Cmcm空间群斜方SrHfO_3的电子结构和光学性质理论计算（英文）

采用基于密度泛函理论(DFT)框架下广义梯度近似平面波超软赝势法,计算了Cmcm空间群斜方SrHfO_3的电子结构和光学性质。计算得到的Cmcm斜方SrHfO_3的平衡晶格常数均与实验值相近。同时,计算得到了Cmcm斜方SrHfO_3的能带结构、态密度和电荷密度。结果表明,斜方SrHfO_3属于直接带隙氧化物,在Hf和O之间主要是共价键结合而在Sr和O之间主要呈现离子键特性。计算还得到了斜方SrHfO_3的复介电函数、折射率和消光系数等,且复介电函数的实部与虚部都与实验结果接近。     

First-Principles Calculations of Electronic Structure and Optical Properties of Si-doped Orthorhombic SrHfO3

采用基于密度泛函理论的平面波超软赝势方法研究了正交相SrHfO3和以Si替换Hf方式形成的掺杂态SrHfO3的形成能,几何结构,电子结构和光学性质。负的形成能表明在由单元素形成Si掺杂态的SrHfO3的反应中,Si占居Hf位置与Sr位置两种情况在能量上是有利的,并且Si原子更加倾向于占居Hf位置。纯的SrHfO3计算得到的晶格常数与文献报道的实验值和理论值是一致的,而Si占居Hf位置后会导致SrHfO3的晶格常数减小。能带结构显示在掺入Si原子后会使带隙变小。布居分析与电荷密度图一致,说明在Hf位置掺入Si后掺杂位置附近的Hf-O键以共价键为主,Sr-O键以离子键为主。最后,对Si掺杂后SrHfO3在(100)方向上的介电常数、反射率、吸收系数、折射率进行了计算与分析。     

Si掺杂正交相SrHfO_3电子结构与光学性质的第一性原理计算（英文）

采用基于密度泛函理论的平面波超软赝势方法研究了正交相SrHfO3和以Si替换Hf方式形成的掺杂态SrHfO3的形成能,几何结构,电子结构和光学性质。负的形成能表明在由单元素形成Si掺杂态的SrHfO3的反应中,Si占居Hf位置与Sr位置两种情况在能量上是有利的,并且Si原子更加倾向于占居Hf位置。纯的SrHfO3计算得到的晶格常数与文献报道的实验值和理论值是一致的,而Si占居Hf位置后会导致SrHfO3的晶格常数减小。能带结构显示在掺入Si原子后会使带隙变小。布居分析与电荷密度图一致,说明在Hf位置掺入Si后掺杂位置附近的Hf-O键以共价键为主,Sr-O键以离子键为主。最后,对Si掺杂后SrHfO3在(100)方向上的介电常数、反射率、吸收系数、折射率进行了计算与分析。     

Al_2O_3的能带结构和光学函数的关系

采用基于密度泛函理论(DFT)的第一性原理CASTEP计算程序,研究Al_2O_3的能带结构和光学函数.结果表明,α-Al_2O_3和γ-Al_2O_3的能带结构形状相似,γ-Al_2O_3的高对称性使得费米面向高能级方向移动,进入导带;对于较常见的几种波长激光,α-Al_2O_3的介电函数虚部均为0,实部随着激光波长增大而减小;γ-Al_2O_3的介电函数虚部、实部随着激光波长增大而增大.γ-Al_2O_3的介电函数虚部、实部和反射率均高于α-Al_2O_3,在激光波长为10.6 ìm时反射率最高,达到40.1%,为α-Al_2O_3的7倍.     

闪锌矿结构AIN、AIP和AlAs的介电和弹性性质的第一性原理研究

采用第一性原理赝势平面波方法对闪锌矿结构AIN、AIP和AlAs的电子结构,介电和弹性性质进行计算,结果表明:基于密度函数扰动理论计算的这些材料的介电和弹性性质与其它第一性原理和分子动力学计算值一致性较好,但与实验值之间有一定的差异:晶格参数的优化、赝势的选取和交换关联项的选择都对计算结果有较大影响.根据计算的弹性常数绘制了这些材料特征平面(101)面的弹性模量图,为这方面材料的力学研究提供参考.     

闪锌矿结构AlN、AlP和AlAs的介电和弹性性质的第一性原理研究

采用第一性原理赝势平面波方法对闪锌矿结构AlN、AlP和AlAs的电子结构，介电和弹性性质进行计算，结果表明：基于密度函数扰动理论计算的这些材料的介电和弹性性质与其它第一性原理和分子动力学计算值一致性较好，但与实验值之间有一定的差异：晶格参数的优化、赝势的选取和交换关联项的选择都对计算结果有较大影响。根据计算的弹性常数绘制了这些材料特征平面（101）面的弹性模量图，为这方面材料的力学研究提供参考。     

K掺杂正交相Ca2Si电子结构和光学性质的第一性原理计算

采用第一性原理的平面波赝势方法和广义梯度近似(GGA),对K掺杂正交相Ca2Si前后的电子结构和光学性质进行比较分析。计算表明,掺K后正交相Ca2Si的能带向高能方向发生了偏移,形成直接带隙的p型半导体,禁带宽度为0.4318 eV,光学带隙变宽;掺杂K后价带主要是Si的3p态,Ca的3d、4s态以及K的3p、4s态的贡献。并利用计算的能带结构和态密度分析了K掺杂正交相Ca2Si前后的复介电函数、能量损失函数、反射光谱及吸收光谱,结果显示掺K增强了材料对太阳光谱中红外波段的能量利用。研究结果说明掺杂是改变材料电子结构和光电性能的有效手段,为Ca2Si材料光电性能的开发与应用提供了理论依据。     

TiO2/Al2O3堆栈结构high-k薄膜的制备及性能

采用磁控溅射法制备了TiO2/Al2O3堆栈结构高k栅介质薄膜,研究了不同后处理条件对等效氧化物厚度,界面电荷和界面扩散的影响.实验结果表明400℃退火后,TiO2已经结晶,退火可以降低漏电流密度和介电层中的电荷密度.同时,退火使Ti进一步向Al2O3层扩散,形成TiO2和A12为O3的混合层,Al2O3层过薄时不能有效阻挡TiO2的扩散.     

第一性原理研究不同压力下正交相SrHfO_3的电子结构(英文)

采用第一性原理研究了压力对正交相Sr Hf O3电子结构的影响。正交相Sr Hf O3在零压力时的结构参数与已有的实验值和理论计算值一致。当施加的压力小于20 GPa时,正交相Sr Hf O3的最小间接带隙在Z-Γ之间。当施加的压力大于20 GPa时,正交相Sr Hf O3的最小间接带隙在S-Γ之间。随着压力的增加,正交相Sr Hf O3的态密度向低能量方向移动。电荷密度分析表明,Hf-O之间主要以共价键结合,Sr-O之间主要以离子键结合。随着压力的增加,Hf-O共价键和Sr-O离子键增强,而Sr-Hf O3之间的离子交互作用减弱。     

First-Principles Study of Electronic Structure of Orthorhombic SrHfO3 under Pressure

采用第一性原理研究了压力对正交相Sr Hf O3电子结构的影响。正交相Sr Hf O3在零压力时的结构参数与已有的实验值和理论计算值一致。当施加的压力小于20 GPa时,正交相Sr Hf O3的最小间接带隙在Z-Γ之间。当施加的压力大于20 GPa时,正交相Sr Hf O3的最小间接带隙在S-Γ之间。随着压力的增加,正交相Sr Hf O3的态密度向低能量方向移动。电荷密度分析表明,Hf-O之间主要以共价键结合,Sr-O之间主要以离子键结合。随着压力的增加,Hf-O共价键和Sr-O离子键增强,而Sr-Hf O3之间的离子交互作用减弱。     

First-principles calculations of electronic and optical properties of Ti-doped monoclinic HfO2

Based on the first-principles density-functional theory, the electronic structures and optical properties of monoclinic HfO₂ and Ti-doped m-HfO₂ are comparatively investigated. The calculated lattice parameters of m-HfO₂ are in good agreement with the experimental values and the previous works, and the incorporation of Ti into HfO₂ induces a decrease in the lattice parameters. Electronic structures of m-HfO₂ and Ti-doped HfO₂ are studied through the densities of states (DOS) and band structures. The results indicate that the Ti substitution of Hf sites modifies the conduction band structure of HfO₂, which leads to a reduction of the band gap of HfO₂. The complex dielectric function and refractive index are calculated and the peak position distributions of imaginary parts of the complex dielectric function have been explained. The calculated optical properties are consistent with the experimental measurements for m-HfO₂.     

Electronic structure and linear optical property of BaSi2N2O2 crystal

The electronic structure and linear optical property of BaSi₂N₂O₂ (BSNO) have been calculated by density functional method with the local density approximation. A direct band gap of 5.17 eV at G is obtained for BSNO. The calculated total and partial densities of states indicate that the top valence band is mainly constructed from the N 2p and O 2p states, the low conduction band mostly originates from Ba 4d and Si 3p states. The calculated linear optical property of BSNO is in good agreement with the experimental measurement.     

Electronic structure of layer type tungsten metal dichalcogenides WX2 (X = S, Se) using Compton spectroscopy: Theory and experiment

In this paper, we report the first ever experimental Compton profile study of WS₂ and WSe₂ employing 20 Ci ¹³⁷Cs Compton spectrometer. To interpret our experimental data, the electronic properties of these compounds have been determined by linear combination of atomic orbitals, full potential linearised augmented plane-wave and spin polarised relativistic Korringa–Kohn–Rostoker (SPR-KKR) schemes. The band structure calculations show that both the WS₂ and WSe₂ are indirect-gap semiconductors. The SPR-KKR calculations are found to be relatively in poor agreement with the experimental electron momentum densities. The relative nature of bonding in both the dichalcogenides is explained in terms of equal-valence-electron-density profiles, Mulliken's population and valence band charge densities.     

Electronic,optical and thermoelectric properties of Ce3PdIn11 and Ce5Pd2In19: An ab initio study

Density functional calculations with Engel and Vosko generalized gradient approximation are applied to investigate the electronic, optical and thermoelectric properties of Ce₃PdIn₁₁ and Ce₅Pd₂In₁₉ compounds. Analysis of the calculated band structure of Ce₃PdIn₁₁ and Ce₅Pd₂In₁₉ demonstrates their metallic character. The calculated densities of states N(E_F) of Ce₃PdIn₁₁ and Ce₅Pd₂In₁₉ at the Fermi level are 19.60 states/eV and 33.50 states/eV, respectively. The bonding nature in these compounds is discussed via the calculated contour map of the charge density in (1 1 0) crystallographic plane. Imaginary parts of the complex dielectric function show considerable isotropy between 3 and 14 eV Ce₃PdIn₁₁ have large dielectric constant. Thermoelectric properties results reveal that both compounds possess high Seebeck coefficient and electrical conductivity at high temperature. This is the first quantitative theoretical prediction of the theremoelectric properties for these investigated compounds and still awaits experimental confirmations.     

Theoretical study of structural, electronic, lattice dynamical and dielectric properties of SrAl2O4

We investigate the structural, electronic, lattice dynamical, and dielectric properties of SrAl₂O₄ within density-function theory. The crystal structure is fully relaxed, and the structural parameters are found to be well consistent with the experimental data. The first pressure derivatives of the bulk modulus are predicted to be 2.5 and 4.3 for local density approximation (LDA) and generalized gradient approximation (GGA), respectively. The electronic band structure shows that the valence band maximum is comprised of O 2p states and a small amount of Al 3s and 3p states, and the conduction band minimum is comprised of Sr 5s and a small amount of O 2p, Al 3s and Al 3p states. The phonon frequencies at the center of the Brillouin zone and the dielectric permittivity tensors are calculated using density-function perturbation theory. The electronic (?_∞) and static (?₀) dielectric permittivity tensors are theoretically predicted by the calculations with both LDA and GGA formalisms. The results show that the electronic dielectric permittivity is isotropic, while the static dielectric permittivity exhibits to be somewhat anisotropic due to the dominant ionic contributions in static dielectric permittivity.     

First-principles calculations and X-ray spectroscopy studies of the electronic structure of CuWO4

First-principles self-consistent band-structure calculations of copper tungstate, CuWO₄, have been made using the full potential linearized augmented plane wave (FP-LAPW) method. Total and partial densities of states of the constituent atoms of CuWO₄ have been derived. The results obtained reveal that the valence band of CuWO₄ is dominated by contributions of the O 2p-like states, while the W 5d-like states are the main contributors into the conduction band of the tungstate. Additionally, the FP-LAPW calculations render that the W 5d- and Cu 3d-like states contribute mainly at the bottom and at the top of the valence band of CuWO₄, respectively. In the present work, the X-ray emission spectroscopy (XES) and X-ray absorption spectroscopy (XAS) methods were also employed to investigate experimentally the electronic structure of copper tungstate. For the mentioned compound, the XES bands reflecting the energy distribution of mainly the W 5d-, Cu 3d- and O 2p-like states were derived and compared on a common energy scale with the X-ray photoelectron valence-band spectrum. A rather good agreement of the experimental and theoretical data concerning electronic properties of CuWO₄ has been obtained in the present paper. Measurements of the energy shift of the XAS W L_III edge of CuWO₄ clearly demonstrate that tungsten atoms in copper tungstate are in the formal valence state +6.     

Synthesis and Structural Determination of Nine-Coordinate K[GdIII(edta)(H2O)3]·5H2O

The title complex K[GdIII(edta)(H2O)3]·5H2O was synthesized, where edta denotes ethylenediamine-tetraacetic acid. The crystal and molecular structure of the complex were determined by single-crystal X-ray structure analysis. The crystal belongs to an orthorhombic crystal system and an Fdd2 space group. The complex anion [GdIII(edta)(H2O)3]- has a pseudo-monocapped square antiprismatic nine-coordinate structure in which six coordinate atoms (two N and four O) are from an edta ligand and three water molecules coordinate to GdIII ion directly. It can be predicted that GdIII ion can also form a nine-coordinate complex with ttha (triethylenetetraminehexaacetic acid) ligand, so the GdIII complex anion [GdIII(Httha)]2- can supply a free non-coordinate carboxyl group used for molecular embellishment in some biological molecules to form a contrast agent of Magnetic Resonance Imagine (MRI) with targeting function.     

极端不可压缩Re2P的电子结构、化学键及弹性性质的第一性原理研究

利用基于密度泛函理论（DFT）的广义梯度近似（GGA）,研究Co2P类型结构的极端不可压缩Re2P的电子结构、化学键和弹性性质。能带结构显示Re2P为金属性材料;态密度和分态密度的计算结果表明,费米能级附近的态密度主要来自Re-5d态;布居分析表明Re2P中的化学键具有以共价性为主的混合离子一共价特征。计算得到Re2P的晶格参数、体模量、剪切模量和单晶的弹性常数,由此导出弹性模量和泊松比。结果表明,Re2P是力学稳定的,且具有一定的脆性。