First-principles study on the optical spectra of ZrO2 crystal with oxygen vacancy

2019 ◽  
Vol 33 (31) ◽  
pp. 1950372
Author(s):  
Rui Guo ◽  
Tingyu Liu ◽  
Yazhou Lu ◽  
Qiuyue Li ◽  
Xuping Jiao ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Density Functional ◽  
Defect Formation ◽  
Finite Size ◽  
Optical Spectra ◽  
Photocatalytic Ability ◽  
Luminescence Peak ◽  
Electron Phonon Coupling ◽  
Correction Scheme ◽  
F Center

In this paper, we present the optical spectra of the ZrO2 crystal containing oxygen vacancy based on the Density Functional Theory (DFT). The finite-size correction scheme (FNV) is employed to eliminate the artificial interactions and correct the defect formation energy of oxygen vacancies with three different charges (0, +1, +2). Besides, we use hybrid density functionals to relieve the band edge problem. Finally, we obtain the optical spectra for the F center and F[Formula: see text] center containing the electron–phonon coupling. The absorption peak of F center of threefold coordinate oxygen vacancy (V[Formula: see text]) near 446 nm (2.78 eV) agrees well with the experimental value (2.83 eV), which can enhance the visible light photocatalytic ability of ZrO2. The luminescence peak of the F[Formula: see text] center of fourfold coordinate oxygen vacancy (V[Formula: see text]) is 561 nm (2.21 eV), which is close to the experimental value (2.5 eV).

Study on the optical spectra of the oxygen vacancy in ZnWO4 crystal

2021 ◽  
pp. 2150471
Author(s):  
Gaiping Lian ◽  
Tingyu Liu ◽  
Le Yu
Keyword(s):  
Oxygen Vacancy ◽  
Density Functional ◽  
Defect Formation ◽  
Finite Size ◽  
Optical Spectra ◽  
Functional Method ◽  
Hybrid Functional ◽  
Electron Phonon Coupling ◽  
Correction Scheme ◽  
The Density Functional Theory

ZnWO4 is easy to color, which will reduce the luminous efficiency of the crystal and limit the application of the crystal. In order to study the origin of the color in the crystal, in this paper, the effects of the oxygen vacancy on the optical properties for the ZnWO4 crystal have been studied based on the density functional theory (DFT). The hybrid functional method (HSE) and the finite-size correction scheme (FNV) are used to correct the band edge problem and eliminate the artificial interaction of the charged defects, respectively. On the basis of the corrected defect formation energy, we obtain the optical spectra of the [Formula: see text] and [Formula: see text] centers containing electron-phonon coupling. The calculated absorption and luminescence peaks are at 2.54 eV and 0.79 eV for the [Formula: see text] center and at 2.98 eV and 1.09 eV for the [Formula: see text] center, respectively. The calculated absorption band of the [Formula: see text] center is close to the experimental value of 2.48 eV (500 nm), so we speculate that the coloring of the ZnWO4 crystal is related to the [Formula: see text] center. Meanwhile, the existence of oxygen vacancy makes ZnWO4 crystal to have self-absorption and to increase decay time, which greatly affects the scintillation properties of the crystal.

First-principles study on optical spectra for the oxygen vacancy in lead tungstate crystal

2020 ◽  
Vol 13 (03) ◽  
pp. 2051011
Author(s):  
Yazhou Lu ◽  
Tingyu Liu ◽  
Qiuyue Li ◽  
Xun Xu ◽  
Xuping Jiao ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
First Principles ◽  
Density Functional ◽  
Finite Size ◽  
Lead Tungstate ◽  
Functional Theory ◽  
Electron Phonon Coupling ◽  
Correction Scheme ◽  
Size Correction ◽  
Finite Size Correction

Based on the first-principles, we simulated the spectral properties of PbWO4 (PWO) crystals with an oxygen vacancy. As density functional theory (DFT) underestimates the band gap, the band edge is modified by Heyd-Scuseria-Ernzerhof (HSE). Moreover, artificial interactions of the charged defect of oxygen vacancies with three different charges have been corrected by finite-size correction scheme (FNV). Finally, the optical properties are obtained containing electron–phonon coupling. The calculated absorption band peaks of the F and F[Formula: see text] centers at 1.7[Formula: see text]eV and 2.47[Formula: see text]eV agree well with the experimental value, respectively.

Study on the optical properties for the F-type color center in BeO crystal with first-principles

2020 ◽  
pp. 2150148
Author(s):  
Jiamei Song ◽  
Tingyu Liu ◽  
Chunyu Shi ◽  
Ruxi Sun ◽  
Kaili Wu
Keyword(s):  
Density Functional ◽  
Luminescence Band ◽  
Formation Energy ◽  
Defect Formation ◽  
Finite Size ◽  
Beryllium Oxide ◽  
Defect Formation Energy ◽  
Oxide Crystal ◽  
F Center ◽  
Optical Line

In this paper, we calculated the defect formation energy of oxygen vacancies with different charge states (0, +1, +2) in beryllium oxide crystal by using density functional theory (DFT). Based on defect formation energy, the positions of charge transition levels are obtained. However, there is a well-known problem that DFT will underestimate the band gap, which leads to the positions of charge transition levels are arguable. To obtain more accurate charge transition levels, we employ the hybrid functionals (HSE) to relieve the band edge problem, as well as use the finite-size corrections (FNV) to correct the defect formation energy. After obtaining the location of the charge transition level, we obtain a reliable description of the optical line shape of the F/F[Formula: see text] center containing electron–phonon coupling. The absorption spectra of the F center and F[Formula: see text] center peak at 7.1 eV and 6.3 eV, respectively. The luminescence band of the F center peaks at 4.7 eV. Furthermore, we speculate that the luminescence band near 3.7 eV is assigned to the F[Formula: see text] center.

Native point defects in multicomponent transparent conducting oxides

2014 ◽  
Vol 1633 ◽  
pp. 37-42
Author(s):  
Altynbek Murat ◽  
Julia E. Medvedeva
Keyword(s):  
Oxygen Vacancy ◽  
Point Defects ◽  
Density Functional ◽  
Defect Formation ◽  
Conducting Oxides ◽  
Cation Vacancies ◽  
Native Point Defects ◽  
Wide Range ◽  
Growing Conditions ◽  
Donor Defect

ABSTRACTThe formation of native point defects in layered multicomponent InAMO4 oxides with A3+=Al or Ga, and M2+=Ca, Mg, or Zn, is investigated using first-principles density functional calculations. We calculated the formation energy of acceptor (cation vacancies, acceptor antisites) and donor (oxygen vacancy, donor antisites) defects within the structurally and chemically distinct layers of InAMO4 oxides. We find that the antisite donor defect, in particular, the A atom substituted on the M atom site (AM) in InAMO4 oxides, have lower formation energies, hence, higher concentrations, as compared to those of the oxygen vacancy which is know to be the major donor defect in binary constituent oxides. The major acceptor (electron “killer”) defects are cation vacancies except for InAlCaO4 where the antisite CaAl is the most abundant acceptor defect. The results of the defect formation analysis help explain the changes in the observed carrier concentrations as a function of chemical composition in InAMO4, and also why the InAlZnO4 samples are unstable under a wide range of growing conditions.

THEORETICAL STUDY OF N2O ADSORPTION AND DECOMPOSITION AT REGULAR AND DEFECT SITES OF MgO (001) SURFACE

2003 ◽  
Vol 02 (01) ◽  
pp. 57-64 ◽  
Author(s):  
YI-JUN XU ◽  
JUN-QIAN LI ◽  
YONG-FAN ZHANG
Keyword(s):  
Oxygen Vacancy ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Defect Sites ◽  
Surface Oxygen Vacancy ◽  
F Center ◽  
Catalytic Reactivity ◽  
Vacancy Site ◽  
Mgo Surface

The adsorption of N 2 O at regular and defect sites of MgO (001) surface has been studied systematically using cluster models embedded in a large array of point charges by density functional method. The calculated results show that the MgO (001) surface with oxygen vacancies exhibits high catalytic reactivity toward N 2 O adsorptive-decomposition at variance with the regular MgO surface or the surface with magnesium vacancies. Much elongation of O–N bond of N 2 O after adsorption at oxygen vacancy site with O end of N 2 O down indicates that O–N bond has been broken with concurrent production of N 2, leaving a regular site instead of the original oxygen vacancy site (F center). Besides, the MgO (001) surface with magnesium vacancies hardly exhibits catalytic reactivity. It can be concluded that N 2 O dissociation is likely occurred at MgO (001) surface oxygen vacancy sites, which is consistent with the generally accepted viewpoint in the experiment.

scholarly journals Anion-Regulated Synthesis of ZnO 1D Necklace-Like Nanostructures with High Photocatalytic Activity

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Xiaoyun Qin ◽  
Dongdong Shi ◽  
Bowen Guo ◽  
Cuicui Fu ◽  
Jin Zhang ◽  
...  
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
High Photocatalytic Activity ◽  
Simple Method ◽  
Functional Theory ◽  
Photocatalytic Ability ◽  
New Ideas ◽  
Subsequent Calcination ◽  
Grain Surface ◽  
Hexagonal Nanoplates

Abstract One-dimensional (1D) nanomaterials with specific architectures have received increasing attention for both scientific and technological interests for their applications in catalysis, sensing, and energy conversion, etc. However, the development of an operable and simple method for the fabrication of 1D nanostructures remains a challenge. In this work, we developed an “anion-regulated morphology” strategy, in which anions could regulate the dimensionally-restricted anisotropic growth of ZnO nanomaterials by adjusting the surface energy of different growth facets. ZnO 1D necklace-like nanostructures (NNS) could be prepared through a hydrothermal treatment of zinc acetate and urea mixture together with a subsequent calcination procedure at 400 °C. While replacing the acetate ions to nitrate, sulfate, and chlorion ions produced ZnO nanoflowers, nanosheets and hexagonal nanoplates, respectively. Density functional theory calculations were carried out to explain the mechanism behind the anions-regulating anisotropic crystal growth. The specified ZnO 1D NNS offered improved electron transport while the grain surface could supply enlarged specific surface area, thus providing advanced photocatalytic ability in the following photodegradation of methyl orange (MO). Among the four photocatalysts with different morphologies, ZnO 1D NNS, possessing the highest catalytic activity, degraded 57.29% MO in the photocatalytic reaction, which was 2 times, 10 times and 17 times higher than nanoflowers, nanosheets and hexagonal nanoplates, respectively. Our work provides new ideas for the construction and application of ZnO 1D nanomaterials.

Effect of oxygen vacancy on electronic structure and optical spectra of SrO crystal

2021 ◽  
Vol 133 ◽  
pp. 105940
Author(s):  
Ru-xi Sun ◽  
Ting-yu Liu ◽  
Chun-yu Shi ◽  
Jia-mei Song ◽  
Kai-li Wu
Keyword(s):  
Electronic Structure ◽  
Oxygen Vacancy ◽  
Optical Spectra ◽  
Effect Of Oxygen

F-CENTER IMPACT ON PHOTOELECTROCHEMICAL PROPERTIES IN HEMATITE

2010 ◽  
Vol 24 (18) ◽  
pp. 1963-1970 ◽  
Author(s):  
ARVIDS STASHANS ◽  
RICHARD RIVERA
Keyword(s):  
Experimental Data ◽  
Optical Properties ◽  
Oxygen Vacancy ◽  
Quantum Chemical ◽  
Vacancy Defect ◽  
Chemical Model ◽  
Photoelectrochemical Properties ◽  
Structural And Optical Properties ◽  
F Center ◽  
Quantum Chemical Model

Structural and optical properties of F-center (two electrons trapped by an oxygen vacancy) defect in hematite have been studied using a quantum-chemical model. Calculated absorption energies, 0.9 eV and 3.6 eV, are discussed in terms of the available experimental data. An explanation for the origin of experimentally observed electron depletion in hematite is proposed.

Pros and cons of time-dependent hybrid density functional approach to optical spectra of solids: a case study of CeO2

2021 ◽  
Author(s):  
Huai-Yang Sun ◽  
Shuo-Xue Li ◽  
Hong Jiang
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Computational Cost ◽  
Optical Spectra ◽  
First Principles Calculation ◽  
Many Body ◽  
Many Body Perturbation Theory ◽  
Pros And Cons ◽  
Hybrid Density Functional

Prediction of optical spectra of complex solids remains a great challenge for first-principles calculation due to the huge computational cost of the state-of-the-art many-body perturbation theory based GW-Bethe Salpeter equation...

A complete ab initio thermodynamic and kinetic catalogue of the defect chemistry of hematite α-Fe2O3, its cation diffusion, and sample donor dopants

2021 ◽  
Author(s):  
Shehab Shousha ◽  
Sarah Khalil ◽  
Mostafa Youssef
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Defect Formation ◽  
Defect Chemistry ◽  
Cation Diffusion ◽  
Functional Theory ◽  
Migration Barriers ◽  
Hubbard U ◽  
And Migration ◽  
Formation Energies

This paper studies comprehensively the defect chemistry and cation diffusion in α-Fe2O3. Defect formation energies and migration barriers are calculated using density functional theory with a theoretically calibrated Hubbard U...

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