Cu2Se电子结构和光学性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理的平面超赝势方法计算研究了Cu2Se的电子结构、态密度和光 学性质。能带结构分析表明Cu2Se为半金属、上价带主要由Se的4p电子构成下价带主要由Cu的3d电子构成静态介电常数为1.41折射率为7.74吸收系数在可见光范围内最小值为1×105cm−1且在高能区对光子的吸收减小为零其电子能量损失峰在26.84eV正好对应反射系数急剧下降的位置光电导率的波谷出现的能量范围与前面的吸收系数和消光系数的峰值和波谷出现的位置完全对应。     

Cu2Se电子结构和光学性质的第一性原理计算

采用基于密度泛函理论(DFT)的第一性原理的平面超赝势方法计算研究了Cu2Se的电子结构、态密度和光 学性质。能带结构分析表明Cu2Se为半金属、上价带主要由Se的4p电子构成下价带主要由Cu的3d电子构成静态介电常数为1.41折射率为7.74吸收系数在可见光范围内最小值为1×105cm−1且在高能区对光子的吸收减小为零其电子能量损失峰在26.84eV正好对应反射系数急剧下降的位置光电导率的波谷出现的能量范围与前面的吸收系数和消光系数的峰值和波谷出现的位置完全对应。     

卤化硅烯结构、电子和光学性质的第一性原理研究

二维硅烯的商业用途通常受到其零带隙的抑制,限制了其在纳米电子和光电器件中的应用.利用基于密度泛函理论的第一性原理计算,单层硅烯的带隙通过卤原子的化学官能化被成功打开了,并综合分析了卤化对单层硅烯的结构,电子和光学性质的影响.研究结果表明卤化使结构变得扭曲,但保持了良好的稳定性.通过HSE06泛函,全功能化赋予硅烯1.390至2.123 eV的直接带隙.键合机理分析表明,卤原子与主体硅原子之间的键合主要是离子键.最后,光学性质计算表明,I-Si-I单层在光子频率为10.9 eV时达到最大光吸收,吸收值为122000 cm^-1,使其成为设计新型纳米电子和光电器件的有希望的候选材料.     

Structural,optical and electrical properties of CuIn5Se8 and CuGa5Se8

Ingots of CuIn₅Se₈ and CuGa₅Se₈ were prepared by direct fusion of the stoichiometric mixture of the elements. The analysis of X-ray powder diffraction data showed the presence of one single phase with tetragonal structure for CuGa₅Se₈ and two phases with hexagonal and tetragonal structure for CuIn₅Se₈. The lattice parameters a and c were refined by means of the program NBS*AIDS83. The phase transition temperatures were obtained by Differential Thermal Analysis measurements performed on samples sealed in evacuated quartz ampoules. Transmittance measurements were used to determine the absorption coefficient α. The values of E_g were obtained from a plot of (αhν)² vs. hν. The electrical resistivity was measured from 10 to 400 K using a four-wire configuration. The activation energies were estimated from the Arrhenius plot of the resistivities.     

UO2的电子结构及光学性质的第一性原理研究

采用局域自旋密度近似 (LSDA)和有效库仑相关能 (U) 方法研究了UO₂的晶格参数、能带结构和光学常数. 计算得到的UO₂晶体的晶格常数为5.40 ?,带隙宽度为1.82 eV,正确预测了UO₂的反铁磁性半导体基态性质. 能带结构和介电函数的分析结果表明,铀的6d电子在晶体场中发生劈裂形成两个能级,与实验结果较为符合.     

N掺杂SnO2材料光电性质的第一性原理研究

采用全电势线性缀加平面波(full potential linearized augmented plane wave method,简记为FP-LAPW)方法,基于密度泛函理论第一性原理计算分析N掺杂SnO₂材料,研究了在N替代O原子和N替代Sn原子情况下的电子态密度、电荷密度分布以及光学性质.研究表明N掺杂替代Sn较之N掺杂替代O原子的带隙要宽,都宽于SnO₂的本征带隙,且两种情况下N分别处于负氧化态和正氧化态,其介电函数谱也与带隙对应发生蓝移,从理论上指出     

First-principles study on the electronic and optical properties of BiFeO3

The structural, electronic, and optical properties of multiferroic bismuth ferrite (BiFeO₃) are investigated using density functional theory within generalized gradient approximation (GGA). The calculated lattice parameters are in good agreement with the experimental data. The electronic structure shows that BiFeO₃ has an indirect (very close to direct) band gap of 1.06 eV. The complex dielectric function, absorption spectra, refractive index, extinction coefficient, energy-loss spectrum and reflectivity are calculated, and the results are compared with the available experimental data. Finally, the optical properties of BiFeO₃ are discussed based on the band structure calculations.     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质。计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好。基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性。从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa 出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合。同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况。     

First-principles study of structural,electronic and optical properties of ZnF_2

The structural, electronic, and optical properties of rutile-, CaC12-, and PdF2-ZnF2 are calculated by the plane-wave pseudopotential method within the density functional theory. The calculated equilibrium lattice constants are in reasonable agreement with the available experimental and other calculated results. The band structures show that the rutile-, CaCl2-, and PdF2-ZnF2 are all direct band insulator. The band gaps are 3.63, 3.62, and 3.36 eV, respectively. The contribution of the different bands was analyzed by the density of states. The Mulliken population analysis is performed. A mixture of covalent and weak ionic chemical bonding exists in ZnF2. Furthermore, in order to understand the optical properties of ZnF2, the dielectric function, absorption coefficient, refractive index, electronic energy loss spectroscopy, and optical reflectivity are also performed in the energy range from 0 to 30 eV. It is found that the main absorption parts locate in the UV region for ZnF2. This is the first quantitative theoretical prediction of the electronic and optical properties of ZnF2 compound, and it still awaits experimental confirmation.     

CaB6电子结构及光学性质的第一性原理计算

采用基于密度泛函理论的第一性原理的分子动力学方法系统地计算了温度为300K时CaB6基态的电子结构、态密度和光学性质.能带结构分析表明CaB6属于一种直接带隙半导体;其导带主要由Ca的3d态电子构成,价带主要由B的2p态电子构成,静态介电常数ε1(0)=7.8,折射率n(0)=2.8,吸收系数最大峰值为4.37×105...     

Al_xIn_(1-x)As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,对各组分Al_xIn_(1-x)As(x为0～1)的晶体结构,电子结构和光学性质进行了第一性原理计算.结果显示,随Al组分x增加,Al_xIn_(1-x)As晶体各键长将缩短,键角发生变化,晶胞体积也将减小,晶格常数的变化符合Vegard定律.另外,随着Al组分x的增加,Al_xIn_(1-x)As的禁带宽度变宽,且能带有从直接带隙结构转变为间接带隙结构的趋势.具有较高In组分的Al_xIn_(1-x)As晶体在可见光区域中的光吸收能力更强,光谱响应范围更大.     

高压下稳态六方Ge2Sb2Te5结构、电子和光学性质的第一性原理研究

采用基于密度泛函理论的广义梯度近似方法研究了稳态六方petrov原子序列结构Ge2Sb2Te5的结构、电子和光学性质.计算所得的平衡态晶格参数与实验数据和先前的理论结果吻合很好.基态的能带结构和态密度表明了稳态六方petrov原子序列结构的Ge2Sb2Te5持有金属性.从压强影响下体积的变化趋势发现稳态六方Ge2Sb2Te5在17 GPa和34 GPa出现不稳定,暗示在此压强下的相变发生,这与2009年Krbal等人的实验结果相吻合.同时,还系统地研究了稳态六方petrov原子序列结构的Ge2Sb2Te5高压下的光学性质,得到了高压下介电函数、吸收率、光反射率、折射率、消光系数和电子能量损失谱在20 eV内的变化情况.     

黑索金电子结构和光学性质的第一性原理研究

利用基于密度泛函理论的第一性原理方法对黑索金晶体的电子结构和光学性质进行了计算. 结果表明: 黑索金是能隙值为3.43 eV的绝缘体, 价带主要由C, N和O的2s与2p态构成, 而导带主要由N-2p和O-2p态构成; 静态介电函数ε₁(0)=1.38, 介电常数的虚部有5个峰值, 其中最大峰值在光子能量4.59 eV处, 并对造成这些峰值的可能的电子跃迁做了详细分析. 利用能带结构和态密度分析了黑索金的光反射系数、吸收系数及能量损失函数等光学性质, 发现黑索金是对光吸收、反射及能量损失不敏感的材料. 关键词： 黑索金 第一性原理 电子结构 光学性质     

First-principles studies of electronic,optical,and mechanical properties of γ-Bi_2Sn_2O_7

The detailed theoretical studies of electronic,optical,and mechanical properties of γ-Bi_2Sn_2O_7 are carried out by using first-principle density functional theory calculations.Our calculated results indicate that γ-Bi_2Sn_2O_7 is the p-type semiconductor with an indirect band gap of about 2.72 e V.The flat electronic bands close to the valence band maximum are mainly composed of Bi-6s and O-2p states and play a key role in determining the electrical properties of γ-Bi_2Sn_2O_7.The calculated complex dielectric function and macroscopic optical constants including refractive index,extinction coefficient,absorption coefficients,reflectivity,and electron energy-loss function show that γ-Bi_2Sn_2O_7 is an excellent light absorbing material.The analysis on mechanical properties shows that γ-Bi_2Sn_2O_7 is mechanically stable and highly isotropic.     

First-principles studies on stabilities and electronic properties of AlN nanostructures

Under the generalized gradient approximation (GGA), the stabilities and electronic properties of semiconductor AlN nanostructures have been investigated by using the first-principles projector-augmented wave (PAW) potential within the density function theory (DFT) framework. The single-walled faceted AlNNTs present an obvious structural modification. The larger the diameter, the more stable the nanowire, and the wires without internal surfaces are more stable than the multiwalled tubes or the SWNT. Therefore, the large-size nanowires are easier to be synthesized than the corresponding multiwalled tubes or single-walled nanotube in experiment. The dangling bonds of surface atoms cause the “localized edge-induced states”. These two nanostructures C and F are still wide band gap semiconductors accompanied by a few surface states located in the band gap of bulk AlN and thus extremely suitable for application in flexible pulse wave sensors, nanomechanical resonators and light-emitting diodes.     

C掺杂AlN的电子结构和光学性质的第一性原理研究

采用基于密度泛函理论(DFT)的平面波超软赝势法,研究了C掺杂铅锌矿AlN的电子结构、磁性和光学性质.结果表明,C掺杂AlN产生了自旋极化,在带隙中引入杂质带形成受主能级,实现p型掺杂,同时表现出较强的半金属铁磁性,半金属能隙为0.315eV,理论上可实现100%的自旋载流子注入.掺杂后体系的介电函数虚部和光吸收系数在低能区出现新的峰值,吸收边向低能方向延展,能量损失明显减少.     

Structural,electronic, and optical properties of bulk Cu2Se

By using first-principles calculations within the density functional theory and the many-body perturbation theory, we investigate the structural, electronic, and optical properties of bulk Cu₂Se with a recently discovered low-temperature layered configuration. We demonstrate that the effects of the van der Waals forces significantly modify the interlayer binding and distance in the layered Cu₂Se, while the band gap is invariant. Our density functional theory and post-processing GW calculations reveal that for the layered structure, GW correction remedies the serious band-gap underestimation of the density functional theory from 0.12 eV to 0.99 eV. By solving the Bethe–Salpeter equation, we find that the optical gap of the layered Cu₂Se is 0.86 eV, which is in close agreement with previous experimental observations. In addition, we show that the high-temperature fluorite structure has no band gap, even after GW correction, explaining that the band gap controversy among the theories stems from different structural models. This work may serve as an important guide in designing and evaluating photovoltaic devices using Cu₂Se-based materials.     

First-principles study of the electronic and optical properties of ZnO nanowires

The geometric, energetic, electronic structures and optical properties of ZnO nanowires (NWs) with hexagonal cross sections are investigated by using the first-principles calculation of plane wave ultra-soft pseudo-potential technology based on the density functional theory (DFT). The calculated results reveal that the initial Zn-O double layers merge into single layers after structural relaxations, the band gap and binding energies decrease with the increase of the ZnO nanowire size. Those properties show great dimension and size dependence. It is also found that the dielectric functions of ZnO NWs have different peaks with respect to light polarization, and the peaks of ZnO NWs exhibit a significant blueshift in comparison with those of bulk ZnO. Our results gives some reference to the thorough understanding of optical properties of ZnO, and also enables more precise monitoring and controlling during the growth of ZnO materials to be possible.     

掺杂Si/SiO_2界面电子结构与光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理方法,在局域密度近似(LDA)下研究了B掺杂Si/SiO_2界面及其在压强作用下的电子结构和光学性质.能带的计算结果表明:掺杂前后Si/SiO_2界面均属于直隙半导体材料,但掺B后界面带隙由0. 74 eV减小为0. 57 eV,说明掺B使材料的金属性增强;对B掺杂Si/SiO_2界面施加正压强,发现随着压强不断增大,Si/SiO_2界面的带隙呈现了逐渐减小的趋势,并且由直隙逐渐转变为间隙.光学性质的计算结果表明:掺B对Si/SiO_2界面在低能区(即红外区)的介电函数虚部、吸收系数、折射率以及反射率等光学参数有显著影响,且在红外区出现新的吸收峰;对B掺杂Si/SiO_2界面施加正压强,随着压强增大,红外区的吸收峰逐渐消失,而在紫外区出现了吸收峰.上述结果表明,对Si/SiO_2界面掺B及施加正压强均可调控Si/SiO_2界面的电子结构与光学性质.本文的研究为基于Si/SiO_2界面的光电器件研究与设计提供一定的理论参考.