Johnson Potential Research Articles

Tuning of optical, thermodynamic, and thermoelectric properties of Cs2CuBiX6 (X = Cl, Br, I) halide perovskites for solar cells and energy harvesting applications

The double perovskites are outstanding materials for solar cells and transport applications to clean harvest energy. Therefore, the Cs2CuBiX6 (X = Cl, Br, I) are discussed comprehensively for energy harvesting by modified Becke and Johnson (mBJ) potential. The studied DPs fit the structural, mechanical, and dynamic stability scale by tolerance factor, Born–Huang criteria, and phonon dispersion band structures. The band gaps (1.20, 1.0, 0.70) eV for (Cl, Br, I) based DPs ensure the Cs2CuBiCl6 has an absorption band in the visible region while Cs2CuBiBr6 and Cs2CuBiI6 has an absorption band in the infrared region. Heavy elements’ spin–orbit coupling effect (Cs, Bi) reduces the band gap to 0.08 eV. Thermoelectric behavior regarding the merit scale against dopant carriers and temperature has been elaborated. The ultralow lattice thermal conductivity, large Debye temperature, hardness, and melting temperature increase their implication for thermoelectric and other thermodynamic applications. The variation in band gap makes them important for diverse optoelectric and thermoelectric applications. The Cs2CuBiCl6 with a band gap of 1.20 eV is suitable for solar cells, while Cs2CuBiBr6 and Cs2CuBiI6 with band gaps of 1.0 eV and 0.70 eV are significant for thermoelectric generators.

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.

Enhancement of the magneto-electronic properties by GGA and TB-mBJ approaches for KMgO3 perovskite oxide

We investigate the structural, elastic, electronic and magnetic properties of KMgO3. First-principal calculations, based on the formalism of the density functional theory (DFT) and the method of full potential augmented and linearized plane waves (FP-LAPW) implemented in the Wien2k code. The exchange and correlation effects were treated by the following two approximations: generalized gradient approximation (GGA) and Tran-Blaha modified beck Johnson (TB-mBJ) potentials. After analyzing the obtained structural parameters, the results revealed that KMgO3compound is most stable in its ferromagnetic configuration. The formation energy value showed that this compound can be experimentally synthesized. Furthermore, the calculated band structures, and density of states (DOSs) indicate the half-metallic behavior of KMgO3. We found also that the total magnetic moment is an integer value of 3μBwhich confirms the half-metallic character. The magnetic moment specially issues from the spin-polarization of p electrons of O atoms.

A DFT insight of the electronic, thermodynamic, and thermoelectric properties of RuO2

In this study, we explore the structural, electronic, thermodynamic, and thermoelectric properties of RuO2 using density functional theory. The derived equilibrium structural parameters agree with other theoretical and experimental results. The widely used modified Becke–Johnson (mBJ-GGA) potential is adopted for accurate electronic band gap estimation. To incorporate the effect of the extended orbital of the Ru atom, spin-orbit coupling has been used in combination with the mBJ potential. The investigation of electronic properties revealed an indirect semi-conducting nature with a band gap along the W-L symmetry. The calculated band gaps are 1.685 and 1.658 eV from mBJ and mBJ + SOC, respectively. The dynamical stability is tested and verified by calculating the phonon dispersion curve. We have employed the quasiharmonic approximation-based Gibbs2 package to determine the pressure and temperature-dependent thermodynamical parameters, such as cell volume, Debye temperature, heat capacity, entropy, and thermal expansion coefficient. This study uses the BoltzTraP simulation algorithm to determine the thermoelectric parameters such as the Seebeck coefficient, electrical conductivity, and thermal conductivity.

A comprehensive DFT analysis of the physical, optoelectronic and thermoelectric attributes of Ba2lnNbO6 double perovskites for eco-friendly technologies

Within the framework of density functional theory (DFT), as executed in WIEN2k as well as semi-classical Boltzmann transport theory, we reported structural, electronic, elastic, optical, thermoelectric, and thermodynamic properties of the double perovskite compound Ba2InNbO6. To employ the exchange–correlation potential, local density approximation (LDA), the generalized gradient approximation (GGA) with Perdew, Burke and Ernzerhof (PBE) and the modified Becke–Johnson (mBJ) potential is considered. The elastic constants are calculated to check the mechanical stability. The electronic calculations show semiconducting nature with a wide band-gap (3.63 eV) for Ba2InNbO6. The optical properties such as complex dielectric constant ε(ω), refractive index n(ω), reflectivity R(ω), absorption coefficient α(ω), optical conductivity σ(ω) and energy loss function L(ω) described with the incidence frequency. The absorption spectrum shows the behaviour of common semiconductors. The Seebeck coefficient (S) as well as electrical conductivity (σ/τ) also demonstrates the semiconducting nature of the studied compounds by holes having highest particles. The PF was 1.85 × 1012 W K−2 m−1 s−1 at 1200 K and thermodynamic studies, the heat capacity as well as Gruneisen parameter were guessed. Based on obtained results we can ensure that the double perovskite compound Ba2InNbO6 is well suitable for optical and thermoelectric applications.

Probing optoelectronic and thermoelectric properties of double perovskite halides Li2CuInY6 (Y = Cl, Br, I) for energy conversion applications

Recently, double perovskite halides (DPHs) become crucial due to their potential applications in optoelectronic devices due to their stability, non-toxicity, superior oxidation resistance, high conversion efficiency, and high temperature stability. In the current study, we explored DPHs Li2CuInY6 (Y = Cl, Br, I) employing Wien2k package to analyze the structural stability, optoelectronic and thermoelectric features. The formation energy and Born stability criteria are computed to confirm thermodynamic and structural stability. Studied DPHs have direct bandgaps nature investigated by modified Becke and Johnson (mBJ) potential. Calculated values of bandgap decreases, when replace halide ion from Cl to I, indicate tuning from visible to infrared (IR) region of electromagnetic spectrum. Their band edge tuning across the visible to infrared border is reliant on replacement, which makes them suitable for projects involving opto-electronic devices. Further, optical features are investigated in terms of incident photon energy in order to assess the optical output. Lastly, electronic thermoelectric performance is computed using the figure of merit (ZT) for all DPs. Computed results of direct bandgap and optical behavior show that DP Li2CuInCl6 can be used as photovoltaic devices as compared to DPs Li2CuInBr6 and Li2CuInI6.

Effect of anion (S−2 & Se−2) replacement on photovoltaic properties in transition metal (Ba-Barium) chalcogenide perovskites

Material scientists have stepped up their search for efficient materials in low-cost, high-stability, nontoxic energy conversion devices. In this paper, emerging materials inspire us to study one of the perovskite chalcogens made from alkaline-earth metals (Barelium). Therefore, we determined some fundamental properties with some application-based properties, which explained their applicability in energy conversion device fabrication by first-principles calculation within the WIEN2K Code. Structure stability has been verified by Birch–Murnaghan fits and thermal stability at different temperatures and pressure ranges is explained by Gibbs function in thermodynamic properties. By using modified Becke–Johnson (mBJ) potential, electronic and optical characteristics of these materials provide insight into their nature: they were revealed to be direct bandgap semiconductors with the calculated values of 1.77[Formula: see text]eV (1.25[Formula: see text]eV) for BaZrS3(BaZrSe3), respectively. Both materials exhibit transparency on low-energy striking photons and demonstrate absorption and optical conduction in the UV region. Both materials exhibit transparency on low-energy striking photons and demonstrate absorption and optical conduction in the UV region. In the thermoelectric parameter, the figure of merit (ZT) is unity at room temperature and decreases up to 0.98 with temperature increment which reveals that these materials will be helpful in thermoelectric devices. As per the application part, we carried out the calculation of the spectroscopic limited maximum efficiency (SLME) and found that efficiency increases from 6.5% to 27.1% (8.1% to 31.9%) for BaZrS3 (BaZrSe3), respectively. The film thickness increased from 100[Formula: see text]nm to 1[Formula: see text][Formula: see text]m at room temperature and then stabilized. This emerging study shows that these materials can be used as an alert substance in energy conversion device fabrications and the proposed outcomes are in good acceptance with the experimental and other theoretical data. As per the optical and thermoelectric parameters of these materials, we infer that both are promising candidates in energy conversion device fabrication.

First-principle simulation of inorganic Na2CuSbX6 (X = Cl, Br, I) halides for photovoltaic and energy conversion applications

The exceptional flexibility of optoelectronic attributes exhibited by inorganic Na2CuSbX6 (X = Cl, Br, I) halides has sparked significant interest in recent research. Our approach involves the utilization of Wien2k and BoltzTrap coding to scrutinize the mechanical, thermoelectric and optoelectronic attributes of studied halides. Structural stability have been investigated through Born stability criteria employing generalized gradient approximation (GGA-PBEsol). In addition, negative formation energy (−2.15 eV for Cl-halide, −1.88 eV for Br-halide and −1.68 eV for I-halide) indicate all halides are thermo-dynamical stable. For accurate calculation of optoelectronic properties, modified Becke and Johnson (mBJ) potential has been employed. Band structure indicate all halides are semiconductor with indirect bandgap nature having bandgap values 1.7 eV for Cl-halide, 1.34 eV for Br-halide and 0.85 eV for I-halide respectively. Substituting Cl-halide with Br and I-halide results in enhanced optical absorption predominantly in the visible region, causing a shift in the absorption edge from visible light to IR. Further, electronic thermoelectric properties are discussed against temperature 300 K to 800 K. The computed higher Seebeck coefficient observed in Na2CuSbI6 suggests that a narrower band gap is more suitable for thermoelectric applications in comparison to Na2CuSbBr6 and Na2CuSbCl6. In a broader context, the computational analysis of thermoelectric and optical properties indicates that Li2CuSbX6 halides is generally well suited for use in solar cell devices and energy conversion applications.

Physical properties and power conversion efficiency of SrZrX3 (X=S and Se) chalcogenide perovskite solar cell

The search for efficient substances in energy conversion devices, which are low-cost, highly stable, and not hazardous to humanity has intensified among material scientists. Here, we have investigated the chalcogenide-based metal (Sr — strontium) perovskites in the context of developing materials. We have identified the electrical and optical features of these materials using the modified Becke–Johnson potential, revealing information about their nature. With computed values of 2.009[Formula: see text]eV for SrZrS3 and 1.096[Formula: see text]eV for SrZrSe3, respectively, they have shown to be direct bandgap semiconductors. We have also found that both materials exhibit transparency to the striking photon at low energy and demonstrate absorption and optical conduction in the UV region. These materials will be useful in thermoelectric devices because the transport property calculation shows that their figure of merit is unity at both low and high temperatures. In regard to applications, we determined the spectroscopic limited maximum efficiency (SLME) of SrZrS3 (SrZrSe3) and discovered that the efficiency increases from 6.3% to 22.3% (7.9% to 32%) when the film thickness is increased from 100[Formula: see text]nm to 1[Formula: see text][Formula: see text]m at 300[Formula: see text]K, after that it stabilizes. This research shows that these materials ought to be utilized as an alert substance in the design of energy conversion products, and the proposed results are supported by experimental and other theoretical data. We suggest that these substances are strong contenders for use in power conversion equipment depending upon their optical and transport characteristics.

Study of mechanical, thermodynamic, thermoelectric, and optical properties of Cs2SbAuX6 (X = Cl, Br, I) for energy harvesting applications

The inorganic double perovskites (DPs) Cs2SbAuX6 (X = Cl, Br, I) are an emerging applicant for solar cells, optoelectronic, and thermoelectrics to acquire clean energy. Therefore, the present research thoroughly addresses the mechanical, thermodynamic, optical, and thermoelectric characteristics by modified Becke and Johnson potential of Trans and Balaha (TB-mBJ) and BoltzTraP code. The structural stability is narrated from the tolerance factor and thermodynamic stability by formation energy. Born criteria assure the mechanical existence of cubic structures. The Cs2SbAu(Cl/Br)6 is ductile, and Cs2SbAuI6 has brittle behavior with a metallic nature. The band structures analysis reports the narrow band gaps for Cl/Br and the zero band gap for I-based DPs. The optical properties are studied by dielectric constants, absorption bands, refractive index, and other dependent optical parameters. Lastly, thermoelectric characteristics regarding Seebeck coefficient, electrical conductivity, power factor, thermal conductivity, and figure of merit in the temperature range 200–600K are analyzed. ZT's significant value at room temperature makes them potential candidates for thermoelectric generators.

A Density Functional Theory Exploration of Cs2B′B″I6 (B′B″: BeCa, BeSr, GeCd, GeBe, GeMg) Halide Double Perovskites for Optimal Solar Cell and Renewable Energy Applications

A comprehensive investigation into the structural, elastic, optoelectronic, and thermoelectric properties of Cs2B′B″I6 halide double perovskites (DPs), where B′B″ represents various combinations, including BeCa, BeSr, GeCd, GeBe, and GeMg, is conducted. Using the full‐potential linearized augmented plane wave approach within the density functional theory framework, this analysis confirms the materials’ structural and dynamic stabilities through negative formation energies and adherence to elastic constant stability criteria. The generalized gradient approximation and the modified Becke–Johnson (mBJ) potential for electronic structure calculations are utilized. Notably, Cs2B′B″I6 DPs with B′B″ as BeCa or BeSr exhibit direct bandgaps (Γ–Γ), while those with B′B″ as GeCd, GeBe, or GeMg display indirect bandgaps (X–L). These findings offer valuable insights into the potential use of these materials in photovoltaic and optoelectronic devices. Furthermore, the exploration of thermoelectric properties, covering electrical conductivity, Seebeck coefficient, electronic thermal conductivity, and figure of merit at temperatures of 300, 600, and 900 K, suggests that Cs2B′B″I6 DPs, regardless of the specific B′B″ composition (BeCa, BeSr, GeCd, GeBe, GeMg), holds promise for applications in thermoelectric devices.

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.

Predicting structural, elastic, and optoelectronic properties of oxide perovskites HfXO3 (X =Be, Mg) employing the DFT approach

This study conducts a comprehensive exploration of the structural, electronic, elastic, and optical properties of HfXO3 (X=Be, Mg) perovskite compounds, employing density functional theory (DFT) within the WIEN2k code. Employing the Birch Murnaghan fitting technique, our structural evaluation establishes the structural stability of these materials, with optimized lattice constants underscoring their stability at specific values. By harnessing the capabilities of the IRelast software, we have determined elastic constants and characterized the anisotropic tendencies, disclosing that both compounds exhibit a pronounced degree of anisotropy. Moreover, an in-depth investigation into electronic attributes, facilitated by the modified Becke–Johnson potential, uncovers these materials as indirect narrow band gap semiconductors, with calculated band gaps of 1.14 eV for HfBeO3 and 0.8 eV for HfMgO3 serving as vital indicators of their electronic character. Furthermore, we delve into the optical traits of these materials, revealing their photon transparency within the energy spectrum of 0 eV to 15 eV. These key optical properties encompass dielectric functions, refractive index, optical conductivity, absorption coefficient, extinction coefficient, energy loss function, and reflectivity. This comprehensive exploration offers a holistic understanding of the optical behaviors exhibited by these materials. By skillfully combining structural, electronic, elastic, and optical analyses, this study significantly contributes to the comprehension of HfXO3 (X=Be, Mg) perovskites, forging a path for their potential applications and serving as a foundation for future research endeavors.

First‐principles studies on physical properties for new half‐metallic perovskites AFeO3 (A = Ca, Sr, Ba): Spintronics and energy harvesting applications

AbstractIn this manuscript, structural, electronic, magnetic, and thermoelectric aspects of AFeO3 (A = Ca, Sr, Ba) have been calculated by means of the Full‐Potential Linearized Augmented Plane Wave Method (FP‐LAPW) using spin‐polarized Density Functional Theory (DFT). The calculated structural parameters have been found to be in good resemblance with previously available work. Enthalpy of formation and cohesive energy along with tolerance factor confirms structural stability. Electronic properties by Trans Blaha modified Becke–Johnson potential (TB‐mBJ) suggest metallic behavior in the spin‐up channel and semi‐conducting behavior in the spin‐down channel that supports half‐metallic behavior with mixed covalent and ionic bonding. Density of States (DOS) analysis confirms the major contribution of Fe‐3d‐states in the conduction band and O‐2p states in the valence band. The half‐metallic nature is further confirmed by the integer value of the total magnetic moment. The real and imaginary parts of dielectric functions, optical conductivities, absorption coefficients, reflectivity, and energy loss function have been calculated to evaluate suitability for optical applications. Thermoelectric properties with temperature range 300–900 K against chemical potential including figure of merit, Seebeck coefficient, thermal conductivities, and power factor, were examined using BoltzTraP code. Findings suggest that AFeO3 (A = Ca, Sr, Ba) compounds suitable for spintronic, thermoelectric as well as energy harvesting applications.

Physical properties of vacancy-ordered double perovskites K2TcZ6 (Z = Cl, Br) for spintronics applications: DFT calculations.

Vacancy-ordered double perovskites (DPs) are emerging materials for spintronics due to their stable structures and non-toxic properties. In this study, we conducted a comprehensive investigation into the role of 4d electrons in Tc to understand their impact on the ferromagnetic properties of K2TcY6 (Y = Cl, Br). We have employed a modified Back and Johnson potential to assess electronic and magnetic characteristics and utilized the BoltzTraP code to investigate thermoelectric effects. Experimental lattice constants confirmed the presence of stable structures and formation energy estimates affirmed their thermodynamic stability. The Heisenberg model and density of electron states (DOS) at the Fermi level provides insights into Curie temperature and spin polarization. The presence of ferromagnetism is evident in the density of states, reflecting the transition of electron spins that support the exchange mechanism. The study delves into how electron functionality influences the control of ferromagnetism, considering exchange constants, exchange energies, hybridization process and the crystal field energies. Moreover, the exploitation of magnetic moments from Tc to K and Cl/Br sites takes precedence in driving ferromagnetism by exchanging electron spins rather than forming magnetic clusters. Additionally, to explore the optical characteristics of the compounds, we investigated their optical absorption, dielectric constants and refractive index within the energy range of 0-10 eV, ensuring absorption across both the visible and ultraviolet regions. Finally, we delve into the impact of the thermoelectric effect on both thermoelectric performance and spin functionality, taking into account factors such as the Seebeck coefficient, power factor, and electronic conductivity.

First Principles Study of Structral, Electronic, and Optical Proeprties of Lead Free Double Perovskites Rb2LiTlX6 (X = Cl, Br, I) for Optoelectronics Applications

The presently, the renewable energy becomes the important source in the world because of shortage of oil and fossil sources and their hazardous. The solar cell is the main frontiers of cheap and clean renewable energy. We have chosen to lead free double perovskites Rb2LiTlX6 (X = Cl, Br, I) for structural, electronic, and optical applications because of their stable structure and direct band gaps. For the calculations, the modified Becke and Johnson potential has been applied (mBJ). The lattice constants are increase from Cl to I while bulk modulus decreases. The phase stability ensures the cubic phase with space group 221_Fm3m. The band structures and density of states show the band gabs (2.62, 1.39, & 0.14) eV. The ideal band gap of Rb2LiTlBr6 ensure the absorption of light in the visible region which has significant importance for solar cells applications.

Insight into the structural, elastic, and optoelectronic properties of XPaO3 (X = Cs, Rb) compounds employing density functional theory

Our research aims to provide a comprehensive understanding of XPaO3 (X = Cs, Rb) compounds, employing density functional theory as a guiding tool. Through the examination of their structural, electronic, elastic, and optical properties, we offer valuable insights into their versatility and potential in emerging technologies. This study strives to make complex materials more accessible, paving the way for their application in practical and innovative contexts. We commence our investigation by studying the structural aspects of XPaO3 (X = Cs, Rb) while using Birch-Murnaghan fitting. We endeavor to reveal the underlying crystal structures, lattice parameters, and overall stability, providing a fundamental understanding of their composition and behavior. Continuing into the electronic realm, we delve into the band structures, electronic density of states, and charge transfer properties of these compounds by using the recommended modified Becke–Johnson potential. This facet of our research sheds light on how they behave in electronic applications, offering insights into their suitability for emerging technologies. Our study also undertakes the mechanical properties of XPaO3 materials, including elastic constants, bulk modulus, and shear modulus utilizing the IRelast package. These mechanical characteristics are pivotal in determining their resilience and suitability for a wide range of practical applications. Lastly, we explore the optical properties of XPaO3 (X = Cs, Rb) by calculating parameters such as dielectric functions, refractive indices, and absorption coefficients. These optical insights hold promise for potential use in optoelectronics, where materials interact with light to power various devices.

Structural Analysis, Characterization, and First-Principles Calculations of Bismuth Tellurium Oxides, Bi6Te2O15

A single crystal of Bi6Te2O15 was obtained from the melt of the solid-state reaction of Bi2O3 and TeO3. Bi6Te2O15 crystallizes in the Pnma space group (No. 62) and exhibits a three-dimensional network structure with a =10.5831(12) Å, b = 22.694(3) Å, c = 5.3843(6) Å, α = β = γ = 90°, V = 1293.2(3) Å3, and Z = 4. The structure was determined using single-crystal X-ray diffraction. An asymmetric unit in the unit cell, Bi3Te1O7.5, uniquely composed of four Bi3+ sites, one Te6+ site, and nine O2− sites, was solved and refined. As a bulk phase, Bi6Te2O15 was also synthesized and characterized using powder X-ray diffraction (XRD), infrared (FT-IR) spectrometry, and the thermogravimetric analysis (TGA) method. Through bond valence sum (BVS) calculations from the single crystal structure, Bi and Te cations have +3 and +6 oxidation numbers, respectively. Each Bi3+ cation forms a square pyramidal structure with five O2− anions, and a single Te6+ cation forms a six-coordinated octahedral structure with O2− anions. Since the lone-pair electron (Lp) of the square pyramidal structure, [BiO5]7−, where the Bi+ cation occupies the center of the square base plane, exists in the opposite direction of the square plane, the asymmetric environments of all four Bi3+ cations were analyzed and explored by determining the local dipole moments. In addition, to determine the extent of bond strain and distortion in the unit cell, which is attributed to the asymmetric environments of the Bi3+ and Te6+ cations in Bi6Te2O15, bond strain index (BSI) and global instability index (GII) were also calculated. We also investigated the structural, electronic, and optical properties of the structure of Bi6Te2O15 using the full potential linear augmented plane wave (FP-LAPW) method and the density functional theory (DFT) with WIEN2k code. In order to study the ground state properties of Bi6Te2O15, the theoretical total energies were calculated as a function of reduced volumes and then fitted with the Birch–Murnaghan equation of state (EOS). The band gap energy within the modified Becke–Johnson potential with Tran–Blaha parameterization (TB-mBJ) revealed a value of 3.36 eV, which was higher than the experimental value of 3.29 eV. To explore the optical properties of Bi6Te2O15, the real and imaginary parts of the dielectric function, refraction index, optical absorption coefficient, reflectivity, the real part of the optical conductivity extinction function, and the energy loss function were also calculated.

Novel investigation by TB-mBJ potential of magneto-electronic properties and magnetic exchange coupling in vanadium (V)-doped PbTiO3 perovskite oxide

ABSTRACT In this paper, we investigated the structural and magneto-electronic properties, and exchange coupling in new vanadium (V)-doped PbTiO3 perovskite oxide such as PbTi1−xVxO3 compounds with compositions of x = 0, 0.25, 0.5, 0.75, and 1. The calculations of these properties are based on density functional theory using the generalized gradient approximation of Wu-Cohen (GGA-WC) and the Tran-Blaha-modified Becke–Johnson potential (TB-mBJ). Our calculations with GGA-WC revealed that the lattice constant for PbTiO3 is in good concordance with other theoretical and experimental results, while for PbTi1−xVxO3 at x = 0.25, 0.5, 0.75, and 1, the lattice constant decreases with increasing vanadium concentration owing to the difference in sizes of Ti and V ionic radii. The improved electronic structures obtained by employing the TB-mBJ potential, demonstrated that the half-metallic ferromagnetic and half-metallic gaps are present in PbTi1−xVxO3 materials at x = 0.25, 0.5, 0.75, and 1, which makes them promising candidate materials for spintronics applications.

Mechanical, Magnetic, and Optical Characteristics of Tm‐Based Chalcogenides for Energy‐Harvesting Applications

Herein, a comprehensive theoretical analysis of Tm‐based chalcogenides MgTm2Y4 (Y = S, Se) is performed to understand magnetic, optical, mechanical, and transport characteristics. And, Perdew–Burke–Ernzerhof generalized gradient approximation (PBEsol‐GGA) functional and modified Becke–Johnson (mBJ) potentials are employed while computing the mechanical and spin‐polarized electronic properties, respectively. The structural stability of both spinels is confirmed using formation energy and Born stability criteria. Both spinels are found exhibiting ductile nature according to the computed Pugh's and Poisson's ratios. For observing the room‐temperature ferromagnetism, Curie temperature is calculated. Furthermore, spin‐polarized electronic properties reveal that both spinels exhibit ferromagnetic nature, which is induced due to coupling among Tm‐ and S/Se‐related constituent states. The potential optoelectronic applications are suggested by computing and discussing dielectric constant, refractive index, and absorption coefficient. BoltzTraP code is used to investigate the thermoelectric features of MgTm2Y4 (Y = S, Se) in the 200–800 K temperature range.