First Principles Study of High-Pressure Phases of ScN

We report the results of first-principles total-energy calculations for structural properties of scandium nitride (ScN) semiconductor compound in NaCl-type (B1), CsCl-type (B2), zincblende-type (B3), wurtzite-type (B4), NiAs-type (B81), CaSi-type (Bc), B-Sn-type (A5), and CuAu-type (L10) structures. Calculations have been performed with the use of the all-electron full-potential linearized augmented plane wave FP-LAPW method based on density-functional theory (DFT) in the generalized gradient approximation (GGA) for the exchange correlation energy functional. We predict a new phase transition from the most stable cubic NaCl-type structure (B1) to the B-Sn-type one (A5) at 286.82 GPa with a direct band-gap energy of about 1.975 eV. Our calculations show that ScN transforms from the orthorhombic CaSi-type structure (Bc) to A5 at 315 GPa. In agreement with earlier ab initio works, we find that B1 phase transforms to Bc, L10, and B2 structures at 256.27 GPa, 302.08 GPa, and 325.97 GPa, respectively. The electronic structure of A5 phase shows that ScN exhibits a direct band-gap at X point, with Eg of about 1.975 eV.

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Computational Investigation of the Folded and Unfolded Band Structure and Structural and Optical Properties of CsPb(I1−xBrx)3 Perovskites

Crystals ◽

10.3390/cryst10050342 ◽

2020 ◽

Vol 10 (5) ◽

pp. 342 ◽

Cited By ~ 1

Author(s):

Hamid M. Ghaithan ◽

Zeyad A. Alahmed ◽

Andreas Lyras ◽

Saif M. H. Qaid ◽

Abdullah S. Aldwayyan

Keyword(s):

Optical Properties ◽

Band Structure ◽

Band Gap ◽

Spectral Weight ◽

Band Gap Energy ◽

Full Potential ◽

Generalized Gradient ◽

Electronic And Optical Properties ◽

Generalized Gradient Approximation ◽

Direct Band

The structural, electronic, and optical properties of inorganic CsPb(I1−xBrx)3 compounds were investigated using the full-potential linear augmented-plane wave (FP-LAPW) scheme with a generalized gradient approximation (GGA). Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) and modified Becke–Johnson GGA (mBJ-GGA) potentials were used to study the electronic and optical properties. The band gaps calculated using the mBJ-GGA method gave the best agreement with experimentally reported values. CsPb(I1−xBrx)3 compounds were wide and direct band gap semiconductors, with a band gap located at the M point. The spectral weight (SW) approach was used to unfold the band structure. By substituting iodide with bromide, an increase in the band gap energy (Eg) values of 0.30 and 0.55 eV, using PBE-GGA and mBJ-GGA potentials, respectively, was observed, whereas the optical property parameters, which were also investigated, demonstrated the reverse effect. The high absorption spectra in the ultraviolet−visible energy range demonstrated that CsPb(I1−xBrx)3 perovskite could be used in optical and optoelectronic devices by partly replacing iodide with bromide.

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Optoelectronic Analysis of CdGa2X4 (X= S, Se): A Promising Material for Solar Cells

Materials Science Forum ◽

10.4028/www.scientific.net/msf.900.69 ◽

2017 ◽

Vol 900 ◽

pp. 69-73 ◽

Cited By ~ 1

Author(s):

Pancham Kumar ◽

Jagrati Sahariya ◽

Amit Soni ◽

K.C. Bhamu

Keyword(s):

Solar Cell ◽

Band Gap ◽

Density Of States ◽

Density Functional ◽

Visible Spectrum ◽

Full Potential ◽

Functional Theory ◽

Augmented Plane Wave ◽

Direct Band Gap ◽

Direct Band

In this paper, the optoelectronic nature of the CdGa2X4 (X = S, Se) solar cell materials are examined using full potential linear augmented plane wave (FP-LAPW) method as embodied in WIEN2K code. In present computation, we have used most suitable modified Backe-Johnson (mBJ) potential under the framework of density functional theory (DFT). The calculated electronic properties like energy band structure and density of states spectra show that these materials exhibit a direct band gap (Γ–Γ) result of 3.22 eV and 2.36 eV for CdGa2S4 and CdGa2Se4 compounds, respectively. Absorption spectra for CdGa2X4 (X = S, Se) compounds have been studied and it has been found that above the band gap, absorption are taking place and it covers wide visible spectrum energy range. On the basis of calculated band gap, density of states and absorption coefficient spectra, it is found that these compounds can be suitably applicable in optoelectronic devices such as solar cell. The evaluated properties pose well agreement with available experimental data.

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First-Principles Calculations on Pure and Ga-Doped Anatase TiO2

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.156-157.1385 ◽

2010 ◽

Vol 156-157 ◽

pp. 1385-1388

Author(s):

Rui Qing Xu ◽

Lan Fang Yao ◽

Lin Li ◽

Shuo Wang ◽

Lin Lin Tian ◽

...

Keyword(s):

Band Gap ◽

First Principles ◽

Density Functional ◽

Correlation Energy ◽

Anatase Tio2 ◽

First Principles Calculations ◽

Generalized Gradient ◽

Functional Theory ◽

The Density Functional Theory ◽

Band Gap Narrowing

First-principles calculations using the plane-wave pseudo-potential (PWPP) method based on the density functional theory (DFT) is employed to study the crystal structure, band gap, density of states of anatase TiO2 doped with gadolinium (Gd). The generalized gradient approximation (GGA) based on exchange-correlation energy optimization is employed to calculate them. The calculated results demonstrate that the mixing of gadolinium dopants induces states with original titanium 3d and oxygen 2p valence band attributes to the band gap narrowing. This can enhance the photocatalytic activity of anatase TiO2.

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Increased Malleability in Tetragonal Zrx Ti1−x O2 Ternary Alloys: First-Principles Approach

Zeitschrift für Naturforschung A ◽

10.1515/zna-2017-0036 ◽

2017 ◽

Vol 72 (6) ◽

pp. 567-572

Author(s):

F. Ayedun ◽

P.O. Adebambo ◽

B.I. Adetunji ◽

V.C. Ozebo ◽

J.A. Oguntuase ◽

...

Keyword(s):

Band Gap ◽

First Principles ◽

Density Functional ◽

Ternary Alloys ◽

Generalized Gradient ◽

Functional Theory ◽

Direct Band ◽

Indirect Band Gap ◽

Projector Augmented Wave ◽

Alloying Effects

AbstractTetragonal phase of ZrxTi1−xO2ternary alloys is studied using generalized gradient approximation (GGA) projector augmented wave-based density functional theory (DFT). The calculations are used to characterize alloying effects of Zr substituting Ti in tutile TiO2. Band gap calculations show a direct band gap atx=0, while at other concentrations, an indirect band gap is observed. Electronic structure analysis shows that Zr alloying is capable of lowering the band gap transition of ZrxTi1−xO2atx=1 by the presence of an impurity state of transition metal Zr 5S2on the upper edge of the valence band. The addition of Zr also results in the corresponding increment in lattice constant with the material becoming more ductile and malleable.

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Direct band gap nature and optical response of BexMgyZn1−(x+y)Se

Modern Physics Letters B ◽

10.1142/s021798491650007x ◽

2016 ◽

Vol 30 (03) ◽

pp. 1650007

Author(s):

Naeemullah ◽

G. Murtaza ◽

R. Khenata ◽

S. Bin Omran

Keyword(s):

Band Gap ◽

First Principles ◽

Density Functional ◽

Experimental Measurements ◽

First Principles Calculations ◽

Functional Theory ◽

Direct Band Gap ◽

Direct Band ◽

First Time ◽

Ultraviolet Energy

For the first time, the electronic and optical properties of the quaternary Be[Formula: see text]Mg[Formula: see text]Zn[Formula: see text]Se alloy have been investigated using first-principles calculations within the framework of density functional theory (DFT). Variations in the direct band gap with the change in [Formula: see text] and [Formula: see text] compositions show agreement with the experimental measurements. Evaluation of the dielectric function and refractive index reveals the optical activity in the visible and ultraviolet energy regions.

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AB INITIO STUDY OF STRUCTURAL, ELECTRONIC AND OPTICAL PROPERTIES OF MgxCd1-xX (X = S, Se, Te) ALLOYS

International Journal of Modern Physics B ◽

10.1142/s0217979212501688 ◽

2012 ◽

Vol 26 (30) ◽

pp. 1250168 ◽

Cited By ~ 19

Author(s):

N. A. NOOR ◽

A. SHAUKAT

Keyword(s):

Optical Properties ◽

Band Gap ◽

Density Functional ◽

Theoretical Calculations ◽

Ternary Alloys ◽

Full Potential ◽

Generalized Gradient ◽

Calculated Density ◽

Electronic And Optical Properties ◽

Direct Band

This study describes structural, electronic and optical properties of Mg x Cd 1-x X (X = S, Se, Te) alloys in the complete range 0≤x ≤1 of composition x in the zinc-blende (ZB) phase with the help of full-potential linearized augmented plane wave plus local orbitals (FP-LAPW+lo) method within density functional theory (DFT). In order to calculate total energy, generalized gradient approximation (Wu–Cohen GGA) has been applied, which is based on optimization energy. For electronic structure calculations, the corresponding potential is being optimized by Engel–Vosko GGA formalism. Our calculations reveal the nonlinear variation of lattice constant and bulk modulus with different concentration for the end binary and their ternary alloys, which slightly deviates from Vegard's law. The calculated band structures show a direct band gap for all three alloys with increasing order in the complete range of the compositional parameter x. In addition, we have discussed the disorder parameter (gap bowing) and concluded that the total band gap bowing is substantially influenced by the chemical (electronegativity) contribution. The calculated density of states (DOS) of these alloys is discussed in terms of contribution from various s-, p- and d-states of the constituent atoms and charge density distributions plots are analyzed. Optical properties have been presented in the form of the complex dielectric function ε(ω), refractive index n(ω) and extinction coefficient k(ω) as function of the incident photon energy, and the results have been compared with existing experimental data and other theoretical calculations.

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Indirect-Direct Band Gap Transition by Van Der Waals Interaction Engineering in MoS2/WS2 Bilayer Heterojunction

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.614.70 ◽

2014 ◽

Vol 614 ◽

pp. 70-74 ◽

Cited By ~ 2

Author(s):

Hai Ning Cao ◽

Zhi Ya Zhang ◽

Ming Su Si ◽

Feng Zhang ◽

Yu Hua Wang

Keyword(s):

Band Gap ◽

First Principles ◽

Electronic Structures ◽

Density Functional ◽

First Principles Calculations ◽

Functional Theory ◽

Direct Band Gap ◽

The Density Functional Theory ◽

Direct Band ◽

Electric Filed

First principles calculations based on the density functional theory (DFT) are employed to estimate the electronic structures of bilayer heterostructure of MoS2/WS2. The dependences of the band structures on external electric field and interlayer separation are evaluated. The external electric filed induces a semiconductor-metal transition. At the same time, a larger interlayer separation, corresponding to a weaker interlayer interaction, makes an indirect-direct band gap transition happen for the heterojunction. Our results demonstrate that electronic structure tailoring of two-dimensional layered materials should include both spatial symmetry control and interlayer vdW interactions engineering.

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First-Principles Calculations on Pure and Y-Doped Anatase TiO2

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.562-565.1166 ◽

2013 ◽

Vol 562-565 ◽

pp. 1166-1170 ◽

Cited By ~ 1

Author(s):

Xiong Tang ◽

Lan Fang Yao ◽

Xin Pei Yan ◽

Jun Long Kang

Keyword(s):

Band Gap ◽

First Principles ◽

Density Functional ◽

Correlation Energy ◽

Partial Density ◽

First Principles Calculations ◽

Generalized Gradient ◽

Functional Theory ◽

Calculation Results ◽

Band Gap Narrowing

Using the First principles calculations, the crystal structure, band gap, total and partial density of states (DOS) of anatase TiO2and anatase TiO2doped with Yttrium were calculated by a plane-wave pseudopotential (PWPP) method based on density functional theory (DFT). The generalized gradient approximation (GGA) based on exchange-correlation energy optimization was employed to calculate them. From the calculation results, the band gap of anatase TiO2and Y3+doped TiO2are about 2.15eV and 0.86eV. The calculated results demonstrated that the mixing of Yttrium (Y) dopants induces states with original titanium 3d and oxygen 2p valence band attributes to the band gap narrowing. This can enhance the photocatalytic activity of anatase TiO2.

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Band Structure of Sr Doped into Bulk Wurtzite ZnO: A DFT Study.

Journal of The Faculty of Science and Technology ◽

10.52981/jfst.vi6.598 ◽

2021 ◽

pp. 10-17

Author(s):

Abdalla Abdelrahman Mohamed ◽

Tasneem Babiker Abdalrahman

Keyword(s):

Band Gap ◽

First Principles ◽

Density Functional ◽

Band Gap Energy ◽

Unit Cell Parameters ◽

Lattice Volume ◽

Cell Parameters ◽

Structural And Electronic Properties ◽

Direct Band ◽

Indirect Band Gap

This work investigates the structural and electronic properties of pure and Sr-doped ZnO using first principles density functional calculations (DFT). The calculations were carried out using GGA-BLYP functional. This functional underestimates the band gap value in semiconductors but does not affect the accuracy of the related properties of the crystals. The Sr-doping caused increase in lattice volume and slight distortions at the unit cell parameters in a wurtzite structure. The doping process presented increase in the band-gap energy Eg at low percentages 25%, 37.5% and 50% with indirect bang gap and direct band gap at high percentages 62.5%, 75%, 87.5% and 100%.which we can called it wide indirect band gap. These results can be use as a foundation for more in depth calculations which can be used on optical and Photo-catalytic applications.

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Strain-induced semimetal-to-semiconductor transition and indirect-to-direct band gap transition in monolayer 1T-TiS2

RSC Advances ◽

10.1039/c5ra16877e ◽

2015 ◽

Vol 5 (102) ◽

pp. 83876-83879 ◽

Cited By ~ 23

Author(s):

Chengyong Xu ◽

Paul A. Brown ◽

Kevin L. Shuford

Keyword(s):

Band Gap ◽

Electronic Properties ◽

Plane Strain ◽

Material Properties ◽

First Principles ◽

Tensile Strain ◽

First Principles Calculations ◽

Direct Band Gap ◽

Direct Band ◽

Uniform Plane

We have investigated the effect of uniform plane strain on the electronic properties of monolayer 1T-TiS2using first-principles calculations. With the appropriate tensile strain, the material properties can be transformed from a semimetal to a direct band gap semiconductor.

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