Electronic band structure of KTaO3

Calculations are presented for the electronic band structure of the perovskite-type crystal KTaO₃. The results are obtained using the LCAO method in a modified form. On comparison with experimental data good agreement was found after a reassignment of one transition.     

Electronic band structure of TiCl3

Energy bands for the 3d? electrons of Ti³⁺ in the high temperature structure of TiCl₃ have been calculated by the tight-binding approximation. Cubic symmetry around each Ti³⁺ is assumed and transfer between the 3p atomic orbitals of Cl^? and 3d? atomic orbitals of Ti³⁺ is considered. Two singlet bands and two doublet bands with no dispersion have been obtained. The dispersionless character is discussed by constructing Wannier functions.     

Electronic structure and properties of NbS2 and TiS2 low dimensional structures

Transition metal dichalcogenides have a laminar structure, weakly bound through van der Waals interactions. Due to their technological applications in catalytic processes the bulk structure of many of them has been widely studied in the last 30 years. Some of them, such as NbTe₂ and TiSe₂, show superconductivity and have been, therefore, the subject of intense study. Novoselov et al. (2005 [1]) achieved to isolate not only graphene but also other bidimensional crystals, among them layers of some dichalcogenides. These bidimensional crystals preserve their monocrystallinity under normal ambient conditions, keeping the crystal structure of the bulk. In this contribution we calculate the magnetic and electronic properties of 2D layers of NbS₂ (non-magnetic metal in 3D) and TiS₂ (non-magnetic semimetal in 3D) as well as quasi 1D chains cut out from these layers.     

萤石结构TiO2的电子结构和光学性质

利用第一性原理计算了立方相萤石TiO₂的晶胞参数,能带结构和电子态密度.结果显示萤石TiO₂属于间接带隙半导体材料,其间接禁带宽度(Γ→X)E_g为2.07eV,比常见的金红石和锐钛矿TiO₂的禁带宽度窄.为了更清楚地了解萤石的光学性质,利用Kramers-Kronig色散关系,分别对萤石和金红石TiO₂的复介电常数、吸收率等参数进行了计算,并将二者结果做了 关键词： 2')" href="#">萤石结构TiO₂ 密度泛函理论 能带结构 光学性质     

萤石结构TiO2的电子结构和光学性质

利用第一性原理计算了立方相萤石TiO₂的晶胞参数，能带结构和电子态密度.结果显示萤石TiO₂属于间接带隙半导体材料，其间接禁带宽度(Γ→X)E_g为2.07eV，比常见的金红石和锐钛矿TiO₂的禁带宽度窄.为了更清楚地了解萤石的光学性质，利用Kramers-Kronig色散关系，分别对萤石和金红石TiO₂的复介电常数、吸收率等参数进行了计算，并将二者结果做了     

Ab initio calculations of band structure and thermophysical properties for SnS2 and SnSe2

The electronic band structure and elastic constants of SnS₂ and SnSe₂ have been calculated by using density-functional theory (DFT). The calculated band structures show that SnS₂ and SnSe₂ are both indirect band gap semiconductors. The upper valence bands originate mainly from S_p and Sn_d electrons, while the lowest conduction bands are mainly from (S, Se) _p and Sn_s states. The calculated elastic constants indicate that the bonding strength along the [100] and [010] direction is stronger than that along the [001] direction and the shear elastic properties of the (010) plane are anisotropic for SnS₂ and SnSe₂. Both compounds exhibit brittle behavior due to their low B/G ratio. Relationships among volumes, the heat capacity, thermal expansion coefficients, entropy, vibrational energy, internal energy, Gibbs energy and temperature at various pressures are also calculated by using the Debye mode in this work.     

Electronic energy band calculation in β-PbO2 comparison with SnO2 and GeO2 energy band structures

The energy band structure of β-PbO₂ is determined semi-empirically by the Kohn-Korringa-Rostoker method. It is believed to be the first PbO₂ calculated band structure that appears in literature. The direct band gap value that is obtained directly from this method is 2.7eV. It is lowered to the value of 1.6 eV which seems to be the most likely value of β-PbO₂ energy gaps that were already obtained. This energy band structure is compared with those of other oxides whose lattices belong to the same space group (D¹⁴_4h).     

Electronic structure and optical properties of wurtzite-kesterite Cu2ZnSnS4

As promising light-absorber material for solar cells, Cu₂ZnSnS₄ was found to have another crystal structure (wurtzite-kesterite) in addition to the conventional zinc blende-kesterite structure. Structural flexibility of Cu₂ZnSnS₄ opens up an avenue to develop light-absorber material with novel exciting properties and applications. However, its electronic and optical properties have not been comprehensively studied yet. For this purpose, the method of density functional theory within hybrid functional of PBE0 was adopted to study the structural, electronic, and optical properties of wurtzite-kesterite Cu₂ZnSnS₄ in this Letter. The calculated results suggested that the energy of its band gap is about 1.372 eV and it has obvious optical anisotropy. Furthermore, its crystal structure leads local internal fields that are especially beneficial to suppress the recombination of photoexcited electron–hole pairs.     

Electronic structure and optical properties of Sb2S3 crystal

The electronic and optical properties of Sb₂S₃ are studied using the full potential linearized augmented plane wave (FP-LAPW) method as implemented in Wien2k. In this approach, the alternative form of the generalized gradient approximation (GGA) proposed by Engel and Vosko (EV-GGA) was used for the exchange correlation potential. The calculated band structure shows a direct band gap. The contribution of different bands was analyzed from total and partial density of states curves. Moreover, the optical properties, including the dielectric function, absorption spectrum, refractive index, extinction coefficient, reflectivity and energy-loss spectrum are all obtained and analyzed in detail.     

Electronic structure and magnetic properties of Laves phase LuFe2

The electronic structure and magnetic properties of the Laves phase of LuFe₂ with C14, C15, and C36 structures has been investigated using the full-potential linearized augmented plane wave method. In order to study the stability of magnetic phases, nonmagnetic and spin-polarized calculations for ferromagnetic ordering were performed. It is found that the ferromagnetic hexagonal C14 phase is the ground-state structure and the C15 phase is an intermediate state between the C14 and C36 structures. There is an increase in the average magnetic moment on the Fe sites in the order of C15 →C14 →C36 structures, whereas the Lu-moment is not significantly different. We also find that there exist both localized and itinerant d electrons, resulting in antiferromagnetic ordering in the three structures. Their density-of-states, equilibrium volumes, and elastic properties are discussed, which is important for the understanding of the physical properties of LuFe₂ and may inspire future experimental research.     

Electronic structure of ErH2

A band structure study reveals that in contrast to the pure rare earth metal, the Fermi level of the dihydride falls near the bottom of the 5d band, in a region of low density of states; consequences on Fermi surface geometry, magnetic properties and resistivity are suggested. Below the metal d states lie two overlapping metal-hydrogen bands, in agreement with Weaver's photoemission data and Switendick's result on YH₂.     

Electronic structure of TiH2

The electronic structure of TiH₂ has been studied using the augmented-plane-wave method and the LCAO interpolation. The density of states and its orbital components show that the conduction band is Ti d-like and that the valence band is largely derived from the hydrogen orbitals with small Ti 3d hybridization. The electronic charges on the hydrogen atom are ～ 1.5 as compared to 1.6–1.7 of the rare-earth metal hydrides.     

Electronic energy band calculations in SnO2

The energy band structure of SnO₂ is determined semi-empirically by the Kohn-Korringa-Rostoker method. A Hartree-Fock-Slater potential model is used for Sn⁴⁺. For O²⁻, we use a HFS potential model corrected by the introduction of an additional Slater orbital. The band gap value which is obtained directly from this method is 4.5 eV; it is lowered to the value of 3.8 eV by fitting the mean potential value.     

Electronic structure and bonding in ThO2 and UO2

Electron energy levels and charge densities for ThO₂ and UO₂ are calculated in a molecular cluster approximation, using spin unrestricted Hartree-Fock-Slater and relativistic Dirac-Slater models. Results compare favorably with X-ray photoelectron spectra and reveal similarities in chemical bonding with rare earth oxides.     

Electronic structure and magnetic coupling properties of EuFe2P2: First-principles calculations

We have investigated the electronic structure and magnetic properties of EuFe₂P₂ using first-principles density functional theory within the generalized gradient approximation (GGA)+U schemes. Our calculated ground state magnetic configurations of EuFe₂P₂ is ferromagnetic which Eu²⁺ spins order along c axis. We argue that this kind of magnetic structure of Eu is determined by the indirect RKKY interactions between Eu and direct coupling interaction between Eu 4f with Fe 3d state by our spin-polarized density of states calculations. From the charge density and the Laplace charge density of EuFe₂P₂, we believe that the magnetic moment of Fe is determined by not only Fe-P coupling interactions but also Fe-Fe directly exchange interactions.     

超晶格SnO2掺Cr的电子结构和光学性质的研究

基于密度泛函理论的第一性原理,采用全势线性缀加平面波方法(FPLAPW)和广义梯度近似(GGA)来处理相关能,计算了Cr掺杂SnO₂超晶格的电子态密度、能带结构、介电函数、吸收系数、反射率和折射率.研究表明由于Cr的掺入,超晶格SnO₂在费米能级附近形成了新的电子占据态,出现了不连续的杂质能带,这是由Cr-3d态和O-2p,Sn-5s态电子所形成.介电谱在0—5.5 eV之间时出现了三个新的介电峰,在高能区介电谱主峰位置发生蓝移,峰值强度减小.吸收谱、反射谱和折 关键词： 超晶格 第一性原理 态密度 电子结构     

Electronic structure and band gap of the negative charge-transfer material Sr3Fe2O7

We studied the electronic structure of the Sr₃Fe₂O₇ compound using X-ray photoelectron spectroscopy (XPS). The charge-transfer satellites in the Fe 2p XPS spectra were analyzed using standard cluster model calculations. The analysis indicates that Sr₃Fe₂O₇ is in the negative charge-transfer regime, and that the ground state is dominated by the configuration (where denotes an O 2p hole in the oxygen band). These results are similar to those found in the related SrFeO₃ and Sr₂FeO₄ compounds. The band gap of the Sr₃Fe₂O₇ compound is split off by the relatively large value of the p-d transfer integral T_σ. The lowest lying excitations are and consequently the band gap is of the p-p type. The band gap in the Sr_n+1Fe_nO_3n+1 series can be understood taking into account the trend in the O 2p bandwidths.     

Electronic structure studies of CeAgSb2

The electronic band structure of CeAgSb₂ has been calculated using the self-consistent full potential nonorthogonal local orbital minimum basis scheme based on the density functional theory. We investigated the electronic structure with the spin-orbit interaction and on-site Coulomb potential for the Ce-derived 4f orbitals to obtain the correct ground state of CeAgSb₂.     

Electronic structure of Li3GaN2

First principles calculations, by means of the full-potential linearized augmented plane wave method within the local density approximation, were carried out for the electronic properties of Li₃GaN₂. The calculated lattice parameter is in good agreement with the measured one. The bandgap is direct at the Brillouin zone centre. The Li-N and Ga-N bonds are both ionic with a small covalent character of the latter one.     

Electronic structure of Sr2FeMoO6

We have used electron spectroscopies to investigate the electronic structure of the double perovskite Sr₂FeMoO₆. The valence-band photoemission spectra present a well-defined cut-off at the Fermi level, indicative of the metallic character of the material. The O 1s X-ray absorption spectrum presents three peaks, which are in good correspondence with the main structures in the unoccupied density-of-states of DF-LDA calculations. The electron energy-loss spectra present two structures which are also interpreted in terms of transitions between the bands obtained in the DF-LDA calculations.