(Co,P)双掺杂MgF2电子结构和光学性质的第一性原理研究

基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,计算了纯MgF2晶体、Co掺杂MgF2晶体、P掺杂MgF2晶体和(Co,P)双掺杂MgF2晶体的电子结构和光学特性.结果表明,掺杂后的MgF2晶体发生了畸变,原子之间的键长也有所变化.(Co,P)双掺杂后,由于非金属原子p态和金属原子d态之间的轨道杂化,在MgF...     

Ru掺杂LiFePO4电子结构和性能的第一性原理研究

基于第一性原理和超软赝势平面波方法,对Ru掺杂LiFePO_4的原子几何结构和电子结构进行了研究。结果表明Ru掺杂后LiFePO_4晶胞参数a和b显著降低,晶胞参数c略微的增大,掺杂后晶胞体积收缩;当掺杂量为0.01时体系Fermi能最高,能量密度高。掺杂体系在Fermi能级附近态密度电子峰强度增大,态密度峰向低能方向移动,掺杂后能级减小,有利于LiFePO_4导电性能增强。能带计算结果显示,随着掺杂量的增加,体系带隙降低,能带下降,导带底向费米面移动,电子从价带跃迁到导带更加容易。电化学性能测试结果显示,当Ru的掺杂量较小时(0.01),费米面附近能带数增加,有利于电子传递,材料表现出最佳的放电比容量和倍率性。当掺杂量较大时(0.05,0.1),过多Ru将阻碍Li~+扩散通道,不利于电极材料的倍率性能。Ru掺杂能影响LiFePO_4电子结构,改善LiFePO_4性能,掺杂量不宜太大。     

Cu掺杂MgF2晶体的电子结构及光学特性

基于密度泛函理论(DFT)的第一性原理平面波超软赝势方法,计算了纯的MgF2晶体和掺杂不同原子分数(2.08%,4.16%,6.24%)Cu的MgF2晶体结构、电学性质以及光学性质.结果表明:Cu的掺入导致MgF2晶体禁带宽度逐渐变窄,并且Cu掺杂使得MgF2晶体折射率和吸收峰增加,特别是在4eV附近区域出现了新吸收峰.同时也给出了引起体系性质变化的物理机制,Cu掺杂MgF2晶体在光电化学方面有着潜在的应用价值.     

LiNiO2及掺杂化合物的结构与稳定性的第一性原理研究

应用第一原理局域密度泛函对LiNiO2及其掺杂化合物的晶体结构、能带结构和态密度进行了研究.结果表明:锂镍氧系正极材料是电子的良导体,在充放电过程中具有良好的稳定性,适合做锂离子电池的正极材料;在LiNiO2晶体中主要是O和Ni之间成键,镍离子和氧离子的相互作用比较强,Li在嵌入层状结构材料后部分失去电子,以离子状态存在.     

CdSe的电子结构和光学性质研究

CdSe是Ⅱ-Ⅵ族半导体材料中一种重要的半导体材料,它有闪锌矿和纤锌矿两种不同的结构,带隙较窄,具有优良的电光特性和广泛的应用前景,得到了人们的广泛关注[1-3].     

In2O3电子结构与光学性质的第一性原理计算

采用基于密度泛函理论框架下的第一性原理平面波超软赝势方法, 计算了In2O3电子结构和光学线性响应函数, 系统研究了In2O3电子结构与光学性质的内在关系. 利用计算的能带结构和态密度分析了带间跃迁占主导地位的In2O3材料的能量损失函数、介电函数、反射图谱, 根据电荷密度差分图分析了In2O3材料的化学和电学特性. 研究结果表明In2O3光学透过率在可见光范围内高达85%, 可作为优异的透明导电薄膜材料. 同时, 计算结果为我们制备基于In2O3透明导电材料的设计与大规模应用提供了理论依据, 也为监测和控制这一类透明导电材料的生长过程提供了可能性.     

Mg、Zn掺杂AlN电子结构的第一性原理计算

采用密度泛函理论(DFT)的第一性原理平面波超软赝势方法, 对Mg、Zn 掺杂AlN 的32 原子超原胞体系进行了几何结构优化, 从理论上给出了掺杂和非掺杂体系的晶体结构参数, 对纤锌矿结构AlN 晶体及AlN:Mg、AlN: Zn 的结构、能带、结合能、电子态密度、集居数、差分电荷分布进行计算和分析. 计算结果表明, AlN:Mg、AlN: Zn 都能提供很多的空穴态, 形成p 型电导, 并且Mg是较Zn 更好的p型掺杂剂.     

Lu掺杂AlN的电子结构和光学性质的第一性原理研究

为了探索AlN在光电器件中的潜在应用,采用第一性原理计算了不同Lu掺杂浓度(以原子分数x表示)的AlN(Al_1-xLu_xN)的电子结构和光学性质。研究结果表明,Al_1-xLu_xN的超胞体积随着Lu掺杂浓度的增加而增加,而带隙则相反。Al_1-xLu_xN的静态介电常数在低能区随掺杂浓度的提高而提高,随后逐渐趋向一致。随着Lu掺杂浓度的增加,反射率和吸收系数的峰值强度降低,峰值向较低能量方向移动。Al_1-xLu_xN的能量损失光谱表现出明显的等离子体振荡特性,且峰值低于本征AlN。Al_1-xLu_xN的光电导率在低能区随能量的增加而急剧增加。     

Lu掺杂AlN的电子结构和光学性质的第一性原理研究

为了探索 AlN在光电器件中的潜在应用,采用第一性原理计算了不同 Lu掺杂浓度(以原子分数 x表示)的 AlN(Al_1-xLu_xN)的电子结构和光学性质。研究结果表明,Al_1-xLu_xN的超胞体积随着Lu掺杂浓度的增加而增加,而带隙则相反。Al_1-xLu_xN的静态介电常数在低能区随掺杂浓度的提高而提高,随后逐渐趋向一致。随着Lu掺杂浓度的增加,反射率和吸收系数的峰值强度降低,峰值向较低能量方向移动。Al_1-xLu_xN的能量损失光谱表现出明显的等离子体振荡特性,且峰值低于本征AlN。Al_1-xLu_xN的光电导率在低能区随能量的增加而急剧增加。     

Y-Cu共掺杂ZnO电子结构与光学性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理平面波赝势法研究了本征ZnO、Y和Cu单掺杂ZnO、Y-Cu共掺杂ZnO的电子结构和光学性质. 计算结果表明, 在本文的掺杂浓度下, Y和Cu单掺杂可以提高ZnO的载流子浓度, 从而改善ZnO的导电性, Y-Cu共掺时ZnO半导体进入简并状态, 呈现金属性. Y 掺杂ZnO可以提高体系在紫外区域的吸收, 而Cu掺杂ZnO在可见光和近紫外区域发生吸收增强现象, 其中由于Y离子和Cu离子之间的协同效应, Y-Cu共掺杂ZnO时体系对可见光和近紫外区域的光子能量吸收大幅增加, 因此Y-Cu共掺杂ZnO可以用于制作光电感应器件.     

Electronic structures and optical properties of BiOX (X = F,Cl, Br,I) via DFT calculations

Based on the density functional theory (DFT), the lattice constants and atomic positions of BiOX (X = F, Cl, Br, I) species have been optimized, and the electronic and optical properties of the relaxed species have been calculated, with Bi 5d states considered or not. Relaxation generally results in the shrinkage in a and the expansion of c. Relaxed BiOCl, BiOBr, and BiOI present indirect band gaps, whereas BiOF exhibits a direct or somewhat indirect band‐gap feature corresponding to the relaxation and calculation with the Bi 5d states or not. The bottom of the conduction band is quite flat for relaxed BiOI, and apparently flat in BiOBr, and shows observable flatness in BiOCl as well when considering the Bi 5d states. The top of the valence band is rather even as well for some species. The obtained maximum gaps for relaxed BiOF, BiOCl, BiOBr, and BiOI are 3.34, 2.92, 2.65, and 1.75 eV, respectively. The density peak of X np states in the valence band shifts toward the valence band maximum with the increasing X atomic number. The bandwidths, atomic charges, bond orders, and orbital density have also been investigated along with some optical properties. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009     

NbC固体表面能带和电子结构的理论研究

采用DFT/BLYP方法对NbC(001)和(111)面的电子结构进行研究。计算结果表明,对于NbC(001)表面,其表面态主要集中于费米能级(EF)下方约4.5eV附近区域,并以表面Nb原子和C原子为主要成分。O2分子在该表面吸附时,趋向于吸附在表面Nb原子上。对于NbC(111)表面,其表面态集中在EF下方0.02.0eV区域,靠近EF的态具有较高的表面活性,其主要成分为表面Nb原子的4dxz/dyz成分。上述结论与光电子能谱实验结果基本一致;但由于金属原子d电子数的差异导致NbC(111)表面态成分与类似的TiC化合物并不相同。     

Electronic structures and nonlinear optical properties of highly deformed halofullerenes C3v C60F18 and D3d C60Cl30

Electronic structures and nonlinear optical properties of two highly deformed halofullerenes C_3v C₆₀F₁₈ and D_3d C₆₀Cl₃₀ have been systematically studied by means of density functional theory. The large energy gaps (3.62 and 2.61 eV) between the highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs) and the strong aromatic character (with nucleus‐independent chemical shifts varying from ?15.08 to ?23.71 ppm) of C₆₀F₁₈ and C₆₀Cl₃₀ indicate their high stabilities. Further investigations of electronic property show that C₆₀F₁₈ and C₆₀Cl₃₀ could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states and frontier molecular orbitals are also calculated, which present that HOMOs and LUMOs are mainly distributed in the tortoise shell subunit of C₆₀F₁₈ and the aromatic [18] trannulene ring of C₆₀Cl₃₀, and the influence from halogen atoms is secondary. In addition, the static linear polarizability and second‐order hyperpolarizability of C₆₀F₁₈ and C₆₀Cl₃₀ are calculated using finite‐field approach. The values of and for C₆₀F₁₈ and C₆₀Cl₃₀ molecules are significantly larger than those of C₆₀ because of their lower symmetric structures and high delocalization of π electrons. © 2010 Wiley Periodicals, Inc. J Comput Chem 2010     

Strain-tunable electronic properties and optical properties of Hf2CO2 MXene

Two-dimensional materials have been extensively applied because of their unusual electronic, mechanical, and optical properties. In this paper, the electronic structure and optical properties of Hf₂CO₂ MXene under biaxial and uniaxial strains are investigated by the Heys-Scuseria-Ernzerhof (HSE06) method. Monolayer Hf₂CO₂ can sustain stress up to 6.453 N/M for biaxial strain and 3.072 N/M for uniaxial strain. Monolayer Hf₂CO₂ undergoes the transition from semiconductor to metal under −12% strain whether it is under biaxial or uniaxial strain. With the increasing biaxial compressive strain, the blue shift of Hf-d, O-p, and C-p orbitals in valence band maximum results in the metallization of monolayer Hf₂CO₂, while the red shift of Hf-d and O-p orbitals in conduction band minimum results in the metallization of monolayer Hf₂CO₂ with increasing uniaxial compressive strain. The analysis of optical properties indicates that uniaxial strain weakens the reflectivity and refractive index of monolayer Hf₂CO₂ in the visible-light range. In addition, the effective mass and the charge distribution under biaxial and uniaxial strains are also explored.     

气相中2Sr+和2Ba+催化N2O与CO还原反应的理论研究

用密度泛函理论DFT-UB3LYP方法,对2Sr+,2Ba+采用相对论校正赝势基组SDD,对C,N,O采用6-311+G(2d)基组,计算研究了气相中碱土金属离子2Sr+,2Ba+催化N2O(X1∑+)+CI(X1∑+)→N2(X1∑+g)+CO2(X1∑+g)反应的微观机理.优化了二重态势能面上各反应物、中间体和过渡...     

A density functional study on the electronic structures of TiN solid

The electronic structures of TiN bulk have been studied by using different theoretical formalisms, and the DFT method, especially the BLYP method can produce reasonable results. The band structure of TiN (001) surface is also investigated and two a type surface states are presented in our results. The state located at 2.9 eV below EF in angle resolved photoemis-sion in (ARPES) is well reproduced in this work, which consists essentially of 2pz orbital of surface N atom. Another surface state is associated with the bands originated from 3d orbital of surface Ti atom. Furthermore, the elastic constants of TiN are also calculated by using BLYP method.     

Evolution of Structural, Electronic and Optical Properties of Monoclinic ZrO2 under High Pressure： A First Principles Study

The structural, electronic and optical properties of the monoclinic ZrO2 were studied by ab initio calculations based on the density functional theory and pseudopotential method. The calculated lattice parameters and band gap are in agreement with the experimental and other theoretical values. The evolution of lattice parameters and electronic properties were illustrated under high pressure. Meanwhile, the optical properties, such as adsorption coefficients, imaginary part of dielectric function, and energy loss function, were investigated under both ambient and high pressures.     

C_(36)聚合体电子结构的理论研究

采用PM3 和DFT/B3LYP方法对2D六方网状,以及1D链状C36聚合体的构型进行全优化,探讨了其电子结构和稳定性;并在从头算水平上计算了相应的能带结构。研究发现,C36形成聚合体后构型发生了显著变化; 与0D 的结构比较,C36聚合为1D或2D结构后,笼内CC键长变化明显。计算表明C36聚合后稳定性提高,呈半导体或绝缘体性质。聚合后C36内部CC键定域化程度的增强是其稳定性提高的主要因素。     

Predicting the electronic and optical properties of IB metals doped monoclinic BiVO4: First principle calculations

The effect of doping IB metals (Cu, Ag, and Au) on the photocatalytic activity of monoclinic Bismuth vanadate (BiVO₄) was investigated by predicting their electronic and optical properties based on the first‐principle calculation. For the Cu‐doped system, the formation of shallow acceptor level will narrow the band gap and trap the electrons which may enhance the separation of photo‐induced carriers. And the doping of Ag has little effect on the electronic structure. However, the doping of Au will introduce a deep localized impurity level which should serve as both charge traps and recombination centers, and hinder the separation of photo‐induced carriers. With incorporation of Cu, the mobility of charge carriers is enhanced due to the smaller effective mass, but the Ag and Au doping would not improve the transfer of charges. In summary, only the doping of Cu has positive effect on improving the photocatalytic activity of monoclinic BiVO₄. © 2015 Wiley Periodicals, Inc.