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.

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.

Tuning magnetism by biaxial strain in native ZnO

2015 ◽  
Vol 17 (25) ◽  
pp. 16536-16544 ◽  
Author(s):  
Chengxiao Peng ◽  
Yuanxu Wang ◽  
Zhenxiang Cheng ◽  
Guangbiao Zhang ◽  
Chao Wang ◽  
...  
Keyword(s):  
Formation Energy ◽  
Defect Formation ◽  
Biaxial Strain ◽  
Defect Formation Energy

Strain conditions have little effect on the defect formation energy of Zn and O vacancies in ZnO, but they do affect the magnetism significantly.

Defect formation energy for charge states and electrophysical properties of CdMnTe

2015 ◽  
Author(s):  
M. A. Mehrabova ◽  
H. R. Nuriyev ◽  
H. S. Orujov ◽  
A. M. Nazarov ◽  
R. M. Sadigov ◽  
...  
Keyword(s):  
Formation Energy ◽  
Defect Formation ◽  
Electrophysical Properties ◽  
Defect Formation Energy ◽  
Charge States

Defect Stability and Electronic Configuration of Off-Stoichiometric Ni-X-In (X = Mn, Fe and Co) Alloys: A First-Principles Study

2016 ◽  
Vol 873 ◽  
pp. 8-12
Author(s):  
Qi Rui Zu ◽  
Jing Bai ◽  
Xiao Shu Wang ◽  
Kai Hong Wu ◽  
Shuai Wang ◽  
...  
Keyword(s):  
Shape Memory ◽  
First Principles ◽  
Density Functional ◽  
Formation Energy ◽  
Defect Formation ◽  
Dominant Role ◽  
Electronic Configuration ◽  
Adjustment Process ◽  
Magnetic Shape Memory ◽  
Co Alloys

Ni-Mn-In is a novel type of magnetic shape memory alloy, its shape memory effect has been realized through magnetic field induced reverse martensitic transformation. A variety of point defects would be generated during composition adjustment process, such as antisite defect, vacancy and exchange. The first–principles calculations within the framework of the density functional theory using the Vienna ab initio software package (VASP) have been used in this paper to investigate the defect formation energy and electronic configuration of the off-stoichiometric Ni-X-In (X= Mn, Fe and Co) alloys. The In antisite on the X sublattice (InX) and the Ni antisite on the X sublattice (NiX) have the lowest formation energies in the investigated series. The formation energy of the Ni vacancy is the lowest, while that of the in vacancy is the highest. It is confirmed that the in constituent plays a dominant role for stabilizing the austenitic phase.

Calculation of Defect Formation Energy from the Thermal Expansion Data for Lead Fluoride

1994 ◽  
Vol 369 ◽  
Author(s):  
Brenda J. Schuler ◽  
T. S. Aurora ◽  
D. O. Pederson ◽  
S. M. Day
Keyword(s):  
Thermal Expansion ◽  
Thermal Expansion Coefficient ◽  
Expansion Coefficient ◽  
Formation Energy ◽  
Defect Formation ◽  
Coefficient Of Thermal Expansion ◽  
Linear Thermal Expansion ◽  
Lead Fluoride ◽  
Defect Formation Energy ◽  
Thermal Expansion Data

AbstractLead fluoride is a superionic conductor with the fluorite structure. Results of the measurement of linear thermal expansion of lead fluoride (reported earlier in literature) showed a large increase in the thermal expansion coefficient near 700 K where the ionic conductivity has been shown to exhibit a sharp increase. It is believed that thermally-generated defects in a crystal lattice affect the thermal expansion coefficient. This idea was applied in the present analysis to calculate the defect formation energy (Ef) by using the literature values of the coefficient of thermal expansion. It was assumed that the thermal expansion in excess of that produced due to the lattice anharmonicity (δ∝) is proportional to the concentration of defects (n). With this assumption, one may write: δ∝ = c nº exp(-Ef/kT), where c is a constant. For lead fluoride, a plot of ln(δ∝) versus (l/T) yielded Ef = 0.56 eV which is lower than the literature values. The assumptions in this analysis and the discrepancy in the result are discussed.

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