Regulation of corundum band gap width by p elements and vacancy co-doping

2020 ◽  
Vol 140 ◽  
pp. 109357
Author(s):  
Veronika M. Zainullina ◽  
Michael A. Korotin
Keyword(s):  
Band Gap ◽  
P Elements ◽  
Co Doping ◽  
Gap Width ◽  
Band Gap Width

Wave propagation in acoustic metamaterials with resonantly shunted cross-shape piezos

2018 ◽  
Vol 29 (13) ◽  
pp. 2744-2753 ◽  
Author(s):  
Shengbing Chen
Keyword(s):  
Wave Propagation ◽  
Band Gap ◽  
Vibration Isolation ◽  
Band Gaps ◽  
Acoustic Metamaterials ◽  
Resonant Frequencies ◽  
Piezoelectric Patch ◽  
Transmission Properties ◽  
Gap Width ◽  
Band Gap Width

Cross-shape piezoelectric patches were originally proposed to improve the band-gap properties of acoustic metamaterials with shunting circuits. The dispersion curves are characterized through the application of finite element method. Also, the theoretical band-gap predictions are verified by simulation results obtained from COMSOL. The investigation results show that the proposed scheme distinguishes itself from the conventional square patches by broader band gaps, whose bandwidth is almost doubled. The inherent capacitance of the piezoelectric patch is strongly related to the boundary conditions, so the local resonant band gap is strongly affected by the shape of piezoelectric patches as well. As a result, the band-gap width and location of metamaterials with different shape patches are rather different, even with the same size patches. Also, negative modulus (NM) and Poisson’s ratio were observed around the resonant frequencies. The transmission properties of finite periods agree well with band-gap predictions. An obvious attenuation zone (AZ) is produced around the band-gap location, in which the wave propagation is decayed strongly. Similarly, the width of AZ of the proposed metamaterial is much larger than that of the conventional one. Hence, the proposed scheme demonstrates more advantages in the application to vibration isolation when compared with the conventional.

Study on Density Functional Theory of Zn1-xMgxO Alloy

2014 ◽  
Vol 556-562 ◽  
pp. 177-180
Author(s):  
Fu Chun Zhang ◽  
Hong Wei Cui ◽  
Xing Xiang Ruan ◽  
Wei Hu Zhang
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Density Functional ◽  
High Energy ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Research Findings ◽  
Gap Width ◽  
Band Gap Width ◽  
Mg Doped

Geometric structure and electronic structures of Zn1-xMgxO alloy under different Mg doped concentrations have been investigated by performing the first-principle calculations based on density functional theory under the generalized gradient approximation (GGA). The calculated results show that there is substantial change in electronic structure of Mg doped MgxZn1-xO alloy, with the constant increase of Mg content, cell parameter a shall be on the gradual increase, with c on gradual decrease and band gap width of MgxZn1-xO alloy on the increase. The research findings show that the position of conduction band bottom is dependent on Mg 2p and Zn 4s. Mg doping results in drift of Mg 2p and Zn 4s toward high energy region, being the root cause for the increase in band gap width,the research results in the paper are in accordance with other experimental results. The above results provide theoretical guidance to the preparation of Zn1-xMgxO alloy in experiment.

Preparation and Optical Properties of One-Dimensional Ag/SiOx Photonic Crystal

2014 ◽  
Vol 576 ◽  
pp. 27-31
Author(s):  
Gai Mei Zhang ◽  
Can Wang ◽  
Yan Jun Guo ◽  
Wang Wei ◽  
Xiao Xiang Song
Keyword(s):  
Photonic Crystal ◽  
Band Gap ◽  
Electromagnetic Waves ◽  
Photonic Band Gap ◽  
Incident Angle ◽  
One Dimensional ◽  
The One ◽  
Photonic Band ◽  
Gap Width ◽  
Band Gap Width

The photonic crystal has the property that electromagnetic waves with interval of frequency in photonic band gap (PBG) can not be propagated, so it has important applying and researching value. The traditional one-dimensional photonic crystal is with narrow band gap width, and the reflection within the band is small, especially the band gap is sensitive to the incident angle and the polarization of light. A new photonic band gap (PBG) structure, metallodielectric photonic crystal by inserting metal film in the medium can overcomes the shortcomings mentioned above. The one-dimensional Ag/SiOx photonic crystal was prepared, and theoretical and experimental researches were developed. The results show that photonic band gap appears gradually and the band gap width increase with increasing of period of repeating thickness. With the thickness of Ag film increasing, the band gap width increases, but the starting wavelength of the photonic band gap keeps unchanged. With thickness of SiOx film increasing, the band gap width of photonic band gap also increases, but it is not obvious and starting wavelength increases.

scholarly journals Влияние ионов In-=SUP=-3+-=/SUP=- и Ga-=SUP=-3+-=/SUP=- на запрещенную зону кристаллов щелочно-земельных фторидов: неэмпирический расчет

2019 ◽  
Vol 126 (4) ◽  
pp. 428
Author(s):  
А.С. Мясникова ◽  
А.И. Богданов
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Quantum Chemical ◽  
Density Functional ◽  
Functional Theory ◽  
Software Complex ◽  
Impurity Ions ◽  
Shallow Traps ◽  
Gap Width ◽  
Band Gap Width

AbstractThe results of nonempirical quantum chemical calculations of CaF_2, SrF_2, and BaF_2 crystals that were activated by In^3+ and Ga^3+ ions have been presented. The calculations were performed in the framework of density functional theory using the VASP software complex. The estimation of the width of the band gap of defect-free crystals have been carried out by different methods and the influence of impurity ions on the band gap width has been estimated as well as the possibility of getting rid of shallow traps by introducing an impurity of indium or gallium has been investigated.

Band gap engineering and transport properties of Ba2In2O5: effect of fluorine doping and hydration

2019 ◽  
Vol 21 (42) ◽  
pp. 23459-23465
Author(s):  
Maxim I. Vlasov ◽  
Nataliia A. Tarasova ◽  
Anzhelika O. Galisheva ◽  
Irina E. Animitsa ◽  
Maxim V. Ananyev
Keyword(s):  
Transport Properties ◽  
Band Gap ◽  
Fluorine Doping ◽  
Band Gap Engineering ◽  
Gap Width ◽  
Band Gap Width

This work discusses the effect of fluorine doping and hydration on the band gap width (Eg) of Ba2In2O5. Several correlations between the Eg behavior and the conductivity properties of the oxide were revealed.

Temperature Dependence of the Band-Gap Width of Mn1.5AgIn8.0S14 Single Crystals

2020 ◽  
Vol 87 (2) ◽  
pp. 236-239
Author(s):  
I. V. Bodnar ◽  
Ch. B. Than ◽  
V. N. Pavlovskii ◽  
I. E. Svitsiankou ◽  
G. P. Yablonskii
Keyword(s):  
Temperature Dependence ◽  
Band Gap ◽  
Single Crystals ◽  
Gap Width ◽  
Band Gap Width

scholarly journals Manufacturing and investigation of physical properties of polyacrylonitrile nanofibre composites with SiO2, TiO2 and Bi2O3 nanoparticles

2016 ◽  
Vol 7 ◽  
pp. 1141-1155 ◽  
Author(s):  
Tomasz Tański ◽  
Wiktor Matysiak ◽  
Barbara Hajduk
Keyword(s):  
Dielectric Constant ◽  
Refractive Index ◽  
Physical Properties ◽  
Band Gap ◽  
Electrospinning Process ◽  
Nanocomposite Polymer ◽  
Dispersion Of Nanoparticles ◽  
Gap Width ◽  
Band Gap Width ◽  
Constant Refractive Index

The aim of this study was to produce nanocomposite polymer fibres, consisting of a matrix of polyacrylonitrile (PAN) and a reinforcing phase in the form of SiO2/TiO2/Bi2O3 nanoparticles, by electrospinning the solution. The effect of the nanoparticles and the electrospinning process parameters on the morphology and physical properties of the obtained composite nanofibres was then examined. The morphology of the fibres and the dispersion of nanoparticles in their volume were examined using scanning electron microscopy (SEM). All of the physical properties, which included the band gap width, dielectric constant and refractive index, were tested and plotted against the concentration by weight of the used reinforcing phase, which was as follows: 0%, 4%, 8% and 12% for each type of nanoparticles. The width of the band gap was determined on the basis of the absorption spectra of radiation (UV–vis) and ellipsometry methods. Spectroscopic ellipsometry has been used in order to determine the dielectric constant, refractive index and the thickness of the obtained fibrous mats.

Effects of nonmetal doping on electronic structures of NaNbO3 based on hybrid density functional calculation

2016 ◽  
Vol 30 (28) ◽  
pp. 1650350 ◽  
Author(s):  
Haifeng Shi ◽  
Benyue Lan ◽  
Chengliang Zhang ◽  
Enjia Ye ◽  
Yanguang Nie ◽  
...  
Keyword(s):  
Band Gap ◽  
Electronic Structures ◽  
Density Functional ◽  
Valence Band Maximum ◽  
Band Gap Energy ◽  
Anion Doping ◽  
P Elements ◽  
Co Doping ◽  
Calculation Results ◽  
Band Gap Narrowing

The influences of a series of anion doping on the electronic structures of sodium niobate (NaNbO3) have been systematically investigated by density functional theory (DFT) calculations with the hybrid B3LYP functional. As for B[Formula: see text](C,[Formula: see text]P)-doped NaNbO3, the isolated B 2p (C 2p, P 3p) states were formed above the valence band maximum (VBM) of NaNbO3, which were too weak to mix with O 2p states and thus produced band gap narrowing. While the band gap of NaNbO3 was slightly narrowed after F doping. As for S-doped NaNbO3, the S 3p states mixed with O 2p states well and thus reduced the band gap energy. According to the calculation results, we tentatively put forward that S doping would be appropriate for single anion doping NaNbO3, while the B[Formula: see text](C,[Formula: see text]P) elements would be suitable candidates for co-doping NaNbO3.

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