Influence of defect pairs in Ga-based ordered defect compounds: a hybrid density functional study

2020 ◽  
Vol 98 (8) ◽  
pp. 770-777
Author(s):  
Sudhir Kumar ◽  
Suman Joshi ◽  
Durgesh Kumar Sharma ◽  
Sushil Auluck
Keyword(s):  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Functional Study ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Lattice Constants ◽  
Donor Acceptor ◽  
The Stability ◽  
Hybrid Density Functional

In the present paper, density functional theory (DFT) based calculations have been performed to predict the stability, electronic, and optical properties of Ga-rich ordered defect compounds (ODCs). The calculated lattice constants, bulk modulus, their pressure derivatives, and optical constants show good agreement with available experimental data. The hybrid exchange correlations functional have been considered to calculate ground state total energy and energy band gap of the material. The calculated formation energy of ODCs comes smaller than pure CuGaSe2 (CGS). Our calculated optical absorption coefficients indicate that the energy band gap of ODCs can be tuned by changing the number of donor–acceptor defect pairs ([Formula: see text]). The band offset has been calculated to understand the reason of band gap alteration while the number of defect pair changes. Our results may be helpful for other experiments to further improve the performance of ODCs.

Density Functional Theory Study on Energy Band Gap of Armchair Silicene Nanoribbons with Periodic Nanoholes

MRS Advances ◽  
2016 ◽  
Vol 1 (22) ◽  
pp. 1613-1618 ◽  
Author(s):  
Sadegh Mehdi Aghaei ◽  
Irene Calizo
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Energy Band ◽  
Quantum Confinement ◽  
Density Functional ◽  
Quantum Confinement Effect ◽  
Density Functional Theory Study ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Silicene Nanoribbons

ABSTRACTIn this study, density functional theory (DFT) is employed to investigate the electronic properties of armchair silicene nanoribbons perforated with periodic nanoholes (ASiNRPNHs). The dangling bonds of armchair silicene nanoribbons (ASiNR) are passivated by mono- (:H) or di-hydrogen (:2H) atoms. Our results show that the ASiNRs can be categorized into three groups based on their width: W = 3P − 1, 3P, and 3P + 1, P is an integer. The band gap value order changes from “EG (3P − 1) < EG (3P) < EG (3P + 1)” to “EG (3P + 1) < EG (3P − 1) < EG (3P)” when edge hydrogenation varies from mono- to di-hydrogenated. The energy band gap values for ASiNRPNHs depend on the nanoribbons width and the repeat periodicity of the nanoholes. The band gap value of ASiNRPNHs is larger than that of pristine ASiNRs when repeat periodicity is even, while it is smaller than that of pristine ASiNRs when repeat periodicity is odd. In general, the value of energy band gap for ASiNRPNHs:2H is larger than that of ASiNRPNHs:H. So a band gap as large as 0.92 eV is achievable with ASiNRPNHs of width 12 and repeat periodicity of 2. Furthermore, creating periodic nanoholes near the edge of the nanoribbons cause a larger band gap due to a strong quantum confinement effect.

scholarly journals STUDY OF TiO2 NANOPARTICLES’ STRUCTURE USING DENSITY FUNCTIONAL THEORY BASED TIGHT BINDING METHOD

2019 ◽  
Vol 1 (27) ◽  
pp. 79-85
Author(s):  
Hung Thanh Phan
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Tio2 Nanoparticles ◽  
Energy Band ◽  
Density Functional ◽  
Anatase Phase ◽  
Tight Binding ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Practical Applications

The different structure and size of TiO2 nanoparticles ranging from 0.8 nm to 2.7 nm with two different phases of anatase and rutile were studied by Density  Functional theory based Tight Binding (DFTB) method. The results showed that the stability of the rutile phase was better than that of the anatase phase. Based on calculation of the electronic properties of particles, the energy band gap of rutile particles was comparable to that of bulk structure. In contrast, the energy band gap of the anatase changed irregularly. Moreover, the formation energy that was used for forming the particles was inversely proportional to their size based on computation of energy. The results provided useful instructions for practical applications in fabrication of TiO2 nanoparticles.

Band gap engineering of ZnO substituted with nitrogen and fluorine, ZnO1−3xN2xFx: a hybrid density functional study

RSC Advances ◽  
2016 ◽  
Vol 6 (101) ◽  
pp. 99088-99095 ◽  
Author(s):  
S. Kumar ◽  
Durgesh Kumar Sharma ◽  
S. Auluck
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Functional Study ◽  
First Principles Calculations ◽  
Functional Theory ◽  
Band Gap Engineering ◽  
Hybrid Density Functional ◽  
Co Doped

A series of first principles calculations within density functional theory (DFT) have been performed for ZnO, co-doped with N and F with the aim of engineering the band gap and improving its application to photo-absorption activity.

scholarly journals Study of Electronic Properties of GaAs Semiconductor Using Density Functional Theory

2021 ◽  
Vol 4 (2) ◽  
pp. 94
Author(s):  
Fikri Abdi Putra ◽  
Endhah Purwandari ◽  
Bintoro S. Nugroho
Keyword(s):  
Density Functional Theory ◽  
Band Structure ◽  
Band Gap ◽  
Electronic Properties ◽  
Energy Band ◽  
Density Functional ◽  
Energy Band Structure ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Direct Band

The properties of GaAs material in zinc blende type was calculated using Hiroshima Linear Plane Wave program based on the Density Functional Theory. This calculation aims to determine electronic properties of GaAs material are based on Density of States and energy band structure. This simulation’s results are DOS shows that hybridization of s orbital of Ga with s orbital of As provides covalent properties. The simulation of energy band structure from GaAs material indicates that semiconductor properties of GaAs is direct band gap. The energy band gap results obtained for GaAs is 0.80 eV. The computational result of the energy band gap calculation form HiLAPW has better accuracy and prediction with good agreement within reasonable acceptable errors when compared to some other DFT programs and the results of the experimental obtained.

scholarly journals Density Functional Theory (DFT) Study on α,α-Bis(2-benzothiophen-1-yl)-4H-cyclopenta[2,1-b,3;4-b′]dithiophene Derivatives for Optoelectronic Devices

2019 ◽  
Vol 8 (2) ◽  
pp. 126-139
Author(s):  
Banjo Semire ◽  
◽  
Olusegun Ayobami Odunola
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Molecular Structures ◽  
Band Gaps ◽  
Photovoltaic Devices ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Molecular Hyperpolarizability

Bis(2-benzothiophen-1-yl)-4H-cyclopenta[2,1-b,3;4-b′]dithiophene derivatives comprised of three series; bis(2-thienyl)-4H-cyclopenta[2,1-b,3;4-b]dithiopene (BTDT), diphenyl4Hcyclopenta[2,1-b,3;4-b]dithiophene (DPDT) and bis(2-benzothiophen-1-yl)-4Hcyclopenta[2,1-b,3;4-b]dithiophene (BBDT) have been studied using Density Functional Theory (B3LYP/6-31G**). In each series, molecules with C=S bridge exhibited the lowest band gap; for instance in BBDT series, the energy band gap could be arranged as 2.29, 2.23 and 1.66 eV for CH2, C=O and C=S bridge respectively. The low band gaps calculated for BBDT-C=S (1.66 eV) and BTDT-C=S (1.82 eV) could facilitate photo-excited electron transfer as one the criteria for a molecule to be used in photovoltaic devices. Also, the results showed that longest UV-vis absorption wavelength was observed for molecules with C=S bridge, i.e. 1013.66, 874.75 and 1097.66 nm for BTDT, DPDT and BBDT respectively. The polarizability (α0) valves calculated for the molecules follow as -CH2 < C=O < C=S bridge in each series, indicating that the higher the polarizability (α0) valve the longer the λmax nm and the lower the energy band gap. The magnitude of the molecular hyperpolarizability β0 showed that molecular structures with -C=O bridge could be best NLO material in each series.

Photoemission and density functional theory study of Ir(111); energy band gap mapping

2010 ◽  
Vol 22 (13) ◽  
pp. 135006 ◽  
Author(s):  
I Pletikosić ◽  
M Kralj ◽  
D Šokčević ◽  
R Brako ◽  
P Lazić ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Density Functional Theory Study ◽  
Energy Band Gap ◽  
Functional Theory

A DENSITY FUNCTIONAL STUDY OF THE STRUCTURE OF SILANE COUPLING AGENT 3–AMINOPROPYLTRIETHOXYSILANE

2005 ◽  
Vol 04 (01) ◽  
pp. 117-126
Author(s):  
N. L. MA ◽  
P. WU
Keyword(s):  
Coupling Agent ◽  
Density Functional ◽  
Solution Structure ◽  
Silane Coupling Agent ◽  
Industrial Applications ◽  
Functional Study ◽  
Stable Form ◽  
Functional Theory ◽  
Silane Coupling ◽  
The Stability

Using density functional theory, we predicted the solution structure of the hydrolyzed 3–aminopropyltriethoxysilane (h–APS), which is a silane coupling agent commonly used in many industrial applications. We have located five stable minima on the potential energy surface of h–APS in which four of them are "neutral", and the remaining one is zwitterionic (dipolar) in nature. Our calculations suggested that the stability of the most stable form of h–APS in water (denoted as II_N) arose from strong intramolecular OH ⋯ N hydrogen bond. The least stable form is the zwitterionic form (I_ZW), which is estimated to be over 90 kJ mol -1 less stable than II_N. The factors governing the relative stabilities of different forms are discussed.

Computational Study of Tetrahedral Fullerenes Containing Fused Pentagon-Triples

2021 ◽  
Vol 21 (4) ◽  
pp. 2419-2426
Author(s):  
Csaba L. Nagy ◽  
Katalin Nagy
Keyword(s):  
Density Functional ◽  
Computational Study ◽  
Chemical Shifts ◽  
Point Group ◽  
Functional Theory ◽  
Global Strain ◽  
The Stability ◽  
Global And Local ◽  
Hybrid Density Functional ◽  
Electronic And Structural Properties

Fullerenes that violate the isolated pentagon rule are too reactive and were obtained only as endoor exohedral derivatives. Density functional theory using the B3LYP hybrid density functional was applied to investigate the electronic and structural properties of the ten smallest tetrahedral (Td or T point group) fullerenes containing four directly fused pentagon-triples. The influence of nitrogen doping and exohedral hydrogenation of the four reactive sites was also analyzed. Nucleus independent chemical shifts values computed using B3LYP/6-31G(d) are used as global and local aromaticity probe. The global strain energy is evaluated in terms of the pyramidalization (POAV) angle. The results show that the stability increases with the elimination of the energetically unfavorable strain.

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