THE EFFECT OF HIGH N-DOPED ANATASE TiO2 ON THE BAND GAP NARROWING AND REDSHIFT BY FIRST-PRINCIPLES

2012 ◽  
Vol 26 (27) ◽  
pp. 1250179 ◽  
Author(s):  
QINGYU HOU ◽  
YONGJUN JIN ◽  
CHUN YING ◽  
ERJUN ZHAO ◽  
YUE ZHANG ◽  
...  
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Formation Energy ◽  
Doping Concentration ◽  
Covalent Bond ◽  
Anatase Tio2 ◽  
Structure Population ◽  
Densities Of States ◽  
N Doping ◽  
Band Gap Narrowing

Anatase TiO 2 supercells were studied by first-principles, in which one was undoped and another three were high N -doping. Partial densities of states, band structure, population and absorption spectrum were calculated. The calculated results indicated that in the condition of TiO 2-x N x (x = 0.0625, 0.125, 0.25), the higher the doping concentration is, the shorter will be the lattice parameters parallel to the direction of c-axis. The strength of covalent bond significantly varied. The formation energy increases at first, and then decreases. The doping models become less stable as N -doping concentration increases. Meanwhile, the narrower the band gap is, the more significant will be the redshift, which is in agreement with the experimental results.

First-Principles Study of Nonmetal-Doped Titanium Oxides

2007 ◽  
Vol 336-338 ◽  
pp. 2507-2509
Author(s):  
Xue Gao ◽  
Jia Xiang Shang ◽  
Yue Zhang
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Lattice Distortion ◽  
Anatase Tio2 ◽  
Titanium Oxides ◽  
Substitutional Doping ◽  
Densities Of States ◽  
Light Activity ◽  
Band Gap Narrowing

The electronic structures of anatase titanium oxides (TiO2) substitutional doping with N, F, C, P and S for O have been studied by first-principles method based on the density functional theory. The lattice distortion and densities of states of nonmetal-doped anatase TiO2 as well as photocatalytic activity were discussed. Comparing the effects of these five nonmetal ions (N, F, C, P and S) in the anatase TiO2, the substitutional doping of N is the most effective to get better visible-light activity because of its least lattice distortion and a large band-gap narrowing effect and the suitable relative position of the impurity states in band gap.

First-Principles Calculations on Pure and Ga-Doped Anatase TiO2

2010 ◽  
Vol 156-157 ◽  
pp. 1385-1388
Author(s):  
Rui Qing Xu ◽  
Lan Fang Yao ◽  
Lin Li ◽  
Shuo Wang ◽  
Lin Lin Tian ◽  
...  
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Correlation Energy ◽  
Anatase Tio2 ◽  
First Principles Calculations ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Band Gap Narrowing

First-principles calculations using the plane-wave pseudo-potential (PWPP) method based on the density functional theory (DFT) is employed to study the crystal structure, band gap, density of states of anatase TiO2 doped with gadolinium (Gd). The generalized gradient approximation (GGA) based on exchange-correlation energy optimization is employed to calculate them. The calculated results demonstrate that the mixing of gadolinium dopants induces states with original titanium 3d and oxygen 2p valence band attributes to the band gap narrowing. This can enhance the photocatalytic activity of anatase TiO2.

A First-Principles Study on Electronic Properties of Ce/N Codoped Anatase TiO2

2014 ◽  
Vol 936 ◽  
pp. 529-533 ◽  
Author(s):  
Si Yu Yang ◽  
Lan Fang Yao ◽  
Hao Chen
Keyword(s):  
Band Gap ◽  
Valence Band ◽  
Conduction Band ◽  
First Principles ◽  
Function Theory ◽  
Pure Tio2 ◽  
Anatase Tio2 ◽  
Photoelectrochemical Activity ◽  
Co Doping ◽  
N Doping

Density function theory is performed in order to investigate the effect of Ce/N co-doping on geometry structure, electronic and optical properties of anatase TiO2. Comparing the energy band and density of states of pure TiO2 and Ce/N doped anatase TiO2. We can conclude that, the valence band of pure TiO2 is main composed of O 2p states and the conduction is mainly composed of Ti 3d states. For N-doped TiO2, the topmost part of the valence band is mainly occupied by N 2p states which is higher than that of the O 2p states which can narrowed the band gap. Ce doping will introduce 4f states which is involved in the conduction band. These may lead the conduction band move down. As for Ce and N co-doped, the top of the valence band is mainly occupied by an admixture N 2p, O 2p and the bottom of the conduction band is predominantly occupied by an admixture of Ce 4f ,Ti 3d. The strong interaction between the dopants and the ions lead the band gap get narrower. We predict that Ce+N doping is one of the best choices for enhancing the photoelectrochemical activity of TiO2.

A first-principles study of the effects of different Al constituents on Ga1−xAlxN nanowires

2016 ◽  
Vol 30 (30) ◽  
pp. 1650217 ◽  
Author(s):  
Sihao Xia ◽  
Lei Liu ◽  
Yike Kong ◽  
Honggang Wang ◽  
Meishan Wang
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Plane Wave ◽  
First Principles ◽  
Formation Energy ◽  
High Energy ◽  
Dielectric Constants ◽  
Interesting Phenomenon ◽  
Densities Of States ◽  
Static Dielectric Constants

In order to investigate the influences of different Al constituents on Ga[Formula: see text]Al[Formula: see text]N nanowires, the formation energy, stability, band structure, densities of states and optical properties of Ga[Formula: see text]Al[Formula: see text]N nanowires with different Al constituents are calculated using first-principles plane-wave ultrasoft pseudopotential method. Results show that Ga[Formula: see text]Al[Formula: see text]N nanowires become more stable with increasing Al constituent. Bandgap of Ga[Formula: see text]Al[Formula: see text]N nanowires increases as the Al constituent increases but with a lower amplification compared with bulk Ga[Formula: see text]Al[Formula: see text]N. The peaks of static dielectric constants show a decreasing trend and move towards high-energy side as Al constituent increases. The absorption of Ga[Formula: see text]Al[Formula: see text]N nanowires shows an interesting phenomenon that it firstly increases and then decreases slightly as the Al constituent increases. Reflectivity of Ga[Formula: see text]Al[Formula: see text]N nanowires is much smaller than that of the bulk. The optical properties of Ga[Formula: see text]Al[Formula: see text]N nanowires show a blueshift effect as Al composition increases. According to these calculations, it is found that Ga[Formula: see text]Al[Formula: see text]N nanowires are appropriate to be applied into photoelectric detecting materials by adjusting the Al constituent of Ga[Formula: see text]Al[Formula: see text]N nanowires.

First-principles self-energy calculations of carrier-induced band-gap narrowing in silicon

1992 ◽  
Vol 45 (23) ◽  
pp. 13741-13744 ◽  
Author(s):  
A. Oschlies ◽  
R. W. Godby ◽  
R. J. Needs
Keyword(s):  
Band Gap ◽  
First Principles ◽  
Energy Calculations ◽  
Self Energy ◽  
Band Gap Narrowing

scholarly journals First principles study of IIIA atoms adsorbed on ZnO (0001) surface and the applications in optoelectronic devices

2021 ◽  
Vol 2083 (2) ◽  
pp. 022002
Author(s):  
Haifeng Zhang ◽  
Caiping Cheng ◽  
Bin Wang
Keyword(s):  
Electronic Structure ◽  
Band Gap ◽  
First Principles ◽  
Electronic Structures ◽  
Formation Energy ◽  
Optoelectronic Devices ◽  
Adsorption Behavior ◽  
Binding Ability ◽  
Impurity States ◽  
Adsorption Sites

Abstract First principles method is used to study the adsorption behavior, formation energy and electronic structure of IIIA (B, Al, Ga, In) atoms adsorbed on Top, T4 and H3 sites of ZnO (0001) surface. The date shows that the formation energy of B, Al, Ga and In atoms adsorbed on Top site is highest, then followed by T4 site, and H3 is a more stable adsorption site. With the periodic increase of B, Al, Ga and In atoms, the formation energy of corresponding models decreases gradually, and the binding ability with O atoms also decreases gradually. The electronic structure of ZnO (0001) surface is sensitive to the adsorption sites. When these atoms are adsorbed on Top sites, the electronic structures of B-Top, Al-Top, Ga-Top and In-Top models have a little change compared with ZnO (0001) surface. However, when these atoms are adsorbed on T4 and H3 sites, the impurity states appear on the VBM, which narrowing the band gap of the corresponding models.

Comparison of the Photocatalytic Activity of N-Doped, P-Doped Titania under Solar Light Irradiation

2010 ◽  
Vol 113-116 ◽  
pp. 2141-2144
Author(s):  
Si Yao Guo ◽  
Bo Chi ◽  
Jin Bing Sun ◽  
Feng Lu Wang ◽  
Lin Yang ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Band Gap ◽  
Band Gap Energy ◽  
Light Irradiation ◽  
Solar Light ◽  
Urea Solution ◽  
Solar Light Irradiation ◽  
N Doping ◽  
Doped Titania ◽  
Band Gap Narrowing

P-, N-doped titania were synthesized by the direct hydrothermal method, which phosphorus from phosphoric acid and the following nitridation from urea solution. The resulting materials were characterized by XRD, XPS analysis, and their photocatalytic activities were tested by the solar light irradiation. N-doping titania resulted in the band-gap narrowing with improved photocatalytic activity. However, the phosphated titania exhibited higher photocatalytic activity than the N-doped one, but with larger band-gap energy.

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