Electronic and optical properties of GaN under pressure: DFT calculations

2017 ◽  
Vol 31 (32) ◽  
pp. 1750261 ◽  
Author(s):  
Sahar Javaheri ◽  
Arash Boochani ◽  
Manuchehr Babaeipour ◽  
Sirvan Naderi
Keyword(s):  
Optical Properties ◽  
Electronic Properties ◽  
Dielectric Function ◽  
Loss Function ◽  
Density Functional ◽  
Electron Transition ◽  
First Principles Calculation ◽  
Main Peak ◽  
Electron Transitions ◽  
Function Loss

Optical and electronic properties of ZB, RS and WZ structures of gallium nitride (GaN) are studied in equilibrium and under pressure using the first-principles calculation in the density functional theory (DFT) framework to obtain quantities like dielectric function, loss function, reflectance and absorption spectra, refractive index and their relation parameters. The electronic properties are studied using EV-GGA and GGA approximations and the results calculated by EV-GGA approximation were found to be much closer to the experimental results. The interband electron transitions are studied using the band structure and electron transition peaks in the imaginary part of the dielectric function; these transitions occur in three structures from N-2p orbital to Ga-4s and Ga-4p orbitals in the conduction band. Different optical properties of WZ structure were calculated in two polarization directions of (100) and (001) and the results were close to each other. Plasmon energy corresponding to the main peak of the energy-loss function in RS with the value of 26 eV was the highest one, which increased under pressure. In general, RS shows more different properties than WZ and ZB.

Electronic and optical properties of AlN under pressure: DFT calculations

2017 ◽  
Vol 31 (02) ◽  
pp. 1650255
Author(s):  
Sahar Javaheri ◽  
Arash Boochani ◽  
Manuchehr Babaeipour ◽  
Sirvan Naderi
Keyword(s):  
Optical Properties ◽  
Electronic Properties ◽  
Dielectric Function ◽  
First Principles ◽  
Density Functional ◽  
Functional Theory ◽  
Zinc Blende ◽  
Rocksalt Phase ◽  
Optical And Electronic Properties ◽  
Theoretical Results

Structural, elastic, optical, and electronic properties of wurtzite (WZ), zinc-blende (ZB), and rocksalt (RS) structures of AlN are investigated using the first-principles method and within the framework of density functional theory (DFT). Lattice parameters, bulk modulus, shear modulus, Young’s modulus, and elastic constants are calculated at zero pressure and compared with other experimental and theoretical results. The wurtzite and zinc-blende structures have a transition to rocksalt phase at the pressures of 12.7 GPa and 14 GPa, respectively. The electronic properties are calculated using both GGA and EV-GGA approximations; the obtained results by EV-GGA approximation are in much better agreement with the available experimental data. The RS phase has the largest bandgap with an amount of 4.98 eV; by increasing pressure, this amount is also increased. The optical properties like dielectric function, energy loss function, refractive index, and extinction coefficient are calculated under pressure using GGA approximation. Inter-band transitions are investigated using the peaks of imaginary part of the dielectric function and these transitions mainly occur from N-2[Formula: see text] to Al-3[Formula: see text] levels. The results show that the RS structure has more different properties than the WZ and ZB structures.

First principles calculation of structural, electronic and optical properties of (001) and (110) growth axis (InN)/(GaN)n superlattices

2021 ◽  
Vol 67 (1 Jan-Feb) ◽  
pp. 7
Author(s):  
B. Bachir Bouiadjra ◽  
N. Mehnane ◽  
N. Oukli
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Scale Up ◽  
Energy Scale ◽  
First Principles Calculation ◽  
Full Potential ◽  
Electronic Band ◽  
Electronic And Optical Properties ◽  
Growth Axis

Based on the full potential linear muffin-tin orbitals (FPLMTO) calculation within density functional theory, we systematically investigate the electronic and optical properties of (100) and (110)-oriented (InN)/(GaN)n zinc-blende superlattice with one InN monolayer and with different numbers of GaN monolayers. Specifically, the electronic band structure calculations and their related features, like the absorption coefficient and refractive index of these systems are computed over a wide photon energy scale up to 20 eV. The effect of periodicity layer numbers n on the band gaps and the optical activity of (InN)/(GaN)n SLs in the both  growth axis (001) and (110) are examined and compared. Because of prospective optical aspects of (InN)/(GaN)n such as light-emitting applications, this theoretical study can help the experimental measurements.

scholarly journals Structural and Electronic Properties of Orthorhombic Phase Bi2Se3 Based On First-Principles Study

2019 ◽  
Vol 16 (2) ◽  
pp. 77 ◽  
Author(s):  
Muhammad Zamir Mohyedin ◽  
Afiq Radzwan ◽  
Mohammad Fariz Mohamad Taib ◽  
Rosnah Zakaria ◽  
Nor Kartini Jaafar ◽  
...  
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
Computer Code ◽  
First Principles Calculation ◽  
Generalized Gradient ◽  
Exchange Correlation ◽  
Percentage Difference ◽  
Structural And Electronic Properties

Bi2Se3 is one of the promising materials in thermoelectric devices and very useful out of environmental concern due to its efficiency to perform at room temperature. Based on the first-principles calculation of density functional theory (DFT) by using CASTEP computer code, structural and electronic properties of Bi2Se3 were investigated. The calculation is conducted within the exchange-correlation of local density approximation (LDA) and generalized gradient approximation within the revision of Perdew-Burke-Ernzerhof (GGA-PBE) functional. It was found that the results are consistent with previous works of theoretical study with small percentage difference. LDA exchange-correlation functional method is more accurate and have a better agreement than GGA-PBE to describe the structural properties of Bi2Se3 which consist of lattice parameters. LDA functional also shown more accurate electronic structure of Bi2Se3 that consist of band structure and density of states (DOS) which consistent with most previous theoretical works with small percentage difference. This study proves the reliability of CASTEP computer code and show LDA exchange-correlation functional is more accurate in describing the nature of Bi2Se3 compared to the other functionals.

DFT study of pressure effects in molecular crystal 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo-[5.5.0.05,903,11]-dodecane

2014 ◽  
Vol 92 (7) ◽  
pp. 616-624 ◽  
Author(s):  
Zhichao Liu ◽  
Qiong Wu ◽  
Weihua Zhu ◽  
Heming Xiao
Keyword(s):  
High Pressure ◽  
Energy Loss ◽  
Loss Function ◽  
Density Functional ◽  
Pressure Range ◽  
Blue Shift ◽  
Pressure Effects ◽  
Ambient Conditions ◽  
Energy Loss Function ◽  
Electron Transitions

Density functional theory was used to study the structural, electronic, and optical properties of crystalline 4,10-dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo-[5.5.0.05,903,11]-dodecane (TEX) under hydrostatic pressure. The results indicate that there is a displacive transition in TEX under compression that has never been found in experiments. As the pressure increases, the band gap gradually decreases but presents an abnormal increase at 61 GPa, called the structural transition; moreover, the gap reduction is more pronounced in the low-pressure range compared with the high-pressure range. An analysis of density of states shows that the electronic delocalization in TEX is enhanced gradually under the influence of pressure. The peaks of the imaginary parts of the dielectric functions, energy-loss function, and reflectivity may come mainly from the electron transitions between the oxygen 2p and nitrogen 2p states. The electron energy-loss function presents a blue shift under compression. TEX has relatively higher optical activity at high pressure than at ambient conditions.

Tunable electronic properties of GaS-SnS2 heterostructure by strain and electric field

2021 ◽  
Author(s):  
Dahua Ren ◽  
Qiang Li ◽  
Kai Qian ◽  
Xingyi Tan
Keyword(s):  
Optical Properties ◽  
Electric Field ◽  
Visible Light ◽  
Electronic Properties ◽  
Electronic Structures ◽  
Density Functional ◽  
Band Alignment ◽  
Promising Candidate ◽  
Functional Theory ◽  
External Strain

Abstract Vertically stacked heterostructures have received extensive attention because of their tunable electronic structures and outstanding optical properties. In this work, we have studied the structural, electronic and optical properties of vertically stacked GaS-SnS2 heterostructure under the frame of density functional theory. We find that the stacked GaS-SnS2 heterostructure is a semiconductor with suitable indirect band gaps of 1.82 eV, exhibiting a type-II band alignment for easily separating the photo-generated carriers. The electronic properties of GaS-SnS2 heterostructure can be effectively tuned by external strain and electric field. The optical absorption of GaS-SnS2 heterostructure is more enhanced by comparison with the GaS monolayer and SnS2 monolayer in the visible light. Our results suggest that GaS-SnS2 heterostructure is a promising candidate for the photocatalyst and photoelectronic devices in visible light.

scholarly journals Effect of Vacancy Defects on the Electronic Structure and Optical Properties of GaN

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Lili Cai ◽  
Cuiju Feng
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Lower Energy ◽  
Density Functional ◽  
Nitrogen Vacancy ◽  
Main Peak ◽  
Generalized Gradient ◽  
Vacancy Defects ◽  
Gallium Vacancy ◽  
Defect Levels

The effect of gallium vacancy (VGa) and nitrogen vacancy (VN) defects on the electronic structure and optical properties of GaN using the generalized gradient approximation method within the density functional theory were investigated. The results show that the band gap increases in GaN with vacancy defects. Crystal parameters decrease in GaN with nitrogen vacancy (GaN:VN) and increase in GaN with gallium vacancy (GaN:VGa). The Ga vacancy introduces defect levels at the top of the valence band, and the defect levels are contributed by N2p electron states. In addition, the energy band shifts to lower energy in GaN:VNand moves to higher energy in GaN:VGa. The level splitting is observed in the N2p states of GaN:VNand Ga3d states of GaN:VGa. New peaks appear in lower energy region of imaginary dielectric function in GaN:VNand GaN:VGa. The main peak moves to higher energy slightly and the intensity decreases.

The band offset barrier and optical properties calculation of Co2VGa/GaAs(001) interfaces: A DFT study

2018 ◽  
Vol 32 (01) ◽  
pp. 1750270
Author(s):  
Negin Fatahi ◽  
Arash Boochani ◽  
Shahram Solaymani ◽  
Elmira Sartipi ◽  
Farzad Ahmadian
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Spin Injection ◽  
Point Of View ◽  
Functional Theory ◽  
Exchange Correlation ◽  
Electron Transitions ◽  
Difference Formula ◽  
Correlation Potential ◽  
Interface Structures

The structural, electronic, optical properties and band offsets of Co2VGa/GaAs(001) interfaces are discussed within the framework of density functional theory (DFT) using the FP-LAPW method, and the exchange-correlation potential is approximated by GGA. All interface structures are stable in the energy point of view, however the V–Ga/As case is found to be more stable than the others. A remarkable potential difference ([Formula: see text]V) appeared in all the interfaces, so the Co2VGa/GaAs(001) interfaces are good candidates for electron injection. In all the cases, there is no full spin polarization at the Fermi level, but high CBO and [Formula: see text] coefficients make them promising candidates for spin injection in the transport devices. Optical studies confirm the high metallic treatment of these interfaces as the main electron transitions had occurred in the infrared and visible regions. The real parts of the dielectric function in the x-direction indicate the different behaviors of “Co–Co/As and V–Ga/Ga” and “Co–Co/Ga and V–Ga/As” in the infrared area. In addition, the plasmon frequencies had occurred at high UV energies.

Newly Determined Crystal Structure and Optical Property of the Intermetallic NiAl and Ni3Al Alloys: A First-Principles Computer Simulated Investigation

2014 ◽  
Vol 989-994 ◽  
pp. 220-223
Author(s):  
Chao Xu ◽  
Dong Chen
Keyword(s):  
Dielectric Function ◽  
Loss Function ◽  
First Principles ◽  
Density Functional ◽  
Peak Height ◽  
Functional Theory ◽  
Lattice Constants ◽  
Light Region ◽  
The Density Functional Theory ◽  
Lower Energy Region

Using quantum mechanics plane-wave approach based on the density functional theory, the lattice constants of NixAl at different Ni concentrations (x=1, 3) are predicted. Optical properties such as dielectric function, energy loss function and reflectivity are also investigated. Results show that with the increase of Ni constituent, the location of the peak in loss function moves to the lower energy region, but the peak height increases. At 0eV, the reflectivity increases rapidly with the Ni concentration. The reflectivity of NiAl and Ni3Al are pronounced in the UV region (not in the visible light region). The dielectric properties, namely the real and imaginary parts of the dielectric function, changed significantly with Ni constituent.

First-principle studies of the optoelectronic properties of ASnF3 (A = Na, K, Rb and Cs)

2017 ◽  
Vol 31 (21) ◽  
pp. 1750148 ◽  
Author(s):  
Imad Khan ◽  
Nasir Shehzad ◽  
Iftikhar Ahmad ◽  
Zahid Ali ◽  
S. Jalali-Asadabadi
Keyword(s):  
Refractive Index ◽  
Optical Properties ◽  
Energy Loss ◽  
Ab Initio Calculations ◽  
Loss Function ◽  
Electron Transition ◽  
First Principle ◽  
Electronic Band ◽  
New Type ◽  
Electronic Band Structures

In this paper, we communicate a new type of Auger-free luminescence (AFL) compounds, alkali tin fluorides ASnF3 (A = Na, K, Rb and Cs). The luminescence in these compounds originates due to the electron transition from the top valence band (VB) of tin-[Formula: see text] orbital to the outermost core levels of halogen, i.e., halogen-[Formula: see text] orbital ([Formula: see text]-[Formula: see text] transitions). The AFL of these compounds is expected to be of L-type. Furthermore, the electronic band structures and optical properties such as dielectric functions, refractive index and energy loss function are also investigated using ab initio calculations.

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