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

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.

scholarly journals Visualizing band structure hybridization and superlattice effects in twisted MoS2/WS2 heterobilayers

2D Materials ◽  
2021 ◽  
Author(s):  
Alfred J. H. Jones ◽  
Ryan Muzzio ◽  
Sahar Pakdel ◽  
Deepnarayanan Biswas ◽  
Davide Curcio ◽  
...  
Keyword(s):  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Twist Angle ◽  
Electronic States ◽  
Single Layer ◽  
Density Functional Theory Calculations ◽  
Layer Transition ◽  
Electronic Band ◽  
Wide Range

Abstract A mismatch of atomic registries between single-layer transition metal dichalcogenides (TMDs) in a two dimensional van der Waals heterostructure produces a moiré superlattice with a periodic potential, which can be fine-tuned by introducing a twist angle between the materials. This approach is promising both for controlling the interactions between the TMDs and for engineering their electronic band structures, yet direct observation of the changes to the electronic structure introduced with varying twist angle has so far been missing. Here, we probe heterobilayers comprised of single-layer MoS2 and WS2 with twist angles ranging from 2° to 20° and determine the twist angle-dependent evolution of the electronic band structure using micro-focused angle-resolved photoemission spectroscopy. We find strong interlayer hybridization between MoS2 and WS2 electronic states at the Γ-point of the Brillouin zone, leading to a shift of the valence band maximum in the heterostructure. Replicas of the hybridized states are observed at the centre of twist angle-dependent moiré mini Brillouin zones. We confirm that these replica features arise from the inherent moiré potential by comparing our experimental observations with density functional theory calculations of the superlattice dispersion. Our direct visualization of these features underscores the potential of using twisted heterobilayer semiconductors to engineer hybrid electronic states and superlattices that alter the electronic and optical properties of 2D heterostructures for a wide range of twist angles.

scholarly journals An ab-initio study on structural, elastic, electronic, bonding, thermal, and optical properties of topological Weyl semimetal TaX (X = P, As)

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. I. Naher ◽  
S. H. Naqib
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Fermi Level ◽  
Density Of States ◽  
Electronic Band Structure ◽  
Optical Parameters ◽  
Electronic Density ◽  
Electronic Band ◽  
Wide Range ◽  
Weyl Semimetals

AbstractIn recent days, study of topological Weyl semimetals have become an active branch of physics and materials science because they led to realization of the Weyl fermions and exhibited protected Fermi arc surface states. Therefore, topological Weyl semimetals TaX (X = P, As) are important electronic systems to investigate both from the point of view of fundamental physics and potential applications. In this work, we have studied the structural, elastic, mechanical, electronic, bonding, acoustic, thermal and optical properties of TaX (X = P, As) in detail via first-principles method using the density functional theory. A comprehensive study of elastic constants and moduli shows that both TaP and TaAs possesses low to medium level of elastic anisotropy (depending on the measure), reasonably good machinability, mixed bonding characteristics with ionic and covalent contributions, brittle nature and relatively high Vickers hardness with a low Debye temperature and melting temperature. The minimum thermal conductivities and anisotropies of TaX (X = P, As) are calculated. Bond population analysis supports the bonding nature as predicted by the elastic parameters. The bulk electronic band structure calculations reveal clear semi-metallic features with quasi-linear energy dispersions in certain sections of the Brillouin zone near the Fermi level. A pseudogap in the electronic energy density of states at the Fermi level separating the bonding and the antibonding states indicates significant electronic stability of tetragonal TaX (X = P, As).The reflectivity spectra show almost non-selective behavior over a wide range of photon energy encompassing visible to mid-ultraviolet regions. High reflectivity over wide spectral range makes TaX suitable as reflecting coating. TaX (X = P, As) are very efficient absorber of ultraviolet radiation. Both the compounds are moderately optically anisotropic owing to the anisotropic nature of the electronic band structure. The refractive indices are very high in the infrared to visible range. All the energy dependent optical parameters show metallic features and are in complete accord with the underlying bulk electronic density of states calculations.

FIRST PRINCIPLE CALCULATION OF ELECTRONIC BAND STRUCTURE AND OPTICAL PROPERTIES OF KIO3

2009 ◽  
Vol 23 (10) ◽  
pp. 2405-2412
Author(s):  
HARUN AKKUS ◽  
BAHATTIN ERDINC
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Electronic Band ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
Functional Methods ◽  
A Value ◽  
Direct Band

The electronic band structure and optical properties of the ferroelectric single crystal KIO 3 have been investigated using the density functional methods. The calculated band structure for KIO 3 evidences that the crystal has a direct band gap with a value of 2.83 eV. The structural optimization has been performed. The real and imaginary parts of dielectric function, energy-loss function for volume and surface, and refractive index are calculated along the crystallographic axes.

BAND STRUCTURE, HARDNESS, THERMODYNAMIC AND OPTICAL PROPERTIES OF SUPERCONDUCTING Nb2AsC, Nb2InC AND Mo2GaC

2013 ◽  
Vol 02 (02) ◽  
pp. 1350007 ◽  
Author(s):  
M. A. HADI ◽  
M. S. ALI ◽  
S. H. NAQIB ◽  
A. K. M. A. ISLAM
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Vickers Hardness ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Population Analysis ◽  
Debye Model ◽  
Electronic Band ◽  
Specific Heats ◽  
First Time

First-principles investigation of the geometry, electronic band structure, Vickers hardness, thermodynamic and optical properties of three superconducting MAX compounds Nb 2 AsC , Nb 2 InC and Mo 2 GaC have been carried out by the plane-wave pseudopotential method based on density functional theory (DFT) implemented in the CASTEP code. The theoretical Vickers hardness has been studied by means of Mulliken bond population analysis and electronic densities of states. The thermodynamic properties such as the temperature and pressure dependent bulk modulus, Debye temperature, specific heats and thermal expansion coefficient of the three 211 MAX phases are derived from the quasi-harmonic Debye model with phononic effect for the first time. Furthermore, all the optical properties are determined and analyzed for the first time for two different polarization directions. The theoretical findings are compared with relevant experiments (where available) and the various implications are discussed in details.

scholarly journals First principle study of structural, elastic, electronic and optical properties of Pb0.5Sn0.5TiO3 and Pb0.5Sn0.5Ti0.5(Zr0.5)O3

2021 ◽  
Vol 24 (1) ◽  
pp. 13702
Author(s):  
S.G. Kuma ◽  
M.M. Woldemariam
Keyword(s):  
Optical Properties ◽  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Theoretical Data ◽  
Poisson's Ratio ◽  
Modern Theory ◽  
Generalized Gradient ◽  
Electronic Band

The structural, electronic, elastic and optical properties of tetragonal (P4mm) phase of Pb0.5Sn0.5TiO3 (PSTO) and Pb0.5Sn0.5Ti0.5(Zr0.5)O3 (PSTZO) are examined by first-principles calculations based on the density functional theory (DFT) using the pseudo-potential plane wave (PP-PW) scheme in the frame of generalized gradient approximation (GGA). We have calculated the ground state properties such as equlibrium lattice constants, volume, bulk modulus and its pressure derivative. From elastic constants, mechanical parameters such as anisotropy factor, elastic modulus and Poisson's ratio are obtained from the Voigt-Reuss-Hill average approximation. Rather than their averages, the directional dependence of elastic modulus, and Poisson's ratio are modelled and visualized in the light of the elastic properties of both systems. In addition, some novel results, such as Debye temperatures, and sound velocities are obtained. Moreover, we have presented the results of the electronic band structure, densities of states and charge densities. These results were in favourable agreement with the existing theoretical data. The optical dielectric function and energy loss spectrum of both systems are also computed. Born effective charge (BEC) of each atoms for both systems is computed from functional perturbation theory (DFPT). Finally, the spontaneous polarization is also determined from modern theory of polarization to be 0.8662 C/m2 (PSTO) and 1.0824 C/m2 (PSTZO).

Establishment of Structural and Elastic Properties of Titanate Compounds Based on Pb, Sn and Ge by First-Principles Calculation

2014 ◽  
Vol 510 ◽  
pp. 57-62 ◽  
Author(s):  
N.H. Hussin ◽  
M.F.M. Taib ◽  
N.A. Johari ◽  
F.W. Badrudin ◽  
O.H. Hassan ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Structure ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Computer Code ◽  
Lattice Parameter ◽  
First Principles Calculation ◽  
Electronic Band ◽  
Equilibrium Lattice Parameter ◽  
Indirect Band Gap

Structural, electronic, and optical properties of PbTiO3, SnTiO3, and GeTiO3 tetragonals (P4mm, 99 space group) were investigated using density functional theory as implemented in pseudo-potential plane wave in CASTEP computer code. The calculated equilibrium lattice parameter, electronic band structure, and optical properties for PbTiO3 (reference compound) are in good agreement with the available experiment data. The result also shows that GeTiO3 has a higher tetragonality (c/a=1.18) compared with SnTiO3 (c/a=1.15) and PbTiO3 (c/a=1.05). Calculations of the elastic constants of PbTiO3, SnTiO3, and GeTiO3 tetragonals show that they are mechanically stable. The electronic band structure shows that PbTiO3 has higher indirect band gap at X-G compared with SnTiO3 and GeTiO3, as explained in detail by the optical properties of ATiO3 (A=Pb, Sn, Ge) through the refractive index and absorption coefficient.

scholarly journals Ni-rich Nitrides ANNi3 (A = Pt, Ag, Pd) in Comparison with Superconducting ZnNNi3

2011 ◽  
Vol 4 (1) ◽  
pp. 1 ◽  
Author(s):  
M. A. Ali ◽  
A. K. M. A. Islam ◽  
M. S. Ali
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Generalized Gradient ◽  
Band Structures ◽  
Electronic Band ◽  
Metallic Behavior ◽  
Reflectivity Spectra ◽  
Densities Of States ◽  
Parameter Values

This article reports on the elastic, electronic and optical properties of predicted Ni-rich nitrides ANNi3 (A= Pt, Ag, Pd) in comparison with isostructural superconducting counterpart ZnNNi3. We have used first-principles density functional theory (DFT) with generalized gradient approximation (GGA). The independent elastic constants (C11, C12, and C44), bulk modulus B, compressibility K, shear modulus G, and Poisson’s ratio υ, as well as the band structures, total and partial densities of states and finally the optical properties of ANNi3 have been calculated. The results are then analyzed and compared with those of the superconducting ZnNNi3. The electronic band structures of the three compounds show metallic behavior with a high density of states at the Fermi level in which Ni 3d states dominate just like the superconducting ZnNNi3. Analysis of Tc expression using available  parameter values suggests that the three compounds are less likely to be superconductors. Optical reflectivity spectra indicate that all the compounds have the potential to be used as a coating to remove solar heating.Keywords: ANNi3; Ab initio calculations; Elastic properties; Electronic band structure; Optical properties.© 2012 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved.doi: http://dx.doi.org/10.3329/jsr.v4i1.9026J. Sci. Res. 4 (1), 1-10 (2012)

AB INITIO APPROACH TO STRUCTURAL, ELECTRONIC AND OPTICAL PROPERTIES OF B-, C- AND N-DOPED ANATASE

2010 ◽  
Vol 24 (31) ◽  
pp. 6049-6067 ◽  
Author(s):  
V. P. ZHUKOV ◽  
V. M. ZAINULLINA ◽  
E. V. CHULKOV
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Band Structure ◽  
Crystal Lattice ◽  
Ab Initio ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Impurity Band ◽  
Theory Approach ◽  
Electronic Band

The effect of doping with boron, carbon and nitrogen on crystal lattice parameters, electronic band structure and optical absorption of anatase has been studied by means of an ab initio density functional theory approach. The investigations included optimization of crystal structure based on the pseudo-potential plane-wave approach. The spin-polarized calculations of the band structure with the account of on-site Coulomb correlations (LSDA+U) employing the tight-binding linear muffin-tin orbitals method (TB-LMTO) have also been performed. The evaluations of optical absorption were based on the calculations of dielectric function with local field effects taken into account. We find that the crystal lattice relaxation around the doping atoms produces noticeable changes in the band structure, magnetic state and optical properties of the doped compounds. The most considerable effects are the collapse of magnetic moment on carbon atom and an essential reduction of the optical absorption in the region of the impurity band — impurity band transitions. Comparing optical absorption for different kinds of doping and taking into account the intensity distribution of the solar light we come to the conclusion than the doping with boron is the most promising kind of doping for photocatalytic applications of the doped anatase.

DFT-BASEDAB INITIOSTUDY OF THE ELECTRONIC AND OPTICAL PROPERTIES OF CESIUM BASED FLUORO-PEROVSKITECsMF3(M = CaANDSr)

2012 ◽  
Vol 26 (32) ◽  
pp. 1250199 ◽  
Author(s):  
M. HARMEL ◽  
H. KHACHAI ◽  
M. AMERI ◽  
R. KHENATA ◽  
N. BAKI ◽  
...  
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Local Density ◽  
Theoretical Data ◽  
Full Potential ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Electronic And Optical Properties ◽  
Structure Density

Density functional theory (DFT) is performed to study the structural, electronic and optical properties of cubic fluoroperovskite AMF3( A = Cs ; M = Ca and Sr ) compounds. The calculations are based on the total-energy calculations within the full-potential linearized augmented plane wave (FP-LAPW) method. The exchange-correlation potential is treated by local density approximation (LDA) and generalized gradient approximation (GGA). The structural properties, including lattice constants, bulk modulus and their pressure derivatives are in very good agreement with the available experimental and theoretical data. The calculations of the electronic band structure, density of states and charge density reveal that compounds are both ionic insulators. The optical properties (namely: the real and the imaginary parts of the dielectric function ε(ω), the refractive index n(ω) and the extinction coefficient k(ω)) were calculated for radiation up to 40.0 eV.

ELECTRONIC AND ELASTIC PROPERTIES OF ZINC-BLENDE MgSe

2013 ◽  
Vol 27 (09) ◽  
pp. 1350027 ◽  
Author(s):  
B. I. ADETUNJI ◽  
P. O. ADEBAMBO ◽  
J. O. AKINLAMI ◽  
G. A. ADEBAYO
Keyword(s):  
Band Structure ◽  
Elastic Properties ◽  
Cohesive Energy ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Electronic Band Structure ◽  
Density Of State ◽  
Generalized Gradient ◽  
Electronic Band ◽  
Zinc Blende

In the present study, ground state and elastic properties of semiconductor MgSe in zinc-blende phase are investigated using density functional theory (DFT). Exchange-correlation potentials are approximated with the generalized gradient approximation (GGA). From the calculated bulk modulus, we determine the refractive index, plasmon energy, cohesive energy and micro-hardness of the MgSe semiconductor binary alloy. The density of state (DOS), projected density of state (PDOS), phonon dispersion frequencies, charged density, electronic band structure and dielectric functions are also reported. From the band structure, a direct band gap of 2.50 eV was observed in close agreement with other reported calculations, but lower than the experimental value of 3.60 eV. Along the high symmetries directions, we found a striking resemblance between MgSe and a III–V semiconductor, while the high cohesive energy in MgSe suggests filled bonding orbitals which might result in decrease in atomic volume with corresponding increased compression of the s-orbitals under any transition series.

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