Tran-Blaha Modified Becke-Johnson Potential Research Articles

Electronic and optical characteristics of CaLiX3 (X = Cl, Br, I) perovskite compounds using the Tran–Blaha modified Becke–Johnson potential

We present the results of a comprehensive investigation using the full-potential linearized augmented plane wave approach to analyze the structural characteristics, electronic structures, and optical spectra of the perovskite compounds CaLiX3 (X = Cl, Br, or I). Various functionals were employed to simulate the exchange–correlation interactions. The calculated equilibrium structural parameters, obtained using the generalized gradient approximation, are consistent with the existing findings in the literature. The computed electronic structures reveal that the Tran–Blaha modified Becke–Johnson potential significantly enhances the bandgap. For all CaLiX3 compounds studied, we predicted an indirect bandgap. Additionally, we observed a gradual decrease in the bandgap as the atomic size of the X element increases. The electronic states constituting the various energy bands were evaluated by computing the partial and total densities of states. In addition, we computed a variety of optical spectra, including the complex dielectric function, absorption coefficient, refractive index, extinction coefficient, reflectivity, and electron energy loss function. The results demonstrate that a decrease in the bandgap leads to an increase in the zero-frequency limit of the dielectric function ε(0). The origins of the peaks and structures in the optical spectra were identified.

Ab initio investigation of mechanical, electronic and optical properties in the orthorhombic [formula omitted] inorganic perovskite

This study employs a first-principles approach to comprehensively investigate the structural, electronic, elastic, and optical properties of two distinct inorganic perovskite phases of CsPbI3, identified as C–CsPbI3 and O–CsPbI3. Utilizing the Wien2K code, simulations are conducted employing various density functional theory (DFT) approximations, including local density approximation (LDA), generalized gradient approximation (GGA), the modified Becke–Johnson potential (mBJ), and the Tran-Blaha modified Becke–Johnson potential (TB-mBJ). Our analysis demonstrates that the orthorhombic phase exhibits greater energetic stability and mechanical robustness compared to the cubic phase. Furthermore, optical analyses reveal a direct bandgap in the compound, with key parameters calculated and interpreted. Notably, both phases demonstrate exceptional electronic, mechanical, and optical properties, suggesting their potential applications in optoelectronics, photovoltaics, and photovoltaic cells. Consequently, this study positions both the cubic and orthorhombic phases of CsPbI3 as promising materials warranting further exploration and development in these technological domains.

Insight into the electronic, optical, and transport properties of novel BaLaCuX3 (X = S, Se, and Te) quaternary chalcogenides

Quaternary chalcogenides are among the most investigated materials for their outstanding performance in optoelectronics and thermoelectric applications. Here we examined the electronic structure, optical, and thermoelectric features of novel BaLaCuX3 (X = S, Se, and Te) within the context of density functional theory. A direct band gap nature at Γ-point for the three materials was noticed using the accurate TB-mBJ (Tran-Blaha modified Becke-Johnson) potential. A decrease in the bandgap by the substitution of S and Se with Te was observed, due to the more electropositive nature of Te as compared to S and Se atoms. We investigated the linear optical properties including all the significant optical parameters and explained them for their possible applications in optoelectronics. Furthermore, the important thermoelectric transport nature of these studied systems was calculated and the obtained results were discussed, suggesting the suitability of these materials in thermoelectric applications. This present work would be a qualitative theoretical investigation of the behavior of these materials in advanced technological applications, including optoelectronics and thermoelectricity.

Structure property correlation study of energetic solid XeO3

In the realm of material science, xenon trioxide (XeO3) is characterized by an significant degree of shock sensitivity, resembling characteristics associated with primary explosives. To determine the underlying principles and quantify such behaviour we present a comprehensive computational study addressing the structural, vibrational, electronic and optical behaviour of energetic XeO3 by employing DFT calculations (Density Functional Theory). Our study demonstrates a good agreement between our computed structural parameters at equilibrium and experimental findings, particularly after incorporating vdW (van der Waals) interactions. Also, the mechanical stability of XeO3 is assessed by computing the Cij (elastic constants) and the B (bulk modulus). The evaluation of elastic constants in various directions indicates that (C33 > C22 > C11) XeO3 is highly shock sensitive along crystallographic a-axis. The computed (B) bulk modulus is determined to be 12.98 GPa, aligning closely with the values observed in other primary explosives. The phonon dispersion spectra computed within the harmonic approximation confirms the dynamical stability of XeO3 in P212121 structure. The spectra also reveal a notable interaction between the acoustic and optical branch, resulting in low thermal conductivity which is a trait for the energetic materials. The precise measurement of the energy band gap is crucial for establishing potential correlations with the photodecomposition process of energetic materials. To support this, we have conducted band structure calculations using the TB-mBJ (Tran-Blaha modified Becke-Johnson) potential, alongside the conventional GGA/LDA methods, generally known to underestimate band gaps. Our TB-mBJ based calculations yielded an energy band gap around 2.5 eV, which can also be compared with other energetic compounds. The rapid fluctuations of the optical constants suggest photodecomposition nature of XeO3 in the near UV region. The insights gained from our study would be of high interest for the study of other xenon (Xe) compounds and their oxides, delivering direction for potential applications across diverse fields.

Sonohydrothermal-assisted ZnS nanocrystals for improved structural, electronic, and optical properties: Experimental and ab initio methods

Herein, ZnS nanoparticles (NPs) with controlled size, crystal structure and effective optoelectronic properties were investigated via facile sonohydrothermal synthesis (SH) at 190 °C for up to 12 h. The average crystallite size of ZnS NPs using SH and hydrothermal (HT) were analysed through Debye–Scherrer equation from the X-ray diffraction (XRD). From current density–voltage (J–V) characteristics, the growth of nanoparticles by SH synthesis exhibits non-linear behaviour and higher current density than the HT method. The optical bandgap of as-synthesized ZnS nanoparticles of HT and SH synthesis were 3.60 and 3.61 eV, respectively. From the first-principles calculations using Tran–Blaha-modified Becke–Johnson potential, the bandgap is consistent with the experimental findings compared with the Perdew–Burke–Ernzerhof approximation. The obtained structural, electronic and optical properties revealed that SH synthesis is a potential alternative that may yield a possible route for developing new material applications in optoelectronics.

Structural, electronic and optical properties of lead free Rb based triiodide for photovoltaic application: an ab initio study

The instability of organic–inorganic hybrid halide perovskites due to light, heat, and moisture restricts them for practical use despite having most suitable photovoltaic properties and higher power conversion efficiency. Several methods such as surface engineering, carbon electrode utilization, and optimization of the components are applied to increase the stability; still, it is far from the practical implementation. Moreover, the toxicity of Pb in most of the efficient hybrid halide perovskites is another major issue. It motivates us to search for a stable and Pb free perovskite solar cell. Hence, a systematic investigation within density functional theory has been made on the structural, electronic, and optical properties of RbMI3 compounds (where M = Ge and Sn). The structural properties such as lattice parameters, formation energy are calculated. The calculated negative formation energy confirms the chemical stability for both compounds. The electronic properties like partial density of states, band structures with Perdew–Burke–Ernzerhof, Tran–Blaha modified Becke–Johnson (TB-mBJ) and HSE06 are discussed. Band gaps are calculated for RbGeI3 (2.645 eV) and RbSnI3 (2.544 eV) with TB-mBJ potential, which is proved to estimate the band gap values accurately for inorganic solids. SOC influences the conduction band minimum without any changes in the valence band maximum and thus reduces band gaps to 2.021 for RbGeI3 and 1.865 eV for RbSnI3. The optical properties like the real and imaginary part of the dielectric constants, absorption coefficients, refractive indices, and reflectivities have also been discussed. Further, transport properties like effective masses, binding energy of excitons, and spectroscopic limited maximum efficiency (SLME) are calculated for both RbMI3 compounds. The excitons for both structures are found to be Frenkel type. SLME for RbGeI3 and RbSnI3 having the thickness of 0.5 μm at a temperature of 300 K are found as 16.5% and 18%, respectively. Finally, the possibility of RbGeI3 and RbSnI3 in the solar cell configuration with TiO2 as the hole transporting material have been explored.

Structural, electronic, optical, thermoelectric, and transport properties of indium-based double perovskite halides Cs2InAgX6 (X = Cl, Br, I) for energy applications

Ab-initio studies are employed to explore physical aspects of indium-based double halide perovskites Cs2InAgX6 (X = Cl, Br, I) using full-potential linearized augmented plane-waves method along with local orbitals. The electronic behaviors are observed by computing the band structures and density of states, which are determined by employing GGA-PBEsol approximation. The Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential is then further applied. The use of TB-mBJ potential has revealed that direct band gap is exhibited by Cs2InAgX6 (X = Cl, Br, I), which are found agreeing with the literature. Various optical parameters are calculated to evaluate all three double perovskites to unveil their potential applications in optical devices. In addition, BoltzTraP code is used to explore the thermoelectric properties within the temperature range 100–800 K. The studied double perovskites have been suggested as highly appropriate candidates for the fabrication of a variety of renewable energy devices.

Modeling the ternary chalcogenide Na2MoSe4 from first-principles

In the ongoing pursuit of inorganic compounds suitable for solid-state devices, transition metal chalcogenides have received heightened attention due to their physical and chemical properties. Recently, alkali-ion transition metal chalcogenides have been explored as promising candidates to be applied in optoelectronics, photovoltaics and energy storage devices. In this work, we present a theoretical study of sodium molybdenum selenide (Na2MoSe4). First-principles computations were performed on a set of hypothetical crystal structures to determine the ground state and electronic properties of Na2MoSe4. We find that the equilibrium structure of Na2MoSe4 is a simple orthorhombic (oP) lattice, with space group Pnma, as evidenced by thermodynamics. Finally, meta-GGA computations were performed to model the band structure of oP Na2MoSe4 at a predictive level. We employ the Tran–Blaha modified Becke–Johnson potential to demonstrate that oP Na2MoSe4 has a direct bandgap at the Γ point that is suitable for optoelectronics. Our results provide a foundation for future studies concerned with the modeling of inorganic and hybrid organic–inorganic materials chemically analogous to Na2MoSe4.

Electronic and thermoelectric properties of the layered Zintl phase CaIn2P2: first-principles calculations

ABSTRACT We have studied the doping concentration dependence of the thermoelectric (TE) properties for the n- and p-doped CaIn2P2 layered Zintl phase at two fixed temperatures: T = 600 and 900 K through first-principles electronic band structure calculations combined with Boltzmann's transport theory within charge-carrier relaxation time and rigid band approximations. The band structure calculated using the Tran-Blaha modified Becke–Johnson potential shows a fundamental indirect energy band gap (E g) of 1.10 eV that comes from the polyanion (In2P2)−2. CaIn2P2 exhibit a mixture of flat and dispersive energy bands in the energy window from to eV, which is a required characteristic for high electrical transport coefficients. The computed lattice thermal conductivity for CaIn2P2 is equal to at 900 K and at 1250 K. This relatively low lattice thermal conductivity of CaIn2P2 can be mainly attributed to its layered crystalline structure. The highest value of the figure of merit of CaIn2P2, viz. ZT = 0.73 (0.71), is obtained for an optimal electron (hole) concentration of () at 900 K.

Ferromagnetism, half-metallicity and spin-polarised electronic structures characterisation insights in Ca1−xTixO

ABSTRACTIn this study, we have computed the structural, electronic and half-metallic ferromagnetic properties of Ca1−xTixO compounds at concentrations x = 0.125, 0.25, 0.5 and 0.75 by employing the first-principle approaches of density functional theory. The generalised gradient approximation of Wu and Cohen (GGA-WC) is used to calculate the structural parameters, whereas the electronic structures and magnetic properties are characterised by the accurate Tran–Blaha-modified Becke–Johnson potential (TB-mBJ). The lattice constant, bulk modulus and indirect gap of CaO are in good agreement with other theoretical and experimental results. The Ca0.25Ti0.75O at x = 0.75 has metallic ferromagnetic nature. The Ca0.875Ti0.125O, Ca0.75Ti0.25O and Ca0.50Ti0.50O compounds have total magnetic moments of 2 μB per Ti atom with a half-metallic character, a spin polarisation of 100% and a large half-metallic gap of 1.345 eV for x = 0.125. Therefore, the Ca1−xTixO material with a low concentration of Ti is a true half-metallic ferromagnet and seems to be a promising candidate for semiconductor spintronics.

Study the optical properties of XC (X = Si, Ge and Sn) nanosheets using TB-mBJ exchange-correlation potential

In this work, dielectric function, energy loss function, absorption, refraction index and reflectivity of graphene-like nanosheets of Si-C, Ge-C and Sn-C are calculated in the presence of a polarized electric field parallel (E||x) and perpendicular (E||z) to the surface of the hexagonal nanosheets. Our calculations are based on the density functional theory (DFT) with full potential linearized augmented plane-waves (FP-LAPW) basis. Generalized gradient approximation (GGA) and the Tran & Blaha modified Becke-Johnson (TB-mBJ) potentials are used for exchange-correlation potential. The results show that the optical properties of all the nanosheets are extremely polarization-dependent and have a significant anisotropic behavior especially in the visible region of the electromagnetic waves. Furthermore, the calculated value of static dielectric constant by TB-mBJ is less than GGA and also it is increased as we go down the periodic table from Si to Sn in our nanosheets. Also, our findings by the two methods demonstrate that for the E||z polarization, the refraction index is nearly constant in the visible region for all the three nanosheets, which shows the promising applications of these nanosheets in optical fiber devices. Finally, since the band gaps obtained by TB-mBJ method are very close to the experimental band gap, the optical properties obtained by TB-mBJ potential of this work may be used for the future optoelectronic applications of these nanosheets.

Ferromagnetic Half-Semiconductor (HSC) gaps in co-doped CdS: Ab-initio study

In this work we have used the density functional theory (DFT) to study structural, magnetic and electronic properties of Co doped CdS in the zinc-blende (ZB) phase. Three approximations have been used to treat the exchange-correlation potential: the (PBE) GGA, (PBE) GGA+U and the model of Tran–Blaha modified Becke–Johnson potential (TB-mBJ). The on–site Coulomb interaction correction given by the Hubbard U has been calculated by the local density approximation constraint for the Co electronic orbitals. The theoretical results show that all the properties under study are affected by the doping of Co atom. Co doped CdS becomes a Ferromagnetic Half-Semiconductors (HSC). The total magnetic moment increases with increasing Co concentration; reaching the value of 9 (in the units of Bohr magneton) at high concentration (x = 18.75 %). The total magnetic moment value is an integer in the GGA+U and TB-mBJ approximations. Furthermore, to validate the effects resulting from the exchange splitting process, we have calculated the values of the spin-exchange constants N0α and N0β, respectively. All these changes make CdS:Co extremely interesting system for the spintronic applications.

First-principles investigation of the structural, optoelectronic and thermodynamic properties of InAsxP1-x ternary alloys under hydrostatic pressure effect

The main objective of our work is the study of structural, optoelectronic and thermodynamic properties of InAsxP1-x alloys in the zinc-blende structure using the full potential linearized augmented plane wave method (FP-LAPW) based on density functional theory (DFT). Different exchange correlation potentials were used, as well as the local density approximation (LDA) and the generalized gradient approximation (GGA) parameterized by Perdew–Burke–Ernzerhof (PBE-GGA) and PBE sol-GGA of Perdew, to estimate structural properties such as lattice parameters, the bulk modulus and its first pressure derivative. For electronic properties, the Tran-Blaha modified Becke–Johnson potential (TB-mBJ) was used for density of states (DOS) and band structure calculations. The results show that the compounds of interest are semiconductors with direct band gaps for the full range of x compositions and that the optical band gap decreases from 1.58 to 0.41 eV with increasing As concentrations. The obtained results show a good agreement with experimental and theoretical data found in the literature. In addition, we have investigated the dielectric function as well as the refractive index and the reflectivity. The electronic and optical properties were studied under hydrostatic pressure (P = 0, 5, 10, 15, 20, and 25 GPa), and it was found that the band gaps of the binary compounds change from a direct to an indirect harmonic Debye model was used, which takes into account the effect of pressure P and temperature T on the lattice parameter, to explore the heat capacity, the Debye temperature and the entropy under pressures ranging from 0 to 20 GPa and temperatures ranging from 0 to 1200 K.

Electronic structure and optical properties of the dialkali metal monotelluride compounds: Ab initio study

Structural parameters, electronic structure and optical properties of the dialkali metal monotelluride M2Te (M = Li, Na, K and Rb) compounds in the cubic antifluorite structure were investigated via ab initio calculations using the all electron linearized augmented plane wave approach based on density functional theory with and without including spin-orbit coupling (SOC). The exchange-correlation interactions were described within the PBEsol version of the generalized gradient approximation and Tran-Blaha modified Becke–Johnson potential (TB-mBJ). Optimized equilibrium lattice parameters are in excellent accordance with existing measured ones. Computed energy band dispersions show that the studied compounds are large band gap materials. Inclusion of SOC reduces the band gap value compared to the corresponding one calculated without including SOC. Determination of the energy band character and interatomic bonding nature are performed using the densities of states diagrams and charge density distribution map. Linear optical function spectra are predicted for a wide energy range and the origin of the dielectric function spectrum peaks are determined.

Optoelectronic Properties of Zinc Oxide: A First‐Principles Investigation Using the Tran–Blaha Modified Becke–Johnson Potential

In this work, density functional theory (DFT) is used to investigate the influence of semi‐local exchange and correlation effects on the electronic and optical properties of zinc oxide. It is found that the inclusion of such effects using the Tran–Blaha modified Becke–Johnson potential yields an excellent description of the electronic structure of this material giving an energy band gap which is systematically larger than the one obtained with standard local functionals such as the generalized gradient approximation. The discrepancy between the experimental and theoretical band gaps is then significantly reduced. We also calculated the dielectric functions of ZnO and find a violet shift to the absorption edge which is in good agreement with experimental results.

Electronic structure and thermoelectric properties of Bi2O2Se with GGA and TB-mBJ potentials

The electronic structure and thermoelectric (TE) properties of Bi2O2Se are studied by the first principles and the semiclassical BoltzTraP theory. The optimized equilibrium lattice parameters are very close to the experimental results. The band gap is enhanced significantly to 1.22 eV with Tran–Blaha modified Becke–Johnson (TB-mBJ). The hybridized densities of states (DOS) of Bi atoms p states and O atoms p states forms [Bi2O2]2+ cation. The peak value of S for TB-mBJ is about three times as high as the peak value of S for generalized gradient approximation (GGA) at 300 K due to the large band gap of TB-mBJ. The σ/τ ratio shows the better TE performance for p-type Bi2O2Se. κ0 can be decreased by using TB-mBJ potential. TB-mBJ shows a larger value of ZeT as compared to GGA. The very broad peaks of ZeT for the TB-mBJ scheme show a broad doping range near the Fermi level for obtaining excellent TE materials.

Theoretical investigation of electronic performance, half-metallicity, and magnetic properties of Cr-substituted BaTe

We have investigated the structural, electronic, and ferromagnetic properties of chromium (Cr)-doped rocksalt BaTe ( $$\hbox {Ba}_{1-x}\hbox {Cr}_{x}\hbox {Te}$$ ) compounds with compositions $$x = 0.25$$ , 0.5, and 0.75, based on density functional theory with generalized gradient approximation of Wu–Cohen (GGA-WC) and Tran–Blaha-modified Becke–Johnson (TB-mBJ) potential using the WIEN2k package. We found that the electronic structure showed half-metallic ferromagnetic character with spin polarization of 100 % around the Fermi level. In addition, the minority-spin bands depicted a half-metallic ferromagnetic (HMF) gap and half-metallic (HM) gap. The improved HMF and HM gaps found with the TB-mBJ potential are higher than with the GGA-WC approximation. These large HM gaps make $$\hbox {Ba}_{1-x} \hbox {Cr}_{x}\hbox {Te}$$ compounds promising candidates for use in spintronics applications.

Theoretical investigation of the structural stabilities, optoelectronic properties and thermodynamic characteristics of GaPxSb1−x ternary alloys

In this theoretical study, we have investigated the structural, phase transition, electronic, thermodynamic and optical properties of GaPxSb1−x ternary alloys. Our calculations are performed with the WIEN2k code based on density functional theory using the full-potential linearized augmented plane wave method. For the electron exchange-correlation potential, a generalized gradient approximation within Wu–Cohen scheme is considered. The recently developed Tran–Blaha modified Becke–Johnson potential has also been used to improve the underestimated band gap. The structural properties, including the lattice constants, the bulk moduli and their pressure derivatives are in very good agreement with the available experimental data and theoretical results. Several structural phase transitions were studied here to establish the stable structure and to predict the phase transition under hydrostatic pressure. The computed transition pressure (Pt) of the material of our interest from the zinc blende (B3) to the rock salt (B1) phase has been determined and found to agree well with the experimental and theoretical data. The calculated band structure shows that GaSb binary compound and the ternary alloys are direct band gap semiconductors. Optical parameters such as the dielectric constants and the refractive indices are calculated and analyzed. The thermodynamic results are also interpreted and analyzed.

Elastic, Optoelectronic and Thermoelectric Properties of the Lead-Free Halide Semiconductors Cs2AgBiX 6 (X = Cl, Br): Ab Initio Investigation

We report a detailed investigation of the elastic moduli, electronic band structure, density of states, chemical bonding, electron and hole effective masses, optical response functions and thermoelectric properties of the lead-free halide double perovskites Cs2AgBiCl6 and Cs2AgBiBr6 using the full potential linearized augmented plane wave (FP-LAPW) method with the generalized gradient approximation (GGA-PBEsol) and the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. Because of the presence of heavy elements in the studied compounds, we include the spin–orbit coupling (SOC) effect. Our calculated structural parameters agree very well with the available experimental and theoretical findings. Single-crystal and polycrystalline elastic constants are predicted using the total-energy versus strain approach. Three-dimensional representations of the crystallographic direction dependence on the shear modulus, Young’s modulus and Poisson’s ratio demonstrate a noticeable elastic anisotropy. The TB-mBJ potential with SOC yields an indirect band gap of 2.44 (1.93) eV for Cs2AgBiCl6 (Cs2AgBiBr6), in good agreement with the existing experimental data. The chemical bonding features are probed via density of states and valence electron density distribution calculations. Optical response functions were predicted from the calculated band structure. Both of the investigated compounds have a significant absorption coefficient (∼ $$ 25 \times 10^{4} \;{\hbox{cm}}^{ - 1} $$ ) in the visible range of sunlight. The thermoelectric properties of the title compounds were investigated using the FP-LAPW approach in combination with the semi-classical Boltzmann transport theory. The Cs2AgBiCl6 and Cs2AgBiBr6 compounds have a large thermopower S, which makes them potential candidates for thermoelectric applications.

Structural, elastic, electronic and optical properties of the novel quaternary diamond-like semiconductors Cu2MgSiS4 and Cu2MgGeS4

The structural, elastic, electronic and optical properties of two newly synthetized quaternary diamond-like semiconductors Cu2MgSiS4 and Cu2MgGeS4 were studied in detail using two complementary first-principles approaches. The calculated equilibrium structural parameters are in good agreement with the available experimental data. Single-crystal and polycrystalline elastic moduli and their related properties, including elastic constants, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, elastic anisotropy indexes, Pugh's criterion, elastic wave velocities and Debye temperature, were predicted. We find that the inclusion of the electronic exchange-correlation through the newly developed Tran-Blaha modified Becke–Johnson potential (TB-mBJ) improves the description of the electronic structure. The TB-mBJ yields a direct band gap (Γ-Γ) of 2.64 and 1.54 eV for Cu2MgSiS4 and Cu2MgGeS4, respectively. Frequency dependence of the dielectric function, refractive index, extinction coefficient, absorption coefficient, reflectivity, energy loss function and optical conductivity were predicted and the origin of the observed electronic transitions were assigned.