First Principles Calculations of Electronic and Optical Properties of Al1-xLaxN

2011 ◽  
Vol 393-395 ◽  
pp. 110-113
Author(s):  
Chang Peng Chen ◽  
Mei Lan Qi
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Density Functional ◽  
Density Functional Method ◽  
High Energy ◽  
Functional Method ◽  
Absorption Region ◽  
Additional Absorption ◽  
Calculation Results ◽  
La Substitution

Based on the density functional method, the electronic structures and the optical properties for Al1-xLaxN(x=0, 0.0625, 0.125, 0.1875) are comparatively investigated in detail. The calculation results indicate that La substitution of the Al sites induces effective reduction of the band gap of AlN, and the band gap being continuously reduced when increasing La doping level. With the increase of La concentration, both the imaginary part of dielectric function and the absorption spectrum show red-shift corresponding to the change of band gaps. Moreover, additional absorption peaks are observed above the absorption edge in the high-energy range which widens the absorption region.

First principles calculations of electronic and optical properties of Zr-doped La2O3

2013 ◽  
Vol 91 (10) ◽  
pp. 801-807 ◽  
Author(s):  
Changpeng Chen ◽  
Jianxiong Xie ◽  
Shuibo Chen ◽  
Yanli Li
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Visible Region ◽  
Potential Candidate ◽  
First Principles Calculations ◽  
Additional Absorption ◽  
Level Shifts ◽  
Calculation Results

Based on the density functional pseudopotential method, the structural properties, the band structure, the density of states, and the optical properties of pure and Zr-doped La2O3 were calculated. The calculation results indicate that the defect of La (Zr) exists steadily with a certain solubility. Zr substitution of the La sites induces effective reduction of the band gap of La2O3, the band gap being continuously reduced when increasing Zr doping level. The Fermi energy level shifts to the conduction band and exhibits metal-like characteristic after the Zr atom is introduced. The calculated optical properties indicate that red shifts are revealed in both the imaginary part of the dielectric function and the absorption spectra corresponding to the change of band gaps. Moreover, additional absorption is observed in the visible region, which implies that Zr-doped La2O3 might be a potential candidate for photoelectrical application. The calculation results are consistent with experimental results that have been reported.

Electronic Structure and Optical Properties of La or In Doped SnO2: First-Principles Calculations

2011 ◽  
Vol 393-395 ◽  
pp. 80-83
Author(s):  
Chang Peng Chen ◽  
Mei Lan Qi
Keyword(s):  
Optical Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
First Principles Calculations ◽  
Effective Reduction ◽  
Calculation Results ◽  
Impurity Elements

Based on the density functional method, the electronic structures and the optical properties for pure and La or In doped SnO2 are comparatively investigated in detail. The calculation results indicate that both the doping of La and the doping of In induce effective reduction of the band gap of SnO2, the impurity elements form new highly localized impurity energy level at the top of the valence band near the Fermi level. The interaction between electrons changed after doping which leads to the change of electrical properties .Meanwhile, red shifts are revealed in both the imaginary part of dielectric function and the absorption spectra corresponding to the change of band gaps

A New Approach for Calculating the Band Gap of Semiconductors within the Density Functional Method

2015 ◽  
Vol 242 ◽  
pp. 434-439 ◽  
Author(s):  
Vasilii E. Gusakov
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Localized States ◽  
Experimental Accuracy ◽  
Functional Theory ◽  
New Approach ◽  
The Density Functional Theory

Within the framework of the density functional theory, the method was developed to calculate the band gap of semiconductors. We have evaluated the band gap for a number of monoatomic and diatomic semiconductors (Sn, Ge, Si, SiC, GaN, C, BN, AlN). The method gives the band gap of almost experimental accuracy. An important point is the fact that the developed method can be used to calculate both localized states (energy deep levels of defects in crystal), and electronic properties of nanostructures.

Density Functional Study of the Electronic, Elastic and Optical Properties of Bi2O2Te

2019 ◽  
Vol 75 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Jia-Xin Chen ◽  
Xiao-Ge Zhao ◽  
Xing-Xing Dong ◽  
Zhen-Long Lv ◽  
Hong-Ling Cui
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Density Functional Method ◽  
Uniaxial Crystal ◽  
Functional Method ◽  
Functional Study ◽  
Layered Crystal ◽  
High Electron ◽  
Covalent Interactions ◽  
Zero Frequency

AbstractLayered crystal Bi2O2Te has recently been found to have high electron mobility and excellent thermoelectric properties for technical applications; however, its other properties are not well studied yet. In this work, the electronic, elastic and optical properties of Bi2O2Te are systematically studied using the density functional method. The results indicate that Bi2O2Te is a narrow band gap semiconductor. The gap is formed by the Te 5p orbital at the top of the valence band and the Bi 6p orbital at the bottom of the conduction band. There are both ionic and covalent interactions within the Bi–O layers, and these layers are linked by the ionic Bi–Te bonds forming the crystal. Bi2O2Te is mechanically stable but anisotropic. It is easy to fracture along the c axis under shear stress. Its shear modulus is far smaller than its bulk modulus, so shape deformation is easier to occur than pure volume change. Its melting point is predicted to be 1284.0 K based on an empirical formula. The calculated refractive index at zero frequency reveals that Bi2O2Te is a negative uniaxial crystal with a birefringence of 0.51, making it a potential tuning material for optical application. The characteristics and origins of other optical properties are also discussed.

Structure of Chromium Atomic Chains

2011 ◽  
Vol 415-417 ◽  
pp. 553-556 ◽  
Author(s):  
Han Xin Shen ◽  
Wen Zhang Zhu ◽  
Ai Yu Li
Keyword(s):  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Electronic Energy ◽  
Present Calculation ◽  
Energy Bands ◽  
One Dimensional ◽  
Atomic Chains ◽  
Calculation Results ◽  
Electronic Energy Bands

The geometric and electronic structures of Cr chains are studied by the first-principles of density-functional method. The present calculation results show that chromium can form planar chains in linear, zigzag, dimer, and ladder form one-dimensional structures. The most stable geometry chain among the studied structures is the ladder-form chain with five nearest neighbors. The dimer structure is found to be more stable than the zigzag one. Further more, the relative structural stability, the electronic energy bands, the density of states is discussed based on the ab initio calculations.

scholarly journals Electronic and optical properties of Mn–S co-doped anatase TiO2 from first-principles calculations

2016 ◽  
Vol 34 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Guohao Wu ◽  
S.K. Zheng ◽  
Xiaobing Yan
Keyword(s):  
Optical Properties ◽  
Visible Light ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Potential Candidate ◽  
Generalized Gradient ◽  
Electronic And Optical Properties ◽  
Enhanced Absorption ◽  
Co Doped

AbstractThe electronic and optical properties of Mn–S co-doped anatase TiO2 were calculated using the plane-wave-based ultrasoft pseudopotential density functional method within its generalized gradient approximation (GGA). The calculated results show that the band gap of Mn–S co-doped TiO2 is larger than that of the pure TiO2, and two impurity bands appear in the forbidden band, one of which above the valence band plays a vital role for the improvement of the visible light catalytic activity. The Mn–S co-doped anatase TiO2 could be a potential candidate for a photo catalyst because of its enhanced absorption ability of visible light.

Band Gap Widening and Quantum Confinement Effects of ZnO Nanowires by First-Principles Calculation

2011 ◽  
Vol 675-677 ◽  
pp. 243-246 ◽  
Author(s):  
Mei Li Guo ◽  
Xiao Dong Zhang
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
First Principles ◽  
Quantum Confinement ◽  
Density Functional ◽  
High Energy ◽  
Zno Nanowires ◽  
First Principles Calculation ◽  
Confinement Effects ◽  
Quantum Confinement Effects

ZnO nanowires are promising for photonic devices, biosensor and cancer cell imaging. We have performed a first-principles study to evaluate the electronic and optical properties of ZnO nanowires. We have employed the Perdew–Burke–Ernzerhof form of generalized gradient approximation in the frame work of density functional theory. Calculations have been carried out at different configurations. With decreasing diameter, the band gap of ZnO nanowires is increased due to the increase of quantum confinement effects. The results of imaginary part of the dielectric function indicate that the optical transition between valence band and conduction band has shifted to the high energy range as the diameter decreases. The ZnO nanowires show size-tunable optical properties.

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