PBE-GGA Approximations Research Articles

Theoretical investigations of structural, electronic, magnetic, and optical properties of group V (X = V, Nb, Ta) added CeO2-X materials for optoelectronic applications.

Depletion of natural resources, responsible for energy production, is a serious concern for researchers to develop alternate energy resources or materials. Scientists have proposed various energy materials which are based on semiconductors and their underlying physics. Cerium oxide (CeO2) is a versatile energy material which receives much attention owing to excellent photocatalytic, photonic, thermal stability, and optoelectronic applications. Even though CeO2 exhibited remarkable physical properties, but yet, they can be enhanced upon suitable doping. Focus on current research is to dope group V elements into CeO2 in order to enhance its electronic and optical response. The density of states (DOS) and band gaps of proposed materials are calculated, and significant improvement is noted after applying TB-mbj method. Optical absorption spectra of V/Nb/Ta-doped CeO2 show blueshift and decrease in reflectivity along with the presence of magnetism illustrate potential uses of these materials in future UV optoelectronics, spintronics, sensing, and energy harvesting devices. This research is based on computational work carried using Wien2k code where PBE-GGA approximation is used to approximate exchange and correlation potentials. Supercells of vanadium/niobium/tantalum-doped CeO2 are constructed, and spin-polarized density of states (DOS) along with optical constant are calculated. TB-mbj method is used to bring improvements in DOS and band gaps of proposed materials. Iterations are conducted using convergence criterion, and non-relativistic calculations are performed.

DFT investigations of structural, electronic, magnetic, and optical properties of CeO2-X (X=Mo/Cr) and Mo-Cr co-doped CeO2 for optoelectronic applications

Current research elucidate investigations on calculating the structural, electronic, magnetic, and optical properties of Mo/Cr doped CeO2 and Mo-Cr co-doped CeO2 using the Wien2k code. The exchange-correlation functional is approximated using the PBE-GGA approximation. Spin-polarized DOS present the magnetic character of proposed materials. A higher magnetic moment (3.749 μB) is noticed for Mo-Cr@CeO2 while lower magnetic moment (2.247 μB) is observed for Mo@CeO2 material. The Ce 4f-, O 2p-, Mo 3d-, and Cr 3d-states appreciably tune electronic properties. Absorption spectra of Mo@CeO2 and Mo-Cr@CeO2 materials exhibit blueshift, while Cr@CeO2 material shows redshift. Curie temperature indicates spintronic applications of these materials. Enhanced conductivity, improved dielectric response, and decreased reflectivity of proposed materials in the UV region implicate their uses in high-frequency UV optoelectronics, photovoltaics, spintronics, photonics and capacitive devices.

First-principles investigation of structural electronic magnetic and thermodynamic properties of CdS alloyed with Co transition metal

This research work investigates the structural, electronic, and magnetic properties of Cd1–xCoxS compounds. The supercells with 16 atoms have been studied by substituting a Cd atom with a Co atom in the cubic unit cell CdS from x = 0 to x = 1 in a Zinc-Blende structure based on the first principles of spin-polarized density functional theory as implemented in the WIEN2k code. The full potential augmented plane wave method FP-LAPW (Full potential linear augmented plane wave) was used in this study to evaluate the structural properties of the compounds, the exchange–correlation term is based on the PBE-GGA (Perdew–Burke–Ernzerhof generalized gradient approximation). For other properties, such as electronic structures, densities of states, and magnetic properties, the TB-mbj GGA (Tight Binding modified Becke–Johnson) exchange potential approximation is utilized. In addition to these properties, the thermodynamic properties were added advantage to clarify their comportment as temperature variation. The analysis of the density of spin-polarized states showed the ferromagnetic character with a from x = 0.125 to x = 0.875. The calculated total magnetic moments of Cd1–xCoxS are addressed concerning the change in lattice parameters. To track the shift brought on by adding Co, we ran our calculationsfrom x = 0.125 to x = 0.875 for Cd1–xCoxS compounds. Hence, the negative energyformation indicates that our compound can be made experimentally. The material may be used for solar cell applications. In summary, our findings represent a guide for future research. The findings of this work might provide useful direction for the usage of this alloy system in a variety of device applications, For example in high-efficiency tandem solar cells, magnetic sensors, and photoconductive detector applications.

Investigation of Zinc and Chromium Substitution Nickel-rich LiNi1−x−yZnyCrxO2 Cathode Materials to Improve the Redox Reaction of Lithium-ion Battery: A First-principles Study

First-principles calculations are employed to investigate the structural, electronic, magnetic, thermoelectric, and electrochemical characteristics of Nickel-rich layered cathodes by substitution of Zn and Cr such as LiNi1−x−yZnyCrxO2 (with x = 0.00, 0.16 and 0.32, y = 0.00 and 0.16). The structure of pure LiNiO2 and substituted are organized in a trigonal arrangement inside the P3m1 space group. Using PBE-GGA approximation, the spin-polarized calculation of pure LiNiO2 in a spin-down channel exhibits a band gap of 0.48 eV. Whereas, Zn and Cr substitution results in the band gap reduction to zero, and metallic behavior is observed. Electronic charge density calculation Ni(Zn, Cr)-O reveals covalent bonding. In electrochemical investigation, by the increasing substitution concentration of Zn and Cr in LiNi1−x−yZnyCrxO2 significant improvements are observed at 4.65–3.89 V potential with a good theoretical discharge capacity of 48–246 mAhg−1. The exchange constants N∘α and N∘β demonstrate negative values that validate the ferromagnetic nature of substituted material. The thermoelectric parameters have been determined using the BoltzTraP code and the highest ZT value of 0.35 is obtained for LiNi0.52Zn0.16Cr0.32O2. These results offer a new perspective on the potential of doping techniques for Nickel-rich cathode materials, providing helpful insight for the development of high-performance cathodes for Lithium-ion battery applications.

Investigation of ordered dispersive effect, charge density, thermal properties and disappearance of spin polarization in perovskite CsBeO3 under the influence of pressure-A DFT perspective

Full Potential Linearized Augmented Plane Wave method (FP-LAPW) was employed to investigate the behavior of cubic perovskite CsBeO3 under the influence of pressure. The spin polarized study has been carried out in PBE-GGA approximation under the application of pressure. The variation of pressure is attained by the appropriate reduction of volume for the compound. At equilibrium volume and at 0 GPa, the compound CsBeO3 is found to exhibit energy gap in the spin up direction and the spin down direction is largely conducting. With the reduction of volume and their corresponding increase in pressure, the electronic behavior changes for the compound. At a pressure of about 10 GPa, the s-orbital of Cs atom undergoes energy excitation to higher energy level due to an ordered dispersive effect at s-orbital. This results in the disappearance of energy gap and the compound becomes conducting in spin up direction and the half metallic ferromagnetism is found to disappear at increased pressure. Thermal properties such as Debye temperature and Curie point have been reported in this work. Elastic constants and anisotropy factor have been determined and compared at different pressures.

Exploring structural, electronic, magnetic, and optical response of GaN-X (X=Sr, ba, cs, mg) materials for optoelectronic applications

This research explores the structural, electronic, magnetic, and optical properties of GaN-X (X = Sr, Ba, Cs, Mg) materials. First principle calculations based on full potential linearized augmented plane wave (FP-LAPW) method is executed in Wien2k code. PBE-GGA approximation is used to approximate exchange-correlation functional. Sr 3d-states, Ba 5p-states, Cs 5p-states, and Mg 2p-states help in improving electronic properties. The magnetic character of the proposed materials is revealed with net magnetic moment values of, 2.9639 μB, 2.3316 μB, 3.4179 μB, and 3.1697 μB, respectively. Optical absorption shows blueshift for Ba@GaN and Mg@GaN while Sr@GaN and Cs@GaN spectra show redshift. Absorption and conductivity are enhanced in the UV region, along with decrease in reflectivity. Optical response of proposed materials illustrate to make use of these materials for production of high energy UV optoelectronics, photonics, memory, spintronics and photovoltaic devices.

First-principles study of potassium-based novel chalcogenide materials for optoelectronic and thermoelectric devices

The structural, electronic, optical, and thermoelectric natures of potassium-based ternary KAuY (Y = S, Se, and Te) materials are studied by employing density functional theory calculations. The LDA and PBE-GGA approximations were used to properly address the strongly correlated electron complexes. The ground-state energies, cohesive energies, and specifically the computed formation energy calculation predicted their stable nature. The calculated electron-effective mass of KAuTe was lower as compared to KAuS and KAuSe suggesting the presence of non-uniformity in energy bands at the conduction band minimum (CBM). The broader energy band gaps display the existence of firmly covalent bonds. The computed band structures calculation well supports their density of states calculations and validates the semiconductor nature of these materials. Moreover, optical constants such as the two components of the complex dielectric function, energy loss functions, absorption coefficients, reflectivity, and refractive index spectra are calculated and also explained for their potential usage in optoelectronic devices. The vital thermoelectric features are computed that suggest the studied material systems’ potential in the thermoelectric application. Principally, the present work would aid in the advancement of integrated and diverse semiconductors for high technological devices.

First-principles calculations of structural, electronic, optical and thermoelectric properties of doped binary chalcogenides Sn1-xAxSe (A= Au and Ag) for energy applications

The first-principles based DFT calculations were used to investigate the effect of transition metal (TM) doping on structural, electronic, optical and thermoelectric properties of Sn1-xAxSe (A = Au and Ag). The PBE-GGA approximation is used to calculate ground state properties of TM doped SnSe. These compounds show the presence of type-II intermediate band (IB) at Fermi level. A considerable energy bandgap is present between IB and conduction band. Significant contributions from Ag/Au and Se-atom in valence bands of Sn1-xAxSe (A = Au and Ag) are evident from presented DOS spectra. The calculated Fermi surfaces and Seebeck coefficient (S) confirms p-type nature of these semiconductors. From ε2(ω) spectra, it is evident that Sn1-xAxSe (A = Au and Ag) absorbs maximum number of incident photons in infrared (at ∼0.5 eV) and visible (at ∼2.2 eV) regions. The calculated values of n(ω) are 2.27 and 2.58 for Sn1-xAgxSe and Sn1-xAuxSe, respectively. We can confirm that Sn1-xAxSe (A = Au and Ag) are promising candidates for energy applications (especially solar cells) based on their optoelectronic and thermoelectric properties.

Investigation of stress-induced effects on structural, optoelectronic, and elastic characteristics of cubic CaHfO3 perovskite oxide; A DFT study

Perovskite oxide being a fascinating class of perovskite materials, captured the significant attention of the scientific community in diverse fields due to its intriguing features. A cubic Calcium Hafnium Oxide (CaHfO3) perovskite supercell was designed using a DFT approach within the CASTEP framework with PBE-GGA approximation. The primary objective was to thoroughly investigate the effect of varying applied stress (0–160 GPa) on the structural, optoelectronic, and elastic characteristics in detail for appropriate device application. Findings reveal that with increasing stress levels, no phase transformation occurs, and cubic structure remains intact, as confirmed from the XRD profile, while a reduction in lattice parameters and volume of the unit cell is observed. Moreover, the optical analysis reveals the reduction in the band gap from 3.170 to 2.299, unveiling the narrow as the stress level rises. Additionally, optical characteristics showed that stress influences optical behaviour, resulting in low loss function, high absorption, high conductivity, and low reflectivity. The elastic constants and their derived parameters were investigated in this study. The results indicate that the material exhibits a ductile nature and anisotropy, as evidenced by Poisson's ratio, Cauchy pressure, and Frantsevich ratio. Notably, the mechanical stability of the material is maintained even as the stress level increases (0, 40, 80, and 120 GPa). These comprehensive findings contribute to a deeper understanding of stress-induced effects on perovskite oxides, offering valuable insights for their potential application and opening new avenues for experimental researchers by bridging the gap between theory and practical implementation for next-generation real practice in diverse fields.

A DFT theoretical and experimental study of the effect of indium doping within electrochemical deposited ZnO

The effect of indium doping within ZnO-NRs nanorods on FTO substrates was studied using integrated theory and experiments. The electrochemical deposited In-ZnO NRs were examined by X-ray diffraction (XRD), Scanning electron microscopy (SEM), UV–vis spectrophotometer, electrochemical cell, and Photocurrent spectroscopy. The obtained electronic and optical characteristics of the developed ZnO and In-ZnO films were validated by density functional theory (DFT) calculations using the TB-mBJ and PBE-GGA approximations. XRD patterns demonstrate that all electrodeposited films were crystalline having a hexagonal wurtzite with a preferred growth orientation (002). Furthermore, the crystallite particle size and (002) diffraction peak intensity of the samples reduces with In doping, suggesting a reduction in crystallinity with increasing indium. SEM images reveal a nicely defined hexagonal shape morphology of pure and In-doped ZnO nanorods, with an approximate mean diameter of ∼100 nm. UV spectrophotometry experiments and DFT calculations showed that the inclusion of In leads to a minor reduction in the optical gap energy. Mott-Schottky analysis displays an improvement in the conductivity attributed to an enhanced electronic injection in In-ZnO the conduction band, thus enhancing the photoelectrochemical properties of the zinc oxide film.

Insight on structural, electronic and thermoelectric properties of perovskite AgBaCl3 by an Ab-initio for solar cell and renewable energy

The physical properties of the Ag-based perovskite compound AgBaCl3 has been studied utilizing FP-LAPW approach as embedded in WIEN2k code. The PBE-GGA approximation has been considered for the structural optimization. The structural and thermodynamical stability of the studied AgBaCl3 is confirmed from its tolerance factor, formation energy and cohesive energy. The band structure and density of states are estimated for electronic characteristics, proving the semiconductor nature, with indirect band gap values for PBE-GGA of 1.8 eV. The optical characteristics of the AgBaCl3 are studied in terms of the real and imaginary dielectric function, refractive index and reflectivity The thermoelectric properties of the compounds are studied at a temperature range of 0–1200 K with temperature. The high-power factor of the studied compound reveals its potential application in thermoelectric devices.

First-principles study on crystal structures and bulk modulus of CuInX2 (X = S, Se, S-Se) solar cell absorber

Chalcopyrite semiconductors are widely used as absorbers in thin film solar cells, especially flexible solar cells, due to their high power conversion efficiency. They also have interesting mechanical properties, making them promising materials for flexible, light, and thin solar cells. In this work, we report the first-principle calculations of the lattice constant and bulk modulus for CuInS2, CuInSe2, and CuIn(S,Se)2 absorber solar materials. All calculations are performed using plane wave as implemented in the Quantum ESPRESSO software package in the framework of density functional theory using PBE-GGA approximations and ultrasoft pseudopotentials. The calculated lattice constant correlates well with the available experimental study. The energy-volume and pressure-volume relations are described using the third order of Birch-Murnaghan’s equation of state to calculate the bulk modulus of the absorber solar material, which is associated to the hardness of a material under particular conditions. The values of bulk modulus obtained for CuInS2 and CuInSe2 are in good agreement with available theoretical results, except for CuIn(S,Se)2, which have been calculated and reported for the first time.

Structural, electronic and optical study of Zr:CeO2 thin films by computational and experimental approach

Transition metal oxide shows some exceptional optical and electronic properties explore in recent investigations. In this context, the current study presents first principal and experimental investigations of pure and Zr doped CeO2 thin films. The simulations were performed using density functional theory based Wien2k-code with PBE-GGA approximation. The uniform and well-distributed granular thin films were grown for experimental investigations. The simulations and experimental results show a good resemblance in outcomes. The density of states predicts the p-d hybridization between Ce and O atoms while band structure reduce with Zr incorporation in CeO2 structure. Crystallographic analysis reveals the presence of crystalline cubic phase with space-group 225-F-m3m in thin films. Experimentally observed bandgap follows the reducing trend with Zr incorporation as predicted by simulations data and found as 2.38 eV for pure CeO2 and 1.51 eV for 6.25% Zr doping content. Optical parameters were recorded as a function of photon energy which strongly influenced by Zr concentration. The sharp increase in optical absorption and real part of dielectric constant in Zr containing composition makes these materials more efficient and favorable for photovoltaic and optoelectronic applications.

Buckling variation effects on optical and electronic properties of GeP2S nanostructure: a first-principles calculation

In this study, by using the first-principles calculations based on density functional theory (DFT), the electronic aspects of GeP2S monolayer under the effect of buckling variation parameter (μ = 0, 2, 4, 6) are theoretically investigated by the PBE-GGA approximation method, and the obtained results have been compared with previous similar structures. The imaginary part of the dielectric function and absorption spectra is presented for in-plane and out-of-plane polarization of GeP2S monolayer by PBE, HSE06, and TD-HSE06 methods. Also, optical aspects for this 2D nanostructure are presented in out-of-plane polarization under buckling variation conditions up to μ = 6. It was shown that particularly for the range of visible light spectrum its optical behaviors match with its electronic ones. Consequently, the obtained results suggest GeP2S as a suitable material for designing optoelectronic devices.

Exploring structural, electronic, optical, and magnetic properties of Os doped and Os-Mn/Ru co-doped GaN

In current research, we study the effect of Os and Os-Mn/Ru co-doping onto the GaN. We study the electronic structure, optical, and magnetic properties of these materials. We employ the PBE-GGA approximation in the Wien2k code using density functional theory. The study of electronic properties reveals that Mn 3d-states, Ru 4d-states and Os 5d-states highly influence the transfer of electrons from valence to conduction band. The Os-Mn/Ru co-doping turns GaN magnetic while Os doping does not alter non-magnetic character of GaN. Optical absorption spectra shows blueshift upon adding impurities and materials shows good absorption in the UV region. A decrease in reflectivity and increase in conductivity in the high energy UV region reveals that these materials may be used for fabrication of devices in the field of photonic, optoelectronic, photovoltaics, solar cells, photodetectors, and power electronics.

Exploring structural, electronic, optical, magnetic, and thermoelectric properties of Pt doped and Pt-Cu/Au co-doped GaN

We present a computational research on investigating the structural, electronic, optical, magnetic, and thermoelectric properties of Pt doped and Pt-Cu/Au co-doped GaN using the Wien2k code. The PBE-GGA approximation is employed in Wien2k code using density functional theory. Study of electronic properties reveals that the d-states of Pt, Cu, and Au atoms participate actively in transferring electron from valence to conduction band and their addition as mono and co-doped formation turns the non-magnetic character of GaN to magnetic. A blueshift in absorption spectrum appear and absorption is more pronounced for Pt-Cu/Au co-doped GaN, suggesting the use of these materials for high energy UV optoelectronics, spintronics, photonic, and sensing devices. However, lower reflection and enhanced conductivity of Pt-Cu/Au co-doped materials in the UV region extends their potential applications in high frequency electronics. Moreover, higher ZT value of Pt@GaN suggest it a better thermoelectric source other than Pt-Cu/Au@GaN.

A study on the electronic properties of A site and B site doped SrTiO3 for thermoelectric applications using first-principles calculations

In SrTiO3, the nature of dopants and their substitution at the A or B site becomes a critical factor in determining the electrical conductivity, Seebeck coefficient, and thermal conductivity. The electronic band structure and the density of states (DOS) for the ab-initio study using different dopants were estimated using PBE-GGA approximation. The size, site of substitution, and nature of dopants cause significant changes in the lattice dimensions, band structure, band curvatures, and the density of states, which reflect as changes in the effective mass The effective mass is calculated from the curvature of the bottom-most conduction band using the one-band effective mass approximation. Pentavalent substitutions on the B site of SrTiO3 affect the conduction band’s curvature differently than with trivalent substitutions on the A site. They also exhibit an opposite trend in the change in band curvature according to the dopant’s ionic radius. In contrast, isovalent dopants showed no change in the band curvature except for the bandgap modification. In this paper, we have provided a semi-quantitative understanding regarding the thermoelectric properties like conductivity and Seebeck coefficient that get affected due to the substituent’s nature and site at which it substitutes.

Computational and experimental investigations on electronic and optical response of oxygenated MoS2

The current study is concerned with the first principle investigations of the oxygenated MoS2 to explore the electronic and optical properties. We consider various oxygen concentrations (MoS2, MoS1.75O0.25, MoS1.5O0.5, MoSO) for the prediction of its impact on parameters using PBE-GGA approximation. A noticeable change in parameters has been observed in the visible regime with the introduction of oxygen content in the MoS2 structure. The results of the electronic properties suggest a string role of Mo d-states, S p-states, and O p-states which, however, show variations for various O concentrations near the Fermi level. The optical absorption spectra for oxygenated MoS2 show a blue shift in the visible range compared to the pure MoS2. The effect of oxygen can also be seen in the experimentally prepared MoS2 thin films as the variation of optical behavior can be seen. Refractive index decreases from 2.5 to ∼2. Similarly, absorption graphs show a lack of absorption phenomenon as the oxygen content increases. The role of oxygen brings appreciable changes in the optical parameters over the different energy ranges.

First-Principles Investigation of structural, Optical, and Electrical properties of MgO Nanocrystals

Nanocrystal interfaces can strongly influence the optical and electrical properties and charging trapping phenomena observed on oxide nanocrystal ensembles. The well-defined shape and controllable size distributions of MgO nanocrystals are a convenient system for studying these effects. Therefore, in the present work focused on the effect of temperature on the optical and electrical properties of magnesium oxide (MgO) nanocrystals, together with the responsible atomic centers, the bulk MgO is a study based on the first principle functional density theory (DFT) using PBE-GGA approximations. The absorption coefficient shows that MgO shows good coverage in the ultraviolet range. The bulk MgO is a direct bandgap nanocrystal at G point in the Brillion Zone despite the temperature applied values. The temperature is applied to alter the bandgap pattern and closes the bandgap at a high temperature. The PDOS and imaginary part of the dielectric function further confirm the insulator properties of the observed bandgap. Our results show that the optical properties are affected by the inconsistent temperature manners despite the different temperatures given to the system. Our absorption curve confirms that the nanocrystal is a good candidate for ultraviolet device application with a significantly high reflectivity percentage.

Structure stability, half metallic ferromagnetism, magneto-electronic and thermoelectric properties of new zintl XCr2Bi2 (X=Ca, Sr) compounds for spintronic and renewable energy applications

Employing full-potential linearized augmented plane waves (FP-LAPW) methods, the structural stability, electronic nature, magnetic and thermoelectric properties of XCr2Bi2 (X = Ca, Sr) were theoretically investigated for the first time. The structure stability of these materials was confirmed by formation energy and cohesive energy. Based on its electronic properties, the energy band gaps were decreased from 1.55 eV to 1.53 eV and from 1.93 eV to 1.6 eV for CaCr2Bi2 and SrCr2Bi2 respectively in the spin down channel in the valence band regime, when we used GGA + U instead of PBE-GGA approximation. The calculated magnetic optimization and larger magnetic moments shows strong ferromagnetism in these compounds. The computed partial density of states (PDOS) plots predicts that the bonding is mainly achieved due to hybridization of Cr-d with Bi-p states. Using Boltztrap code we have calculated the variation of thermoelectric properties of these compounds that is electrical conductivity (σ/τ), Seebeck coefficient (S), electronic thermal conductivity (k/τ) and essentially Power factor (PF) in both spin channels.