1173 K, and the reduction mechanism of the oxides by the calcium reductant was explored. These oxide particles, metallic calcium as a reducing agent, and calcium chloride as a molten salt were placed in a titanium crucible and heated under an argon atmosphere. Titanium dioxide was reduced to metallic titanium through a calcium titanate and lower titanium oxide, and the materials were sintered together to form a micro-porous titanium structure in molten salt at high temperature. The reduction rate of titanium dioxide was observed to increase with decreasing particle size; accordingly, the residual oxygen content in the reduced titanium decreases. The obtained micro-porous titanium appeared dark gray in color because of its low surface reflection. Micro-porous metallic titanium with a low oxygen content (0.42 wt%) and a large surface area (1.794 m2 g−1) can be successfully obtained by reduction under optimal conditions. 相似文献
77.
The effective mass of strained graphene is investigated by tight-binding and density-functional theory calculations. For graphene strained in the zigzag direction, we find a strong anisotropy in the effective mass near the gap opening, with an abrupt increase of the effective mass at the critical strain in one direction and a smooth variation perpendicular to it. There is no band-gap opening for isotropic strain, but at an expansive strain of about 28%, the lower edge of the s-band reaches the Fermi level and makes the graphene metallic. 相似文献
78.
Using first-principles density functional theory within the generalized gradient approximation method, the effect of Zn doping on electronic and magnetic properties of NiFe2O4 ferrite spinel has been studied. The crystal structure of the compounds is assigned to a pseudocubic structure and the lattice constant increases as the Zn concentration increases. Our spin-polarized calculations give a half-metallic state for NiFe2O4 and a normal metal state for ZnxNi1−xFe2O4 (0<x≤0.5). Based on the magnetic properties calculations, it is found that the saturation magnetic moment enhances linearly with increase in the Zn content in NiFe2O4. The Zn doping in NiFe2O4 also induces strong ferrimagnetism since it decreases the magnetic moment of A-sites. 相似文献
79.
Sungkoo Lee Sangmyung Lim Eunhee Lim Kyeong K. Lee 《Journal of Physics and Chemistry of Solids》2010,71(4):483-9829
Graphene sheets were produced by chemical reduction of graphite oxides in the solution of ionic conductive polymer, Nafion. The obtained graphene, coated with Nafion, can be re-dispersed in water, and readily forms stable dispersed state. The polymer-coated graphene had been characterized by FT-IR spectroscopy, UV-vis and X-ray photoelectron spectroscopy (XPS). The PEDOT film with Nafion-coated graphene increased significantly from 0.25 S/cm for pure PEDOT film and reached 12 S/cm. Further, the films of PEDOT doped Nafion-coated graphene had also higher conductivities compared to films doped PSS-coated graphene. 相似文献
80.
To obtain a rigorous definition of the chemical bonds in binary transition-metal aluminides, topological analyses were performed for VAl3 and TiAl3 in the D022 and L12 structures. The analyses were based on the valence charge densities calculated with the ab initio density functional theory. To better understand the formation mechanism of the pseudogap in these compounds, the band structure, the density of states (DOS) and the band decomposed charge density (BDCD) were calculated. The topological analyses reveal that the interactions between the (V, Ti) and Al atoms are all pure shared-shell interactions, the bonds are covalent and clearly have π-bond character. The study of the band structure, DOS and BDCD shows that the formation of the pseudogap is due to the crystal field energy splitting of the (V, Ti)-3d orbitals combined with the inter-unit-cell orbital interaction. 相似文献