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We perform a first-principles simulation to study the electronic and optical properties of wurtzite Zn1 xCuxO.The simulations are based upon the Perdew-Burke-Ernzerhof form of generalised gradient approximation within the density functional theory.Calculations are carried out in different concentrations.With increasing Cu concentration,the band gap of Zn1 xCuxO decreases due to the shift of valence band.The imaginary part of the dielectric function indicates that the optical transition between O 2p states in the highest valence band and Zn 4s states in the lowest conduction band shifts to the low energy range as the Cu concentration increases.Besides,it is shown that the insertion of Cu atom leads to redshift of the optical absorption edge.Meanwhile,the optical constants of pure ZnO and Zn0.75Cu0.25O,such as loss function,refractive index and reflectivity,are discussed. 相似文献
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使用多体微扰理论(many-body perturbation theory, MBPT)计算了锰原子的3p63d54s2→3p53d54s2nd系列里德堡共振结构.在耦合方程方法中考虑了Auger图式,计算表明,Auger图式有效地抑制了3p→nd系列共振结构的发散. 相似文献
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具有单(纯)色上转换荧光发射特性的发光材料,有望在三维显示、照明、生物成像、促进植物生长以及提高太阳能电池光电转换效率等领域得到应用,受到研究人员的广泛关注.本研究通过玻璃热处理析晶的方法,在稀土离子Yb3+/Er3+共掺的氟硅酸盐玻璃中原位生长出了钙钛矿型的KMn F3氟化物纳米晶体,并观测到了显著增强的高单色性上转换红色发光.采用具有高分辨率的透射电子显微测试分析技术和第一性原理计算相结合,研究了稀土离子在KMn F3纳米晶复合微晶玻璃中的掺杂机制,并讨论了稀土离子微观分布和能量传递效应对其上转换发光性能的影响.实验结果表明:稀土离子将通过优先取代KMn F3晶体中K~+格位的方式选择性富集在具有低声子能量的氟化物纳米晶体中,并由此获得显著增强的上转换发光强度. 相似文献
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Electronic and optical properties of GaN/AlN quantum dots with adjacent threading dislocations 下载免费PDF全文
We present a theory to simulate a coherent GaN QD with
an adjacent pure edge threading dislocation by using a finite
element method. The piezoelectric effects and the strain modified
band edges are investigated in the framework of multi-band $\bm
k\cdot \bm p$ theory to calculate the electron and the heavy hole
energy levels. The linear optical absorption coefficients
corresponding to the interband ground state transition are obtained
via the density matrix approach and perturbation expansion method. The
results indicate that the strain distribution of the threading
dislocation affects the electronic structure. Moreover, the ground
state transition behaviour is also influenced by the position of the
adjacent threading dislocation. 相似文献
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In this paper, potential energy curves for the X 1 Σ+ , a3 Π, a′3 Σ+ , d3 , A1 Π and I 1 Σ states of CO have been calculated using complete active space self-consistent field and multi-reference configuration interaction methods. The calculations have been performed at 108 nuclear separations from 0.7 to 4.0 A by the aug-cc-PV5Z basis set. Spectroscopic constants for the six low-lying electronic states are found in good agreement with experimental data. The vibrational states of the X1Σ+ and A1Π states are also calculated, which are reliable and accurate by comparison with the experimental data and the other theoretical values. The transition dipole moment (TDM) shows that the TDM of the two states (X1Σ + A1Π) are reduced strongly with increase of bond length. 相似文献
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Electronic structure and optical properties of the zinc-blende InxGa1 - xNyAs1-y system are calculated from the first-principles. Some relative simulations are performed using CA-PZ form of local density approximation in the framework of density functional theory. The supercell of intrinsic GaAs is calculated and optimized by using different methods, and the LDA-CA-PZ gives the most stable structure. The band gap of InxGa1 - xAs tends to decrease with the increasing In concentration. For the case of In0.0625Ga0.9375NyAs1 -y, the band gap will show slight difference when N concentration is larger than 18.75%. The optical transition of In dopant in GaAs exhibits a red shift, while it is a blue shift for the N dopant in InGaAs. Besides, dielectric function, reflectivity, refractive index and loss function in different doping model of InxGa1 - xNyAs1 - y are also discussed. 相似文献
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Surface diffusion of Si,Ge and C adatoms on Si (001) substrate studied the molecular dynamics simulation 下载免费PDF全文
Depositions of Si, Ge and C atoms onto a preliminary Si (001) substrate at different temperatures are investigated by using the molecular dynamics method. The mechanism of atomic self-assembling occurring locally on the flat terraces between steps is suggested. Diffusion and arrangement patterns of adatoms at different temperatures are observed. At 900 K, the deposited atoms are more likely to form dimers in the perpendicular [110] direction due to the more favourable movement along the perpendicular [110] direction. C adatoms are more likely to break or reconstruct the dimers on the substrate surface and have larger diffusion distances than Ge and Si adatoms. Exchange between C adatoms and substrate atoms are obvious and the epitaxial thickness is small. Total potential energies of adatoms and substrate atoms involved in the simulation cell are computed. When a newly arrived adatom reaches the stable position, the potential energy of the system will decrease and the curves turns into a ladder-like shape. It is found that C adatoms can lead to more reduction of the system energy and the potential energy of the system will increase as temperature increases. 相似文献