Blaha Modified Becke Johnson Exchange Research Articles

Unveiling the potential of CuAlxGa1−xSe2 (x = 0.25) chalcopyrite as absorbent for photovoltaic application: first-principles insights into the structural, elastic, mechanical, electronic, thermodynamic and optical properties

This study explores the structural, elastic, mechanical, electronic, and optical properties of CuAlxGa1−xSe2 (x = 0.25) chalcopyrite, a crucial material in photovoltaic cells. Utilizing type II-IV-V2 chalcopyrite, widely employed in high-efficiency solar cell production, we employ first-principles calculations with Tran–Blaha-modified Becke–Johnson exchange potential techniques. We aim to determine the band gap and optical properties to understand the compound’s morphology, crucial for solar cell development. Results show CuAlxGa1−xSe2 as a 1.36 eV direct band gap semiconductor. Optical characteristics, including dielectric tensor components and absorption coefficient, are calculated to assess its suitability for solar cell applications. Predictions of Young’s modulus E, Poisson’s ratio ν, bulk B, and shear G moduli provide insight into the crystal’s mechanical behavior. Additionally, phonon, dynamical stability, and thermodynamic properties are discussed, shedding light on the material’s potential in photovoltaic technology.

First Principle Study of Structural, Electronic, Optical Properties of Co-Doped ZnO

In this theoretical study, the electronic, structural, and optical properties of copper-doped zinc oxide (CZO) were investigated using the full-potential linearized enhanced plane wave method (FP-LAPW) based on the density functional theory (DFT). The Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) was employed to enhance the accuracy of the electronic structure description. The introduction of copper atoms as donors in the ZnO resulted in a reduction in the material’s band gap from 2.82 eV to 2.72 eV, indicating enhanced conductivity. This reduction was attributed to the Co-3d intra-band transitions, primarily in the spin-down configuration, leading to increased optical absorption in the visible range. The Fermi level of the pure ZnO shifted towards the conduction band, indicating metal-like characteristics in the CZO. Additionally, the CZO nanowires displayed a significant blue shift in their optical properties, suggesting a change in the energy band structure. These findings not only contribute to a deeper understanding of the CZO’s fundamental properties but also open avenues for its potential applications in optoelectronic and photonic devices, where tailored electronic and optical characteristics are crucial. This study underscores the significance of computational techniques in predicting and understanding the behavior of doped semiconductors, offering valuable insights for the design and development of novel materials for advanced electronic applications.

Energy Bandgap of Cd1−xZnxTe, Cd1−xZnxSe and Cd1−xZnxS Semiconductors: A First-Principles Analysis Based on Tran–Blaha–Modified Becke–Johnson Exchange Potential

Energy Bandgap of Cd1−xZnxTe, Cd1−xZnxSe and Cd1−xZnxS Semiconductors: A First-Principles Analysis Based on Tran–Blaha–Modified Becke–Johnson Exchange Potential

Insight into the exemplary structural, elastic, electronic and optical nature of GaBeCl3 and InBeCl3: a DFT study.

In the scheme of density functional theory (DFT), Structural, elastic, electronic, and optical properties calculations of GaBeCl3 and InBeCl3 are carried out using Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) installed in Wein2k software. Structurally the compounds of interest are found to be stable. Both compounds possess elastic stability, anisotropy, and ductility determined by the elastic studies. The electronic-band structure analysis shows the semiconductor nature of GaBeCl3 and InBeCl3 compounds with indirect band gaps of ∼3.08 eV for GaBeCl3 and ∼2.04 eV for InBeCl3 along with the symmetrical points from (X–Γ). The calculated total density of states (TDOS) and partial density of states (PDOS) of these compounds reveal that for the GaBeCl3 compound, the contribution of Ga (4p) and Cl (3p) orbital states in the valence, as well as the conduction band, is dominant. While for InBeCl3, the contribution of Cl (3p) states as well as In (5s) is large in the valence band and in that of Cl (3p-states) states in the conduction band. The type of chemical bonding is found to be ionic in both compounds. The optical properties i.e., the real (ε1(ω)) and imaginary (ε2(ω)) parts of dielectric function, refractive index n(ω), optical reflectivity R(ω), optical conductivity σ(ω), absorption coefficient α(ω), energy loss L(ω) and electron extinction coefficient k(ω) are also discussed in terms of optical spectra. It is reported that n(ω) and k(ω) exhibit the same characteristics as ε1(ω) and ε2(ω) respectively. Efficient application of these materials can be seen in semiconducting industries and many modern electronic devices.

Toward accurate electronic, optical, and vibrational properties of hexagonal Si, Ge, and Si1−xGex alloys from first-principle simulations

A new hexagonal phase of Si1−xGex alloys have been successfully synthesized through efforts in recent reports. Utilizing the combined first-principle calculations and special quasi-random model, we precisely investigated the structural, electronic, optical, and vibrational properties of hexagonal Si and Ge and disordered hexagonal Si1−xGex random alloys. We found a large negative deviation between the calculated lattice constants within the revised Perdew–Burke–Ernzerhof for solids functional and the linear fitting results. The electronic structures obtained by using the Tran–Blaha modified Becke–Johnson exchange potential confirm that hexagonal Si1−xGex (x > 0.625) alloys present direct bandgaps. Through solving the Bethe–Salpeter equation, the linear optical spectra of hexagonal Si and Ge are demonstrated. We reveal that the peaks of complex dielectric functions are redshifted with the addition of Ge atoms. Also, the real and imaginary parts exhibit strong anisotropy, which makes hexagonal Si1−xGex alloys potentially useful as nonlinear crystals. The transition is allowed in the infrared region for the hexagonal Si1−xGex (x > 0.625) alloys, and the linear optical spectra can be continuously tuned over a wide range of frequency with Ge addition in the infrared region. Furthermore, density-functional perturbation theory calculations were carried out to predict the off-resonance Raman activity. The results suggest that the vibrational modes of the Si–Si bond exhibit a strong dependency on the compositions, which provides a useful way to identify the most probable atomic configurations of hexagonal Si1–xGex alloys in future experiments.

Investigation of the photovoltaic properties of BaHf1-xZrxS3 ([formula omitted]) chalcogenide perovskites using first principles calculations

Electronic, optical, and photovoltaic properties of BaHf1-xZrxS3 (x = 0.00, 0.25, 0.50, 0.75, and 1.00) alloys were evaluated using first principles calculations via the density functional theory. The exchange-correlation potential is treated with generalized gradient approximation. Additionally, the Tran–Blaha modified Becke–Johnson exchange potential is employed, because it gives very accurate results of the band gap in solids. The band structure calculations reveal that these compounds exhibit a semiconductor behavior with a small band gap (Eg < 2 eV). To investigate the optical transitions in these compounds, the real and imaginary parts of the dielectric function are examined. The coefficient absorption (α) is calculated and discussed as well. We found a remarkable α exceeding 105 cm−1 near Eg, which is suitable for the absorption of visible light. To exploit the high photo-absorptivity and evaluate the photovoltaic performance of these alloys, the power conversion efficiency is computed using the spectroscopic limited maximum efficiency method. Our predicted alloys have the characteristics required for photovoltaic applications with a maximum photovoltaic efficiency (η) between 22.22% and 30.09% for thickness L = 500 nm. Particularly, BaHf0.75Zr0·25S3 reveals a performance comparable to that of the best-known photovoltaic materials such as CH3NH3PbI3.

DFT prediction of structural, electronic and magnetic properties of Sr0.75TM0.25S (TM is 3d transition metals)

ABSTRACTIn recent years, the scientific community has done great efforts to search for new materials suitable for spintronics applications. Diluted magnetic semiconductors have been considered as prospective candidates to be used in spintronic devices. In this paper, we have used the full-potential linearised augmented plane wave (FP-LAPW) method within density functional theory framework to study the structural, electronic and magnetic properties of the strontium sulfide SrS doped with 3d transition metals (TM) with TM concentration (). The generalised gradient approximation proposed by Wu-Cohen (GGA-WC) was adopted to deal with the exchange-correlation effect and the Tran–Blaha modified Becke–Johnson exchange potential was also employed to calculate the electronic and magnetic properties in order to obtain accurate results. Our calculations show that the SrS doped with Ti, V, Cr, Mn, Fe and Ni are half-metallic with relatively wide ferromagnetic band gap E. However only five materials, namely, , , , and may be candidates for spintronic applications as they exhibit a wide half-metallic band gap of 1.002, 0.587, 1.201, 0.533 and 0.661 eV, respectively. Finally, results indicate that TM atoms are those that determine the magnetic properties of materials at hand.

Evaluation of structural, electronic, thermoelectric, and optical results of C‐doped HfO 2 by first‐principle's investigation

In this work, we report the ab initio numerical simulation investigation on the crystal lattice, electronic structure, optical, and transport properties of pure and C-doped crystalline hafnium dioxide (c-HfO2) using FP-LAPW method. Different exchange correlation functionals like generalized gradient approximation (GGA) of PBE-sol and Tran and Blaha's modified Becke-Johnson exchange potential (mBJ) within density functional theory have been used. Two kinds of defects in cubic pure HfO2 have been investigated: one is substitution of Hf atom by C impurity and other substitution of O atom by C impurity in crystalline HfO2. The computed results indicate that impurity energy bands as a result of 2p states of C are found to present in the band gap of c-HfO2. Few of these bands are present at the conduction band minimum, which results to a noteworthy band gap contraction, and hence electrons close to Fermi level get transferred in doped c-HfO2. We have also analysed the dielectric function, absorption coefficient, optical conductivity, optical function, electron energy loss, and reflectivity for both pure HfO2 and doped with C. Furthermore, the temperature-dependent transport properties of C-doped HfO2 are also discussed in terms of Seeback coefficient, thermal conductivities, electronic conductivities, power factor, and figure of merit in the temperature range 0 to 1200 K. The calculated value of PF for pure HfO2 was found to increase from 0.01 × 1012 WK−2m−1s−1 at 50 K to 1.79 × 1012 WK−2m−1s−1 at 1200 K and for HfO2(1 − x)Cx it was found to increase from 0.06 × 1012 WK−2m−1s−1 at 50 K to 0.25 × 1012 WK−2m−1s−1 at 1200 K.

Structural, optoelectronic and thermoelectric properties of antiperovskite compounds Ae3PbS (Ae = Ca, Sr and Ba): A first principles study

In the last years, alkaline-earth based antiperovskite compounds with small semiconductor band gap have been proven to be promising candidate for optoelectronic and thermoelectric applications. In this work, the structural, electronic, optical and thermoelectric properties of Ae3PbS (Ae = Ca, Sr and Ba) compounds have been predicted using first principles calculations based on the full-potential linearized augmented plane-wave (FP-LAPW) method and semiclassical Boltzmann transport theory. Exchange-correlation effect is treated with the generalized gradient approximation with Perdew–Burke–Ernzerhof scheme (GGA-PBE) and Tran–Blaha modified Becke–Johnson exchange potential. The lattice constant of considered materials increases as Ae goes in order from Ca to Ba and the hardness slightly decreases in this order. Ca3PbS and Sr3PbS are semiconductor with direct band gap of 0.199 eV and 0.116 eV, respectively, while Ba3PbS is nearly metallic. Important optical responses of studied antiperovskites are found in the visible and ultraviolet energy range. Finally, the thermoelectric properties including Seebeck coefficient, electrical conductivity, thermal conductivity, power factor and figure of merit are calculated. Obtained results show that Ca3PbS and Sr3PbS could be candidate for applications in thermoelectric generators at low and moderate temperatures due to their high figure of merit values.

Comparative study of structural, electronic, optical and thermoelectric properties of GaS bulk and monolayer

ABSTRACTThe structural, electronic, optical properties of GaS in bulk and monolayer forms have been studied by means of full-potential linearised augmented plane wave calculations within framework of the density functional theory. Generalised gradient approximation and Tran–Blaha modified Becke–Johnson exchange potential (mBJ) were employed for the treatment of exchange-correlation effect in calculations. Our calculated lattice parameters are in good agreement with previous theoretical results and available experimental data. The negative formation enthalpy and cohesive energy indicate that both bulk and monolayer GaS can be synthesised and stabilised experimentally. Our electronic results show that the band gap of GaS monolayer is higher than that of bulk counterpart and strong hybridisation between electronic states of constituent atoms is observed in both cases. The optical properties such as reflectivity, absorption coefficient, refractive index and optical conductivity were derived from calculated complex dielectric function for wide energy range up to 35 eV. Finally, the thermoelectric properties of GaS bulk and monolayer also were calculated using semi-classical Boltzmann theory within the constant relaxation time approximation for investigating their applicability in thermoelectric devices.

Assessing the performance of the Tran–Blaha modified Becke–Johnson exchange potential for optical constants of semiconductors in the ultraviolet–visible light region

We report on the performance of density functional theory (DFT) with the Tran–Blaha modified Becke–Johnson exchange potential and the random phase approximation dielectric function for optical constants of semiconductors in the ultraviolet–visible (UV-Vis) light region. We calculate optical bandgaps Eg, refractive indices n, and extinction coefficients k of 70 semiconductors listed in the Handbook of Optical Constants of Solids [(Academic Press, 1985), Vol. 1; (Academic Press, 1991), Vol. 2; and (Academic Press, 1998), Vol. 3] and compare the results with experimental values. The results show that the calculated bandgaps and optical constants agree well with the experimental values to within 0.440 eV for Eg, 0.246–0.299 for n, and 0.207–0.598 for k in root mean squared error (RMSE). The small values of the RMSEs indicate that the optical constants of semiconductors in the UV-Vis region can be quantitatively predicted even by a low-cost DFT calculation of this type.

Ab-initio investigation of AGeO3 (A = Ca, Sr) compounds via Tran–Blaha-modified Becke–Johnson exchange potential**Project supported by the Deanship of Scientific Research at King Saud University, Saudi Arabia (Grant No. RGP-VPP-311).

We employ ab-initio calculations to analyze the mechanical, electronic, optical and also thermoelectric properties associated with AGeO3 (A = Ca, Sr) compounds. The full-potential linearized augmented plane wave (FP-LAPW) technique in the generalized gradient approximation (GGA-PBEsol) and the lately designed Tran–Blaha-modified Becke–Johnson exchange potential are utilized to examine the mechanical and optoelectronic properties respectively. To explore the thermoelectric quality, we use the semi-classical Boltzmann transport theory. The particular structural stabilities regarding AGeO3 (A = Ca, Sr) materials are validated simply by computations from the elastic constants. The energy band structural framework and the density of states are displayed to indicate indirect bandgap under ambient conditions. The particular computed optical attributes that reveal prospective optoelectronic applications are usually elucidated simply by studying ε1(0) and also Eg, which can be connected by means of Penn’s design. The optical details uncover the actual suitability to power ranging products. Finally, the BoltzTraP code is executed to analyze the actual thermoelectric properties, which usually presents that the increase of internal temperatures can enhance the electric conductivity, thermal conductivity and also the power factor, whilst Seebeck coefficient decreases. Therefore, the studied materials will also be ideal for thermoelectric products to understand helpful option for alternative energy resources.

Theoretical Investigation of Cubic BaVO3 and LaVO3 Perovskites via Tran–Blaha-Modified Becke–Johnson Exchange Potential Approach

The full potential linearized augmented plane wave method of density functional theory has been used to investigate the structural, electronic, magnetic and thermoelectric properties of cubic perovskites BaVO3 and LaVO3. The ferromagnetic ground state has been found to be stable by comparing the total energies of non-spin-polarized and spin-polarized calculations performed for optimized unit cells. For both compounds, the bond length and tolerance factor are also measured. From the band structures and density of states plots, it is found that both compounds are half-metallic. We found that the presence of V at the octahedral site of these perovskites develops exchange splitting through p-d hybridization, which results in a stable ferromagnetic state. The observed exchange splitting is further clarified from the magnetic moment, charge and spin of the anion and cations. Finally, we also presented the calculated thermoelectric properties of these materials, which show that half-metallic BaVO3 and LaVO3 materials are potential contenders for thermoelectric applications.

Optical conductivity enhancement and band gap opening with silicon doped graphene

The linear optical and electronic properties of a monolayer graphene sheet are investigated using the Density Functional Theory within the Full Potential Linearized Augmented Plane Wave (FP-LAPW) formalism. Three approaches are used in this work: The Generalized Gradient Approximation (GGA), the Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ); implemented in WIEN2K code; and GW (Green function G and screened Coulomb interaction W) implemented in Yambo code.The band gap of graphene with and without silicon doping and the effect of silicon on optical properties of graphene are calculated. The silicon doping opens the band gap of graphene and increases its optical conductivity. This material may be used in solar cell application. Other optical properties such as reflectivity and refractive index are also studied.

Theoretical investigation of spontaneous polarization, electronic and optical properties of cubic perovskite BaHfO3

Electronic, optical properties and spontaneous polarization of cubic perovskite BaHfO3 have been investigated using the Full Potential Linear Augmented Plane Wave method, implemented in the Wien2k code, in connection with the Generalized Gradient Approximation (GGA) and the Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ). The calculation of band structure and density of state using TB-mBJ approach shows that the gap of BaHfO3 is direct and equal to 5.9 eV which is in good agreement with the experiment data (6.0 eV), compared with GGA which gives 3.9 eV. The absorption coefficient α (ω) and the complex dielectric function e (ω) are also investigated and predict that this compound can be effectively used in UV based optoelectronic devices. Furthermore, Using the PI approach, we can calculate the spontaneous polarization which is equal to 0.40 C/m2 and predict that is in the same order as the Ps of other perovskite.

Comparative study between TB-mBJ and GGA+U on magnetic and optical properties of CdFe2O4

Full Potential Linearized Augmented Plane Wave (FP-LAPW) based on density functional theory (DFT) is carried out to study the density of states, optical properties and XMCD properties of bulk spinel ferrite CdFe2O4. The exchange correlation potential was solved by Generalized Gradient Approximation (GGA) that underestimates the band gap value, therefore, the later needed to be corrected using two approaches: Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ) and GGA plus the multi-orbital mean-field Hubbard potential (GGA+U). These methods provide accurate results in good agreement for the optical properties and band gap with experimental data.CdFe2O4 has a coefficient of absorption more than 104/cm in the visible range. The first critical point known as optical absorption edge calculated with GGA+U and TB-mBJ appears at 1.56eV and 1.88eV, respectively.The XMCD spectra show a double pic in L3 edge indicating the presence of both Fe2+ and Fe3+ ions, occupying the octahedral sites. However, using GGA+U the charge of the atoms is well localized and subsequently the double peak does not reproduce.The crystal field creates additional levels that provide radiation in the visible, having these properties; this compound promotes its use for device applications operating over a wide energy range based on CdFe2O4 in optoelectronics.

Electronic and optical modeling of solar cell compound CuXY2 (X = In, Ga, Al; Y = S, Se, Te): first-principles study via Tran–Blaha-modified Becke–Johnson exchange potential approach

The electronic and optical properties of the ternary CuXY2 (X = In, Ga, Al; Y = S, Se, Te) compounds have been investigated using the density functional theory based on the full potential linear augmented plane wave method via Tran–Blaha-modified Becke–Johnson exchange potential techniques. From this study, it is found that these compounds are direct band gap semiconductor and in good agreement with reported results. The optical properties such as dielectric tensor components and the absorption coefficient of these materials are determined in order to investigate their usefulness as solar cell materials.

Optoelectronic response of spinels CdX2O4 with X = (Al, Ga, In) through the modified Becke–Johnson functional

Structural, electronic, and optical properties of CdAl2O4, CdGa2O4, and CdIn2O4 are investigated using the first principles technique based on the new potential approximation known as the Tran–Blaha modified Becke–Johnson exchange potential approximation (TB-mBJ). We discuss the improvements in the band gap determination using TB-mBJ compared to the standard generalized gradient approximation in density functional theory. The calculated equilibrium lattice parameters are in reasonable agreement with the experimental results. Electronic properties have been studied through the calculation of band structure and density of states. Based on our electronic structure obtained using the mBJ method, we have calculated various optical properties, including the complex dielectric function ε(ω), complex index of refraction n(ω), reflectivity coefficient R(ω), absorption coefficient α(ω), and the electron energy-loss function L(ω) as functions of the photon energy. We chose these three representative oxides spinel due to their potential applications in optoelectronics and optical fields.