Role of Vacancies in Zigzag Graphene Nanoribbons: An Ab Initio Study

We have studied the effects of vacancies on the structural, electronic and magnetic properties of zigzag-edged graphene nanoribbons (ZGNRs). Our calculations were carried out using an abinitio density functional pseudopotential computational method combined with the generalized gradient approximation for the exchange-correlation functional. The equilibrium geometries, electronic charge spin density distributions, electronic band structures, and magnetic moments were examined in the presence of single vacancy and double vacancies. Structural optimization showed that vacancies induce substantial structural changes in ZGNRs. We found that introducing vacancies into ZGNR changes the spatial distribution of neighbor atoms, particularly those located around the vacancies. Our calculations showed that the vacancies have significant effect on the magnetization of ZGNR. The calculations showed that the changes in the structural geometry, the electronic structure and the magnetization of ZGNR depend on the location of the vacancies with respect to the ribbon edges. These results suggest that vacancy defects can be used to modify the electronic and the magnetic properties of ZGNR.

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DFT Study of Cs/Sr/Ag Adsorption on Defective Matrix Graphite

Science and Technology of Nuclear Installations ◽

10.1155/2020/4921623 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Zengtong Jiao ◽

Xiaotong Chen ◽

Chao Fang ◽

Gang Xu ◽

Chi Zhang ◽

...

Keyword(s):

Point Defects ◽

Electronic Structures ◽

Density Functional ◽

Fission Products ◽

Generalized Gradient ◽

Single Vacancy ◽

Vacancy Defects ◽

Adsorption Behaviors ◽

Matrix Graphite ◽

Adsorption Energies

The geometries, adsorption energies, and electronic structures of Cs, Sr, and Ag atoms on matrix graphite surface with point defects were calculated and analyzed using the density functional theory (DFT) and the Perdew–Burke–Ernzerhof (PBE) formulation of the generalized gradient approximation (GGA). Three different types of point defects, i.e., single vacancy and “bridge” and “spiro” interstitials are considered using approximate van der Waals (vdW) correction methods. The results of adsorption energies show that the metal fission products of Cs, Sr, and Ag are more stable on single vacancy defects than “bridge” or “spiro” interstitial defects. This is further confirmed by the analysis of electronic structures, such as charge density difference (CDD) and density of state (DOS). All these results indicate that dangling bonds play an important role in the adsorption behaviors of metallic fission products on matrix graphite.

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Ab initio calculation on the Optical Properties of AA- Stacked two dimensional Graphene, Silicene, Germanene, and Stanene

International Journal of Computational Physics Series ◽

10.29167/a1i1p46-50 ◽

2018 ◽

Vol 1 (1) ◽

pp. 46-50

Author(s):

Rita John ◽

Benita Merlin

Keyword(s):

Optical Properties ◽

Band Structure ◽

Density Functional ◽

Electronic Band Structure ◽

Complex Refractive Index ◽

Single Layer ◽

Generalized Gradient ◽

Electronic Band ◽

Wide Range ◽

Optical Region

In this study, we have analyzed the electronic band structure and optical properties of AA-stacked bilayer graphene and its 2D analogues and compared the results with single layers. The calculations have been done using Density Functional Theory with Generalized Gradient Approximation as exchange correlation potential as in CASTEP. The study on electronic band structure shows the splitting of valence and conduction bands. A band gap of 0.342eV in graphene and an infinitesimally small gap in other 2D materials are generated. Similar to a single layer, AA-stacked bilayer materials also exhibit excellent optical properties throughout the optical region from infrared to ultraviolet. Optical properties are studied along both parallel (||) and perpendicular ( ) polarization directions. The complex dielectric function (ε) and the complex refractive index (N) are calculated. The calculated values of ε and N enable us to analyze optical absorption, reflectivity, conductivity, and the electron loss function. Inferences from the study of optical properties are presented. In general the optical properties are found to be enhanced compared to its corresponding single layer. The further study brings out greater inferences towards their direct application in the optical industry through a wide range of the optical spectrum.

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First-principles investigation of the electronic band structures and optical properties of quaternary ABaMQ4 (A = Rb, Cs; M = P, V; and Q = S) metal chalcogenides

International Journal of Modern Physics B ◽

10.1142/s021797921850337x ◽

2018 ◽

Vol 32 (30) ◽

pp. 1850337

Author(s):

Shahid Ullah ◽

Hayat Ullah ◽

Abdullah Yar ◽

Sikander Azam ◽

A. Laref

Keyword(s):

Optical Properties ◽

First Principles ◽

Density Functional ◽

Correlation Energy ◽

Electronic Charge ◽

Electromagnetic Spectrum ◽

Metal Chalcogenides ◽

Electronic Band ◽

Charge Densities ◽

Electronic Band Structures

In this paper, we study the optoelectronic properties of quaternary metal chalcogenide semiconductor ABaMQ4 (A = Rb, Cs; M = P, V; and Q = S) compounds using state-of-the-art density functional theory (DFT) with TB-mBJ approximation for the treatment of exchange-correlation energy. In particular, the electronic and optical properties of the relaxed geometries of these compounds are investigated. Our first-principles ab-initio calculations show that the CsBaPS4 and RbBaPS4 compounds have direct bandgaps whereas the CsBaVS4 compound exhibits indirect bandgap nature. Importantly, the theoretically calculated values of the bandgaps of the compounds are consistent with experiment. Furthermore, our analysis of the electronic charge densities of these compounds indicates that the above quaternary chalcogenides have mixed covalent and ionic bonding characters. The effective masses of these compounds are also calculated which provide very useful information about the band structure and transport characteristics of the investigated compounds. Similarly, high absorptivity in the visible and ultraviolet regions of the electromagnetic spectrum possibly predicts and indicates the importance of these materials for potential optoelectronic applications in this range.

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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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First-Principles Study of Interaction of Lithium Atoms with (3, 3) Carbon Nanotubes

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.687-691.4311 ◽

2014 ◽

Vol 687-691 ◽

pp. 4311-4314 ◽

Cited By ~ 1

Author(s):

Shun Fu Xu ◽

Ling Min Li

Keyword(s):

Carbon Nanotubes ◽

First Principles ◽

Density Functional ◽

Vacancy Defect ◽

Single Wall Carbon Nanotubes ◽

Generalized Gradient ◽

Hydrogen Atoms ◽

Functional Theory ◽

Vacancy Defects ◽

Adsorption Mechanisms

In this paper, we have employed first-principles calculations to investigate the adsorption mechanisms of one lithium atom on the sidewalls of 1/2/3 H-adsorbed indefective/defective (3, 3) single-wall carbon nanotubes (CNTs) which have vacancy defects. Our calculations are performed within density functional theory (DFT) under the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhof (PBE).Our results show that the lithium atoms strongly binds to the H-adsorbed (3, 3) nanotube. Lithium atoms can chemically adsorb on (3, 3) nanotube with the vacancy defect (MVD) without any energy barrier. The lithium adsorption will enhance the electrical conductivity of the nanotube. Further more, the structure of the (3, 3) nanotube with the MVD and hydrogen atoms will become more stable after the three kinds of lithium adsorption.

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DEFECT FORMATION AND MAGNETIC PROPERTIES OF COPPER DOPED ZnO NANOWIRES

Modern Physics Letters B ◽

10.1142/s0217984912500819 ◽

2012 ◽

Vol 26 (13) ◽

pp. 1250081 ◽

Cited By ~ 9

Author(s):

LI-BIN SHI

Keyword(s):

Magnetic Properties ◽

Density Functional ◽

Oxygen Vacancies ◽

Defect Formation ◽

Zno Nanowires ◽

Energy Calculation ◽

Generalized Gradient ◽

Total Energies ◽

Doped Zno ◽

P Type

Theoretical calculation based on density functional theory (DFT) and generalized gradient approximation (GGA) has been carried out in studying defect formation energies, ionization energies and magnetic properties of copper doped ZnO nanowires (NW). It is found from formation energy calculation that n-type Cu-doped ZnO NW is non-FM and p-type Cu-doped ZnO NW could be FM. The results show that total energies of FM coupling are lower than those of AFM coupling for majority of 12 configurations, indicating that the FM coupling between Cu atoms is more stable than AFM coupling. The FM stability is interpreted by Cu 3d energy level coupling. In addition, zinc and oxygen vacancies affecting FM coupling is also discussed. It is found that FM coupling can be tuned by zinc and oxygen vacancies.

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Structural, electronic and elastic properties of the B2-ScM (M =Au, Hg and Tl) intermetallic compounds: Ab initio calculations

International Journal of Computational Materials Science and Engineering ◽

10.1142/s2047684115500207 ◽

2015 ◽

Vol 04 (04) ◽

pp. 1550020

Author(s):

Ahmad A. Mousa ◽

Jamil M. Khalifeh

Keyword(s):

Mechanical Properties ◽

Bulk Modulus ◽

Intermetallic Compounds ◽

Elastic Constants ◽

Density Functional ◽

Electronic Band Structure ◽

Local Density ◽

Full Potential ◽

Generalized Gradient ◽

Electronic Band

Structural, electronic, elastic and mechanical properties of ScM (M[Formula: see text][Formula: see text][Formula: see text]Au, Hg and Tl) intermetallic compounds are studied using the full potential-linearized augmented plane wave (FP-LAPW) method based on the density functional theory (DFT), within the generalized gradient approximation (GGA) and the local density approximation (LDA) to the exchange-correlation approximation energy as implemented in the Wien2k code. The ground state properties including lattice parameters, bulk modulus and elastic constants were all computed and compared with the available previous theoretical and experimental results. The lattice constant was found to increase in contrast to the bulk modulus which was found to decrease with every substitution of the cation (M) starting from Au till Tl in ScM. Both the electronic band structure and density-of-states (DOS) calculations show that these compounds possess metallic properties. The calculated elastic constants ([Formula: see text], [Formula: see text] and [Formula: see text] confirmed the elastic stability of the ScM compounds in the B2-phase. The mechanical properties and ductile behaviors of these compounds are also predicted based on the calculated elastic constants.

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Electronic Structure and Ferromagnetic Properties of Doped Calcium Sulfide Ca1−xTMxS (TM = V, Cr and Co)

SPIN ◽

10.1142/s2010324720500137 ◽

2020 ◽

Vol 10 (02) ◽

pp. 2050013 ◽

Cited By ~ 1

Author(s):

Amina Aiche ◽

Abdelkader Tadjer ◽

Hadj Moulay Ahmed Mazouz ◽

Bendouma Doumi ◽

Houari Khachai

Keyword(s):

Magnetic Properties ◽

Electronic Structure ◽

Density Functional ◽

Double Exchange ◽

Ferromagnetic State ◽

Spin Splitting ◽

Full Potential ◽

Generalized Gradient ◽

Metallic Behavior ◽

Half Metallic

The electronic structure and magnetic properties of diluted Ca[Formula: see text]TMxS (TM[Formula: see text][Formula: see text][Formula: see text]V, Cr and Co) in the rocksalt structure at concentrations [Formula: see text], 0.125 and 0.25 were studied using the full-potential linearized augmented plane wave approximation of the density functional theory with the Wu-Cohen generalized gradient approximation (WC-GGA) and the Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential. Features such as lattice constant, bulk modulus, spin-polarized band structures, total and local densities of states and magnetic properties have been computed. The electronic structure show that Ca[Formula: see text](V, Cr)xS at all the studied concentrations and the diluted Ca[Formula: see text]CoxS with [Formula: see text] compounds are half-metallic ferromagnets with spin polarization of 100%. The calculated total magnetic moments for Ca[Formula: see text]VxS and Ca[Formula: see text]CoxS show the same integer value of 3[Formula: see text][Formula: see text] per formula unit and Ca[Formula: see text]CrxS exhibit a total magnetic moment of 4[Formula: see text][Formula: see text], which confirm the half-metallic behavior of these compounds. We also calculated the values of the band edge spin splitting of the valence and conduction bands and the exchange constants. We have found that the ferromagnetic state is stable by the p-d exchange associated with the double-exchange mechanism. The diluted Ca[Formula: see text](V,Cr,Co)xS are found to be new promising candidates for spintronic applications.

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First-Principles Study of the New Half-Metallic Ferromagnetic Quaternary-Heusler Alloys NaXNO (X=Ca, Sr, Ba)

SPIN ◽

10.1142/s2010324720500228 ◽

2020 ◽

Vol 10 (03) ◽

pp. 2050022 ◽

Cited By ~ 1

Author(s):

K. Belkacem ◽

Y. Zaoui ◽

S. Amari ◽

L. Beldi ◽

B. Bouhafs

Keyword(s):

Magnetic Properties ◽

Density Of States ◽

First Principles ◽

Density Functional ◽

Heusler Alloys ◽

Exchange Potential ◽

Energy Calculation ◽

Full Potential ◽

Electronic Band ◽

Half Metallic

The first-principles approach based on density functional theory (DFT) and the full-potential linearized augmented plane-wave method were employed to investigate the structural, elastic, electronic and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. The generalized gradient approximation (GGA) as parameterized by Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson exchange potential were used. As far as we know, we present our results which for the first time quantitatively account for the electronic structures and magnetic properties of Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys. From the total energy calculation using three possible atomic configurations ([Formula: see text], [Formula: see text] and [Formula: see text]), it is found that the Na[Formula: see text]NO ([Formula: see text], Sr and Ba) quaternary half-Heusler alloys are more stable in the ferromagnetic [Formula: see text]-phase. From our estimated elastic constants [Formula: see text], it is found that all the considered Heusler alloys are mechanically stable in the [Formula: see text]-phase. We have also investigated the robustness of the half-metallicity with respect to the variation of lattice constants in these alloys. We have found that these alloys are half-metallic ferromagnets (HMFs) with a magnetic moment of 2[Formula: see text][Formula: see text] per formula unit at their equilibrium volumes. The spin-polarized electronic band structure and density of states of these quaternary half-Heusler alloys calculated by GGA (mBJ-GGA) show that the minority spin channels have metallic nature and the majority spin channels have a semiconductor character with half-metallic gaps of 0.49[Formula: see text]eV (2.17[Formula: see text]eV), 0.72[Formula: see text]eV (2.28[Formula: see text]eV) and 0.96[Formula: see text]eV (2.22[Formula: see text]eV) for NaCaNO, NaSrNO and NaBaNO quaternary half-Heusler alloys, respectively. Analysis of the density of states and the spin charge density of these quaternary alloys indicates that their magnetic moments mainly originate from the strong spin-polarization of 2[Formula: see text] states of N atoms and O atoms.

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Structural, Electronic, and Magnetic Properties of Mn4N Perovskite: Density Functional Theory Calculations and Monte Carlo Study

Journal of Superconductivity and Novel Magnetism ◽

10.1007/s10948-019-05345-9 ◽

2019 ◽

Vol 33 (5) ◽

pp. 1507-1512 ◽

Cited By ~ 1

Author(s):

A. Azouaoui ◽

M. El Haoua ◽

S. Salmi ◽

A. El Grini ◽

N. Benzakour ◽

...

Keyword(s):

Density Functional Theory ◽

Monte Carlo ◽

Magnetic Properties ◽

Density Functional ◽

Density Functional Theory Calculations ◽

Generalized Gradient ◽

Critical Temperatures ◽

Metallic Behavior ◽

Functional Theory ◽

Electronic And Magnetic Properties

AbstractIn this paper, we have studied the structural, electronic, and magnetic properties of the cubic perovskite system Mn4N using the first principles calculations based on density functional theory (DFT) with the generalized gradient approximation (GGA). The obtained data from DFT calculations are used as input data in Monte Carlo simulation with a mixed spin-5/2 and 1 Ising model to calculate the magnetic properties of this compound, such as the total, partial thermal magnetization, and the critical temperatures (TC). The obtained results show that Mn4N has a ferrimagnetic structure with two different sites of Mn in the lattice and presents a metallic behavior. The obtained TC is in good agreement with experimental results.

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