Study of Electronic Structures and Transport Properties on Saturated GaN Nanowires

Geometry structure, electronic structure and electronic transport properties of saturated hexagonal single crystalline GaN nanowires in the [001] growth direction have been investigated based on generalized gradient approximation (GGA) of density functional theory (DFT) and non-equilibrium green's function (NEGF) method. The results show, there is a contraction of the bond lengths of the saturated GaN nanowires after optimization; the nanowires have direct band gap, and band gap decreases with the increase of the cross section of nanowires; the electronic density of state and electronic transmission spectra of two-probe system have their own pulse-type sharp peaks with almost the same location of electron energy; the curves of I-V characteristics of the three saturated GaN nanowires are symmetric over the entire bias-voltage range, and they are semiconducting.

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ELECTRONIC STRUCTURES AND TRANSPORT PROPERTIES OF SINGLE CRYSTALLINE GaN NANOTUBES

NANO ◽

10.1142/s1793292012500142 ◽

2012 ◽

Vol 07 (03) ◽

pp. 1250014 ◽

Cited By ~ 4

Author(s):

ENLING LI ◽

LIPING HOU ◽

ZHEN CUI ◽

DANNA ZHAO ◽

MANCANG LIU ◽

...

Keyword(s):

Transport Properties ◽

Electronic Structures ◽

Density Functional ◽

Single Layer ◽

Generalized Gradient ◽

Electronic Density ◽

Single Crystalline ◽

Pulse Type ◽

Direct Band ◽

Inner Diameter

The electronic structures and transport properties of single crystalline GaN nanotubes with 0.92 nm inner diameter and different wall thicknesses of 0.08 nm, 0.26 nm and 0.54 nm are studied based on the generalized gradient approximation (GGA) of density functional theory (DFT) and the nonequilibrium green's function (NEGF). The research shows that (1) the three single crystalline GaN nanotubes have direct band gaps, decreasing with the increase of wall thickness; (2) the electronic density of state and electronic transmission spectra of two-probe system have their own pulse-type sharp peaks with almost the same location of electron energy; (3) under different bias-voltages, two-probe systems of the single crystalline GaN nanotubes have the I–V properties which reveal that the single-wall GaN nanotube and the single-layer GaN nanotube are semiconducting and the double-layer GaN nanotube appears nearly metallic.

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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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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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The energy band structure of Si and Ge nanolayers

Modern Physics Letters B ◽

10.1142/s0217984916504029 ◽

2016 ◽

Vol 30 (34) ◽

pp. 1650402 ◽

Cited By ~ 1

Author(s):

Xueke Wu ◽

Weiqi Huang ◽

Zhongmei Huang ◽

Chaojie Qin ◽

Yanlin Tang

Keyword(s):

Band Gap ◽

Energy Band ◽

Density Functional ◽

Band Gaps ◽

First Principles Calculation ◽

Generalized Gradient ◽

Quantum Confinement Effects ◽

Calculation Results ◽

Direct Band ◽

Band Gap Structure

First-principles calculation based on density functional theory (DFT) with the generalized gradient approximation (GGA) were carried out to investigate the energy band gap structure of Si and Ge nanofilms. Calculation results show that the band gaps of Si(111) and Ge(110) nanofilms are indirect structures and independent of film thickness, the band gaps of Si(110) and Ge(100) nanofilms could be transfered into the direct structure for nanofilm thickness of less than a certain value, and the band gaps of Si(100) and Ge(111) nanofilms are the direct structures in the present model thickness range (about 7 nm). Moreover, the changes of the band gaps on the Si and Ge nanofilms follow the quantum confinement effects. It will be a good way to obtain direct band gap emission in Si and Ge materials, and to develop Si and Ge laser on Si chip.

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Effect of Nitrogen and Boron Localization on the Electrical Properties of Porous Graphene

NANO ◽

10.1142/s1793292017501090 ◽

2017 ◽

Vol 12 (09) ◽

pp. 1750109 ◽

Cited By ~ 1

Author(s):

Mahmoud Jafari ◽

Shima Nazifi ◽

Mohamad Asadpour

Keyword(s):

Electrical Properties ◽

Band Gap ◽

Density Functional ◽

Generalized Gradient ◽

Functional Theory ◽

Text Type ◽

Porous Graphene ◽

The Density Functional Theory ◽

Direct Band ◽

Metal Properties

The electrical properties of porous graphene (PG) are investigated by using the density functional theory (DFT) with the generalized gradient approximation (GGA). The addition of Boron and nitrogen impurities could change the semiconductor into the [Formula: see text] or [Formula: see text]-type. Results showed that PG had pseudo-metal properties and a direct band gap. Furthermore, adding two impurities resulted in a greater decrease in the energy of the band gap as compared to the other states. In particular, when two impurities were of the boron type, the reduction was more tangible. Moreover, the addition of impurity could also increase the conductivity and pushed the electrical properties toward being a metal.

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First Principles Study of High-Pressure Phases of ScN

Ukrainian Journal of Physics ◽

10.15407/ujpe66.8.699 ◽

2021 ◽

Vol 66 (8) ◽

pp. 699

Author(s):

R. Yagoub ◽

H. Rekkab Djabri ◽

S. Daoud ◽

N. Beloufa ◽

M. Belarbi ◽

...

Keyword(s):

Band Gap ◽

First Principles ◽

Density Functional ◽

Correlation Energy ◽

Band Gap Energy ◽

Type Structure ◽

Full Potential ◽

Generalized Gradient ◽

Direct Band Gap ◽

Direct Band

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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Performance of SCAN Meta-GGA Functionals on Nonlinear Mechanics of Graphene-Like g-SiC

Crystals ◽

10.3390/cryst11020120 ◽

2021 ◽

Vol 11 (2) ◽

pp. 120

Author(s):

Qing Peng

Keyword(s):

Mechanical Properties ◽

Density Functional ◽

Large Strains ◽

Two Dimensional ◽

Nonlinear Mechanics ◽

Generalized Gradient ◽

Mechanics Of Materials ◽

Nonlinear Mechanical ◽

Direct Band ◽

Simulations And Modeling

Although meta-generalized-gradient approximations (meta-GGAs) are believed potentially the most accurate among the efficient first-principles calculations, the performance has not been accessed on the nonlinear mechanical properties of two-dimensional nanomaterials. Graphene, like two-dimensional silicon carbide g-SiC, has a wide direct band-gap with applications in high-power electronics and solar energy. Taken g-SiC as a paradigm, we have investigated the performance of meta-GGA functionals on the nonlinear mechanical properties under large strains, both compressive and tensile, along three deformation modes using Strongly Constrained and Appropriately Normed Semilocal Density Functional (SCAN) as an example. A close comparison suggests that the nonlinear mechanics predicted from SCAN are very similar to that of Perdew-Burke-Ernzerhof (PBE) formulated functional, a standard Density Functional Theory (DFT) functional. The improvement from SCAN calculation over PBE calculation is minor, despite the considerable increase of computing demand. This study could be helpful in selection of density functionals in simulations and modeling of mechanics of materials.

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Properties of Novel Non-Silicon Materials for Photovoltaic Applications: A First-Principle Insight

Materials ◽

10.3390/ma11102006 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2006 ◽

Cited By ~ 3

Author(s):

Murugesan Rasukkannu ◽

Dhayalan Velauthapillai ◽

Federico Bianchini ◽

Ponniah Vajeeston

Keyword(s):

Band Gap ◽

Density Functional ◽

Crystalline Silicon ◽

Visible Region ◽

Initial Population ◽

First Principle ◽

Direct Band Gap ◽

Depth Analysis ◽

Photovoltaic Applications ◽

Direct Band

Due to the low absorption coefficients of crystalline silicon-based solar cells, researchers have focused on non-silicon semiconductors with direct band gaps for the development of novel photovoltaic devices. In this study, we use density functional theory to model the electronic structure of a large database of candidates to identify materials with ideal properties for photovoltaic applications. The first screening is operated at the GGA level to select only materials with a sufficiently small direct band gap. We extracted twenty-seven candidates from an initial population of thousands, exhibiting GGA band gap in the range 0.5–1 eV. More accurate calculations using a hybrid functional were performed on this subset. Based on this, we present a detailed first-principle investigation of the four optimal compounds, namely, TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO. The direct band gap of these materials is between 1.1 and 2.26 eV. In the visible region, the absorption peaks that appear in the optical spectra for these compounds indicate high absorption intensity. Furthermore, we have investigated the structural and mechanical stability of these compounds and calculated electron effective masses. Based on in-depth analysis, we have identified TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO as very promising candidates for photovoltaic applications.

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Electronic structure, Mechanical and Thermodynamic properties of CoYSb (Y= Cr, Mo, W) half-Heusler compounds as potential spintronic materials

10.21203/rs.3.rs-1033376/v1 ◽

2021 ◽

Author(s):

O. T. Uto ◽

J. O. Akinlami ◽

S. Kenmoe ◽

G. A. Adebayo

Keyword(s):

Density Functional ◽

Electronic Band Structure ◽

Structural Phase ◽

Covalent Bond ◽

Stable Phase ◽

Type I ◽

Generalized Gradient ◽

Electronic Density ◽

Electronic Band ◽

Half Metallic

Abstract The CoYSb (Y = Cr, Mo and W) compounds which are XYZ type half-Heusler alloys and also exist in the face centred cubic MgAgAs-type struc-ture conform to F ̄43m space group. In the present work, these compoundsare investigated in different atomic arrangements called, Type-I, Type-II andType-III phases, using Generalized Gradient Approximation (GGA) in the Density Functional Theory (DFT) implemented in QE (Quantum EspressoAb-Initio Simulation Package). The ferromagnetic state of these alloys is studied after investigating their stable structural phase. The calculated electronic band structure and the total electronic density of states indicated nearly half-metallic behaviour in CoMoSb with a possibility of being used in spintronic application, metallic in CoWSb and half-metallic in CoCrSb, with the minority spin band gap of 0.81 eV. Furthermore, the calculated mechanical properties predicted an anisotropic behaviour of these alloys in the stable phase. Finally, due to its high Debye temperature value, CoCrSb possesses a stronger covalent bond than CoMoSb and CoWSb, respectively.

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Effect of Yb Concentration on the Structural, Magnetic and Optoelectronic Properties of Yb Doped ZnO: First Principles Calculation

10.21203/rs.3.rs-877060/v1 ◽

2021 ◽

Author(s):

Mohamed Achehboune ◽

Mohammed Khenfouch ◽

Issam Boukhoubza ◽

Issam Derkaoui ◽

Bakang Moses Mothudi ◽

...

Keyword(s):

Band Gap ◽

Conduction Band ◽

Density Functional ◽

Blue Shift ◽

First Principles Calculation ◽

Theoretical Research ◽

Generalized Gradient ◽

Functional Theory ◽

Doped Zno ◽

Good Agreement

Abstract Density functional theory-based investigation of the electronic, magnetic, and optical characteristics in pure and ytterbium (Yb) doped ZnO has been carried out by the plane-wave pseudopotential technique with generalized gradient approximation. The calculated lattice parameters and band gap of pure ZnO are in good agreement with the experimental results. The energy band-gap increases with the increase of Yb concentration. The Fermi level moves upward into the conduction band after doping with Yb, which shows the properties of an n-type se miconductor. New defects were created in the band-gap near the conduction band attributed to the Yb-4f states. The magnetic properties of ZnO were found to be affected by Yb doping; ferromagnetic property was observed for 4.17% Yb due to spin polarization of Yb-4f electrons. The calculated optical properties imply that Yb doped causes a blue shift of the absorption peaks, significantly enhances the absorption of the visible light, and the blue shift of the reflectivity spectrum was observed. Besides, a better transmittance of approximately 88% was observed for 4.17% Yb doped ZnO system. The refractive index and the extinction coefficient were observed to decrease as the Yb dopant concentration increased. As a result, we believe that our findings will be useful in understanding the doping impact in ZnO and will motivate further theoretical research.

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