Tran-Blaha Modified Becke-Johnson Research Articles

Theoretical insight into physical characteristics of lead-free perovskites Rb2TlSbX6 (X = Cl, Br, I) for optoelectronic devices.

Novel optoelectronic and thermoelectric properties with broad compositional range, non-toxic nature and structural stability make halide-based double perovskites fascinating for flexible optoelectronic devices. In this work, the structural electronic, optical and transport properties of Rb2TlSbX6 (X = Cl, Br, I) were studied using density functional theory for optoelectronic devices. The elastic analysis demonstrates ductile nature, mechanical stability, anisotropic behaviour and feasibility for flexible optoelectronic devices. The band structure study using Tran-Blaha-modified Becke-Johnson (TB-mBJ) potential shows that all studied materials have direct bandgap. In addition, the bandgap of Rb2TlSbCl6 is more appropriate for optoelectronic devices. The small loss and maximum absorption in visible regions make these materials prime candidates for optoelectronic devices. The transport features indicate that all the studied double perovskites reflect p-type semiconducting behaviour as highlighted by positive Seebeck coefficient values. Furthermore, the high power factor values of Rb2TlSbX6 (X = Cl, Br, I) double perovskites make them suitable for thermoelectric device applications at high temperatures. Based on electronic optical and thermoelectric properties Rb2TlSbCl6 is the best candidate for flexible optoelectronic devices. In this paper, structural optimization of Rb2TlSbX6 (X = Cl, Br, I) double perovskites was conducted utilizing the Wien2k software based on first principle calculations with Perdew-Burke-Ernzerhof's generalized-gradient approximation (PBE-sol approximation). The TB-mBJ potential was employed to compute the accurate band gap of studied materials. The thermoelectric properties are evaluated with BoltzTraP code, showing a predominance of P-type charge carriers in all studied perovskites. This methodological strategy verifies the material's remarkable stability and optical properties and offers a solid framework for examining its potential in optoelectronic devices.

A DFT study on structural, electronic, and optical properties of cubic perovskite semiconductors InXF3 (X = Be and Ca) for optoelectronic applications

First principles calculations were employed to study the structural, electronic and optical properties of Indium based cubic perovskite materials, specifically focusing on InBeF3 and InCaF3 compounds. The generalized gradient approximation Perdew–Burke–Ernzerhof (GGA_PBE) approximation and Tran–Blaha modified Becke–Johnson (TB-mBJ) approximations were used to study and compare the electronic and optical properties. The compound InBeF3 is predicted to have an indirect band gap of 2.51 eV in GGA_PBE and 2.96 eV in TB-mBJ. InCaF3 is found to have a direct wide band gap of 3.61 eV in GGA_PBE and 4.37 eV in TB-mBJ approximation. The partial density of states predicts the significance of In-5p and F-2p states in the conduction and valence bands, respectively. The dielectric constants decrease under the TB-mBJ approximation, with InCaF3 demonstrating lower values owing to its larger band gap. Optical activity analysis indicates transparency for both compounds with notable absorption peaks, suggesting potential applications in transparent coatings. Refractive indices decrease with photon energy, with values dropping below 1.0 in the TB-mBJ approximation, indicating superluminal behavior in wave propagation. The drop in refractive index value below1.0 is earlier for InCaF3 than InBeF3. Examination of the extinction coefficient reveals UV absorption peaks, indicating potential for optoelectronic applications. From this study it can be noticed that the compounds under study can be used for optoelectronic applications, supported by their predicted structural and optical properties study.

Opto‐Electronic Properties of Gap1‐xSbx Alloys for IR Applications

AbstractThe full potential linearized augmented plane wave (FP‐LAPW) method is used to compute structural, electronic, and optical properties of III‐V semiconductor ternary alloys GaP1‐xSbx (0≤x≤1) using first‐principle calculations within density functional theory. To calculate the ground state parameters of the structure, the energy exchange‐correlation Wu‐cohen generalized gradient approximation is employed in the wiek2k program. The Tran–Blaha‐modified Becke–Johnson (TB‐mBJ) pseudopotential is employed in addition to the Wu‐Cohen generalised gradient approximation to achieve a precise bandgap. After this, WC‐mBJ is used to examine optical properties such as real and imaginary parts of the dielectric constant, and energy loss. This study illustrates the nonlinear dependency on the various Sb compositions by examining the composition impacts on the bandgap, bulk modulus, and lattice constant. Using WC‐mBJ, the estimated band structures for alloys GaP0.75Sb0.25, GaP0.50Sb0.50, and GaP0.25Sb0.75 show direct energy bandgaps of 2.008 eV (617 nm), 1.482 eV (836 nm), and 1.055 eV (1174 nm), respectively. As a result, this material system has enormous potential for use in applications spanning the visible to infrared spectrum.

Comprehensive investigation of half Heusler alloy: Unveiling structural, electronic, magnetic, mechanical, thermodynamic, and transport properties

This study employs density functional theory (DFT) using Wien2k to comprehensively analyze the essential properties of two half-Heusler alloys, KCrSi and KCrGe. Our findings demonstrate that the ferromagnetic Type 2 configuration exhibits superior stability over non-magnetic and antiferromagnetic states for all KCrZ (Z = Si, Ge) alloys. These alloys exhibit complete spin polarization and half-metallic character, with calculated magnetic moments of 3 μB for both KCrSi and KCrGe. The Curie temperature (TC) is determined using the mean field approximation. Mechanical stability is assessed through second-order elastic constants (SOECs), and electronic properties are analyzed using local spin density approximation (LSDA), Perdew-Burke Generalized Gradient Approximation (PBE-GGA), and Tran-Blaha modified Becke-Johnson (TB-mBJ) schemes, confirming the retention of the half-metallic nature. The negative enthalpy of formation (ΔH) suggests material stability. The use of semi-classical Boltzmann theory, incorporated through the sophisticated scheme of BoltzTraP, explores transport coefficients. High pressures and temperature discrepancies in thermodynamics are considered by implementing the quasi-harmonic Debye approximation to illustrate stability. Finally, optical properties are summarized to assess the applicability of this alloy for optoelectronic applications. The overall characteristics of these particular alloys suggest potential applications in sustainable thermoelectric and optoelectronic features.

Ab Initio Investigation of the Structural, Elastic, Dynamic, Electronic, and Magnetic Properties of Cubic Perovskite CeCrO3.

We presented the results of various aspects related to structural, elastic, electronic, dynamic, and magnetic parameters of cubic perovskite CeCrO3 by means of the full-potential linearized augmented plane wave (FP-LAPW) approach. The calculation of the unit cell volume against the total energy curve confirms that CeCrO3 exhibits higher energetic stability in the ferromagnetic (FM) order. Calculated structural aspects at equilibrium demonstrate excellent similarity to present information, lending credibility to our results. Moreover, monocrystalline elastic constants have been analyzed numerically. These constants provide insights into several related properties, including elastic anisotropy, mechanical stability, and several polycrystalline elastic aspects. Furthermore, the phonon dispersion curves obtained from our calculations reveal the existence of soft modes, which suggests the potential metastability of CeCrO3. Through an analysis of the energy band dispersions, the half-metallic nature of this material is confirmed, such as Eg = 3.00 and 3.13 eV for the HM state within generalized gradient approximations Perdew-Burke-Ernzerhof (GGA-PBE) and Tran-Blaha modified Becke-Johnson (TB-mBJ) calculations, respectively, as well as the FM total magnetic moment of 4.000 μB. Partial density of states (PDOS) aided in identifying the electronic states that contribute to the energy bands. Finally, the computed total magnetic moment aligns fit the theoretical findings available in the literature.

Enhanced mechanical, optoelectronic and thermoelectric properties of binary CdO by under pressure: An ab initio study

AbstractThis manuscript presents, under the effect of different pressures (0–60 GPa), the structural, mechanical, electronic, optical, and thermoelectric properties of CdO with NaCl type structure by using the FP‐LAPW (Full Potential Linearized Augmented Plane Wave method) with Generalized Gradient Approximation (GGA) whose basis is the Density Functional Theory (DFT). PBE‐GGA was used to compute the structural, elastic, optical, electronic, and thermoelectric properties using Tran‐Blaha modified Becke‐Johnson (TB‐mBJ) potential. Different terms like formation energy, cohesive energy, and phonon were used for the computation of thermal stability and that is further confirmed by elastic properties. Bulk moduli and pressure‐dependent lattice constants were achieved by using the optimization method. From the results, we can say that the increase in pressure is directly related to the band gap and inversely related to the lattice constant. The mechanical properties show that CdO is highly ductile and mechanically stable and ductility is directly related to pressure. The minimum conduction band goes to a higher energy level when the pressure increases while the maximum valance band goes to a lower energy level ultimately the energy band gap increases. The optical parameter curve does not change by increasing pressure but the peaks start moving towards the higher energies slightly. Calculations reveals that band gap increases by increasing pressure which shows the blue shift in optical properties. The optical properties spectrum was studied, including reflectance, dielectric coefficient, and absorption coefficient. The optical constants show that the phase of CdO with NaCl structure was translucent. In the end, the thermoelectric feature in terms of thermal conductivity (K), power factor (PF), Seebeck coefficient (S), and electrical conductivity (σ) were studied by using the BoltzTrap code as a function of temperature. Thermoelectric and optical aspects revealed that pressure induces the possible use of CdO material for various TE and optical applications.

First principle study of structural, electronic, optical, and thermoelectric properties of Zr1-x MxNiSn (M = Ta, Nb and x = 0.25, 0.5, 0.75) half Heusler compounds: Green energy applications

In the present paper, the physical properties of doped Zr1-x MxNiSn (M = Ta, Nb and x = 0.25, 0.5, 0.75) half Heusler compound were investigated using density functional theory (DFT) with GGA-PBE and Tran-Blaha modified Becke-Johnson (TB-mBJ) exchange potentials. The Full Potential Linearized Augmented Plane Wave (FP-LAPW) technique was used as incorporated in the WIEN2k code. The band structures, as well as the density of states (DOS), are also studied. The lattice constants of 6.15 Å for pure and 6.12 Å reinforced compounds are obtained. The results show that pure alloys are semiconducting, and doped alloys are metallic. The elastic properties were also examined, and the results indicate that the compounds are mechanically stable. The optical properties such as absorption coefficient (I), optical conductivity (σ), electron energy-loss (L), refractive index (n), and extinction coefficient (K) were determined using the dielectric constants (ε). The optical results revealed that the materials are potential candidates for optoelectronic energy applications. The transport properties were also studied. The doping of Ta and Nb in ZrNiSn alloy increases the electrical conductivity in both GGA-PBE and TB-mBJ approaches. The electrical conductivity for pure ZrNiSn at room temperature is 4.67 × 1018 Ω−1m−1s−1 and it increases to 4.34 × 1020 Ω−1m−1s−1 for Zr0.5Ta0.5NiSn in GGA-PBE approach. The thermal conductivity's electrical component is increased by substituting Ta and Nb in the pure compound. The optical and thermoelectric properties make the materials a suitable candidate for green energy applications.

Comprehensive computational prediction of elasto-mechanical and thermoelectric properties of Co2PdAl and Co2AgAl full Heusler compounds

Without a profound knowledge of technological growth and future perspectives of materials their physical properties cannot be explained. Heusler compounds belong to class of prominent materials with special characteristics which ultimately land them as multifunctional materials. The results of this work stem the investigations of structural phase stability, elasto-mechanical and thermoelectric properties of Co2AgAl and Co2PdAl full Heuslers with the density functional theory (DFT). This theory is successfully executed in Boltzmann transport theory and WIEN2k program package to obtain the desired results. The generalised-gradient approximation (GGA) scheme and Tran Blaha modified Becke-Johnson (TB-mBJ) potential are embraced to compute the ground state properties. The approximations approves both compounds ideal for thermoelectric as well as for elasto-mechanical applications. The computation for mechanical parameters such as Young’s modulus, Shear modulus, Pugh’s ratio elastic constants and Poisson’s ratio are investigated. The mechanical tolerance ultimately revealed that both compounds Co2AgAl and Co2PdAl are stable with ductile nature and exhibit low rigidity. The thermodynamic parameters like Seebeck coefficient, thermal conductivity electrical conductivity, lattice thermal and electronic conductivity, power factor (ɳ) and electrical figure of merit (zT) have been computed within relaxation time approximation as a function of high temperature.

Exploring the multifaceted properties: electronic, magnetic, Curie temperature, elastic, thermal, and thermoelectric characteristics of gadolinium-filled PtSb3 skutterudite.

The investigation of binary and filled skutterudite structures, particularly PtSb3 and GdPt4Sb12, has gained significant attention, becoming a focal point in scientific research. This comprehensive report delves into the intrinsic characteristics of these structures using Density Functional Theory (DFT). Initially, we assess the structural stability of PtSb3 and GdPt4Sb12 by examining their total ground state energy and cohesive energy, employing the Brich Murnaghan equation of state to determine stability in various configurations. Further insights are gained by exploring second-order elastic constants (SOEC's) to extend our understanding of structural stability. The electronic structures are then meticulously defined through a quantum mechanical treatment, employing a combination of two distinct spin-polarized approximation schemes: Perdew-Burke-Ernzerhof Generalised Gradient Approximation (PBE-GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ). The resulting band structures reveal a symmetry in electronic behavior, showcasing spin-magnetic moments of 3 μB and 7.58 μB per formula unit, with the primary contributions emanating from the Pt 3d and Pt4+ 3d-transition elements. To gauge thermal stability, we evaluate the phonon-dependent Grüneisen parameter (γ) across specific temperature ranges. The study extends to exploring transport properties as a function of chemical potential (μ - EF) at various temperatures. The findings suggest that these designed materials hold substantial potential for diverse applications, particularly in conventional spin-based and thermoelectric technologies. The comprehensive insights obtained through this investigation pave the way for a deeper understanding and broader implications in various 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.

Electronic, optical and thermoelectric properties of Cs2XInCl6 (X = Ag, Na) halide double perovskites

Herein, the optoelectronic, structural, thermoelectric and elastic features of halide double perovskites (HDPs) Cs2XInCl6(X=Ag, Na) are examined by using full‐potential linearized augmented plane wave (FP‐LAPW) technique. The Generalized Gradient Approximation (GGA) and Tran‐Blaha modified Becke‐Johnson (TB‐mBJ) potential is employed to figure out the features of mentioned compounds. The computed values of direct band‐gaps (Eg) for Cs2AgInCl6 and Cs2NaInCl6 compounds are 2.52 and 5.24 eV, correspondingly. The stability of perovskites is confirmed in terms of formation energy ΔHf, tolerance factor (τ) and octahedral factor. Furthermore, optical properties analysis demonstrates that studied compound exhibit conductivity and absorptivity across a broad range of incident photon energy with minimum R(ω). Moreover, outcomes of elastic parameters display isotropic and ductile nature for both materials. Thermoelectric (TE) properties like thermal conductivity (k/τ), power factor (PF), electrical conductivity (σ/τ) and Seebeck coefficient (S) are also calculated by utilizing BoltzTrap code. Cs2NaInCl6 attained the maximum value of ZT (0.76) with PF of 0.42. Computed TE and optical parameters indicate that Cs2XInCl6(X=Ag, Na) are promising for usages in solar absorbing and energy conversion devices.This article is protected by copyright. All rights reserved.

The effect of Cu doping on the thermoelectric properties of Cs2CuxAg1-xBiBr6 perovskites

This study focuses on examining the thermoelectric properties of Cs2CuxAg1-xBiBr6 perovskites and investigates the influence of lattice thermal conductivity on their thermoelectric performance. To achieve this, the study utilizes a combination of first-principles calculations and Boltzmann transport theory. The calculated structural properties, obtained through the generalized Perdew-Burke-Ernzerhof approximation (GGA-PBE), closely align with both experimental and theoretical data for lattice constants and bulk modulus. The electronic properties were assessed using the TB-mBJ (Tran-Blaha-modified Becke-Johnson) method, indicating relatively small band gaps within the range of 1.146 eV for Cs2CuBiBr6 and 2.072 eV for Cs2AgBiBr6. The materials exhibit significant Seebeck coefficients and controllable lattice thermal conductivity between 0.067 and 0.662 W/mK at room temperature, with the relaxation time being determined using the Drude model. The study revealed that the most significant zT values, approximately 0.80, were observed when x = 0.5 in the Cs2CuxAg1-xBiBr6 perovskite material. This indicates that these perovskites possess the ability to efficiently and inexpensively convert heat into electrical energy. Consequently, these findings propose the potential of Cs2CuxAg1-xBiBr6 perovskites as a favorable option for real-world thermoelectric applications. The study further highlights the importance of utilizing lattice thermal conductivity to enhance the overall thermoelectric performance of such materials.

Electronic structure calculations on copper substituted silver iodide through modified Becke-Johnson exchange potential

Silver iodide (AgI) has a rich phase diagram with the γ-AgI being one of the forms. γ-AgI is a n-type semiconductor that crystallizes into zinc blende structure and found to be stable at ambient temperature and pressure. The electrical transport in γ-AgI is mediated by the migration of Ag+ cationic interstitial defects, while the Cu + Frenkel defects are responsible for the conduction in γ-CuI, a p-type semiconductor. This intrigues to understand the transition of the nature of electrical transport with the replacement of Ag by Cu. In this regard, we report the computational study on the Cu substituted γ-AgI using the density functional theory (DFT) with Tran-Blaha modified Becke-Johnson (TB-mBJ) scheme. The calculations are performed on γ-Ag1-xCuxI (x = 0.00–1.00) supercell through full potential linearized augmented plane wave (FP-LAPW) method. The lattice parameter and bulk modulus are found to vary nearly linear with copper concentration x, whereas band gap values follow a non-linear variation.

Characterizing Nickel Oxide Thin Films for Smart Window Energy Conversion Applications: Combined Experimental and Theoretical Analyses

AbstractIn this work, we have analyzed key characteristics of nickel oxide (NiO) thin films using combined experimental and computational approaches for smart window applications. Thermo Gravimetric Analysis (TGA) depicts that nickel oxide films are stable beyond 275 °C.The XRD pattern revealed the single phase of the materials. FTIR studies confirm the stretching vibrational band of Ni−O. The current‐voltage analysis shows the semiconducting behavior of the materials. The synthesized NiO thin films have shown prominent electrochromic response with a wide linear range, better cyclic stability, high durability, and fast response time. The sample having concentration of 0.05 M/25 mL has best semi‐conductive response as rapid increase in current occurs above 0.8 V. Moreover, the electrochemical and optical properties have shown reversible redox behavior of the synthesized NiO thin films with changing their appearance from original greenish gray to the dark brown in the selected potential range. In addition, the computational study has also been performed for deep study of electronic charge conduction mechanism and photo response of NiO thin layer using Tran‐Blaha modified Becke Johnson (TB‐mBJ) approach. These fabricated NiO thin films have been utilized as an active electrode for electro chromic devices in smart window applications.

Density functional theory and Monte Carlo simulation insights into electronic structure and magnetic properties in HoSi and CeSi

The electronic and magnetic properties of heavy fermion bulk CeSi and HoSi were studied using density functional theory (DFT) and Monte Carlo simulation (MCS). The exchange correlation (XC) potential was solved by GGA (generalized gradient approximation), TB-mBJ (Tran Blaha modified Becke Johnson) approximations, and also by TB-mBJ and GGA combined with U (Hubbard parameter). Calculations of the electronic structure indicate that CeSi and HoSi compounds are metals and reveal antiferromagnetic behavior. However, the calculations within the TB-mBJ+U approach predict ferrimagnetic behavior for HoSi. The magnetic moments of Ce and Ho in HoSi and CeSi have been estimated. The values of N é el temperature, TN, are found to be 6.61 K and 22.5 K for CeSi and HoSi, respectively. The theoretical TN value of CeSi is very close to that found experimentally, 6.1 K. The maximum of susceptibility is investigated for both compounds.

DFT modeling techniques to understand the potential applicability of novel double perovskite semiconductor Ba2LuNbO6 for sustainable thermoelectrics and optoelectronic perspectives

Searching for novel functional materials represents an important direction in the research and development of renewable energy. Herein, experimentally synthesised Ba2LuNbO6 (BLNO) host double perovskite has been theoretically computed by first principles techniques to understand its several physical properties like electronic-structure, mechanical behaviour, transport along with optical and thermal properties upon the basis of full potential linearized augmented plane wave (FP-LAPW) followed by density functional theory (DFT). First and foremost, the attempt was significant made to relax the molecular crystal structure of BLNO at an experimental lattice constant to evaluate its total ground state and cohesive energy (Ecoh) for descripting its required structural stability. After that, we have overseen its mechanical stability from the computation of second order elastic constants (SOEC's). Later on, the electronic properties of this alloy have been executed within the two potential schemes like Perdew-Burke Generalized gradient approximation (PBE-GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) which alternatively certifies the retention of the semiconducting nature respectively. Besides this, the essential use of semi-classical Boltzmann theory within the sophisticated scheme of BoltzTraP has been inducted to explore its transport coefficients. And finally, the optical has been summarised to see the applicability of this particular alloy towards optoelectronic application purposes. Therefore, the overall tendency of this particular alloy can favor their potential multiple applications in sustainable thermoelectrics, optoelectronic features etc.

DFT based atomic modeling and Analog/RF analysis of ferroelectric HfO2 based improved FET device

In this study, we systematically investigated the Analog/RF and linearity parameter of SM DGNCFET (single metal double gate negative capacitance field effect transistor) and DM DGNCFET (double metal double gate negative capacitance Field effect transistor) with the help of Cogenda Visual TCAD simulator, and also demonstrated the enhancement in the electronic and optical properties of Si-doping bulk structure by using the Quantum ATK. The analog parameters are enhanced for SM DGNCFET such better performance of switching ratio 279 times better, DIBL 54% lower, SS decay, and some other improved parameter transconductance, TGF and Radio frequency parameter is also enhanced, transconductance frequency product (TFP) for improving reliability and stability of device. Linearity parameters like that second and third order transconductance (gm2, g m3), voltage intercept point for 2nd, 3rd. Tran Blaha modified Becke Johnson (TB-mBJ) approxiamation gives the accurate band gap of crystal. In DFT based atomic study, 12.5% of Si doping in bulk structure reveals better results for ferroelectric HfO2 based crystal in the direct band gap of bandstructure is zero, Density of state (DOS) is also improved conductivity for Si doping crystal. Hence, Si doping in crystal structure is also better for conductivity.

Heat reflux sonochemical synthesis of Cu3BiS3 quantum dots: Experimental and first-principles investigation of spin–orbit coupling on structural, electronic, and optical properties

Semiconductor quantum dots (QD) exhibit promising electrical and optical properties in photovoltaic cells by improving their stability and efficiency enhancement. Therefore, in this study, novel Cu3BiS3 (CBS) ultrafine QDs were synthesized to function as effective solar absorbers, using a facile heat reflux sonochemical synthesis process under inert (N2) atmosphere. Using high-resolution transmission electron microscopy (HRTEM) analysis, the size of CBS QDs was found to be in the range of 3–8 nm. Furthermore, the crystallite size (D), strain (ε), and dislocation density (δ) of the QDs were investigated in detail by confirming the orthorhombic wittichenite structure. The photocurrent density (PCD) of CBS QDs obtained at a voltage range of 0.5–1 V was found between 0.2 and 0.6 mA/cm2 under illumination; otherwise, it has a linear nature and good ohmic behavior in the range of − 0.1 V to + 0.1 V. In additionally, the spin–orbit coupling (SOC) interaction was computed using the Perdew–Burke–Ernzerhof (PBE) and Tran-Blaha-modified Becke–Johnson (TB-mBJ) functionals in the density functional theory (DFT) framework. The results showed a bandgap transition from direct to indirect with the inclusion of SOC, as confirmed by the electronic band structure. Moreover, the DFT-calculated bandgap using the TB-mBJ functional (∼1 eV) achieved near consistency with the experimentally obtained bandgap (∼1.4 eV). Therefore, based on the experimental and computational results, this study can pave the way toward developing novel copper chalcogenide QDs for application in future photovoltaic cells.

First-principles calculations to investigate structural, electronic, phonon, magnetic and thermal properties of stable halide perovskite semiconductors Cs2GeMnI6 and Cs2GeNiI6

Since, the systematic and extensive study on halide double perovskite’s (HDP’s) have triggered a considerable interest, thus became a new thrust to the scientific research. In this organised report, we present a new promising halide double perovskite structures Cs2GeMnI6 and Cs2GeNiI6 to understand, more in-depth their intrinsic characteristics by means of Density Functional Theory (DFT). Initially, we reported the structural stability of both these crystal structures by evaluating their total ground state energy in stable configuration and cohesive energy at the behest of Brich Murnaghan equation of state. Afterwards, the structural stability is moreover extended to see their corresponding tolerance factor (τ) values and second order elastic constants (SOEC’s). Subsequently, the density functional perturbation theory (DFPT) has been inducted to predict the dynamical context of these ordered systems. Later on, the quantum mechanical treatment of defining their electronic structures by the calibration of mix of two distinct spin-polarised approximation schemes like Perdew-Burke-Ernzerhof Generalised gradient approximation (PBE-GGA) followed by Tran-Blaha modified Becke-Johnson (TB-mBJ). Meanwhile, the unsymmetrical behaviour of electronic structures from their resulting band structures demonstrates the occurrence of spin-magnetic moment of 5 µB and 2 µB/formula unit respectively having the maximum contribution solely coming from the Mn+2 and Ni2+ 3d-transition elements. The evaluation of phonon dependent Grüneisen parameter (γ) defines the possible thermal stability against specific temperature regimes. And finally transport properties as a function of chemical potential (µ-EF) at distinct temperatures has been keenly explored. Therefore, the overall tendency of these designed materials can be envisaged to descript vast implications in various extending applications for conventional spin-based and thermoelectric technologies.